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Experimenting with Resin printing (MSLA) for detailed parts

jhitesma

Some guy in the desert
Mentor
#1
I've been interested in resin based printing almost as long as I've been interested in FDM (filament based) printing. In fact before I got my first printer when I was researching cheap ways to build my own I considered a DLP resin printer design a few times and backed the failed Peachy printer SLA printer.

But - I've always been warned that resin printing is dirty, stinky, requires a lot of post-processing and the resulting parts aren't as functional because they're very brittle and it's hard to get accurate parts due to shrinkage while curing and other issues.

Still, the incredible detail possible intrigued me, and I've had a couple of projects where I've 3D printed small parts and even at 0.10 layer heights was unable to get the detail I wanted. Heck one of the very first things I shared on Thingiverse was a replacement button for my battery charger - and I was never happy with the print quality since FDM lacked the resolution to do the smooth top I wanted: https://www.thingiverse.com/thing:1360018

Being bored with COVID restrictions and trying to find ways to entertain myself I again found myself building a project where I'd have to 3D print some small detailed parts. And while I was able to get usable FDM parts....I just wasn't happy with them. And with the Anycubic Photon 0 being available for <$200 and getting pretty good reviews I figured maybe I'd give resin printing a try.

But the more I read about the Photon 0 and really looked at the reviews critically the more I realized it's a bit limited. It's lower resolution than other low cost MSLA printers and the positive reviews were mostly because of the wash and cure station anycubic released at the same time. So I widened my search and instead looked at the Photon (full photon not the zero) and Elegoo Mars. If my goal was to make highly detailed parts then it seemed silly to cheap out on a printer with lower resolution. (The Photon zero has 115 micro X/Y resolution compared to the 47 micro X/Y of the full photon and mars.) Then I saw a 3rd printer I hadn't heard of before - the Phrozen Sonic mini which really intrigued me despite it's slightly lower 62 micron resolution.

Quick review - SLA is short for Sterolithography. Plain SLA uses a laser to trace out each layer and expose the photosensitive resin causing it to harden. DLP printing instead uses a DLP projector to expose a full layer of resin at once. MSLA which is what most lower cost consumer machines use is Masked SLA where an array of high power UV led's project light through a LCD screen that acts as a mask allowing it to expose a full layer at once. Since DLP and MSLA both expose a full layer at once the amount of stuff on the build plate doesn't change the print time - only the number of layers affects the print time. Which is both a curse and a benefit - if you're just doing a quick test print of one little part it's a curse since it takes just as long as printing a full build plate of parts. But if you're printing that full build plate it's a benefit since it doesn't take any longer than one little test part of the same Z height.

So what makes the Phrozen Sonic Mini attractive despite it's lower resolution? It uses a monochrome LCD which allows more UV through letting it cure layers much faster than other similar printers. The LCD is also a consumable part of these printers that's put under a lot of stress - with the LCD's on most common printers only rated for 500 hours of use...but the Sonic Mini's monochrome screen is rated for 2,000 hours of use. And since you can use shorter exposures that means you rack up fewer hours of use doing the same prints so it can theoretically last a LOT longer. And some reviewers have claimed to get sharper more detailed prints with the Sonic mini than they do with their other higher resolution machines (possibly because of the shorter exposure times, or maybe because being monochrome it's mask is sharper than the color LCD's others use.)

There were two big negatives to the Sonic Mini. 1 - it came with a plastic resin vat which a lot of people reported cracking and being incompatible with some resins. 2 - it's build plate is just a flat sheet of aluminum so resin pools on top and is a lot messier to clean up after a print. Phrozen has addressed both of these issues though - they now ship with an aluminum vat (though they also raised the price of the printer a little bit to compensate) and they offer a upgraded build platform - though it's an extra cost.

At this point I knocked the Photon out of my consideration. It's a nice machine but a bit dated now and has a smaller x/y build plate than the Sonic Mini and Mars. And it turned out Elegoo released an updated version of the Mars that's about $70 more but has a number of nice updates - the Mars Pro. I debated for a few days about whether or not I really wanted a printer in the first place and if so which...and finally pulled the trigger ordering a Sonic Mini.

I ordered from a shop called 3dprintersbay which had an address listed in CA. They advertised 2 day shipping (though not free shipping) but said it was 3-6 days from when you order until they ship. The printer was out of stock on Amazon at the time and 3dprintersbay offered the upgraded build plate for just $20 when ordered with a new printer compared to $40 to get the upgraded build plate off of Amazon. What they didn't make clear was that they basically just drop-ship from the manufacturer. And 2 days after I ordered Phrozen took a week long holiday for their local "Dragon boat festival" in Taiwan. After 2 weeks my order still hadn't shipped and I started to wonder if it ever would. I sent a message to 3dprintersbay inquiring and when I didn't hear back in 24 hours I decided the printer probably wasn't coming and got ready to call my credit card company and paypal to reverse the charges.

I also went ahead and ordered an Elegoo Mars Pro off of Amazon. Then a few hours later 3dpritnersbay finally responded and apologized for the delay explaining that they were waiting on Phrozen who also replied saying it should ship in the next 2-3 days. I wasn't convinced enough to cancel the Mars pro....though I was a bit upset that my original plan of getting a $170 printer had now turned into buying 2 $250+ printers. Oops.

But - I figured this is a good opportunity to compare the two printers and then I can sell whichever one I'm less than happy with.

The Mars pro arrived last Thursday and the Phrozen sonic mini arrived the day after. For the past week I've been printing like crazy and have learned a lot about resin printing in general, both machines quirks, and why this is a terrible time to get into resin printing.

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How do they compare? If I had to buy one today knowing what I know which one would it be? What have I learned about the process overall?

Let's find out...in my next few posts :D
 

jhitesma

Some guy in the desert
Mentor
#2
The mars came first. Out of the box it was a great experience. Unboxing and setup took less than 10 minutes. I had already ordered some black anycubic resin and white elegoo resin off Amazon when I ordered the Phrozen so I'd had them for about a week already. This was my first mistake.

Since SLA/MSLA (note, as I already explained these are both MSLA printers...but I'll probably just say SLA in most places because I'm too lazy to type the M :LOL:) is a photosensitive process and color affects photo sensitivity the color of the resin will greatly affect how it prints. Most SLA users stick with grey resin because it's by far the easiest to get good results with a great overall compromise since most people doing SLA printing plan on painting their prints so color doesn't matter to them. I fairly quickly ordered some grey "ABS Like" resin that's supposed to be tougher than regular resin, and some grey "water washable" - more on that later. But for the first day All I had was white or grey. Since the printer was an Elegoo and the white resin was Elegoo I figured I'd try the white first.

The setup pretty much just consists of pulling protective plastic off of a few things and leveling the print bed. This doesn't have to be done very often since it locks in place really well. You just loosen two large allen head bolts then home the machine with a piece of paper over the LCD screen. Once it's homed you tighten the two screws, then adjust the z height in 0.1mm increments until you can pull the paper out with some resistance - but can't push it back in without it buckling. Note - I found this just slightly tricky because when you tighten the bolts the bed can shift a little...the paper will still have tension - but it will be obvious that it's tighter in one corner than the others. I found gently pressing down on the bed plate while tightening the screws helped as well as just barely snugging one screw, then the other, then going back and tightening them.

With the bed level I poured some white resin into the vat and hit print on the provided sample print. The famous hollow rook test piece.

20200702_133108.jpg



Which is a 3.5 hour print. And what I found extra agonizing is that for the first 2 hours you can't even tell if it's printing or not because the lifts between layers are so small it doesn't come up out of the vat. But after 2 hours it was raising high enough I could see the print bed...and there was nothing on it. Uh oh. Cancel print!

I poured the resin in the vat back into it's bottle (using one of the fine strainers that was provided with the machine) and found two partial prints stuck to the bottom of the vat. I washed them in simple green (more on washing in a bit) and then set them outside to cure in the sun for a few minutes (again, more on post-processing in general in a bit.) The results were semi-encouraging...the detail I could see was exciting...but why the failure?

20200702_155016.jpg


I didn't yet know it...but apparently the test file is notoriously difficult to print on this machine. Not knowing any better I figured the problem was I didn't clean the build plate. I remembered peeling protective plastic off of it...but in my excitement to do a test print I neglected to clean it. Maybe that was why the print came loose. Easy enough to fix and try again! I used some sprayaway glass cleaner (which is ammonia free and alcohol based so apparently great for cleaning resin) to clean the build plate and tried again.

2 hours later....I again saw an empty build plate :(

This time it got a bit farther before failing. But it still failed.

At this point I figured the white resin was the issue. White requires less exposure than grey (and black requires more) - maybe overexposing it was causing it to stick to the vat? Rather than reslice the provided sample STL and have to wait 2 hours into a 3.5 hour print to see if it worked I decided to try printing the parts that inspired me to get this machine in the first place.

See, I'm building a physical interface for a software defined radio I got last year. It's a great radio...but I found I really miss having knobs to twiddle and don't like having to be attached to a computer to use it. (Yeah, there's a Raspberry pi hiding in the interface, but it's easier to ignore since I'll have knobs to play with.) The issue is those knobs. The interface design used concentric rotary encoders, expensive little buggers but they let you pack twice as many controls into the same amount of space and really make sense for some of the controls on a radio. Unfortunately knobs for those encoders are almost impossible to find unless you're buying them in large quantities. I only need four sets...and don't know enough other people building one of these to justify ordering 1,000 of them!

But someone designed some printable knobs. I printed them on my FDM and while usable I wasn't entirely happy with them:

20200617_154843.jpg


They work...but...they just look amateur. Even at 0.10 resolution the layer lines really detract from them.

I tried printing them in ABS and vapor smoothing them....but then they just look lumpy to me...and I only have green and pink ABS...and I hate printing ABS. Even with an enclosure around my printer the smell drives me crazy:

20200617_225918.jpg


So...I loaded the files into the SLA slicer - only an hour to print, great! And I can print all 4 sets at once just as quick as printing 1 knob! Woo Hoo! Let's load it up and try it!

First, let's re-level the bed just in case...maybe that's why I'm having failures.

Success!

20200702_191822 (1).jpg


Well, mostly. I don't like the way the white resin yellows after curing. And you may notice some serious elephant foot on the bottom of the prints. That's something I've learned is very tricky to avoid with SLA/Resin printing and is a bit part of why most resin printing parts are always supported instead of printed right on the bed.

But with a bit of work with a razor and sandpaper I got that cleaned up and could put them on an encoder:
20200702_210208.jpg


The photo doesn't show it but they're actually a bit loose. They were over sized to compensate for inaccuracies of FDM printing - I later found I have to reduce them 1-2% in size to get them to print the correct size in SLA.

But the quality blew me away! They look like injection molded or cast parts! There's NO layer lines at all - just perfectly smooth knobs! And while brittle they're also very hard and tough. I put one in my dremel desk vise and tightened it as hard as I could but was unable to break it in any orientation I tried. (thin parts do break very easily though - you can see how the thin elephant foot on bottom chipped.)

Ok, with some success I felt more confident that the bed was correctly leveled and decided to try the rook test again. I did tweak the settings after starting the print to reduce the exposure time 2 seconds as well to compensate for the white resin. 2 hours later I saw rooks coming out of the vat! And 3.5 hours later:

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My jaw just dropped. The detail on these is amazing. Note - it was still a little wet from post-processing in these photos - the top is actually clearer and more defined once it dried off.

Now I was getting excited! The Phrozen Sonic Mini was scheduled for delivery the next day...it was coming with 3 bottles of Phrozen's aqua blue default resin and I was excited to see how it compared.

More in my next post....which will be a bit later...have to eat some lunch and do some actual work before I can continue ;)
 

PsyBorg

Wake up! Time to fly!
#3
NOW 3d printing has my attention and more then passing interest.

Looking forward to different function parts to see how the durability and longevity of these new materials are now.
 

jhitesma

Some guy in the desert
Mentor
#4
NOW 3d printing has my attention and more then passing interest.

Looking forward to different function parts to see how the durability and longevity of these new materials are now.
Well, hang on for the rest. But don't get too excited just yet. So far I'm finding SLA is great for small detailed decorative parts - scale modelers would benefit greatly from having one in their shop. But...for functional parts...it's really hard to get some things to come out accurately. And while very hard the resin is also VERY brittle. I woudln't print a micro quad frame out of this stuff for example. But...there are other tougher resins I haven't tried yet. And there's flexible resin, which I have but haven't tried printing yet. I've seen videos of people driving over parts printed in flexible and it slowly coming back to shape. And some people apparently mix resins - adding the flexible resin to the regular resin to get parts that have a bit more give to them before breaking.

And while I will be comparing the pros and cons of the two printers I wound up with...I'm not currently in a rush to sell either because I'm having a REALLY hard time deciding which I like more.

But I'll get into all that and more this evening and over the next few days/weeks.

I will give this tease though. I decided the 3D printed knob design wasn't good enough for me. It just wasn't detailed enough to look as finished as I wanted. So I started working on my own design and it's getting pretty close to what I pictured:

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I also found a way to deal with the elephant foot issue. Here's the bottom of the top knob straight off the printer printed right on the bed:
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The concentric circles are the pattern machined into the base of the Mars build plate to give prints more grip. I gave the part a 0.5mm chamfer and that almost perfectly absorbs the elephants foot even with this black resin which takes VERY long initial exposures (60 seconds and up) which usually makes the elephants foot REALLY bad. The only real limit to this trick is if you want a sharp edge you're not going to get it. There is a slight chamfer left...but it's VERY slight.

Oh, and the white bits on the knobs. That's just lint from the paper towel I used to dry them off after cleaning. The knurling is so small and sharp it's really tricky to get it clean and keep that kind of stuff off and the black shows all!

You can see by the size of my fingers just how small these knobs are. The detail these printers can do is amazing.

And even the lower resolution Sonic can do this:

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A closer look:
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And an angle where you can see some layer lines. This was printed at 0.05mm The printers can both easily do 0.03mm as well...and are theoretically capable of 0.01mm but it would take 5 times longer and given how these look without magnification I don't see myself ever needing that!

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Oh and the broken/deformed bits in that last shot where my fault while cleaning the part not the printers. I'm just a bit clumsy to be dealing with this level of detail :D
 

Attachments

LitterBug

Troll Spammer
#5
Where is the LOVE button? I've thought about getting a resin printer, but... yeah no. have 3 FDMs already. Need to sell at LEST one of the old ones off.
 
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jhitesma

Some guy in the desert
Mentor
#6
Where is the LOVE button? I've thought about getting a resin printer, but... yeah no. have 3 FDMs already. Need to sell at LEST one of the old ones off.
Yeah, My FDM's are definitely NOT being replaced (even though only one is actually functional right now.) I still find them far more useful overall. And when I get to the discussion of post-processing and hazards...and...why this is a terrible time to be getting into resin printing. It will damper some of the excitement the results can cause :D (Hint - if you can't find alcohol and nitrile gloves at your local stores...NOT a good idea to try resin! And my local stores are still completely out of both.)
 

Boberticus

Active member
#7
I'm also curious about cost per print too, 20 dollars for 1000g PLA/PETG makes a print 2 cents a gram, last i had looked the prices were 80 bucks for 500ml, which makes it hard to compare, and the rinsing and filtering and straining process to get usuable liquid for another print seemed less than 100 percent re-use and adds cost to post processing. It also seemed to get more expensive the more exotic materials you look for. not detracting, i really want a SLA/MSLA printer, i just had decided that was the reason for no for me. havent really looked since the photon first got released, would be very pleased to be surprised by cheaper resin.
 

PsyBorg

Wake up! Time to fly!
#8
Oh Im wayyy to broke to be investin in this stuff. Im just sayin ill watch more things others do with it hehe.

Pretty sure the insurance company is on another round of their BS cause Im missing the last two checks again with ZERO warning. May be off line again for a bit here shortly hehe.
 

dap35

Well-known member
#9
Oh Im wayyy to broke to be investin in this stuff. Im just sayin ill watch more things others do with it hehe.

Pretty sure the insurance company is on another round of their BS cause Im missing the last two checks again with ZERO warning. May be off line again for a bit here shortly hehe.
Our local library has both styles of 3d printers available. While its not free to use, its pretty close.
 
#10
Yeah i havent spent a cent on RC stuff since January. Ive been printing facemasks and faceshield bands for local businesses and felt bad spending money on parts needed just to keep my printer working. Definitely in maintenance mode here. Its good to live vicariously through others willing to get their hands dirty and their wallets skinnier (and their shop smelly)

I keep filling up shopping carts with project parts, and then just delete them, been getting my piece-together-parts-for-a-build fix that way.

speaking of smell, @jhitesma you mentioned you hated printing ABS due to smell, hows the curing resin compered? Ive never printed ABS is it really that bad?

what about when the machine is fully cleaned and stored, any residual odors? can i put it on my closet shelf and wear my hang up clothes?
 

LitterBug

Troll Spammer
#11
Yeah, My FDM's are definitely NOT being replaced (even though only one is actually functional right now.) I still find them far more useful overall. And when I get to the discussion of post-processing and hazards...and...why this is a terrible time to be getting into resin printing. It will damper some of the excitement the results can cause :D (Hint - if you can't find alcohol and nitrile gloves at your local stores...NOT a good idea to try resin! And my local stores are still completely out of both.)
Your local liquor store might be a better place to look for alcohol right now... guess it depends on what % you are looking for. I have an old bottle of 90% for hobby use. Can't say I have looked for or seen 180 proof anything. 151 yes.... 180 no.
 

jhitesma

Some guy in the desert
Mentor
#12
So I was going to get to the Sonic Mini and a comparison between the two machines next...but let's answer a few questions first!

Resin cost. It has come down, but is still generally more expensive than filament. Some places sell by volume some by weight...but you can get standard resin on amazon for $22 for about 500ml/500g from multiple suppliers. Buying 1l/1kg bottles sometimes saves a bit - but most places just send 2 small bottles and the price is about the same.

The ABS like tough resins are a few dollars more and the water washable resins are a few dollars more than that. The flexible and engineering grade start in the $30 range for 500ml. There are also specialty resins designed for high temperature use (they can even be used to print injection molds for shot runs of injection molded parts.) And then the resins designed for casting can run $100 for 500ml...and the bio compatible for dental appliances and such can run $300 for 500ml.

The stuff also seems to collect quickly around here:
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There are more I really want to try...but for now this is more than I can justify...and two bottles hadn't arrived yet when I took this photo.

On the left of 3 500ml bottles of Phrozen aqua green which I got at a discounted price for buying with the sonic mini (spoiler alert - it's my favorite resin so far.) The next to bottles are Tenacious from Sirya tech - that's the more expensive flexible resin which I've yet to actually print with (I really want to try blending it with one of the other resins but am waiting until I finish a bottle of something so I'll have somewhere to store any I don't use immediately.) Then on the right in front is a bottle of elegoo standard white and a bottle of anycubic standard black behind it.

Shortly after I took this photo Amazon delivered 500ml of Elegoo grey abs like and 1l of elegoo grey water washable.

Smell. Well...it varies. Some of the resins have minimal smell, some are pretty strong. Supposedly the Anycubic plant based resin is very little smell and is less toxic...but it's twice the price of standard resin and out of stock most places right now. Honestly though the smell of the simple green I was using for print cleaning bothers me WAY more than the smell of even the worst resin (though I've been warned the Tenacious is really strong smelling.) A lot of people say the prefer washing prints with simple green over isopropyl alcohol because it doesn't smell as bad...but I don't find the smell of alcohol off-putting while the smell of simple green makes me want to gag and gives me a headache.

As for smell while printing - again it varies. One of the upgrades on the Elegoo Mars pro is the addition of a rubber seal on the case and a charcoal filter on the fan. As you can see in the photos I had the printers on my kitchen counter and the Elegoo I could barely smell unless the cover was off or I was within a foot or so of it. The Phrozen on the other hand has a looser fitting cover, no seal, and no charcoal filter. And with some resins I can smell it from the other side of the room (about 15-20' away.) Neither of them really have much smell when there's no resin in them other than any residual smell of any cleaners you use. Like the sprayaway window cleaner which to me smells like a freshly cleaned hotel room. Honestly my biggest problem with smell was that &#!*@#! simple green. I'm not sure if any residual smell would build up on the machine over time though - as I said I've only had them a week so far.

The smell of ABS in my FDM printer didn't bother me at first - but quickly started to bother me more and more. Some brands smell more than others. The Hatchbox ABS I have doesn't smell nearly as bad as the generic ABS Folgertech sold me with my first printer. If you want to know what it smell like put a Lego on a grill or hotplate and let it melt...that's the smell.

The resins are urethane based. If you've ever worked with urethane resins for anything else you're recognize the smell. I recognized it from a client of ours who made sunglasses - their shop had the same chemical smell. If you've had a white filling on a tooth you've probably smelled it as well. Though the smell is a lot more intense when it's coming from plastic curing in your mouth than in a machine with a hood over it. On the other hand curing a dental filling takes less than a minute - while a print will easily run for many many hours. (that Eiffel tower was 6.5 hours on the Sonic mini and would have been almost 9 on the Mars Pro.)

The other big expense though is post-processing. And this is where we also get into why now is a pretty lousy time to be starting with this.

Most resin manufacturers recommend using isopropyl alcohol of at least 85% strength, though I've heard people report success with 70% it definitely seems that the higher the concentration the better. Unfortunately right now IPA can be very hard to find and expensive when it is available. I've yet to find it at any local stores and prices on Amazon are crazy high (and most of them are only available to COVID responders.) Denatured alcohol (or methalyted spirits in Europe) also works but around here it's $18 a gallon and also in low supply...and I don't much care for the smell of denatured alcohol even though IPA doesn't bother me. If it's allowed to be sold in your state everclear or other high proof grain alcohol can be used - but again it's probably pricey.

That said - alcohol is a great solvent for removing resin that works quick and effectively. And it can be re-used. Just keep it in a sealed container and the dissolved resin will settle to the bottom. You can decant off the alcohol, top up with fresh and keep re-using it. The dissolved resin and remaining alcohol should be set out in the sun so the alcohol can evaporate and the UV will cure the resin making it safe to throw away. You can't just dump this stuff down your drain!

Some people are now using acetone for print washing - but it can damage prints so you have to be careful...I would only suggest it for purely decorative parts and then only after testing the resin for compatibility.

The next most popular cleaner is "Mean Green" which is apparently usually only $5 a gallon or so at Lowes and Walmart. But there's none in stock here locally and people are reporting a hard time finding it all over. I did find a bottle of the Mean Green Citrus cleaner...and gave it a try...it didn't seem overly effective as a primary rinse but was ok as a secondary rinse. The Simple Green I used is also recommended as a popular option - but I found it doesn't rinse nearly as effectively and as I've repeatedly said the smell bugs the heck out of me :sick: Finally some people have said that Mr. Clean works well...but again I couldn't find any in stock.

So I'm stuck with $18 a gallon for denatured alcohol right now. Other than the flowery smell I don't mind it and it seems to clean well, the resin settles out quickly and as long as I keep it in a covered container it doesn't evaporate way too quickly.

Then there's the water washable resin. I'm of mixed opinion on it. I like that it doesn't need solvent to clean...but it doesn't seem to settle out of the water as well as the regular resins settle out of alcohol. Setting the vat out in the sun the resin will harden - but then stick to the tub I had it in. It also seems to clump up in the water instead of just rinse off...so while it doesn't require harsh solvents it more work to clean off in some ways.

Another optional post-processing expense is an ultrasonic cleaner. I already had a small one I use for cleaning my glasses and mechanical parts - it does seem to do a very effective job of cleaning...but it's not a safe idea to use volatile solvents in one since it can create a fire/explosion risk. I'm using a 1:1 simple green or mean green orange to water mix in mine for a final rinse after the initial denatured alcohol or water wash and it does seem to help and be effective. It's easier than hand washing...but not necessarily any quicker or more effective. Just more hands off. It may be better at getting to areas a brush can't reach though like the shaft holes on my knobs or the inside of a hollowed print.

The other two things that add expense - and even more expense than normal right now - are paper towels and nitrile gloves. Nitrile gloves are almost impossible to find around here and the ones I got off Amazon were over $20 for 100 and took two weeks to get here. Thankfully I usually have gloves on hand anyway since I use them when working on my vehicles, or painting, or other jobs where I want to protect my hand. But most of mine are heavier gloves so you don't get nearly as many in a box and I was going through my supply fast! Vinyl and Latex gloves won't work - the resin will eat right through them.

And yeah...the resin is NASTY stuff. Not only does it stink but it can also cause chemical burns do a google search and you can find some scary photos and videos of what can happen if you get uncured resin on your skin and don't wash it off quickly enough. You also need to protect any surfaces you're working on as it can stain or damage all kinds of materials. Once it's cured - it's just regular old inert urethane. But before it cures...nasty nasty stuff.

And paper towels. Thankfully they're not impossible to find here anymore...though the shelves are still less full than normal and I feel bad going through them so quickly. You don't need fancy or highly absorbent ones though so I got a pack of walmart generic select-a-size towels so I can use half sheets which are usually sufficient and help me not go through a roll as fast. Any paper towels that get resin on them should also be set out in the sun or under a UV light to cure before disposal. That's kind of the go-to method of cleaning resin off of anything - cure it with UV light and then chip it off or dissolve it with alcohol.

Oh yeah - the final part of post-processing and another possible expense. Curing. While the UV exposure in the printer solidifies the resin into your part it does not fully cure it. Even after you wash off the excess uncured resin the parts will still be soft and easily damaged so you need to cure them under UV light. Here in the desert that's pretty easy to do in the daytime. Just a few minutes in my sun does it just fine. But I also picked up a UV lamp off amazon for about $20 which I use to cure at night. I also got a little $10 solar powered turntable. So I just put the parts on the turntable, turn on the lamp, and put a little aluminum foil tent over it to reflect the UV around and keep the UV in rather than expose my room to it.


So - hope that helps cover some of the initial questions and downsides to resin printing. Next let's take a look at the Phrozen Sonic mini and how it compares to the Elegoo Mars Pro!
 

"Corpse"

Elite member
#13
So I was going to get to the Sonic Mini and a comparison between the two machines next...but let's answer a few questions first!

Resin cost. It has come down, but is still generally more expensive than filament. Some places sell by volume some by weight...but you can get standard resin on amazon for $22 for about 500ml/500g from multiple suppliers. Buying 1l/1kg bottles sometimes saves a bit - but most places just send 2 small bottles and the price is about the same.

The ABS like tough resins are a few dollars more and the water washable resins are a few dollars more than that. The flexible and engineering grade start in the $30 range for 500ml. There are also specialty resins designed for high temperature use (they can even be used to print injection molds for shot runs of injection molded parts.) And then the resins designed for casting can run $100 for 500ml...and the bio compatible for dental appliances and such can run $300 for 500ml.

The stuff also seems to collect quickly around here:
View attachment 174214

There are more I really want to try...but for now this is more than I can justify...and two bottles hadn't arrived yet when I took this photo.

On the left of 3 500ml bottles of Phrozen aqua green which I got at a discounted price for buying with the sonic mini (spoiler alert - it's my favorite resin so far.) The next to bottles are Tenacious from Sirya tech - that's the more expensive flexible resin which I've yet to actually print with (I really want to try blending it with one of the other resins but am waiting until I finish a bottle of something so I'll have somewhere to store any I don't use immediately.) Then on the right in front is a bottle of elegoo standard white and a bottle of anycubic standard black behind it.

Shortly after I took this photo Amazon delivered 500ml of Elegoo grey abs like and 1l of elegoo grey water washable.

Smell. Well...it varies. Some of the resins have minimal smell, some are pretty strong. Supposedly the Anycubic plant based resin is very little smell and is less toxic...but it's twice the price of standard resin and out of stock most places right now. Honestly though the smell of the simple green I was using for print cleaning bothers me WAY more than the smell of even the worst resin (though I've been warned the Tenacious is really strong smelling.) A lot of people say the prefer washing prints with simple green over isopropyl alcohol because it doesn't smell as bad...but I don't find the smell of alcohol off-putting while the smell of simple green makes me want to gag and gives me a headache.

As for smell while printing - again it varies. One of the upgrades on the Elegoo Mars pro is the addition of a rubber seal on the case and a charcoal filter on the fan. As you can see in the photos I had the printers on my kitchen counter and the Elegoo I could barely smell unless the cover was off or I was within a foot or so of it. The Phrozen on the other hand has a looser fitting cover, no seal, and no charcoal filter. And with some resins I can smell it from the other side of the room (about 15-20' away.) Neither of them really have much smell when there's no resin in them other than any residual smell of any cleaners you use. Like the sprayaway window cleaner which to me smells like a freshly cleaned hotel room. Honestly my biggest problem with smell was that &#!*@#! simple green. I'm not sure if any residual smell would build up on the machine over time though - as I said I've only had them a week so far.

The smell of ABS in my FDM printer didn't bother me at first - but quickly started to bother me more and more. Some brands smell more than others. The Hatchbox ABS I have doesn't smell nearly as bad as the generic ABS Folgertech sold me with my first printer. If you want to know what it smell like put a Lego on a grill or hotplate and let it melt...that's the smell.

The resins are urethane based. If you've ever worked with urethane resins for anything else you're recognize the smell. I recognized it from a client of ours who made sunglasses - their shop had the same chemical smell. If you've had a white filling on a tooth you've probably smelled it as well. Though the smell is a lot more intense when it's coming from plastic curing in your mouth than in a machine with a hood over it. On the other hand curing a dental filling takes less than a minute - while a print will easily run for many many hours. (that Eiffel tower was 6.5 hours on the Sonic mini and would have been almost 9 on the Mars Pro.)

The other big expense though is post-processing. And this is where we also get into why now is a pretty lousy time to be starting with this.

Most resin manufacturers recommend using isopropyl alcohol of at least 85% strength, though I've heard people report success with 70% it definitely seems that the higher the concentration the better. Unfortunately right now IPA can be very hard to find and expensive when it is available. I've yet to find it at any local stores and prices on Amazon are crazy high (and most of them are only available to COVID responders.) Denatured alcohol (or methalyted spirits in Europe) also works but around here it's $18 a gallon and also in low supply...and I don't much care for the smell of denatured alcohol even though IPA doesn't bother me. If it's allowed to be sold in your state everclear or other high proof grain alcohol can be used - but again it's probably pricey.

That said - alcohol is a great solvent for removing resin that works quick and effectively. And it can be re-used. Just keep it in a sealed container and the dissolved resin will settle to the bottom. You can decant off the alcohol, top up with fresh and keep re-using it. The dissolved resin and remaining alcohol should be set out in the sun so the alcohol can evaporate and the UV will cure the resin making it safe to throw away. You can't just dump this stuff down your drain!

Some people are now using acetone for print washing - but it can damage prints so you have to be careful...I would only suggest it for purely decorative parts and then only after testing the resin for compatibility.

The next most popular cleaner is "Mean Green" which is apparently usually only $5 a gallon or so at Lowes and Walmart. But there's none in stock here locally and people are reporting a hard time finding it all over. I did find a bottle of the Mean Green Citrus cleaner...and gave it a try...it didn't seem overly effective as a primary rinse but was ok as a secondary rinse. The Simple Green I used is also recommended as a popular option - but I found it doesn't rinse nearly as effectively and as I've repeatedly said the smell bugs the heck out of me :sick: Finally some people have said that Mr. Clean works well...but again I couldn't find any in stock.

So I'm stuck with $18 a gallon for denatured alcohol right now. Other than the flowery smell I don't mind it and it seems to clean well, the resin settles out quickly and as long as I keep it in a covered container it doesn't evaporate way too quickly.

Then there's the water washable resin. I'm of mixed opinion on it. I like that it doesn't need solvent to clean...but it doesn't seem to settle out of the water as well as the regular resins settle out of alcohol. Setting the vat out in the sun the resin will harden - but then stick to the tub I had it in. It also seems to clump up in the water instead of just rinse off...so while it doesn't require harsh solvents it more work to clean off in some ways.

Another optional post-processing expense is an ultrasonic cleaner. I already had a small one I use for cleaning my glasses and mechanical parts - it does seem to do a very effective job of cleaning...but it's not a safe idea to use volatile solvents in one since it can create a fire/explosion risk. I'm using a 1:1 simple green or mean green orange to water mix in mine for a final rinse after the initial denatured alcohol or water wash and it does seem to help and be effective. It's easier than hand washing...but not necessarily any quicker or more effective. Just more hands off. It may be better at getting to areas a brush can't reach though like the shaft holes on my knobs or the inside of a hollowed print.

The other two things that add expense - and even more expense than normal right now - are paper towels and nitrile gloves. Nitrile gloves are almost impossible to find around here and the ones I got off Amazon were over $20 for 100 and took two weeks to get here. Thankfully I usually have gloves on hand anyway since I use them when working on my vehicles, or painting, or other jobs where I want to protect my hand. But most of mine are heavier gloves so you don't get nearly as many in a box and I was going through my supply fast! Vinyl and Latex gloves won't work - the resin will eat right through them.

And yeah...the resin is NASTY stuff. Not only does it stink but it can also cause chemical burns do a google search and you can find some scary photos and videos of what can happen if you get uncured resin on your skin and don't wash it off quickly enough. You also need to protect any surfaces you're working on as it can stain or damage all kinds of materials. Once it's cured - it's just regular old inert urethane. But before it cures...nasty nasty stuff.

And paper towels. Thankfully they're not impossible to find here anymore...though the shelves are still less full than normal and I feel bad going through them so quickly. You don't need fancy or highly absorbent ones though so I got a pack of walmart generic select-a-size towels so I can use half sheets which are usually sufficient and help me not go through a roll as fast. Any paper towels that get resin on them should also be set out in the sun or under a UV light to cure before disposal. That's kind of the go-to method of cleaning resin off of anything - cure it with UV light and then chip it off or dissolve it with alcohol.

Oh yeah - the final part of post-processing and another possible expense. Curing. While the UV exposure in the printer solidifies the resin into your part it does not fully cure it. Even after you wash off the excess uncured resin the parts will still be soft and easily damaged so you need to cure them under UV light. Here in the desert that's pretty easy to do in the daytime. Just a few minutes in my sun does it just fine. But I also picked up a UV lamp off amazon for about $20 which I use to cure at night. I also got a little $10 solar powered turntable. So I just put the parts on the turntable, turn on the lamp, and put a little aluminum foil tent over it to reflect the UV around and keep the UV in rather than expose my room to it.


So - hope that helps cover some of the initial questions and downsides to resin printing. Next let's take a look at the Phrozen Sonic mini and how it compares to the Elegoo Mars Pro!
I had no clue that this detail was even possible with printing! It's so amazing at how it looks like it was molded. I wonder if there's a way if you can make a composite with carbon fiber so you can get the detail while still being strong. Once again, AMAZING!
 

jhitesma

Some guy in the desert
Mentor
#14
The Phrozen sonic mini despite being ordered 2 weeks before the Mars Pro arrived the day after. Unboxing and setup was very similar to the Mars Pro and again only took me about 10 minutes. Maybe a bit less this time since I already knew what I was doing and there was less protective plastic on things. Both printers are the same basic form factor and same X/Y build plate dimensions but the Mars Pro has an extra 25mm of of Z height. That's not a big difference and honestly I've yet to try and print anything where Z height was the limit. In fact I try to minimize Z height on almost all prints just because the more Z the longer the print will take.

I did immediately swap to the upgraded build plate on the Phrozen - and both the upgraded and stock plates get leveled the same way. At first I felt the leveling on the Sonic was a bit less refined than the leveling on the Mars - the ball joint and spring on the mars with the two big beefy allen bolts seemed very well thought out and simple to use. But I've leveled the mars about 4 times and I'm still not sure I've got it really leveled well. The Phrozen on the other hand uses 4 small M4 bolts and the plate just kind of hangs loose until they're tightened up. But It's easier to keep the plate from shifting as you tighten them so even though it's twice as many bolts and they're smaller so more likely to strip out I found leveling the Phrozen to be more reliable even if it feels like a less thought out system.

20200703_112930.jpg


Instead of the rook the Phrozen comes with a set of 3 rings as a test print. So I poured some of the Phrozen resin in and hit print. 2 hours later as they became visible I confirmed it was looking good...and after about 3 hours I had 3 perfect rings:

20200703_135251.jpg


It's hard to get a photo that shows the detail well. The color kind of messes with the camera in my phone. But again I was blown away by the quality I could get.

The intro story to the Phrozen is a bit shorter because I had zero issues. I wasn't sure if that's because the bed leveling worked better, or maybe because I had a bit of experience at this point. But for the first few days I had zero issues with failed prints on the Phrozen sonic mini...but had a string of time consuming failures or partial failures on the Mars pro. Then I decided to swap resins. I put the phrozen resin in the Mars Pro and put the elegoo washable grey in the sonic mini.

Suddenly prints that had been failing on the mars were failing on the sonic and the mars was printing flawlessly with no failures. Same prints on both printers would come out perfect with the phrozen resin but fail (either coming off the build plate entirely or more often pulling away from their supports) with any of the other resins I tried. So it seemed more and more like the difference wasn't necessarily the printer...but the resin. I really wish I had got some plain grey standard elegoo or anycubic resin to compare instead of the abs like, water washable, white and black. For now the Phrozen is my more reliable resin and I've yet to have a single failure of any print I tried with it.


The fine detail inspired me to try and print some specialty m4 hardware. I've been working on my K40 laser again (I need to update that thread...but am waiting to make more progress on the laser first...then these printers sucked away all my project time!) and I needed a better way to mount the expanded metal bed I was using. It needed to be 12mm above the M4 standoffs the stock bed was mounted to so I had printed off some little 12mm tall thumbscrew like pads for it to sit on. Printed with my Prusa MK3s in PLA they came out ok...but didn't look super fancy and lost a lot of detail. But I was able to print usable threads.

Printed on the resin printers they looked like commercial hardware. The detail in the thumbscrew part was shockingly better. And since they printed solid I had great hopes that they'd be stronger as well. One of the issues I had with the PLA prints was they were delicate and even printed with 100% infill it was easy to break the threads off while chasing them with a die or threading them into the standoffs.

20200703_153301.jpg


You can see how refined the resin printed versions are compared to the grey FDM print. But...the brittleness got me. The one with just the tip broken off I had tried threading without chasing it with a die. The one with the whole threaded section broken off I was chasing with a die when it broke.

I tried them again in the ABS like resin and was able to get one chased with a die...but apparently I cross threaded the die because even though it was the same M4 die I used on the FDM parts it was too small and just went right into the threads without actually threading :( I tried just threading an ABS like one into the standoff without chasing it first...and it got almost all the way in before it broke - that was fun to drill out :(

I'm going to try this experiment again when I get to the flexible resin and see if I can't get a mix of standard resin and flexible that will work. Part of the problem may be how I modeled the chamfer on the end of the threads too...It seems the first thread gets a bit cut off there. So I may revise that in CAD and see if I can get the threads to work well right off the printer.

(Note - the small hole in the shoulder of the SLA parts is because I printed the heads hollow and needed a spot for the trapped resin to come out.)


So ... with both printers working and having done enough experiments to find my initial frustrations with the Mars were likely due to my choice of resin....how do they compare?
 

jhitesma

Some guy in the desert
Mentor
#15
Ok. The comparison. This is hard. I'm going to say right up front that if I had to choose one to keep today...I don't know which I'd choose. They're both capable of amazing quality and are very similar machines. But...there are also a lot of differences.

I want to like the Mars Pro more. It's obviously the more refined machine and feels like a quality well built device while the phrozen feels more like a prototype or cheaply made Chinese clone (even though they're both Chinese made.)

The Mars Pro has a lot more metal in it's construction. It's almost twice the weight of the Phrozen. And the fit and finish on it is fantastic. The Phrozen just feels cheap. It's got it where it counts though with the monochrome LCD, higher power UV Lights, and a good solid Z axis that's equal to the Mars Pro....but everything else about the Phrozen feels cheap and tacked on.

The Mars Pro comes with a box of starter tools that includes just about everything you need to get going. A nice plastic scraper for getting resin off the print bed and tank, a metal scraper for getting parts off the print bed, a pair of flush cutters for cutting supports off parts, 3 pairs of nitrile gloves, 2 face masks, a small beaker for measuring resin, strainers for pouring unused resin back into the bottle without letting any little cured chunks fall back in, extra screws, allen wrenches to fit every screw used on it. It's a great package that you just need to add paper towels, resin and IPA to.

The Sonic mini...includes a much chintzier plastic scraper, a really lame metal scraper that's almost useless, a tiny funnel, one pair of gloves, 2 spare screws and an allen wrench for the build plate. And that's it. Honestly the tools that came with the Sonic are what I expected from both - throw away space fillers you won't ever actually use. Compared to the tools that came with the Mars which impressed me that they were actually decent quality and I've been happily using them.

They both use a hiwin style linear rail for the Z. On the Mars Pro this one of the upgrades over the standard Mars. The Mars pro also has a slightly more efficient LCD and higher power UV Led's making it a bit faster than the standard Mars (with standard resin the mars pro claims 6 second layers while the original mars claims 8...the sonic does 2.2 seconds). The pro upgrade also includes newer firmware that supports a new file format that's more efficient and reliable, a charcoal filter on the fan, gasket on the cover, the USB port is moved to the front ( a small thing but MUCH nicer than the side mounted port on the original mars and sonic mini), the resin vat on the Pro is improved over the standard Mars and holds more resin, and the build plate saw some minor updates with bigger screws and a textured surface to help with bed adhesion. The price difference between the stock mars and the Pro is about $70 and I'd say it's easily worth it.

Both the mars pro and the sonic mini run the same basic firmware which is provided by the company that makes the Chitubox slicer they both recommend. The Sonic mini however uses Phrozens own .phz format while the Mars pro accepts the more standard .cbddlp and newer improved .ctb formats. (there may be other formats they can read...I just haven't experimented with that and honestly see no need to.)

I like the menu layout on the sonic a bit better - the main menu has bigger buttons and is a bit easier to use. But the mars pro has some extra options like a "tank clean" which turns on the UV lamps to cure the entire build area in a thin layer. This helps cleanup after a failed print since it captures all the little cured bits of resin in one sheet. The sonic doesn't have that option - but it does have a LCD test option that can be used to the same basic thing - just a bit less obviously. The version numbers on them are different enough that I can't tell which is newer even though they're both obviously made by the same 3rd party supplier.

The power supply for the Mars Pro is an external brick style supply with a 2 prong power cord coming off of it. It's a nice long cord and the plain 2 prong cable takes up little space in an outlet or power strip. The Sonic Mini uses a wall wart style supply that takes up more space in the outlet and has a noticeably shorter cord. The prongs on the sonic's power supply also seem a bit undersized and the walwart doesn't feel secure in any outlet I plugged it into. In fact it fell out at least once. I dread it falling out several hours into a multi-hour print! The elegoo shows much more attention to detail and quality here again.

They both use a similarly sized resin vat. But they mount differently. The Elegoo vat is loosely held in position by a recess in the top of the printer it slides into and then held down with 2 thumbscrews you never fully remove. The Sonic vat is placed over the top of two studs that hold it in position, and you have to remove the thumbscrews entirely to get it on or off. The elegoo vat is a stepped design which supposedly helps with giving it move volume, and it has a max fill mark on one side, it's also covered in a smooth power coating that is easy to clean. The Sonic vat has straight walls and seems like a much simpler/cheaper design. It also has a textured finish that is tricky to effectively clean. Again, the Mars Pro is just more refined and nicer to use.

When printing the Mars has minimal smells, but the Sonic...I can definitely smell from across the room. It needs to be used in an area with better ventilation.

And sound...this is a tough one. The mars has 2 fans. One for ventilation and one to cool the UV lights. At least one and possibly both run continuously and are fairly noticeable. They aren't loud or obnoxious...but you can tell it's on. But that's the only sound it makes. The Z motion is silent, or at least quieter than the fans. There's occasionally a quiet pop when a layer is peeled off the FEP film that makes up the bottom of the vat - but all MSLA printers do that. The Sonic on the other hand I can't hear any fan at all (I'm pretty sure there's one on the UV lamp) but the Z axis stepper makes a noticeable noise. It's not loud by any means...even my Prusa Mk3 with it's amazingly quiet stepper drivers is about the same...but I can hear it from two rooms away. And while I can easily tune out the constant hum of the Mars Pro fans the intermittent whirr of the Z on the Sonic is both louder and more annoying.

Also - the Mars is pretty well sealed. You can't see UV light leak anywhere. The Sonic.....

20200704_131127.jpg


Leaks light like a sieve.


So - overall the Mars is a physically a nicer more thought out and polished machine. But the simplicity of the sonic actually works to it's advantage in some ways as evidenced by me getting the bed leveled first try and not having to touch it since...while the Mars bed I've leveled four times and am still not convinced it's as level even though it's mechanism feels better and seems more refined.

The final thing the sonic mini has going for it over the Mars pro is it's speed. A lot of reviewers really like this and rave about it. I'm not that impressed. It is faster. But it's not a LOT faster. As I mentioned earlier the Eiffel tower print took 6.5 hours on the Sonic vs. almost 9 on the Mars. But the smaller prints I'm doing the time difference is less noticeable. The knobs I'm printing are about 45 minutes on the Sonic vs. 1 hour on the Mars.

The thing is even if the exposure is shorter there are other factors that affect speed as well - lift speed (which gets into peeling which is a whole separate topic I'm still very much learning about!) and they pause between layers to let the resin flow back in. So actual layer exposure is only a fraction of the time that goes into a layer.

I want to keep the mars because it's a much better thought out more polished and refined machine. But I want to keep the sonic because it works and it's a little quicker. So...for now I'm keeping them both. I don't really have room for two so I should eventually make up my mind...but...I don't really have room for one either.

After two and a half days on the kitchen counter my daughter who likes the smell of the resin (she likes all kinds of nasty chemical smells for some reason) declared they had to go out into my shop. I think she was more upset about the time I was spending with them than she was about the smell or mess. But I agreed - long term they'd have to live in my shop. So I picked up a cheap $40 cart at wallmart doing my grocery shopping and that's where they now live:

20200705_141843.jpg


This works pretty well. I have the two printers on top (I've since replaced the plywood sheets with some cheap lunch trays I got off amazon since they can catch any spills or drips better) washing supplies on the middle shelf, and spare parts, resin and other less frequently used stuff on the bottom. (the PTFE lube and blue microfiber cloths are for the FEP film in the vats...more on that in a future post!)

Oh - you can also see one other accessory I got with the phrozen that's kind of nice. A rubber vat cover. You shouldn't leave resin in the vat more than a day or two but since the sonic doesn't seal well leaving resin in it at all can be stinky. With the vat cover though the resin is protected from light and the smell is kept in. It was worth the $15. There are 3d printable covers for the mars - I'll have to load up my TPU and crank one out this weekend.

I need to make up some kind of paper towel rack on the side of the cart still that would be nice. And honestly if I only had one printer this would be just the right size as I could move the washing vat and ultrasonic cleaner up to the top. Right now with two printers it's a bit cramped...but I can live with it.

Tomorrow I'll get more into what I've learned about what does and doesn't work with preparing prints and how prints seem to fail.
 

jhitesma

Some guy in the desert
Mentor
#16
I had no clue that this detail was even possible with printing! It's so amazing at how it looks like it was molded. I wonder if there's a way if you can make a composite with carbon fiber so you can get the detail while still being strong. Once again, AMAZING!
Well, in some ways it's already stronger than PLA on a FDM printer. But...just like PLA is stiffer than ABS but more brittle - the resin parts are even stiffer and more brittle. I'm really excited about trying the ABS like resin on bigger prints and mixing the flexible resin in with standard to make parts that are still stiff but less brittle. I'm fairly confident I could at least do a micro quad frame that would stand up decently well. And I'm pretty sure go-pro mounts could be printed in the flexible resin and would stand up just as well or better than TPU.

But it's definitely better for detailed cosmetic parts than strong functional parts with the standard resin. Over the next week or two I'll be doing more tests with the fancier resins to see how functional parts do.

The other issue with doing functional parts is accuracy. While SLA printing is highly detailed...I'm finding it's not necessarily as accurate due to shrinkage (which varies from resin to resin) and how you have to support prints due to the way SLA works. That gets complex though and is something I'm going to go into detail on tomorrow. It's also something I'm still experimenting with and learning a lot about!

Here's a sneak peek at one of my support tests as it came off the printer:
20200703_184305.jpg


And after cleaning:
20200703_193620.jpg


That's 3 different print orientations each supported 4 different ways. Most of them are probably usable...but none of them are perfect and all have various compromises. Plus this particular test I didn't wash as well as I though I did so there was some residual resin left that confuses the results some. The most dimension-ally accurate print was actually one of the least likely to be usable due to the way SLA overexposes the first few layers!
 

PsyBorg

Wake up! Time to fly!
#17
Next time you print could you do a short video how its all set up initially to do a print. I cant get passed picturing a whole lot of liquid to do such small print jobs. Is there various size "tubs" that are used or separation walls?
 

jhitesma

Some guy in the desert
Mentor
#18
I haven't done a video on anything in almost 3 years...but I could give it a go for old times sake :)

I got tied up with other stuff today and didn't get to my next post with details about supporting parts and the difficulties in getting accurate parts. That will have to wait a bit longer.

But...I did finally give the tenacious flexible resin a try. Wow...this is cool stuff! I just printed a little exposure test piece - this is usually a quick 6-8 minute print that's very short but lets you check details to see how good your exposure setting is. I couldn't find a setting for the Tenacious on the sonic mini (which I was going to use since the mars was still printing some knobs) so took a guess based on the times given for other printers. I went with 60 seconds on the first layers and 10 seconds on normal layers. Quite a bit longer than normal since with standard resin I can do 2.2 second layers on the sonic! But tenacious is almost clear - just very slightly yellow so it needs a bit more exposure time. It also needs slow lifts since it's a bit more viscous and the parts can stretch when peeled off the FEP and need a bit of time between exposures.

But - the print came out pretty impressive. Looks like I got the exposure right on - though it's hard to tell because of it being clear. You look at the places where positive and negative come together on this test to judge exposure - they should be crisp and clean. If there are gaps you're underexposing, and if they bleed together you're over exposing:

20200711_205914.jpg


The print looks ugly because 1) It picked up the detail of little scratches on the build plate and they're showing through since it's almost clear...and I had just shaken up the resin and there were still some bubbles in it which got caught in this print. But Looking at the spots whre the positive and negative reliefs come together it looks pretty good.

And the properties of this print are remarkable. All the other exposure tests I've done like this have snapped because of how brittle the resin is. It doesn't take much to snap them either. Either I've snapped them scraping them off the bed or while holding them and just very gently flexing them.

The tenacious though:

20200711_215859.jpg


And it comes back to it's original shape by itself. It doesn't snap back...it takes it a minute or two depending on how much it was flexed...but it does come back.

I have a print going now testing a normal part printed entirely in the flex resin...but...I'll be asleep before it's done. I really can't wait to try mixing it with regular resin - but still need to finish off a bottle of regular resin before I try that.

I did get my knob design finalized today...and just for kicks whipped up a second design that's a bit more like the knobs on a commercial version of the interface I'm building:

20200711_215641.jpg


On the left is the design I'm going with...on the right is the design a bit more like the commercial version. It's not quite there though...the commercial ones are a bit thinner at the top of the lower section....and I don't have the top part pushed on all the way because it's fitting VERY snugly and I didn't want it to get stuck. It should sit down a few more mm which gives a nicer gap at the top where it mates with the lower knob. You can see the commercial version of what I'm building here: https://apache-labs.com/al-products/1054/Controller-V2.html

Unfortunately while I could print the lower knobs with the thin section like the commercial product - I don't think they'd look right as the black is actually slightly transparent. If you look at the lower knob you can kind of see some banding because the top and bottom sections are much thinner than the center where the part that engages with the encoder is.

And yeah...I'm zoomed in pretty close on these knobs. In person at a normal viewing distance they look a lot nicer.

I'll see if I can whip up a video tomorrow. no promises...but I'll try to try ;)
 

jhitesma

Some guy in the desert
Mentor
#19
Psyborg - I didn't forget your video, I just decided to take a day off from printing to focus on some other projects.

I did pull off the test I did in the flexible resin and am pretty impressed:
20200713_110759.jpg


Despite the slight yellow cast the clarity is really impressive. But - it also looks like I am overexposing this stuff a bit since the threads lost a lot of resolution.

That said - I was able to screw it into a stud without chasing it with a die:

20200713_110810.jpg


Except...it pretty much chewed off the threads doing so. There's enough thread left I can't just pull it out...but there's so little left that it just spins like there are not threads and never fully tightens.

So...the flexible by itself is a bit too soft. It would probably make a really great go-pro mount or damper though. It does have give and is flexible...but is also stiff and strong when printed thick. Again I tried crushing these and they basically just bounced back. I even tried snapping off the threads and they just bent and came back even bent past 90 degrees.

I'm REALLY looking forward to mixing this with standard resin to get just the right mix of flexibility and strength for some of the parts I plan o making.

I'll probably get some more prints started later today and try to get a video of the process.

And I'll try and find time later today for the next post in the series discussing what I've learned about the difficulties in getting accurate functional parts with SLA - why it's difficult, and what workarounds I've found to deal with the difficulties.
 

PsyBorg

Wake up! Time to fly!
#20
All good mate. Im just curious. No need to do anything special to answer my questions. Im sure at some point in all the videos I will see my answers and have a light bulb moment.