Cutting foam sheets... with a needle!

[Headbang]

I still kind of regret taking my MMU out of the box and installing it

I do seem to finally have it working mostly reliably. But my Mk3 went from being amazingly reliable to nothing but trouble when I added the MMU. After re-building the extruder again I finally had the printer with MMU working reliably:

View attachment 141426

View attachment 141425

But don't see myself using the MMU much. It's so wasteful - the purge block on this print weighed more than the print. And it turned a 2 hour print into a 8 hour print by switching it to 3 colors. And honestly I don't print things for "looks" I print for functionality. And the only prints I've found that need the MMU are just for looks. At least my daughter appreciates it

The main reason I wanted the MMU was for soluble supports - but supports on the Mk3 print so much better and are so much easier to remove than on my old printer I haven't felt the need for soluble yet. And soluble material is crazy expensive and needs to be stored in a drybox which is more pain/expense. And with the MMU not being super reliable for me I've been hesitant to risk the expense of soluble material.

And I had my printer setup with the lack enclosure which I loved but with the MMU it no longer fit. I just finished the new v2 lack enclosure but that was a solid week of printing and when I put the printer back in I managed to get one set of power wires swapped around. Thankfully it seems I didn't kill anything...but after the jostling and moving of getting into the enclosure the MMU is acting up again and working on it inside the enclosure is way more frustrating.

Oh - and the instructions on the v2 lack enclosure IMHO have you cut the PTFE tubes a bit too short. I cut them exactly as long as suggested but it puts a pretty severe bend on 2 or 3 of them which I suspect is a big part of why the MMU is acting up now. So I need to order more PTFE since it's kind of hard to make things longer once they've been cut

And that is exactly why I have not done it yet! Maybe I will order and build a second printer, put it on that one. Lots of times I find myself with a list of parts and a lack of patience, so a second machine would be useful.

 

[glambert10]

I'm building the "Another DIY Foam Board Cutter" based on the Low Rider CNC. I'm having trouble with accurate Z-Axis movement. Can I get some advice on the setting to alter either in Marlin or Estlcam to get accurate Z-Axis movement?

 

[dkj4linux]

I'm building the "Another DIY Foam Board Cutter" based on the Low Rider CNC. I'm having trouble with accurate Z-Axis movement. Can I get some advice on the setting to alter either in Marlin or Estlcam to get accurate Z-Axis movement?

If your Z movement is controlled and repeatable... command a movement in Z and measure the actual movement.
Then use the following ratio to adjust the Z steps/mm value in Marlin's "Configuration.h"...

( Commanded / actual ) * current Z steps/mm

So, for example... command 10mm move in Z... measure only 9.4mm... therefore 10 / 9.4 = 1.064

In "Configuration.h", find the line with steps/mm values.... multiply the 3rd value by 1.064. Save, compile, and upload. Now you should see 10mm of actual movement when commanded to move 10mm.

-- David

 

[dkj4linux]

I'm building the "Another DIY Foam Board Cutter" based on the Low Rider CNC. I'm having trouble with accurate Z-Axis movement. Can I get some advice on the setting to alter either in Marlin or Estlcam to get accurate Z-Axis movement?

BTW if you're interested, I built this same machine starting with this post -- Moebeast's Foam Ripper -- about a year ago. And I love it... it's about the only machine I've played with, since building it. I built it first, pretty much just as Mark designed it... and then developed an alternative carriage to give a bit more Z travel (https://www.thingiverse.com/thing:3582124). It currently carries both a needle cutter and a 2.5 watt laser. The whole build is documented in the pages following that first post. -- David

 

[Headbang]

BTW if you're interested, I built this same machine starting with this post -- Moebeast's Foam Ripper -- about a year ago. And I love it... it's about the only machine I've played with, since building it. I built it first, pretty much just as Mark designed it... and then developed an alternative carriage to give a bit more Z travel (https://www.thingiverse.com/thing:3582124). It currently carries both a needle cutter and a 2.5 watt laser. The whole build is documented in the pages following that first post. -- David

Now you did it! Was supposed to be home 2hrs ago but I read your post, followed the links, and went down the rabbit hole!
Quick question, the sleeve needle cutter you designed. How is it holding up? I like the bearing solution over wrapping wire around a bearing.

 

[dkj4linux]

"'Will you walk into my parlor?' said the Spider to the Fly."

The slip-on flywheel seems to work quite nicely... and seems far better and easier to balance than previous versions. I can't speak to the longevity as I'm not really doing a lot of foam-cutting -- and am now in the throes of sorting/packing for my upcoming move/life-change -- but I suspect it'll do pretty well. It does require a pretty dialed-in printer to get a snug slip-fit over the motor bell and, of course, if you use a different motor you'd have to make some adjustments for the bell diameter but I've detected no slippage so far. I suspect a gummy adhesive would work fine to keep things in place if it did. It easily/comfortably spins up several thousand rpms higher than earlier models. -- David

 

[Headbang]

"'Will you walk into my parlor?' said the Spider to the Fly."

The slip-on flywheel seems to work quite nicely... and seems far better and easier to balance than previous versions. I can't speak to the longevity as I'm not really doing a lot of foam-cutting -- and am now in the throes of sorting/packing for my upcoming move/life-change -- but I suspect it'll do pretty well. It does require a pretty dialed-in printer to get a snug slip-fit over the motor bell and, of course, if you use a different motor you'd have to make some adjustments for the bell diameter but I've detected no slippage so far. I suspect a gummy adhesive would work fine to keep things in place if it did. It easily/comfortably spins up several thousand rpms higher than earlier models. -- David

Good to know. Think I will give it a whirl. I cut a lot of planes for people and my own prototyping, running at 7500ish rpm has been working, but if I can ramp it up, speed up the process, it will help a lot with time management.

 

[Apple Pie]

Jumping into the needle cutting world with both feet! I have an Xcarve cnc which I used to make the attached needle cutter following the flywheel design and many of the great suggestions in this forum. First cuts came out really well. I did some depth of cut tests but didn’t have my tach in the shop so not sure on the actual rpm I was running at but it felt like around 7000 rpm or so. Using 500mm/min feed rates I’m guessing around 14 revs per mm. Minimal fuzzing of the water resistant foam board on the entry and exit sides. Question, is it normal to have the foam edge slightly melted by the needle? Oh this is going to be a major improvement over printing plans and cutting with a blade!

 

[dkj4linux]

Jumping into the needle cutting world with both feet! I have an Xcarve cnc which I used to make the attached needle cutter following the flywheel design and many of the great suggestions in this forum. First cuts came out really well. I did some depth of cut tests but didn’t have my tach in the shop so not sure on the actual rpm I was running at but it felt like around 7000 rpm or so. Using 500mm/min feed rates I’m guessing around 14 revs per mm. Minimal fuzzing of the water resistant foam board on the entry and exit sides. Question, is it normal to have the foam edge slightly melted by the needle? Oh this is going to be a major improvement over printing plans and cutting with a blade! View attachment 141765

Really nice looking build, ApplePie! Tis a slippery slope... but welcome!

Melting of the foam is usually a sign of too high rpm and/or too slow feed rate. I assume there's a Mig-welding tip under there, serving as a guide? If the tip gets hot enough to transfer sufficient heat to the needle and it dwells in one spot too long then melting of the foam may occur. I'd recommend speeding up the feed rate slightly and/or lowering the cutter speed to see the effect, if any. The tach will tell you for sure the cutter rpms... and then it'll be an easy matter to set the feed rate to give the 10-15 perforations per mm that has always worked for me with DTFB. The waterproof foam might be slightly different... but I'd try getting closer to 10 perfs per mm and see if the foam melting goes away.

Again... welcome to the party!

-- David

 

[dkj4linux]

Good to know. Think I will give it a whirl. I cut a lot of planes for people and my own prototyping, running at 7500ish rpm has been working, but if I can ramp it up, speed up the process, it will help a lot with time management.

If you don't mind, Headbang, please share a little bit about the planes you're cutting... for yourself and others. Is this a paid service you offer? It's obvious you're really putting some good mileage on your needle cutter and I'd really like to hear more about your, and others, impressions of needle-cut planes.

 

[Headbang]

If you don't mind, Headbang, please share a little bit about the planes you're cutting... for yourself and others. Is this a paid service you offer? It's obvious you're really putting some good mileage on your needle cutter and I'd really like to hear more about your, and others, impressions of needle-cut planes.

Not a paid service. I just have a few friends and club members into foam board planes, and we build a lot of them! I have cut many explorers, a bunch of seaducks, bunch of viggens, most of the ft war birds, some of @nerdnic's designs, tons of modified designs. The edges are very clean (500mm/min at 7300-7600rpm) and go together better then a speed build kit (square edge without the indent a laser leaves). Most of the board being cut is white dtfb. Ft water resistant board cuts just as well.

My bed is within 1mm tolerance, so depths are very accurate. After I got my mpcnc up and running and my needle cutter running, I then spent a lot of time building as perfectly flat of a table as possible, then as flat of a vacuum bed as possible. This was where things went from so so unreliable to almost perfect cuts every time. It also allows me to do all the reference marks, and labels at .5mm accurately. This makes a big difference for those newer to building fb planes.

 

[dkj4linux]

Not a paid service. I just have a few friends and club members into foam board planes, and we build a lot of them! I have cut many explorers, a bunch of seaducks, bunch of viggens, most of the ft war birds, some of @nerdnic's designs, tons of modified designs. The edges are very clean (500mm/min at 7300-7600rpm) and go together better then a speed build kit (square edge without the indent a laser leaves). Most of the board being cut is white dtfb. Ft water resistant board cuts just as well.

My bed is within 1mm tolerance, so depths are very accurate. After I got my mpcnc up and running and my needle cutter running, I then spent a lot of time building as perfectly flat of a table as possible, then as flat of a vacuum bed as possible. This was where things went from so so unreliable to almost perfect cuts every time. It also allows me to do all the reference marks, and labels at .5mm accurately. This makes a big difference for those newer to building fb planes.

Fantastic, Headbang! That's all so good to hear. A really active group of folks/friends you have... what fun! And the care you've taken to insure your machine is accurate and level is obviously paying off, big-time!

I'd meant to mention that in addition to the sturdiness and reliability your needle cutter has shown... I think it is important to note that you run at pretty conservative feeds and speeds as well. It's tempting to want to go as fast as possible, of course, but in my experience a cutter usually has a "sweet spot", where it settles in comfortably and without undue stress... and that's a good place to be. I'm sure that's contributed greatly to your cutter's needle life and reliability. I'm really hoping the new slip-on flywheel setup -- which seems much more smooth and better balanced than my earlier versions -- will move that sweet spot out a little higher for you, save a bit of time, and preserve the quality of the cuts you're getting.

Thanks for sharing. And, well done!

-- David

 

[Apple Pie]

Quick update. I cut out the five boards for an FT Edge 540 out of WRFB today. The settings I found that gave me very good results were 8250 no load rpm (drops to about 7600 at 6mm depth of cut) and 650 mm/min. Score cuts at 1mm, 50% cuts at 3mm, full depth cuts at 6mm. Zero the needle just into the top of the paper to ensure full cut through. I checked the motor temp during operation as well as the mig tip guide. They were both at 28c (85f) which seems pretty low to me so I’m happy with that. I absolutely love the vacuum table for this application. Simple and quick foam board changes and a deadly flat board make for a really nice finished product.

I can’t say enough thanks to all the people who posted their designs in this forum. So many great ideas that have been shared!

Now to go make a few of the temporary attachments a little more permanent. This one is a keeper!

 

[dkj4linux]

Outstanding results, ApplePie! It sounds as though a little feeds/speeds tuning did the trick? And, with both you and Headbang, showing the benefits of a vacuum setup, a flat worksurface, and conservative feeds/speeds... who can argue with the results?

Well done... both of you!

-- David

 

[Apple Pie]

A couple of questions for the knowledgeable folks here
1) does anyone have a really good way to dynamically balance their flywheels? I’ve seen some fairly complex ways for larger rotating equipment involving twin level rails and rolling it on a shaft but wondering what people here are doing for these tiny light flywheels.
2) what kind of upper rpm limits are people running their flywheels at?
3) so obviously 1 & 2 above lead to the question of what rpm are people pushing their setups at? I’ve tached mine at 11500 rpm max but it vibrates too much for my liking at that speed. Just wondering if I’m barking up the wrong tree or not. Any other problems encountered at high rpm?

 

[Keno]

What I did was assemble the cutter mount on a board and fire it up very carefully. Then added screws until I achieved best smooth run.
But there is probably better ideas than mine. Happy building.

 

[Headbang]

My plan was to balance the fly wheel using a prop balancer first. Then once setup and running, make small adjustments to account for the needle and friction of the needle. First balance would be exactly the same as I would do for a spinner.

 

[dkj4linux]

I used to do something similar with my earlier flywheels... getting as close as possible to static balance on a couple of knife edges and then chuck it up in a Dremel tool and then make small adjustments to get smoothest operation to at least 8000 rpm or so.

Not sure exactly why but the slip-on flywheel I'm using now seemed to balance and run smoothly right off the bat... and with just a SWAG (scientific wild-a$$ guess) at how much counter-weight to add. My primary goal had been to shorten the "cantilever" and the motor bell itself serve as the "flywheel"... but a pleasant discovery was the very smooth operation up to 10k rpm as well.

 

[Headbang]

I used to do something similar with my earlier flywheels... getting as close as possible to static balance on a couple of knife edges and then chuck it up in a Dremel tool and then make small adjustments to get smoothest operation to at least 8000 rpm or so.

Not sure exactly why but the slip-on flywheel I'm using now seemed to balance and run smoothly right off the bat... and with just a SWAG (scientific wild-a$$ guess) at how much counter-weight to add. My primary goal had been to shorten the "cantilever" and the motor bell itself serve as the "flywheel"... but a pleasant discovery was the very smooth operation up to 10k rpm as well.

Last week my printer was in overdrive finishing the parts for a new stainless burly mpcnc machine. This week is all about the needle cutter. Can not wait to try the slip on design!

 

[Springer]

David, I trust your packing is going well and the move will also go smoothly! I finally got a user's for these forums, as it seems the needle/cnc discussion is much more alive and well here (as you noted during our visit.) I followed your lead and picked up a 2.5 watt laser for my machine and temporarily swapped out the needle cutter. Wow, that thing is potent! I tried a simple circle in square gcode on card stock at full power and burned through it and can inch of pink foam of my vacuum table! I now have it tamed and have been cutting N numbers for my planes from colored packing tape. Tape on glass plate, and Model Plane Foam under the glass to stop the penetration. (Interesting that while laser won't cut MPF, it lights it up, diffusing the beam, so works as a spoiler board). I got some vinyl and transfer film from Michael's yesterday and cut some numbers and logos in it. At a 40 setting it burns a 1/32 line in vinyl, but leaves the release paper intact. Worked well!