Cutting foam sheets... with a needle!

[jhitesma]

Ok, back to MPCNC and foam cutting

Decided to have a bit of fun tonight...and try something different.



And on the machine



Now, before you go calling me a traitor....I mostly did this for the fun of adapting it to my machine. Someone on the Vicious forums was talking about cutting cardboard and considering trying a needle cutter because he was currently using this: https://www.thingiverse.com/thing:2494258 drag knife, but was having issues working out how to get clean corners. I shared my experience cutting cardboard with the needle....but I have been curious to see how a drag knife could work...they're kind of fun to watch in action after all.

So I fired up onshape and modified the bearing housing to work with the hicwic mount, only took a few minutes:


And the project if anyone wants it: https://cad.onshape.com/documents/3...52d822f3b48df6fb32/e/7aaa239783b57998f7639466

My wife was home sick today so I fired up the printer over my lunch break. And when I got home had the bearing housing waiting for me. Plated up the rest of the bits, and by the time dinner was over they were done. Dug out some suitable hardware from my stash (lucked out on having a 70mm M8 screw!) and it looks like it should work.

But now I have to figure out the corner actions. Donek has a spreadsheet that will do them...but it's in imperial and all my gcode is in metric and Marlin expects metric. So...converting back and forth seems like a pain. I may have to see if I can reverse engineer the Donek tool and write my own that works in metric - shouldn't be too hard I suspect. Tricky bit is I don't have excel so figuring out just what their tool does is the hard part for me.

Even if I get it working I'm not sure what I'll use it for. Maybe cutting postboard though I'm not sure if that's thick enough to even allow the blade to swivel. I don't really want to try and cut DTFB with it since the current DTFB tears and pills so easily, plus wears out blades so quickly, and I can't see it doing tight radius turns well.

With the needle cutter off the machine so I could mount up the drag knife I figured it was a good chance to take a look at what's wrong with my needle. Sure enough it's bent:



No wonder it was making angled cuts and running hot!

The end is also pretty dull - but considering I've done about 20 sheets of foam since I last sharpened it I'm not shocked:


I should just make up a new needle...but this one IS glued to the bearing and I don't feel like removing it right now. So I broke out some pliers and straightened it out. It's not perfect...but MUCH better than it was and runs smooth again. Fire up the dremel and dress the tip...ready to cut some more foam!

Now to try and figure out what to do with this drag knife now that I've got it.....

 

[jhitesma]

Well, first the good news. Rebending the needle worked well, did a bit of cutting with it last night and it came out great again even though I didn't even bother to re-sharpen it yet.

However, even though it's running cooler again I still had the "issue" of parts being looser than they were before and basically falling out when I lift the sheet. Interestingly the cuts seem even cleaner than before the vac table, I wonder if it's holding the foam that much more securely so I'm getting an even better cut now and that's why the edges seem cleaner and the parts fall out. The fall out still seems to be because they're sticking to the wasteboard...I wonder if that's because I'm now using DTFB as wasteboard instead of pink foam - or due to the vacuum. Interesting either way.

Now the bad news. I got dxf2gcode working on windows (don't even try it on mac unless you really know python and qt5!) and think I figured it out. Managed to generate some gcode (for the mini-dr1 turtle deck) and gave it a dry run. Looked like it worked and included corner actions...but didn't home at the end. I figured that was just a setting I missed in dxf2gcode...though I also noticed my coordinates were reading 0,0,0 at the end even though it didn't home so that seemed odd.

All the same I gave it a go. And the results...well...



I'm not sure if the problems are my drag knife, dxf2gcode's actions, my settings in dxf2gcode, the blades I'm using...or something else. But overall the results were very disappointing.

I could see it doing corner actions when it cut but the blade didn't seem to swivel as well as I'd hoped. Maybe the spring I've got in it is too stiff - I can try a weaker spring. It also seemed like it was stuck in too deep when doing corner actions so that may be a setting I can change. But even on straights it didn't cut well - which is apparently because the 8mm bolt that serves as a shaft doesn't fit perfectly in the skate bearings. I can probably shim it to get rid of some slop there...and it may even be the blades I have aren't that "pointy" even when new.

But honestly I'm not sure I want to bother. My laser, needle and spindle work great already. The drag knife is quieter than the needle or spindle and less smoky than the laser....but the vac table kind of negates any sound benefits and cutting poster board the laser doesn't make that much smoke.

I can't see it cutting foam well...due to the shape of the blade it's just never going to do tight curves as well as the needle or even the spindle.

It's a neat tool...and fun to have. But just doesn't seem very useful for what I do. Cutting things without sharp corners out of thin material...great! But anything else it just seems more hassle than it's worth.

 

[jhitesma]

update about the vac table.* Overall WOW!* I can't believe the difference it's making in my cut quality.* I was super happy with the needle cutter before but now I'm blown away.* I didn't realize how poor my work holding was before just pinning the foam board down in the corners.* My cuts are cleaner and my Z is more consistent.* There's still something off with my machine that causes about a 1mm difference in Z from left to right (even though the X and Y rails are level all the way across so it must be something in the gantry rails.)* but 1mm of difference over 4' isn't keeping me from doing anything I want to do right now.

Now the parts practically fall out of the material when I'm done.* Before I'd have to punch them out - didn't take much effort but they weren't falling out by themselves.* In fact, now if I don't kind of twist the workpiece as I remove it the parts stay on the vac table (even with the vacuum off.)* This could be due to a couple of things that have changed.

First, my waste board is now the same DTFB that I'm cutting not pink foam.* So maybe the paper top layer is somehow bonding with my work when the needle goes all the way through.* Second my Z is more accurate so I don't need to penetrate as deep with the needle but I haven't adjusted my gcode so I'm cutting deeper into the waste board (Before I'd use 6.5mm of cut even though the foam is nominally 4.5mm thick...even then I'd sometimes get areas that it didn't fully cut due to warps in the foam.* Now 5mm cuts always go all the way through but I'm still using 6.5mm cuts out of habit.)* Third, my needle is running a little hotter than it was because I bent it when I had the problems cutting the first sheet of the vac table.* I straightened it out...but it's still got a tiny kink in it where it runs in the mig tip of my cutter so that's causing more friction and heat.* So it might be the foam is melting a little and causing it to stick to the waste board.

I don't mind parts falling out of the stock though - with cuts this clean and the ability to even do 0.5mm "cuts" to add notes and annotations on the pieces (which only pierce the top layer of paper but don't cut into the foam) I'm super happy:






What I'm not so happy about is my shop-vac

I just burned out my old original one.* Yeah, it's over 15 years old now (My wife got it for me the first Christmas after we met) and has been making funny noises for awhile...but as I feared drawing this high of a vacuum with a shopvac is apparently not a great idea.

Now...to be fair I probably should have given it a better once over before using it for this...Turns out some of it's filters have seen better days:



Didn't even know that filter was there until I started taking it apart!

From the sounds it was making I thought I lost a bearing...but from the smell it was making I thought I must have burned out a motor winding.* Once opened up though I think I know what happened:



I'm not positive...but I strongly suspect those black bits in there are what's left of at least one brush.* Doubt I can find replacements for it...but I may try and see what I can do.* It was still too hot to dig into any deeper though tonight.

I'm hesitant to use my new shopvac I just got for fathers day on it now.* It's bigger and louder for one thing (and that's the other thing I'm still not big on - the extra noise of running the vac for needle cutting) but it's also brand stinking new so I don't want to risk burning it up!

The new vac is a VacMaster vbv1210 and blows away my old 6gallon shopvac brand vac.* I think it has separate cooling too...as there are grills on it where it seems to suck in and blow out air separate from the vacuum air.* But the exhaust from it does get hotter than I'd like after 15 minutes of running the vac table.

Google gives a lot of mixed info on this application.* Some people say they burned out shop vacs almost immediately...others say they've been running them in production shops for 4-8 hours a day for 2-4 years with no issues.* Probably depends a lot on the style of vac and how much leakage is in the table.

I did remove a bit of foam between two "fingers" of the printed adapter so there's a gap that lets it bleed some air and get more flow now....but it just made things a LOT louder and the exhaust air still gets warmer than I'd like.* But...I see vacuum motors like these:*http://www.centralvacuummotor.com/shopbot.htm (which are more than I'd like to spend) which say a 1/4" hole in the plenum provides enough leakage to keep them cool.

I may just look for a cheap shopvac this weekend to dedicate to this and see how it does.* I did see that the donek drag knife people use a cheap "$25" shopvac:

And apparently they use that in production work...so I may have to see if I can track one of those down this weekend.


One more thing suggesting it may just have been time for my old vac to die...when I took it apart I noticed that it doesn't appear to use vacuum air for cooling. The motor is in a separate compartment that has no openings to the main vacuum air. It has that little fan over the motor and the cover that goes over this part sits on posts allowing fresh air to flow in and around it. It's not quite as nice as my new vac which has obvious inlet/outlet ports for the motor - but it does seem that the motor had separate cooling and didn't use airflow from the vacuum for cooling.

Of course running restricted does run the motor faster and hotter than normal...so still not a great thing for motor/brush longevity.

 

[moebeast]

I've been using a little 2.5hp 2.5 gal Shop Vac. It is quieter than the big one, with plenty of power for this application. It has about 75 hours running the table.

 

[jhitesma]

I've been using a little 2.5hp 2.5 gal Shop Vac. It is quieter than the big one, with plenty of power for this application. It has about 75 hours running the table.

How much leakage to you allow? I removed the middle layer of foam between two fingers to create a leak...I can feel good suction around it but my big vac still gets a lot warmer than I'd like after 10 minutes. It was enough to noticeably weaken the tables ability to hold my foam...but the foam is still held well enough.

I'll see what kind of small cheap shop vac I can find locally to dedicate to the table...pretty sure I saw those little 1.5 gallon ones like the Donek guy is using for $25 at wallmart the other day.

 

[ironkane]

I just wanted to throw in a alternative vacuum table design. I've seen a lot of them where they had used their CNC to route out a grid of channels in a sheet of 3/4" MDF with a central hole to which a flange/vacuum hose attachment is secured. I have a friend with a Shapeko who went to do this for me. Our communications about the design weren't perfect and he ended up routing out the central hole on the wrong side. Oh well, he was doing me a favor. Plus doing this with a CNC router was super time consuming. I wanted to get this up and running ASAP.

Well he had mentioned to me previously that it would probably be faster if I just used a table saw. So that's what I did. I have a table saw and I had purchased a dado blade kit from Harbor Freight previously for $35 https://www.harborfreight.com/8-inc...o-blade-set-with-saws-and-chippers-40745.html for those who are unfamiliar with what a dado blade is, it's a couple of circular saw blades with spacers and chip breaker blades in between that let's you make thicker/wider cuts.

So I set it up, plotted out my grid and ran my 20x30 piece of MDF through it to make a grid with 1/4" channels and 3/4" islands. I used a couple of hole saws to drill my recessed hole for the vacuum adapter flange. Then I stripped the paper off of a sheet of DTFB and just using some blue painters tape to secure it to the vacuum table. I then made a simple frame to go around the perimeter of the table to close off the open channels. Lastly, I used a very small metal tube (in my case, a large diameter syringe tip) to poke holes through the DTFB into the channels for the air flow.

I'm sorry I don't have any pics, but I'm not ready to retire my DTFB waste board just yet. I've only gone through about a case of DTFB and it's still going strong and it almost looks like R/C art. But this is a very quick and easy way to get a vacuum table going. It didn't even take much more than an hour on the table saw. The outer frame is screwed together so all I have to do is loosen the screws slightly to remove it for waste board replacement.

I think that if I was to make an improvement to it, that I'd install some kind of bleeder valve on the perimeter of the frame so that I could adjust the amount of vacuum so as not to tax my little Porter Cable Shop Vac ($30 Costco) as much. Ok, one other improvement would be a noise dampening enclosure for the vacuum. Damn those things can be loud, lol.

Not saying mine is the best, but it's cheap and easy for anyone with or access to a table saw. It looks very much like this one https://www.youtube.com/watch?v=MR-WS8CUHrs but doesn't take 8 hours on the CNC router.

 

[moebeast]

This little guy is supposed to be 5 amps at 12vdc. It could be run of the same power supply as the machine, and controlled using the bed heater circuit.

https://www.homedepot.com/p/Stanley-1-Gal-12-Volt-DC-Wet-Dry-Vacuum-SL18125DC/204226940

It could probably be hacked down and built into the table.

Just an idea.

 

[moebeast]

How much leakage to you allow? I removed the middle layer of foam between two fingers to create a leak...I can feel good suction around it but my big vac still gets a lot warmer than I'd like after 10 minutes. It was enough to noticeably weaken the tables ability to hold my foam...but the foam is still held well enough.

I'll see what kind of small cheap shop vac I can find locally to dedicate to the table...pretty sure I saw those little 1.5 gallon ones like the Donek guy is using for $25 at wallmart the other day.

I didn't allow any leakage on my new pad. My MPCNC has a 1/4" hole on the side opposite of the vacuum connection. It was accidental when I milled the pocket in the blue foam. I don't know if it helps or not.

 

[moebeast]

Well, Monday is the deadline for Ryan's MPCNC video contest...and since I've been busy I haven't had any time to prepare anything.

Guess that's a good enough excuse to make my vac table finally...and try to film it

Looks like you are winning again! You might have to build another machine to make use of that board.

 

[jhitesma]

I saw that little 12v stanley...but I'm worried it may not be strong enough. Big deciding factor will be what I find in stock locally

So you don't have leakage in your pad...but you still have a 1/4" hole providing leakage? The bit I removed from my pad gives me considerably more than 1/4"....what does the exhaust air from your vac feel like? My whole shop starts feeling warm when I'm running the vac table because the vac (either the old one or the new one) throws off so much heat.)

I see whole house vac motors on ebay for about $50 which are kind of temping....But a $25 shop vac is still what I'm looking for.

And yeah, I've got the lead but just barely! And to be honest geodave's openscad work is VERY impressive and deserving of a win!

I'm not even sure what I'd do with an archim if I do win. Apparently the guy who ported marlin to it for ultimachine has moved on and isn't interested in supporting his port anymore...and the new 2.0 branch of Marlin has support for the Archim2 which isn't out yet (but sounds almost the same only with Trinamic TMC2130 drivers like Prusa is using on their new stuff.) So...not sure the Archim is really a board with any kind of future But...I do have my almost built low rider so wouldn't mind putting the archim on my printer and using that RAMPS on the low-rider once I finally save up the bucks for some stainless tubes. (which will hopefully happen soon, just got the latest electric bill and we're finally past summer AC levels with this bill dropping almost 50% compared to the month before!)

 

[CaptCaveman37]

I'm thinking of running my vacuum hose into a Y fitting and adding a gate valve to to one side to control the amount of bypass. You should be able to open it enough to get suction and allow cooling air into the vacuum. I also wonder if you mounted it without the collection bin would help. Just some thoughts.

Jamie

 

[moebeast]

I saw that little 12v stanley...but I'm worried it may not be strong enough. Big deciding factor will be what I find in stock locally

So you don't have leakage in your pad...but you still have a 1/4" hole providing leakage? The bit I removed from my pad gives me considerably more than 1/4"....what does the exhaust air from your vac feel like? My whole shop starts feeling warm when I'm running the vac table because the vac (either the old one or the new one) throws off so much heat.)

I see whole house vac motors on ebay for about $50 which are kind of temping....But a $25 shop vac is still what I'm looking for.

Sorry for the confusion, I have two vacuum pads. The original where I milled out a pattern in my blue foam spoil board has the leak. The pad on my "Foam Ripper" is exactly like yours.

Someone with free time should do a science project measuring vacuum produced by various vacuum models and the effect of airflow on that vacuum and motor temperature.

 

[TEAJR66]

Did some work to the MPCNC today. First order of business was to create a storage system for the tools that are not being used. Gotta keep things neat and organized.

There was a lot of engineering thought and effort put in to this.

 

[TEAJR66]

Now for the real improvements.

First we closed up the bottom of the table.



Then we made some holes in the bed and added X and Y axis stops.



Added a holder for the needle cutters power supply.



Made a hole for a shop vac tube and threw in a piece of plastic to keep the cable chain on the table.



Made some more holes and covers to control airflow.



Turned on the vac, positioned the waste board and foam board, closed the vents till the board sucked down well.



Made the first cut on the vacuum bed and it worked great. I am pretty happy with this set up. Probably going to purchase a dedicated vacuum for this or buy a blower motor. I think a blower on the back of the table would be a lot quieter.

 

[ftwingnut]

Wow! I'm finally here!

I've been reading this thread from the beginning up to current, and it has taken me a couple months. I honestly feel like I know you guys personally, David, Jason, Mark, Tommy, etc.

David, great news on the new (old) house and all the room you have now to stretch your arms, and your hobbies. Jason, you're finally getting there with your cnc, but have you addressed your curtain-hook wiring yet? Mark, I spoke with you at length during FFE17 and you cut me an Arrow kit, thanks very much. You gave me great advice about checking out the new version of the mpcnc that was available.

I had discovered the mpcnc about a year ago and was wanting to build one, but was tight on time and money, so I had started printing parts, but even that got pushed to the back burner. Now I am almost finished printing the parts for the new version, I have my bearings, belts, pulleys and hardware, and will be ordering steppers and controllers in the next month or two (maybe I'll put them on my Christmas list!). I have a Davinci 3D printer, and it has been reflashed with Repetier firmware and I really love it. In fact, as I type this, I am watching it work on a 23 hour print job for the nut traps, the nut lock, and the XY's (all in one print job).

Since I am very familiar with Repetier, and I control my printer from a dedicated PC, I will probably set up my cnc to be controlled from my Repetier PC as well. To start, it will mostly be used to needle-cut DTFB for airplanes, but eventually I would like to mount my dremel to it for some light engraving, and after that, a laser to do etching and cutting of light materials (not DTFB).

I am planning on probably a 36" x 48" table, and I will definitely be making a removable vac table to hold my DTFB. I was sold on that when I saw Mark's table in action at FFE. Being an IT guy, I really liked the idea of using CAT5 jacks in the conduit and using patch cables to connect the motors to the controllers, and then I found some 3D printed adapters on thingiverse for that exact use, so I will be printing up some of those to run the wiring inside the conduit. I still haven't decided on whether to use some printed cable chains, seeing as how some of you use them and some don't.

So, to close my first post, I just want to say THANK YOU to all of you for your ideas, inspiration, and most of all, your trial-and-error.

Brian

 

[RAGII]

New laser mount

So I ordered some filament to use on our company 3D printer so I could finally print some real mounts for the tools I use. Maker Geeks was having a 25% off sale so I did the grab bag and chose standard PLA and Transparent PLA. Got Translucent Green and Hot White.

I started with the HicWic quick change and most of the laser mount for it. I decided to do the laser housing in the translucent hoping it would glow like David's. I am utterly disappointed in that aspect of it. It does not glow at all. The mount worked well and will be a lot nicer than my cobbled up wood mounts but no cool glowing effect. Just need to print out the top piece that holds the laser driver board and then I can clean up some of my wiring. Did not want to wait around at work for my print to finish. (They have a policy no unattended printing).

I did notice that the fan I am using is deeper than the typical fans so I may have some issues with this last piece. Not sure how I can take the STL file and just stretch the top so I may need to go look for another fan.

Off to do some soldering on an FT Gremlin. So many projects, not enough time.

Rob

 

[jhitesma]

Wow! I'm finally here!

Welcome!

Jason, you're finally getting there with your cnc, but have you addressed your curtain-hook wiring yet?

Hey, I like my curtain hooks They're the one part of my wiring I don't really want to change because they work so well. And with the needle cutter now controlled through the RAMPS my tool wiring is improved...but I still have more cleanup to do to make swapping tools cleaner/easier.

The RAMPS wiring...well...let's not talk about that yet

I did however swing by walmart on the way home from work today and grabbed the little 1.5hp 1gal Stanley vac for $19.95. Hooked it up and...it works, but isn't great. It's not much (if any) quieter than my bigger vac, and the hose on it is smaller so has to go into the adapter moebeast designed deeper to seal. It's lower power for sure though and with the vent I added for my big vac it barely holds the foam down. I filled that back in and it sucks things down nice and tight again. It also seems to have separate air passages for the motor so I have hopes it will last. We'll see. I also picked up a couple of cheap cutting boards I'm going to try milling into some super cheap quad frames just to see if I can

 

[TEAJR66]

Wow! I'm finally here!

Welcome.

I'm fairly new here myself. But I did not have the stamina to read through the whole thread.

The prints were the painful part. Once those were complete, it started coming together nicely.

I did not fully understand how this all worked as I was totally new to all this machinery stuff. Then when I saw the needle cutter in action at FF, I knew I had to start looking into it. The Vicious1 site made it all pretty simple and straight forward. Then when I was still screwing it up, A-1 support from Mark.

Can't wait to see how yours comes out. Good luck with it all.

 

[jhitesma]

Note to self. Unless I upgrade the wiring to my shop so I have more than a single 15amp circuit in there....Running two shop vacs and a router and my AC and my computer and the CNC at the same time. Is as bad of an idea as I suspected it would be

Got 80% through the cut before the breaker finally said "I'm afraid I can't let you do that Jason"

Extra fun since it was 10:30 last night when I did it so I got to stumble around in the dark after.

On the upside...the vac table worked far better than I expected cutting a sheet of PVC with the router. I was cutting some fairly small parts and worried that the vac wouldn't be able to hold them - but I left an "onion skin" on the bottom so the vac wouldn't loose seal but the parts would still be easy to remove/clean.

This particular project may still be a total failure...gotta see if I can solvent weld PVC sheet...if I can...then this may have potential....

 

[TEAJR66]

So, to date, i have cut planes from my designs in SketchUp, shared DXF files, and Flite Test PDF's.

The Flite Test PDF plans to Gcode was the most challenging. But it worked excellent.

Thank you jhitesma for taking the time to explain that process. Your video is very helpful. I keep the URL in my favorites for quick reference.