Cutting foam sheets... with a needle!

SteveRobey

Member
So I just had the thought that what you're doing here is essentially building large CNC tattoo machine.. Dear god I hope nobody tries to tattoo themselves with this thing..

I did have an idea though, and I don't know if it will work or help or cause problems so I'll just pass it along and see where it goes. So obviously in this cutting machine, the point of the needle is doing all of the work, simply knocking out a little bit of material on each stroke, and if you go too fast the needle starts to flex and can potentially break right? Well I'm wondering if it would help to add a little bit of a knurl to the last quarter inch or so of the needle shaft to give it some grit and possibly allow this machine to move along a little faster? I had the idea because of the mentions of using a MIG welding tip for the guide tube, you know the little round brushes you use to clean your MIG tip and the tip of your Oxy torch? What about something like that with a sharp point on the end? that way you not only have the puncture action, you also add a little bit of sawing action.

Here's an image of what I'm talking about, sort of hard to see but hopefully you get the idea if you have not seen one of these before..

615ILopZ7nL._SX355_.jpg
 

dkj4linux

Elite member
Hey David,

I keep bugging Mark about an OpenBuilds Phlatprinter now and then, but he seems to be too busy overall. He did release the Phlatprinter build video a few weeks ago though so I could finally see how the roller mechanism works. I still love the overall design of that machine, because one of the biggest issues I have with CNCs is the space requirement...

Balu

Hey, Balu! Good to hear from you!

I saw that Mark [Carew] had released the plans for the Phlatprinter recently and was interested in the same thing you were... the rollers. I took a cursory look at the build video... speeding through the bulk of it to the assembly of that mechanism. It was pretty much what I expected... and a bit more complex than I'd hoped. That whole machine is actually quite intricate to be made out of MDF... it's impressive.

I've thought about a compact printed gripper mechanism -- a stepper motor with short pressure and drive rollers/grippers -- that grips just the very edge of the foam, one on each side... synced and driven just as the gantry motors on the MPCNC. Passive support underneath the material with thin slot for the needle to extend through. One side movable to accommodate different material widths.... think tractor-drive for the old dot-matrix printers... or the little HP7475 desktop plotter I had sitting on my desk when I worked in industry ;)

I recently played with printed rollers/gears when doing my... wait for it!... Mostly Printed PEA SHELLER (MPPS?). Manual model with hand-crank...

20170701_193540.jpg

20170701_193610.jpg

and motorized...

20170801_073620.jpg

20170801_073543.jpg

It was a fun little project and a great 3d-printing exercise. I was thrilled to see the precision and accuracy of the fit of all the printed parts to the bearings, bolts, nuts... and each other. Plenty good enough, I think, that a foam gripper/roller mechanism could be fashioned and made to work nicely for a Phlatprinter-style machine.

But I think I'll save it for a rainy day... unless/until the spirit moves me otherwise :rolleyes:

Again... it's great to hear from you!

-- David
 

dkj4linux

Elite member
So I just had the thought that what you're doing here is essentially building large CNC tattoo machine.. Dear god I hope nobody tries to tattoo themselves with this thing..

I did have an idea though, and I don't know if it will work or help or cause problems so I'll just pass it along and see where it goes. So obviously in this cutting machine, the point of the needle is doing all of the work, simply knocking out a little bit of material on each stroke, and if you go too fast the needle starts to flex and can potentially break right? Well I'm wondering if it would help to add a little bit of a knurl to the last quarter inch or so of the needle shaft to give it some grit and possibly allow this machine to move along a little faster? I had the idea because of the mentions of using a MIG welding tip for the guide tube, you know the little round brushes you use to clean your MIG tip and the tip of your Oxy torch? What about something like that with a sharp point on the end? that way you not only have the puncture action, you also add a little bit of sawing action.
...

Steve,

Home-made prison-style tatoo guns have certainly been mentioned before... and my "non-flywheel" versions of the cutter, with its bent crank-pin, resembles them greatly.

More precisely, however, rather than "punching" through, or "knocking out", the foam, the very thin (0.025" diameter), relatively stiff, music-wire needle, with its short, conical point (like a sharpened wooden pencil), actually just displaces (pushing to the side) the soft foam and generates virtually no debris at all... not at all unlike your arm skin/muscle when getting a shot/injection with a needle. A very small "wound"... a perforation that does little/no real mechanical damage to skin/muscle. Cutting action occurs, however, when these perforations begin to *overlap*... leaving a "kerf" of closely spaced holes behind as it travels along the cut-path. I've found, through experience, that 10-15 perforations per millimeter of linear travel yields a clean cut in DTFB... and yields parts, with clean/square edges, that are very easily removed from the sheet upon job completion. So, for 6000-7000 rpm on the cutter, I target a feed rate of about 600 mm/minute... and there's nothing really critical as long as you are in the ballpark. A factor of 10, cutter rpm to feed rate, is easily remembered and easy to compute... so it works for me.

The needle is moving up and down so fast, relative to the feed rate, that there is (or should be) little/no "sawing action" taking place at all. If the feedrate is too fast (or the cutter rpm too slow), the needle will drag in the foam and the quality of the cut will suffer... and/or you will bend/break the needle. At the other extreme, too slow feed rate, too high cutter rpm, and/or a blistering-hot needle guide, localized heating in the foam around the needle may take place and molten foam will start to coat the needle...leading to even more friction/heat, and -- quite quickly, in real time -- catastrophic needle failure occurs. I'm afraid a rough needle would only aggravate this situation and suffer from that same clogging/breaking issues that a high-speed rotary bit most often suffers from when trying to cut DTFB; i.e. it's the paper coating that causes the most problems.

I know this is a long thread -- and I apologize for the inconvenience/difficulty it presents in finding specific information -- but almost everything you might want to know about this needle cutter and its development is in here somewhere. In your just-before-bedtime "light" reading you may want to begin scanning through it, stopping only when something grabs your attention... it'll start to make more sense as you occasionally pause for thought. And I'll do my best to help as you have questions. Good luck!

-- David
 
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Michael9865

Elite member
New Z Axis Parts

Jason and Mark - Nice articles. Great work.

Anybody - I am wanting to update my Z axis to the new type after seeing Mark's at Flite Fest East 2017. Are the files with the arrow the ones I need to have printed to update my machine? Is the C-Nut_Trap for the new Z the same as the old or do I need a new one? Thank You for the assistance.

I will be updating the X & Y axis parts later this winter.

MPCNC Z Axis Parts.jpg
 

moebeast

Member
Jason and Mark - Nice articles. Great work.

Anybody - I am wanting to update my Z axis to the new type after seeing Mark's at Flite Fest East 2017. Are the files with the arrow the ones I need to have printed to update my machine? Is the C-Nut_Trap for the new Z the same as the old or do I need a new one? Thank You for the assistance.

I will be updating the X & Y axis parts later this winter.

View attachment 92260
Those are the ones. You only need one of the c-nut locks depending on the style of nut you have. You could print both and use one in place of the spacer. The traps have not changed.
 

PhenomPilot

New member
After talking to Moebeast at FF17, I am about half way done the MPCNC build. Planning on cutting conduit tomorrow. Any suggestions on size? I was planning on cnc area of 24"x36" so it could fit a sheet of dtfb. Is 4" z height adequate?
 

jhitesma

Some guy in the desert
Mentor
After talking to Moebeast at FF17, I am about half way done the MPCNC build. Planning on cutting conduit tomorrow. Any suggestions on size? I was planning on cnc area of 24"x36" so it could fit a sheet of dtfb. Is 4" z height adequate?

4" of z should be adequate. For cutting foam you really don't need much Z at all. Just enough to clear your spoil board and/or vac table if you plan on using one. You'll only be using maybe 10-15mm of z motion total durring a cut and that's jsut over 1/2".

I would suggest going a bit bigger than 24"x36" if you can. I'm not sure if you'll be able to fully cut a 20"x30" sheet with that size of machine. Mine is 36"x48" and I have plenty of room...and honestly would go a bit smaller if I did it again.. But you do loose quite a bit of usable space due to the design of the MPCNC. Ryan the designer of the MPCNC has a really good page on size here: https://www.vicious1.com/assembly/machine-size/ And there is a calculator for determining size here: https://jscalc.io/calc/Y1Db347ni9eckSKc (It took me awhile to find that calc and I knew it was there....it's linked off of the page about cutting conduit here: https://www.vicious1.com/assembly/conduit-rails-tubes-pipes/)

According to the calculator for a 32"x22" work area (giving you an extra 1" on all sized of a seet of DTFB) you'd need to bulid a 42.4" x 32.4" machine

Or if your 24"x36" specificaiton is for the work area not the machine size then your machine size will be 46.4" x 34.4"

The Z I'd stay go with the stock 4" and you can always cut the tubes down if you find you want to go shorter/stiffer.
 

jhitesma

Some guy in the desert
Mentor
Thanks jhitesma! Might go with 46" by 36" conduit lengths so it still fits on a 48" sheet of MDF. That calculator makes it easy.

No problem, that's why I went with 48"x36" as well. Figured I'd use half a sheet of 4x8 for the top of my table and may as well build as big as I can.

I would suggest doing center span supports on the 48" side if you do go that big. I'm using these: https://www.thingiverse.com/thing:1800589 but there are a couple different designs out there.

Honestly though like I said above if I did it again I'd probably go with something like 44" or 45" instead as I ran into a lot more problems once I made my machine bigger. Finding conduit that was straight the full length was a lot harder and there's more flex to deal with. But if all you plan on doing is cutting foam and maybe running a laser then that's not as big of a deal. If you plan on hooking up a router then stiffness is way more important.

Either way one thing I did learn is I'd print at least one center support leg even if I didn't plan on using it - then when assembling the machine I'd use it as a gauge while leveling to make sure both sides of a span are the same height. Then I'd use it to check the span along it's full length. If it's not quite straight I'd rotate the conduit until the curve faces down - then I would use the support in the middle to push it back up level.

Again, not a huge issue on the shorter axis...but on once you're over 40" that long axis can get finicky.
 

dkj4linux

Elite member
My needle cutter almost ready to test!

Sadly, I never found my previous "production" cutter with the red EMAX 2822 motor... just goes to show how much "production" I do, huh?

So I went through my stash of parts and found a brand new 1200kv RCTimer 2822 motor and decided to use all new parts for this cutter... and apply all our latest revision ideas as well. I'm also using my "calculated" balancing procedure to see just how close to "well-balanced" the flywheel actually is, using only the calculated torques... and before ever spinning it up :eek:

So here it is, in all its glory...

First, I went into Onshape and imported and scaled/redrew the needle holder/keeper that Moebeast showed... I'm using a 8mm x 4mm x 3mm bearing robbed from a junker motor. Then I exported the STL and printed it. Found my 0.025" music wire, cut a short length, put the small bend in the wire to sit in the recess and inserted the bearing...

20170802_095800.jpg

20170802_091013.jpg

20170802_090718.jpg

Then I weighed the assembled needle keeper, bearing, and mounting hardware... 48 gn at the normal 6mm location on my flywheel gives 288 gn-mm...

20170802_093718.jpg

To counter-weight, 19.2 gn at the 15mm position (or, 26.2 gn at the 11mm position) on the opposite side should do... a 12mm M3 screw and nut seems pretty close...

20170802_100956.jpg

Flywheel all assembled...

20170802_094331.jpg

Flywheel assembly installed on motor shaft...

20170802_100405.jpg

Alignment looks reasonable...

20170802_100419.jpg

I think it's ready to test. But first, I'll need to go find an ESC and solder on the proper connectors to hook it all up... since I can't find any of my stuff from before. Slow as I am, it may be a while... :rolleyes:

-- David
 

moebeast

Member
Sadly, I never found my previous "production" cutter with the red EMAX 2822 motor... just goes to show how much "production" I do, huh?

So I went through my stash of parts and found a brand new 1200kv RCTimer 2822 motor and decided to use all new parts for this cutter... and apply all our latest revision ideas as well. I'm also using my "calculated" balancing procedure to see just how close to "well-balanced" the flywheel actually is, using only the calculated torques... and before ever spinning it up :eek:

So here it is, in all its glory...

First, I went into Onshape and imported and scaled/redrew the needle holder/keeper that Moebeast showed... I'm using a 8mm x 4mm x 3mm bearing robbed from a junker motor. Then I exported the STL and printed it. Found my 0.025" music wire, cut a short length, put the small bend in the wire to sit in the recess and inserted the bearing...

View attachment 92368

View attachment 92367

View attachment 92366

Then I weighed the assembled needle keeper, bearing, and mounting hardware... 48 gn at the normal 6mm location on my flywheel gives 288 gn-mm...

View attachment 92370

To counter-weight, 19.2 gn at the 15mm position (or, 26.2 gn at the 11mm position) on the opposite side should do... a 12mm M3 screw and nut seems pretty close...

View attachment 92369

Flywheel all assembled...

View attachment 92371

Flywheel assembly installed on motor shaft...

View attachment 92372

Alignment looks reasonable...

View attachment 92373

I think it's ready to test. But first, I'll need to go find an ESC and solder on the proper connectors to hook it all up... since I can't find any of my stuff from before. Slow as I am, it may be a while... :rolleyes:

-- David

Looking good David. I was wanting photos like these when I wrote my article, but was too lazy to pull mine apart or print a new one. I am exited to hear how the needle holder works for you.

Another thing you can do with your current model is put some oiled cotton in the cavity beween the wood blocks. My little wad keeps flying out, so I just oiled the wood and let it go.

The fins I put on the MIG tip are cooling it to the point of being able to keep my finger on it after 20 minutes cutting at 1200 mm/min.
 

jhitesma

Some guy in the desert
Mentor
Another thing you can do with your current model is put some oiled cotton in the cavity beween the wood blocks. My little wad keeps flying out, so I just oiled the wood and let it go.

With the stacked wood construction....could add a top layer with a slightly smaller hole to act as a retainer for the cotton.....kind of defeats the funnel shape a little but just a thought. I considered doing something similar on my latest cutter and making the opening in the PLA a reverse funnel to hold the cotton in. But I found just packing it in there fairly well keeps it in place just fine.
 

dkj4linux

Elite member
I had indeed considered the possibility of using the "plastic cavity" between the upper and lower blocks for a cotton-wad oiler but want to see how well I can get the cutter to operate without it first. I know some of "youse guys" who've built needle cutters have seen positive benefit from the oiler addition but I'm still unconvinced... while I know it certainly doesn't hurt anything, I've simply not used the cutter enough to actually see any definitive improvement.

The stacked makeup of the upper and lower blocks is already showing some benefit however. I'm going to change the 4mm, 3mm, 2mm, 1mm upper stack to be 3mm, 2mm, 1mm, 1mm... the needle never comes close to touching the 4mm piece.

-- David
 

moebeast

Member
I had indeed considered the possibility of using the "plastic cavity" between the upper and lower blocks for a cotton-wad oiler but want to see how well I can get the cutter to operate without it first. I know some of "youse guys" who've built needle cutters have seen positive benefit from the oiler addition but I'm still unconvinced...

-- David

Maybe a photo of one of my sheets with random black oil spots all over it would convince you :D

I think my wood block is lubricated enough for a while.
 

jhitesma

Some guy in the desert
Mentor
Maybe a photo of one of my sheets with random black oil spots all over it would convince you :D

I think my wood block is lubricated enough for a while.

I do get a few oil drips occasionally when breaking in a wad of cotton if I over oil it. But...after cutting a sheet or two I find that one quick drop before each sheet keeps it lubricated without any drops getting on the foam. I also seemed to have a bigger issue with oil getting on the foam with the inflation needles instead of the mid tip for some reason....

I can also definitely hear and feel a difference with the oil. It just sounds smoother and the tip stays noticeably cooler to the touch even at higher RPM's. So I really feel it's worth it. Even if I sometimes gets a few small spots on a sheet of foam :)

Though my new setup also runs much cooler overall.

BTW - the other day when I took it off to put the router on the machine and cut some wood I noticed something I found interesting about how the guide bearings work:


I mean...it makes sense now that I think about it. But I had assumed both of the power bearings would always be turning because it seemed a tight enough fit on the needle. Either things have "clearanced" a bit from wear or the fit isn't quite as snug as I first suspected.
 

Michael9865

Elite member
4" of z should be adequate. For cutting foam you really don't need much Z at all. Just enough to clear your spoil board and/or vac table if you plan on using one. You'll only be using maybe 10-15mm of z motion total durring a cut and that's jsut over 1/2".

The Z I'd stay go with the stock 4" and you can always cut the tubes down if you find you want to go shorter/stiffer.

Good advice. As I am updating my setup, I am planning to shorten my Z axis, the height is just unnecessary added weight to the setup.

I would suggest doing center span supports on the 48" side if you do go that big. I'm using these: https://www.thingiverse.com/thing:1800589 but there are a couple different designs out there.

Thank you for pointing that out. I am not a fan of the old supports that I printed. These are added to my updates as well.
 

ironkane

Member
Hi All, I'm glad to see that this thread is still alive. It's been a long time coming, but I have my MPCNC foam board cutter.

I tried the crank shaft method. I wrapped my own spring crank shafts. Even made some spring winding jigs. Got pretty good at it. Didn't help, I had too much problems with the Z height varying because of flex in the crank shaft arm. Fortunately, I've befriended a guy who has a small metal lathe and I'm currently using version 1 of an aluminum flywheel.

Nothing fancy, just like most of your printed ones except it only has two holes in the face. One for the needle/bearing assembly and one for counter weight. The difference was noticeable. My cuts, especially with the waterproof foam board, are sharp and clean using a 0.32" needle. I'm using a HF Mig tip, bolted to a piece of scrap aluminum heat sink scavenged from some electronics. The heat sink is then bolted to the cutter bed.

Why would you use wood? It's insulates and you want to dissipate heat, right?

I love the teardrop needle holder idea! I just think it probably should be aluminum as well. I might be able to fabricate one by hand. I was working on a cylindrical one. I guess I wasn't thinking outside of the box far enough. I do think you're on to something there.

HicWic's "Quick Change" Tool Mount..... isn't. My vision for a foam board CNC includes hot swappable toolheads so that I can first add a Pen to plot out any graphics and then quickly swap out the pen holder for the needle cutter. Here's a work in progress for a true quick change http://a360.co/2rVF2G5 It has a hook at the bottom that goes over a roll pin pressed through the bottom hinge and a bolt at the top to secure it. I don't have one in use right now, although I have printed both parts. I noticed some gotcha's and need to edit the design.

Aside from all of that, I really came to this thread today to ask you guys a question about vacuum tables. I have one and it sticks great. Maybe too great. I can actually see the grid pattern in the foam I cut after I'm done. FYI, I have a piece of de-papered foam board taped down over the vacuum table channels as a waste board. I have had to poke some holes through it initially because of it being closed-cell foam, but I figured it'd get swiss cheesier after running several sheets through. Any thoughts on controlling the amount of vacuum?

Keep up the good work.
 

dkj4linux

Elite member
Hi All, I'm glad to see that this thread is still alive. It's been a long time coming, but I have my MPCNC foam board cutter.

I tried the crank shaft method. I wrapped my own spring crank shafts. Even made some spring winding jigs. Got pretty good at it. Didn't help, I had too much problems with the Z height varying because of flex in the crank shaft arm. Fortunately, I've befriended a guy who has a small metal lathe and I'm currently using version 1 of an aluminum flywheel.

Nothing fancy, just like most of your printed ones except it only has two holes in the face. One for the needle/bearing assembly and one for counter weight. The difference was noticeable. My cuts, especially with the waterproof foam board, are sharp and clean using a 0.32" needle. I'm using a HF Mig tip, bolted to a piece of scrap aluminum heat sink scavenged from some electronics. The heat sink is then bolted to the cutter bed.

Why would you use wood? It's insulates and you want to dissipate heat, right?

I love the teardrop needle holder idea! I just think it probably should be aluminum as well. I might be able to fabricate one by hand. I was working on a cylindrical one. I guess I wasn't thinking outside of the box far enough. I do think you're on to something there.

HicWic's "Quick Change" Tool Mount..... isn't. My vision for a foam board CNC includes hot swappable toolheads so that I can first add a Pen to plot out any graphics and then quickly swap out the pen holder for the needle cutter. Here's a work in progress for a true quick change http://a360.co/2rVF2G5 It has a hook at the bottom that goes over a roll pin pressed through the bottom hinge and a bolt at the top to secure it. I don't have one in use right now, although I have printed both parts. I noticed some gotcha's and need to edit the design.

Aside from all of that, I really came to this thread today to ask you guys a question about vacuum tables. I have one and it sticks great. Maybe too great. I can actually see the grid pattern in the foam I cut after I'm done. FYI, I have a piece of de-papered foam board taped down over the vacuum table channels as a waste board. I have had to poke some holes through it initially because of it being closed-cell foam, but I figured it'd get swiss cheesier after running several sheets through. Any thoughts on controlling the amount of vacuum?

Keep up the good work.

Welcome, Ironkane. Yes, we are still alive... nothing scripted/planned here, we just evolve. Please note that this thread chronologically traces the development(s) of the needle cutter (with related/interesting side-trips) over the past year and a half -- all out in the open and where everybody can see it -- and is a work in progress... not just a set of assembly instructions for a finished product. And the strength of the process is that this hasn't been a one-man show... any/all the talented folks who've chosen to show up and present/demonstrate an idea/method (or just lurk!) has been welcome. And it's been demonstrated time and again that there is generally more than one way to do something... not a lot of room for "it should be this" or "it must be that" ;)

A strength of the design itself... almost any material, or combination thereof, can be used to build a cutter. My first cutters were wood and metal... and then plastic, when the 3d printer came along. Nothing about the design is supposed to get TOO hot, though there's enough slop/friction that some heat does get generated, especially with higher cutter speeds and the needle guides of the earliest versions... and before all our efforts to lessen generated heat with straight-line motion of the needle in the guide. There's usually enough heat generated to make plastic unsuitable for direct contact with the needle guide but not so much as to disqualify metal... or wood. Successful cutters have been built with massive heatsinks... others use hardly any metal at all. Almost anybody, of any skill level, with or without a workshop, can build a functional needle cutter using most anything they have on hand, or can get with a quick trip to the Dollar store... and the build is simple/inexpensive enough (KISS rules!) that the whole cutter, or any part of it, can be replaced/rebuilt in short order.

The Hicwic mount was popular for a time and "guick-change" is relative. That mount is still okay for some, including me, for light tools such as laser, pen, or needle cutter. I've built several MPCNC's and that mount was both convenient and sufficient for my need... though it lacks rigidity for heavier tools and tool forces. Your design looks like it has great merit... and I'm sure we'd all like to see it in action. Pictures and video will go a long way to generate some excitement and get the creative juices flowing.

Vacuum hold-down is probably best addressed by Moebeast... who has used it probably as much or more than anybody here at the FliteFest event. Several designs were presented in the thread (page 47 or so) and I've always thought a suitable vacuum setup for foam could be as simple as a lamination of 3 or more DTFB sheets, needle-cut with channels and holes, clamped/glued to a piece of MDF or held in a light frame.

Again, welcome. I look forward to seeing development of your cutter.

-- David

PS: If you haven't already, check out the FT articles that Moebeast and Jhitesma recently submitted. Moebeast presented his MPCNC foam cutter system (including vacuum hold-down) and Jason presented his needle-cutter design. Both have been major contributors to this thread. Congrats to both!
 
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moebeast

Member
Hi All, I'm glad to see that this thread is still alive. It's been a long time coming, but I have my MPCNC foam board cutter.

I tried the crank shaft method. I wrapped my own spring crank shafts. Even made some spring winding jigs. Got pretty good at it. Didn't help, I had too much problems with the Z height varying because of flex in the crank shaft arm. Fortunately, I've befriended a guy who has a small metal lathe and I'm currently using version 1 of an aluminum flywheel.

Nothing fancy, just like most of your printed ones except it only has two holes in the face. One for the needle/bearing assembly and one for counter weight. The difference was noticeable. My cuts, especially with the waterproof foam board, are sharp and clean using a 0.32" needle. I'm using a HF Mig tip, bolted to a piece of scrap aluminum heat sink scavenged from some electronics. The heat sink is then bolted to the cutter bed.

Why would you use wood? It's insulates and you want to dissipate heat, right?

I love the teardrop needle holder idea! I just think it probably should be aluminum as well. I might be able to fabricate one by hand. I was working on a cylindrical one. I guess I wasn't thinking outside of the box far enough. I do think you're on to something there.

HicWic's "Quick Change" Tool Mount..... isn't. My vision for a foam board CNC includes hot swappable toolheads so that I can first add a Pen to plot out any graphics and then quickly swap out the pen holder for the needle cutter. Here's a work in progress for a true quick change http://a360.co/2rVF2G5 It has a hook at the bottom that goes over a roll pin pressed through the bottom hinge and a bolt at the top to secure it. I don't have one in use right now, although I have printed both parts. I noticed some gotcha's and need to edit the design.

Aside from all of that, I really came to this thread today to ask you guys a question about vacuum tables. I have one and it sticks great. Maybe too great. I can actually see the grid pattern in the foam I cut after I'm done. FYI, I have a piece of de-papered foam board taped down over the vacuum table channels as a waste board. I have had to poke some holes through it initially because of it being closed-cell foam, but I figured it'd get swiss cheesier after running several sheets through. Any thoughts on controlling the amount of vacuum?

Keep up the good work.
As for why I use wood, it was easy, on hand, and I was looking for insulating the heat from the plastic. I am using a simple set of fins on the tip now, and it stays relatively cool. Using a heat sink to mount the tip sounds good as well.
For vacuum.hold down I don't see any deformation of my stock. My channels are only 1/4" wide and my spoil board has paper on both sides. Originally, I took the paper off the bottom side, but I forgot to do that when I replaced it after about 100 cuts. I also have a small leak where my milling the channels operation went away. I didn't plug it since I am using a shop vac and it needs some airflow to cool the motor. My waste board is perforated with 1/4" holes in a 2" grid. It works well, but if I make another one, I will add another channel in each direction so they are 1" from the edges.
 
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