Cutting foam sheets... with a needle!

[dkj4linux]

SnowB1,

Jason Hitesman did the Onshape CAD of a vacuum scheme we talked about back in the summer 2016 in this thread... and it's the one I used with my FoamRipper. Several design ideas were presented but the simplest was the 3 sheet stack of DTFB... bottom layer of N-S slots, middle layer of E-W slots and a top layer of holes at the intersections of the slots. All slots and holes are 1/4" (6.35mm), spaced 2" (50.8mm) apart, and centered on the sheets so that when stacked with edges aligned, all the slots and holes also align.

The sheet being cut is, of course, placed on top of the stack and vacuum applied. The whole stack sucks down to the worktable and holds the uncut sheet securely. I have found that using an inexpensive router speed control, at lowest speed setting, with the shop vac reduces the noise greatly while still providing enough suction to keep the stack in place. You may find it necessary to start suction at full-speed to "set" the stack and then reduce the speed to maintain it while cutting.

Jason's Onshape design is here ... Jason's CAD documents. This link along with Moebeast's Foam Ripper are both in the description of Jason's construction video... which I recommend watching. Moebeast's fancy printed plenum is one of the "things" he provides on his TV page.

Enjoy! And let us know of your progress

-- David

 

[dkj4linux]

I found the DXF files I used to create gcode for my vacuum pad...

 

[Snow-B1]

I found the DXF files I used to create gcode for my vacuum pad...

Thank you so much, this will help out so much.
Randy

 

[jhitesma]

I'm actually getting ready to make a new vacuum table. The one I made in that video has served me well but the top sheet is really getting ratty...and I stored it on it's side and something fell against it so it's now warped and my little quieter vac isn't strong enough to force it flat anymore But for $3 in materials it's served me very well the past few years and I don't mind spending another $3 and 30 minutes to make a new one

 

[Danjoga]

Hello all. This is my first time posting but I've been following this thread somewhere what and actually built a needle cut for my MPCNC. I've basically have had some success and some problems like most people. I also made a vacuum table. But in my search for knowledge and trying to come up with a better design, I decided to take an old jigsaw apart and was going to basically scale it down to a smaller size and power it from a RC motor.
I came across a small jigsaw that runs on 12vdc at 6900 strokes per minute. I couldn't come across any specs for the stroke length but went a head and ordered one at a cost of $65.00 plus shipping. I just got it today and the first thing I did was measure the stroke, which is just under 6mm. I figure that even if I have to set it up to do 2 passes it should work ok.

That is a picture of it setting next to my needle Cutter for a size comparison.

That is a picture of the output shaft which has a round hole in the center that seems to hold a piece of .025 music wire nicely and with a little practice one should be able to get it to go straight up and down with no flex.
I did a test cut by hand and here is the results.

I ordered it from www.micromark.com.
It comes with a cord that is just over 3' long. They sell a couple different power supplies. One is a constant 12vdc and the other is a variable with digital read it for voltage and current. I opted to just use 12 vdc from my MPCNC which is a 30 amp 12 vdc.

If I put this in the wrong place or if it's too lengthy I apologise.
I may try and take a video of a hand test cut and post it.
Hopefully I did this right. Here is a link to the video on YouTube.

 

[dkj4linux]

Danjoga,

Thanks for posting... and welcome. This is a fine place to talk about what you've done here and the length is not a problem

That's an interesting little jigsaw... looks like fun to play with.

I'm more interested, however, in your "some successes and some problems" with the MPCNC and needle cutter you've already built. What you show looks pretty good and I'd suspect you're very close to having a really nice foam-cutting system... and you've already done all the hard part!

I'd love to help you get that needle cutter going. What are the problems you are seeing with it?

I'm not trying to talk you out of playing with the little jigsaw -- please don't stop playing with it -- but, long term, I really think that the needle cutter will give longer life and more satisfactory service. The needle cutter is very inexpensive and purpose-built and can be made to work quite nicely... and you've already built it! And you won't have to just "settle" for the extra expense and operational limits the little jigsaw's manufacturer provides.

Again, welcome!

-- David

 

[Danjoga]

Okay, here goes. First I'm going to explain the basic setup of my machine and try to give credit where it's do that I can remember.

My MPCNC I bought the kits from V1. The printed parts, pre-burly. The hardware nuts, bolts bearings etc, Rambo V1.4 with display. My original goal was to be able to cut a 4 X 8 sheet of plywood for Christmas decorations. Was going to go with 4 X 4 initially with plans to expand. And yes I know the "Should have gone with the Low Rider" but at the time Ryan was in the process of the redesign of the Low Ryder and the kits were out of stock so I figured I would try the MPCNC. I initially put a Dewalt 660 on it. I also have a couple diode lasers for it. 1 - 5 watt and 1 - 15 watt.
I ended up with about 900mm X 900mm X 150mm usable area. I was also thinking about trying to add an extruder to it. I started out with 6 amp 12 volt power supply. When I bought my 3D printer the 30 amp power supply that came with it wouldn't handle the heated bead that came on the printer and the voltage would drop by over 2 volts which fried the main board and display. I put a 50 amp on the 3D printer and re-purposed the 30 amp for the MPCNC.

I built a vacuum table out of blue styrofoam from Lowes.
For a vacuum source I used a 3D printed cyclone that I found an Instructable on by Nikus that uses a 12 volt dc motor.
I used some ideas from Peter Passuello at CNCNutz Episode 210 and 211, mainly the hole pocket size and the small hole to the vacuum chamber and the idea of the news paper between the table and the foam board that I'm cutting.

Now the part about "some successes and some problems"
1. I haven't been able to get things balanced very good on the flywheel and I'm getting quite a bit of vibration.
2. My Z axis is dropping on me. When I start to cut things are ok but as it progresses the needle starts to drag across the foam when it's suppose to be above the foam. My temporary solution is a mechanical stop for the Z to keep it from going too low. I think that this might be caused by item 1.
3. I keep breaking needles where I've bent the loop to go around the bearing. I actually ordered v-groved bearings which are pretty cheap and I've had to replace 3 already, good thing they came in a 10 pack. I think I got the breaking problem solved. I found an article on heat treating music wire by Roy Vaillancourt
http://www.vaillyaviation.com/images/Working Heat Treated Music Wire _web_.pdf
4. It seams as though the cut lines are pretty jaged. I started with a .035 mig tip and have went to a .030 mig tip. I bought some. .025 mig tips but the wire that I got is bigger then the hole. By going with the .030 it smoothed the cut out some but its still not where I would like it to be.

When I get home from work today my first step is going to be to design and print a mount for the mini jigsaw and see what kind of results that I get. I will also try and get some pictures of my set up of the vacuum table and such.

 

[dkj4linux]

..I ended up with about 900mm X 900mm X 150mm usable area
...
Now the part about "some successes and some problems"
1. I haven't been able to get things balanced very good on the flywheel and I'm getting quite a bit of vibration.
2. My Z axis is dropping on me. When I start to cut things are ok but as it progresses the needle starts to drag across the foam when it's suppose to be above the foam. My temporary solution is a mechanical stop for the Z to keep it from going too low. I think that this might be caused by item 1.
3. I keep breaking needles where I've bent the loop to go around the bearing. I actually ordered v-groved bearings which are pretty cheap and I've had to replace 3 already, good thing they came in a 10 pack. I think I got the breaking problem solved. I found an article on heat treating music wire by Roy Vaillancourt
http://www.vaillyaviation.com/images/Working Heat Treated Music Wire _web_.pdf
4. It seams as though the cut lines are pretty jaged. I started with a .035 mig tip and have went to a .030 mig tip. I bought some. .025 mig tips but the wire that I got is bigger then the hole. By going with the .030 it smoothed the cut out some but its still not where I would like it to be.
...

That is a large, nearly 4'x4', MPCNC... okay for light loads (laser, needle cutter, etc), not so much for Dewalt or extruder. The MPCNC's I used at the beginning of this thread were 4'x4' and were fine for needle-cutting or pen-plotting, but not much more

Flywheel balance is pretty crucial, as you've seen. Just looking at your first photo (and I could be wrong)... at what appears to be a relatively old cutter body design, adapted for bearings vs sideboards? It looks a bit short-bodied, motor shaft to guide bearings, compared to later designs (shorter results in more severe needle flex), the eccentric bearing looks to be positioned further out on the flywheel (again, resulting in more severe needle flex), your mounting hardware and bearings appear pretty heavy (heavier weight, positioned further out, is much harder to balance out), and you are using thicker/stiffer needle wire (more resistant to tight bends and flex over a shorter distance) if it won't go through the hole in a 0.025" welding tip (hole diameter ~0.032"). I suspect these are the major culprits for vibration problems and needle breakage issues you cite.

My most successful needle cutters to date work best with ~ 0.025" music-wire needles, a motor shaft to guide separation of about 2.5" (65mm) minimum, an eccentric offset of 6mm-7mm (total stroke of 12mm-14mm), and minimal/lightest bearing and mounting hardware (easier to balance). I use a 0.025" welding tip with the 0.025" needle and get decent cuts in DTFB at cutter speeds of 6000-8000 rpm and feed rate of 600-1000 mm/min (10-15 perforations per mm). I also trust the factory heat-treatment of the music-wire to be better than what I could do... so I don't do any and have never had problems with needle breakage. Ragged cuts can result from a number of things... too little/soft spoilboard support, too fast/slow cutter speed and/or feed rate, dull/bent/barbed needle point, etc.

If/when you want to start playing with the needle cutter, I think you'll have better success if you'll stick pretty close to the dimensions and operating parameters listed above.

One option, since you are using the same Emax CF2822 motor I am -- and can 3d print... you could try the slip-on flywheel I've been using on my last couple of cutters. It seems to be far easier to balance than shaft-mounted flywheels, runs smoothly to 8000 rpm and more, and yields a more compact cutter. It can be a tricky print as it's a snug fit over the motor bell (but doable with just a bit of trial and error) and provides a small free-wheeling "post" though the eccentric bearing's center to affix the needle to... far easier than the larger-loops-on-outer-race you're currently using. Check here and in the following posts to see how to set it up... and all the parts are out on Thingiverse, including a blank cutter body for the shorter "cantilever" length. Here it is in action...

Another option is to use Jason Hitesman's popular needle cutter design, or similar... Improved needle cutter. Lots of these have built and it seems to work well for most folks.

Please keep us posted with your progress with the little jigsaw and needle cutter. And let us know if you need further information and/or assistance.

-- David

 

[Danjoga]

That is a large, nearly 4'x4', MPCNC... okay for light loads (laser, needle cutter, etc), not so much for Dewalt or extruder. The MPCNC's I used at the beginning of this thread were 4'x4' and were fine for needle-cutting or pen-plotting, but not much more

Flywheel balance is pretty crucial, as you've seen. Just looking at your first photo (and I could be wrong)... at what appears to be a relatively old cutter body design, adapted for bearings vs sideboards? It looks a bit short-bodied, motor shaft to guide bearings, compared to later designs (shorter results in more severe needle flex), the eccentric bearing looks to be positioned further out on the flywheel (again, resulting in more severe needle flex), your mounting hardware and bearings appear pretty heavy (heavier weight, positioned further out, is much harder to balance out), and you are using thicker/stiffer needle wire (more resistant to tight bends and flex over a shorter distance) if it won't go through the hole in a 0.025" welding tip (hole diameter ~0.032"). I suspect these are the major culprits for vibration problems and needle breakage issues you cite.

My most successful needle cutters to date work best with ~ 0.025" music-wire needles, a motor shaft to guide separation of about 2.5" (65mm) minimum, an eccentric offset of 6mm-7mm (total stroke of 12mm-14mm), and minimal/lightest bearing and mounting hardware (easier to balance). I use a 0.025" welding tip with the 0.025" needle and get decent cuts in DTFB at cutter speeds of 6000-8000 rpm and feed rate of 600-1000 mm/min (10-15 perforations per mm). I also trust the factory heat-treatment of the music-wire to be better than what I could do... so I don't do any and have never had problems with needle breakage. Ragged cuts can result from a number of things... too little/soft spoilboard support, too fast/slow cutter speed and/or feed rate, dull/bent/barbed needle point, etc.

If/when you want to start playing with the needle cutter, I think you'll have better success if you'll stick pretty close to the dimensions and operating parameters listed above.

One option, since you are using the same Emax CF2822 motor I am -- and can 3d print... you could try the slip-on flywheel I've been using on my last couple of cutters. It seems to be far easier to balance than shaft-mounted flywheels, runs smoothly to 8000 rpm and more, and yields a more compact cutter. It can be a tricky print as it's a snug fit over the motor bell (but doable with just a bit of trial and error) and provides a small free-wheeling "post" though the eccentric bearing's center to affix the needle to... far easier than the larger-loops-on-outer-race you're currently using. Check here and in the following posts to see how to set it up... and all the parts are out on Thingiverse, including a blank cutter body for the shorter "cantilever" length. Here it is in action...

Another option is to use Jason Hitesman's popular needle cutter design, or similar... Improved needle cutter. Lots of these have built and it seems to work well for most folks.

Please keep us posted with your progress with the little jigsaw and needle cutter. And let us know if you need further information and/or assistance.

-- David

The wire I bought is labeled as .025" and actually measures as .0285"
This is the link for the stuff that I used. https://www.thingiverse.com/thing:1211039
The bearing that I used is 2.2 grams.
I downloaded the improved cutter but the motor hole pattern doesn't match my motor.

 

[Danjoga]

Here is my first test with the mini jigsaw.

And here is a video of my basic setup.

 

[dkj4linux]

Danjoga,

I'm actually quite impressed the jigsaw does as well as it does... but you'll need to slow the feed rate in order to get complete cuts. Judging from the distance between holes, I'd suggest trying 1/2, 1/3, 1/4, etc. the feed rate you are currently using.... until the perforations overlap, say 50%, and the cut is smooth and complete. It seems to have promise!

Jason's cutter was, of course, designed with a particular motor hole pattern in mind. If you have, or can get, one that's great... if not, you might try altering his cutter body to fit a similar motor you might already have on hand (which is what I generally do). What CAD program(s) are you familiar with? With many, it's pretty straight-forward to do boolean operations to fill, or create, holes... and merge bodies together. If you don't have a favorite, Tinkercad is a free, online, easy to use program that has this capability... I've used it many times to quickly alter, or create new, features on existing STL's, such as a different tool mount or mounting hole pattern. Just bring in the appropriate STL's -- say, a cutter body and a mount you want to use -- difference out the bits of each that you don't need and then align and union the remaining parts.

Yeah, the cutter body you used from Thingiverse is a pretty old design. Please recognize that the needle cutter's on-going development is strictly DIY and has been done completely out in the open (in the forum "fishbowl")... where all can see. And what is presented is a 3-1/2 year chronological timeline of all developments, both mine and others... both good and, sometimes, not so good. Generally speaking, it is preferable to borrow ideas from more recent designs than earlier ones... as many improvements, some quite subtle, have been made over that time. My slip-on flywheel and cutter tries to incorporate those improvements... as did Jason's cutter, from 1-1/2 years ago. Even my earliest cutters, however, successfully cut foam... so a carefully constructed early version cutter might well out-perform a later version, that's not as carefully constructed. The general dimensions, components, and operational guidelines I gave in my previous post -- and my critique of what I saw in your photo -- reflects what we've learned over that time period... and why I recommended them to you. While they are not "gospel" or sacred... they do represent good starting points.

-- David

 

[Danjoga]

Danjoga,

I'm actually quite impressed the jigsaw does as well as it does... but you'll need to slow the feed rate in order to get complete cuts. Judging from the distance between holes, I'd suggest trying 1/2, 1/3, 1/4, etc. the feed rate you are currently using.... until the perforations overlap, say 50%, and the cut is smooth and complete. It seems to have promise!

Jason's cutter was, of course, designed with a particular motor hole pattern in mind. If you have, or can get, one that's great... if not, you might try altering his cutter body to fit a similar motor you might already have on hand (which is what I generally do). What CAD program(s) are you familiar with? With many, it's pretty straight-forward to do boolean operations to fill, or create, holes... and merge bodies together. If you don't have a favorite, Tinkercad is a free, online, easy to use program that has this capability... I've used it many times to quickly alter, or create new, features on existing STL's, such as a different tool mount or mounting hole pattern. Just bring in the appropriate STL's -- say, a cutter body and a mount you want to use -- difference out the bits of each that you don't need and then align and union the remaining parts.

Yeah, the cutter body you used from Thingiverse is a pretty old design. Please recognize that the needle cutter's on-going development is strictly DIY and has been done completely out in the open (in the forum "fishbowl")... where all can see. And what is presented is a 3-1/2 year chronological timeline of all developments, both mine and others... both good and, sometimes, not so good. Generally speaking, it is preferable to borrow ideas from more recent designs than earlier ones... as many improvements, some quite subtle, have been made over that time. My slip-on flywheel and cutter tries to incorporate those improvements... as did Jason's cutter, from 1-1/2 years ago. Even my earliest cutters, however, successfully cut foam... so a carefully constructed early version cutter might well out-perform a later version, that's not as carefully constructed. The general dimensions, components, and operational guidelines I gave in my previous post -- and my critique of what I saw in your photo -- reflects what we've learned over that time period... and why I recommended them to you. While they are not "gospel" or sacred... they do represent good starting points.

-- David

First off I use Fusion 360 for the most part. I'm still in the learning stage but I've used Auto Cad at work for years.

Okay, I did have the feed rate a little bit high. That was at 4000mm/min. I slowed it down to 1000mm/min.

I've attached some pictures of the cut with my new mount for the jigsaw.

I may actually need to adjust my z-axis home down a little to compensate for the taper of the needle. I actually did the cut in 2 passes. I probably cold have done it in 1 pass. The next time I will try 1 pass.


A video of the jigsaw cutting. It's hard to get a picture of the needle because of the base.

I put the holder up on Thingaverse. This the first time so I hope it made it there.
I included a some more pictures of the jigsaw in the holder and one with the needle fully extended and one with it fully retracted.

https://www.thingiverse.com/thing:3670793

 

[dkj4linux]

Danjoga,

That's quite impressive. That's the first time I've ever seen a store-bought, practically out-of-the-box working cutter. Most of the time they don't have enough stroke to cut completely through DTFB... but the DOC on that little machine appears to be ~9/32" (max cut). That might well be a great option for folks that don't have the tools, time, or desire to build one. $65 for the jigsaw seems reasonable enough... did you also have to purchase the $95 transformer?

I assume that last photo is a stack of cut edges? Looks as though the foam has been cut beautifully. Only the bottom-side paper shows any sign whatsoever of incomplete cuts... but, of course, a few minutes with an Xacto blade won't be a problem for most here. If you can tolerate just a few minutes more per sheet and maybe have the parts drop out of the sheet... you might want to check out feed rates of 600-700 mm/min. If the cutter is actually running 6900 strokes per min at 12v, a feed rate of 690 mm/min should give 10 perforations per mm of linear travel. In my experience, 10-15 perforations per mm gives very nice, complete cuts in DTFB, with paper on.

Again, impressive. I think you're really on to something here. I guess all that remains to be seen is how durable and long-lasting it is

Good work... and thanks for sharing. I -- and I'm sure a bunch of other folks -- will be interested in hearing more about this neat little machine and the work you're doing with it. Keep us posted, please!

-- David

 

[Danjoga]

Pictures of latest cuts. This was done with multiple passes at 1000mm/min. The temperature rise on the mini jigsaw was 25 deg F. It went from about 80 deg ambient to 105 or so over about 1 hour. The parts came out with out much effort.

 

[dkj4linux]

This is a DIY and CNC forum and you give virtually no information about what you're trying to do. You don't HAVE to do anything. And you're probably in the wrong place if you can't determine if you need a "jigsaw" or not. Danjoga is using a *tiny* modeler's jigsaw in a very unconventional way to cut foam... I prefer DIY needle cutter at 1/8 the $$$ and purpose-built to my need.

 

[rockyboy]

I think that's a spammer's initial post creation without the links to the malicious sites to get past the security. In a couple hours the account will go back and edit the post to insert the nasty links to try and lure people in.

 

[dkj4linux]

Thanks, Rockyboy! Not being a "real" moderator... is there something I need to do? Can posts like that be deleted?

 

[rockyboy]

Thanks, Rockyboy! Not being a "real" moderator... is there something I need to do? Can posts like that be deleted?

I hit the little "report" button next to the post and one of the moderators took care of it.

Thanks for all you do for this hobby & thread David!

 

[dkj4linux]

Thank you!

 

[Snow-B1]

Just when I think I am ready to cut out a new plane, I keep breaking needles. I have tried the needle keeper like Mobeast and the wire around the bearing like David and Jason. Each time I set my rpm to around 6000 rpms and let the machine just run without the needle even touching the foam board. Around 5 min of running the needle will break, so far I have tried different motors, motor mounts, esc's with no luck. Last night I think I found my problem, I think I have a faulty servo tester. Using my tach, I took constant readings that went from 12000 rpm's to the motor just bumping, without touching the dial. I then pecked the servo tester and the motor started again. The servo tester that I am using is a inexpensive one that I purchased from Amazon. Does anyone know of a better option or a more reliable servo tester or did I just get a dud.​