Cutting foam sheets... with a needle!

[x33]

....you have to take care of a good, long needle guide to minimize the movement to the sides...the needle is suppost to punch "straight"...

a quick and dirty illustration

the excenter is moving the needle in a "not-only-linear" motion, as you can see on the right.
You can minimize this by using long guide-rails (left side and photo)

 

[IsmaelPR77]

a quick and dirty illustration
View attachment 121150
the excenter is moving the needle in a "not-only-linear" motion, as you can see on the right.
You can minimize this by using long guide-rails (left side and photo)
View attachment 121151

After tweaking, I realized that even though I have the phone book secured all the way around there are areas in the center where the foam board kind of bows up a little bit due to the fact that foam board is never perfectly flat. so at any point when the foam board that is being cut isn't perfectly flat against the spoil board underneath that's when you get jagged edges on the underside of the cut. I am going to work on a guide of sorts that sits underneath the needle cutter that basically just comes in contact with the foam bored enough to just keep it perfectly flat but not dent or markup the foam board.

 

[dkj4linux]

Until you get a vacuum hold-down setup built... place the foamboard on the spoilboard "crown down" (like a giant dinner plate) so that the center section presses against spoilboard. Then simply weight/pin the corners/edges and the foamboard should lie reasonably flat for cutting. You really don't need anything too fancy.

A good project for your new needle cutter might be to make a vacuum hold-down pad. Three sheets of foamboard... slots east-west on one, slots north-south on second, and holes at the "intersections" of the stacked slotted sheets on the third.

Print "moebeast"'s really neat plenum...

and, finally, contruct the foamboard stack, fit the plenum, hook up a shop-vac and... voila! A vacuum pad hold-down for your needle cutter system... please forgive the noise and poor video quality

A even better, more informative video from Jason ("jhitesma") detailing the construction of a foamboard vacuum hold-down system can be found here:

Have fun!

-- David

 

[IsmaelPR77]

I have thought about the idea of a vacuum table (which looks awesome) but I have my MPCNC located in my office/workshop inside my house and the sound would be too much too work in that space while the vacuum is running. I am working on a spring loaded guide of sorts that will be attached to my needle cutter and will lower with the needle cutter and make light contact with the foam board keeping it flat while a cut is being made. Still testing a rough prototype I just need to make it more permanent. I really appreciate all the help and tips that I have received so far in this group!

 

[x33]

The "MPW-CNC " ---> (Mostly Professionell Wired CNC"


Hi, I'm just renovating the older HAASE CUT 2000...so I cleaned all the lead screws and rails very carefully...but the test run with the new electronics (based on arduino) was not very satisfying at higher speeds --> The machine was skipping some steps on the main axis!

I found out that the cables to the steppers are real thin...as you can see on the photo (the marked wires).

These thin cables are very long (nearly 2m) which will be no very clever idea....the next funny thing is to run the motor-wires in parallel within the same cable-shielding as the wires for the microswitches!

After taking the pictures, I ripped off all this mess and connected (for a test) the x-axis with 4 single wires to the amp...and everything was working fine.

So I will redo all the wiring, using thicker strands and using extra shielded cables for the switches....may be, this will look a little more professionell

Greeting...Joachim

 

[IsmaelPR77]

Hi @dkj4linux while the thought of a vacuum hold down is tempting, I don't want to deal with the noise from a running shop vac, especially on late nights. My ideas is to create some sort of guide that will lower and come in contact with the foam board but here is my dilema. I cut at the following depths .5mm, 2mm and 6mm when cutting plans. So I will need a guide that will come down and touch the foam board when the .mm cuts are being made but that it doesn't have too much resistance and allows the cutter to come down another 6mm when doing the full cuts. I hacked together the following (see pictures) basically a pencil with a felt pad to allow it to slide around as the needle cutter moved along. The issue there is that the pencil could only be set to come in contact with the foam board at one depth. I need something that won't take up too much room, can take the lateral forces when the cutter is moving around and not bend or bread but still keep light but contact pressure on the foam board keeping it perfectly flat while it is being cut. I have confirmed that when the foam board is nice and flat the cut lines are crisp but when the board isn't flat then what happens is that it "bounces" while being cut leading to jagged and rough edges. I was able to replicate and confirm this issue over and over. FYI I am running near 10k RPMs and cutting at 20mm/s and the cuts look great when the foam board is pressed nice and flat. The motor barely pulls 1A.

Any ideas on what I could use or design to provide that needed tension? A spring setup or plunger? A guide of some sort? Looking for ideas.

 

[dkj4linux]

Check out Neil's (iGull) depron cutter and presser foot posts from earlier in this thread... he's made a really slick machine. Note that his cutter motor pivots slightly (up/down), under servo control, relative to the main needle guide... this allow setting different cut depths with a stationary guide. The presser foot lightly presses against the surface of the foamboard... similar to the presser foot on a sewing machine.

I don't see why your idea wouldn't work as well... though I suspect a coaxial setup like Neil's would be better than an offset pressor foot, for when you approach the edges of the foamboard.

I like where you are going with this. Please keep us posted on your progress. -- David

 

[IsmaelPR77]

Check out Neil's (iGull) depron cutter and presser foot posts from earlier in this thread... he's made a really slick machine. Note that his cutter motor pivots slightly (up/down), under servo control, relative to the main needle guide... this allow setting different cut depths with a stationary guide. The presser foot lightly presses against the surface of the foamboard... similar to the presser foot on a sewing machine.

I don't see why your idea wouldn't work as well... though I suspect a coaxial setup like Neil's would be better than an offset pressor foot, for when you approach the edges of the foamboard.

I like where you are going with this. Please keep us posted on your progress. -- David

That looks like a neat idea but the more that I mess with it, it looks like it will either hit my edge clamps at the front or back (depending on setup_ when cutting close to the edge. May need to rethink it, as I am very opposed to running a shop vac at this time.

 

[jhitesma]

I've thought about the foot idea for awhile...just haven't had the time or energy to try and implement anything.

I remember someone used a plastic spoon as a foot and I like the general idea - something rounded so it can glide over already cut spots and edges.

I also agree that something like Neil's which goes around the guide makes sense. But his design relies on raising/lowering the motor which isn't easy to implement in a traditional CNC. I mean it would be possible to do some crazy over engineered setup with gears that adjust the foot distance based on the Z height. That could be fun to design but I don't think it would be very practical.

So I'm leaning towards something spring loaded, that rides over the needle guide. I don't think a 3D printed foot would be optimal though since I'd want it to be smooth. Yeah, you could sand it and such to make it smooth...but I'd rather find something common that most people would have on hand - and is nicer looking than a plastic spoon

 

[x33]

Hi, this guy had problems milling thin materials even with a vacuum table
http://www.cnc-area.de/wbb3/index.php?thread/7262-cnc-niederhalter-für-80mm-spindeln/

He is pressing down the sheet with a bigger ring..
Links to pictures
https://www.dropbox.com/s/67act99xbhogoa7/CNC-Niederhalter für 80mm-Spindeln 22.jpg?dl=1
https://www.dropbox.com/s/wudyypg7jjre94i/CNC-Niederhalter für 80mm-Spindeln 18.jpg?dl=1

...where the sliding part is made from POM
https://www.dropbox.com/s/89mffurv1frbfbg/CNC-Niederhalter für 80mm-Spindeln 15.jpg?dl=1

The problem with this construction will be in not hitting the clamps ;-)

 

[jhitesma]

Interesting setup...I had to google POM...most US people would probably recognize DuPont's version "Delrin" more readily. But it's also known as Acetal or Polyacetal when not referencing the trademarked name.

Definitely a good choice for a foot. Delrin is nice slippery stuff that's super easy to machine.

Interestingly enough I just learned that you can 3d print it: https://gizmodorks.com/acetal-3d-printer-filament/

Though it sounds tricky to work with. Doesn't stick to most common printer bed materials, likes to warp, shrinks after printing, and heat it a bit more than needed for printing and it will start to give off formaldehyde gas

Definitely a better material to machine than print! Thankfully most needle cutters can also run a spindle

 

[x33]

Here comes a source where you can buy laser cutted parts
https://www.sculpteo.com/en/lasercutting/laser-cutting-materials/pom-material/

workshop in San Leandro, California.
Sculpteo
169, 11th Street
San Francisco, CA 94103
UNITED STATES
Tel : 1-800-814-1270

A few more infos on the material
https://hackaday.com/2016/03/03/materials-to-know-acetal-and-delrin/

 

[IsmaelPR77]

So I have changed my mind on the needle cutter setup. I bought a 1/32 inlay router bit for my Dremel, designed up a mount for my MPCNC and will not look back! Cutting reliably at 25 - 30mm/s. Clean crisp cuts, I can even do reference cuts/marks as well. Not too shabby. One sheet the Dremel barely warms up.

 

[Nactan]

So I have changed my mind on the needle cutter setup. I bought a 1/32 inlay router bit for my Dremel, designed up a mount for my MPCNC and will not look back! Cutting reliably at 25 - 30mm/s. Clean crisp cuts, I can even do reference cuts/marks as well. Not too shabby. One sheet the Dremel barely warms up.

Where did you find that bit? All the 1/32" inlay bits I've found only have a 1/8" max depth of cut.

 

[IsmaelPR77]

Where did you find that bit? All the 1/32" inlay bits I've found only have a 1/8" max depth of cut.

I bought it on Amazon but they are now out of stock and the listing is gone!

But I am going to get some of these, they have an even slightly deeper cut https://www.ebay.com/itm/1-32-Dia-x...e&pageci=e71d8ac9-7aa9-4e29-84a5-5fa1bc9f9288

 

[Nactan]

I'd be curious to know if a downcut or upcut makes a difference. I suppose downcut would leave a nice pretty top surface but the bottom surface might have some fuzz. Then vice versa for the upcut.

 

[Headbang]

Jhitesma thank you. Followed your setup for a vacuum table. My cuts have never so accurate! I am within 0.5mm end to end now!

 

[IsmaelPR77]

The second plane that I cut with my MPCNC Needle Cutter. The FT Mini Sportster. I'm happy with it.

 

[dkj4linux]

The second plane that I cut with my MPCNC Needle Cutter. The FT Mini Sportster. I'm happy with it.

Absolutely super needle cutter and plane! I'd love to see more pics/detail with regards to your cutter... any plans to share it? -- David

 

[TheSFReader]

Oh, yes, and what that sensor is ? Is it used to control speed on the motor ? Do you use any kind of feedback control ?