Cutting foam sheets... with a needle!

[Michael9865]

I recently used the needle MPCNC to cut MPF. I was impressed with how smooth it cut compared to DTF. I had the needle at 5,800 rpm and 500 mm/m.
The MPCNC do not like cutting past about 32". MPF comes 24"X48", so it garbled to cuts over the last section. I made sure that the printer bed in Repetier and Estlcam. So I had a lot of waste.
The pieces stayed in place when I lifted the sheets off the print bed. I started to use a blade to release the cut parts, but I noticed if I bent the sheet on the cuts the parts released and fell out. I guess the needle did a little melting as it cut. I also had to replace the inflation needle because the needle section started rotating away from the head. It was a little bent so it caused some of my straight lines to be a little wavy.
I also added David's cotton and light oil addition to the top of the inflation needle. That helped the needle temp and also changed the sound that the needle head makes while operating. Thanks David for the great idea.
Over all I am happy with the Needle MPCNC. It definitely helps an old fellow with poor grip and problems with his hands going numb.

 

[dkj4linux]

I recently used the needle MPCNC to cut MPF. I was impressed with how smooth it cut compared to DTF. I had the needle at 5,800 rpm and 500 mm/m.
The MPCNC do not like cutting past about 32". MPF comes 24"X48", so it garbled to cuts over the last section. I made sure that the printer bed in Repetier and Estlcam. So I had a lot of waste.
The pieces stayed in place when I lifted the sheets off the print bed. I started to use a blade to release the cut parts, but I noticed if I bent the sheet on the cuts the parts released and fell out. I guess the needle did a little melting as it cut. I also had to replace the inflation needle because the needle section started rotating away from the head. It was a little bent so it caused some of my straight lines to be a little wavy.
I also added David's cotton and light oil addition to the top of the inflation needle. That helped the needle temp and also changed the sound that the needle head makes while operating. Thanks David for the great idea.
Over all I am happy with the Needle MPCNC. It definitely helps an old fellow with poor grip and problems with his hands going numb.

It's very good to hear from you again, Michael... and glad your needle cutter is working well. I used to cut a lot of fan-fold insulation foam (24"x48") with my 26"x19" working-area CNC... I just made sure to lay out parts and generate gcode only for the working area and, after cutting, neatly cut off the excess 22" or so. After a couple of full-sheet cuts, I'd take the two off-cut panels and hot-glue their straight edges to make another near-full sized panel. The needle cutter had no problem with the narrow seam and I was able to minimize the waste that way. And I know what you mean about the hands... mine are now weak and arthritic and tend to cramp a lot when I over-use them. -- David

 

[dkj4linux]

Trying to get back on track...

Playing Jurassic Park and trying to determine the capabilities of my laser was fun but I recognize that I was starting to get rather far afield... so here's my feeble attempt to steer back to something more related to the subject(s) of our thread...

I've really been digging into Inkscape, trying to get a feel for how to generate single-pass (not retraced!) paths for the laser cutter... and using the PDF output from BoxDesigner (http://boxdesigner.connectionlab.org/), I was able to get a test box...



which I then "morphed" (all editing in Inkscape) into a full-sized mockup of the needle cutter...









Finally, I have a lot of thin plywood paneling that I thought I'd try cutting... but it has a really nasty paint on one side that fills the house with a horrible smell. Oh, well...





So, next is to try using the 4.75mm ply from previous tests to make one for real. The motor mount isn't right for some reason and I need to recheck a dimension or two but the joints and fit is near-perfect on the mockup... so I'm overall pretty pleased -- David

 

[GremlinRC]

An upgrade may be a downgrade?

hmmm. i did some work on my cutter today with the objective of enabling higher cutting speed and/or improving quality.

So for the upgrade I replaced the 750kv outrunner with a 1200kv motor. I also replaced the airbrush needle with a mig welding tip. The tip is 0.8mm and is almost a bearing fit for the piano wire needle I have. On first run up there was a mid speed harmonic which nearly blew the thing apart so I added a stabiliser to keep this in check. The stabiliser is ust a spinner nut from the same motor which is sitting on top of a bolt. The nit is deliberately loose so it can rotate left and right slightly as the needle oscillates from side to side. It worked insofar as it kept the resonance in check and I could spin up the needle without the whole thing wanting to launch itself to Mars!



So far so good.

I did some tests continually ramping up the feed speed. I could reach 1000mm/min no problem. That did leave quite a bit of attached foam threads across the cut, but otherwise the cut was clean. The problem I'm seeing is its now started to sort of mash the foam a bit at corners.



I'm at a bit of a loss as to why its doing this. Could I have made the thing just too darn rigid? Maybe it needs a little slack in the guide tube?

 

[x33]

...
...I replaced the 750kv outrunner with a 1200kv motor.
...I did some tests continually ramping up the feed speed.
...The problem I'm seeing is its now started to sort of mash the foam a bit at corners.
...Could I have made the thing just too darn rigid? Maybe it needs a little slack in the guide tube?

Are you heating up the needle (and the foam) too much with the higher speed???

I did some further testing with a more precise needle guide and replaced the ball bearings with a curved guide (on both sides) to prevent the needle to bend to the outside or to run into some resonance oscillations...and balanced the flywheel with a counterweight.
With this, I can work with very high revs, even with a thin needle (0,5mm)

----> By doing some high speed tests, the Depron was slightly smelling (like hot wire cutting).
The reason for heating up was NOT the friction in the guide (had the same effect with some oil in the guide)...the heat was produced from running the needle tip very fast thru the Depron (this kind of foam is "eating" knife blades also)

This was only a test to look for the limits..I will run the cutter with more moderate speed, that will help to keep the whole construction "longer alive"

===> If you are using the cutter for a longer time, it will be a good idea to balance the flywheel very carefully...the small ballbearings in the motor are normaly not very "hightec"...they are cheap mass production parts and will start to make noise after a short time.
.....
Next week, we will start to cut the first real project.



The drawing was made in TurboCad and exported via .dxf into Estlcam to generate the CAM/GCode.
I've found are a few progs for controlling the the GCode

---> CAMotics (free)
http://camotics.org/

---> a BrowserProg (free)
https://nraynaud.github.io/webgcode/

---> NC Corrector v4.0 (free)
http://www.nc-corrector.inf.ua/index_EN.htm

---> a virtual CNC (Milling, Lathe, 3d-Print, Laser Cutter, Robotic )
This is free for 180 days (?????)
https://youtu.be/6p8rTMARzrM

Greetings from Germany...Joachim

 

[dkj4linux]

hmmm. i did some work on my cutter today with the objective of enabling higher cutting speed and/or improving quality.

So for the upgrade I replaced the 750kv outrunner with a 1200kv motor. I also replaced the airbrush needle with a mig welding tip. The tip is 0.8mm and is almost a bearing fit for the piano wire needle I have. On first run up there was a mid speed harmonic which nearly blew the thing apart so I added a stabiliser to keep this in check. The stabiliser is ust a spinner nut from the same motor which is sitting on top of a bolt. The nit is deliberately loose so it can rotate left and right slightly as the needle oscillates from side to side. It worked insofar as it kept the resonance in check and I could spin up the needle without the whole thing wanting to launch itself to Mars!

View attachment 80316

So far so good.

I did some tests continually ramping up the feed speed. I could reach 1000mm/min no problem. That did leave quite a bit of attached foam threads across the cut, but otherwise the cut was clean. The problem I'm seeing is its now started to sort of mash the foam a bit at corners.

View attachment 80318

I'm at a bit of a loss as to why its doing this. Could I have made the thing just too darn rigid? Maybe it needs a little slack in the guide tube?

Dave,

I like the novel way you have added a simple stabilizer into the system... and I suspect that using it will allow you to run a tighter fit needle-in-guide.

Running 1000 mm/min and getting cuts as complete as those seem to be looks as though you are easily putting down 10-15 perforations/mm or more... but that would require 10k-15k rpm on the cutter. Are you really running the cutter that fast?

I'd first try slowing to 6000 rpm and 600 mm/min and see the quality of cut (especially at the corners) for 10 perforations/mm... that's what I recommend for most of us, at least to start with, in DTFB. Then check it at 9000 rpm and 600 mm/min if you can... that is usually on the verge of melting the foam for DTFB (not sure with the FT foam). Find the "sweet spot" for best cut in your foam and then try keeping that speed/feed ratio as you increase the feed rate. Lots of trial and error but once you've got it you should be good to go.

Otherwise, if I had to guess why the "mashing" in the corners, I suspect the needle may need to be sharpened a bit better... aim for a symmetric, conical point, like a sharpened wooden pencil point. I've not cut any of that waterproof foamboard but cutting a tougher, more dense paper may have something to do with it?

Also, with my flywheel cutters especially, I've always tried to equalize the needle flex to each side... striving for a symmetric needle blur. With the larger needle loop to go around the bearing, I've always used round-nose pliers to center the needle's exit angle rather than coming off at a tangent...



to go from a blur like this...



to a blur like this...



-- David

 

[dkj4linux]

Needle cutter progress...

Oh, my! Woke this morning to the patter of little feet... I shouldn't have given up on Tri. He's sturdier than I thought and/or the 3 year-old grand-daughter apparently showed him some mercy. Anyway I thought he and Vel (that's what I call his velociraptor playmate...) were happy but seems Tri's been on the prowl and shows up this morning with *more than a playmate* in tow...





Okay! Enough of that...

I decided to try laser cutting the needle cutter from the 4.75mm plywood from previous tests and was only semi-successful... they're not the cleanest of cuts and the edges are pretty blackened and ugly. I couldn't bear the thought of listening to the air-compressor for a couple of hours however... so simply used the aquarium pump instead for at least some level of air-assist. Apparently there was a "hard" spot of some sort in the area from which the triangular side pieces were so had to finish with an exacto blade... 5 passes at 100 mm/min and a little coaxing and here's the result...



















Actually -- all things considered -- I suppose it was a very successful attempt even though the parts didn't exactly drop out of the sheet. It was all done with just a 3-wattt laser, was certainly less work than cutting by other means... and the fit is fantastic. This has the increased spacing, motor shaft to needle guide, that allows a more relaxed flex and longer needle life. And I still need to add a mount of some sort to affix to my MPCNC. But it's a start... :black_eyed:

Oh! And Rob... Go Cowboys! -- David

 

[RAGII]

David,

I am not expecting much out of the Packers defense today. I fully expect Cowboys to win. Also, where did you find those dinosaur plans. I would love to try some of those when I get my laser running.


So Saturday got done with the in-laws flooring much sooner than I thought. When I got home I cut out some planes that some of my fellow club members have requested before last nights basketball game so I could get a start on the laser setup today. Unfortunately there were other plans made for me. Halfway through the first half of the Basketball game my back started to hurt. By the end of the first half I was in agony and had my wife take me to the ER where I was told I have a Kidney Stone Got home around 10:30 I tried to get some sleep. I can now just about function so it looks like my laser setup will need to wait a few more days yet.

 

[GremlinRC]

By the end of the first half I was in agony and had my wife take me to the ER where I was told I have a Kidney Stone Got home around 10:30 I tried to get some sleep. I can now just about function so it looks like my laser setup will need to wait a few more days yet.

Oh dear. Thankfully I've never had kidney stones, but I understand its up there with the worst pain there can be. I hope you get it sorted asap. Hopefully they can do some ultrasonic blasting and have them cleared up in no time. The lasers and all the other doofers will still be here when you get the important stuff (i.e. your health) sorted. Wishing you the very best for a speedy recovery mate.

Best Wishes,

Dave.

 

[GremlinRC]

I've had a busy day with needle cutter. I decided to go back to basics a bit and get my needle cutter back performing as well as it had been doing and then any new experiments will take place on a nely built cutter. I reinstated the 750kV motor. I found thatthe heat geberated by the high speed and the tight fit of the needle inside the mig welding tip was causing differential expansion in the two metals and thus binding. So in addition to restoring the 750kV, I center drilled the mig weld tip out to 1.5mm. This leaves plenty of room for expansion. I kept the spinner nut stabiliser which works very well for such a simple apparatus.



I took David's advice and reworked the needle to equalise the travel on both sides of the flywheel. I also reduced the travel of the needle by turning a new flywheel with the bearing hub closer to center. This gives me a total needle travel of 9.5mm which minimises the flexure of the needle when cutting. The other thing I hadn't noticed befor was the needle rubbing against the flywheel, so I did a little rework to correct that keeping the needle clear of the flywheel. This also makes the whole thing a lot less noisy.





The end result is a cut which is probably a little tidier that I had before, certainly a little less "hairy" than before.



I also discovered that Joachim is right about too much speed heating the needle an melting the foam. I found that 500/600mm/min works ok with the cutter as is. In theory on 12v I the 750kV motor should go to 9000rpm. So that should be a good fit for 15/holes/mm. I guess going a bit faster would be ok too. I'll try some more tests and see where the line between acceptable an unacceptable falls.

Cheers
Dave.

 

[dkj4linux]

David,

I am not expecting much out of the Packers defense today. I fully expect Cowboys to win. Also, where did you find those dinosaur plans. I would love to try some of those when I get my laser running.


So Saturday got done with the in-laws flooring much sooner than I thought. When I got home I cut out some planes that some of my fellow club members have requested before last nights basketball game so I could get a start on the laser setup today. Unfortunately there were other plans made for me. Halfway through the first half of the Basketball game my back started to hurt. By the end of the first half I was in agony and had my wife take me to the ER where I was told I have a Kidney Stone Got home around 10:30 I tried to get some sleep. I can now just about function so it looks like my laser setup will need to wait a few more days yet.

Rob,

I'm sorry to hear about the kidney stone. My late wife had a successful lithotripsy procedure on hers many years ago. Interesting procedure from a technical viewpoint -- and better than a surgery -- and she was pretty uncomfortable for a few days... but it broke it up and eventually all the pieces passed.

The Packer/Cowboy game was a good game... unfortunately the "wrong" team won. Aaron Rogers is IMO the smartest, cleverest quarterback in the NFL... and, with him running their offense, the Packers best defense is their offense

Though I laser-cut these dinosaurs from 3mm cardboard they can also be needle-cut from foam (or cardboard)... check back in post #1 to see a larger T-rex from DTFB I did for my grandson. I found these particular ones at...

https://discuss.inventables.com/t/dinosaur-and-other-animal-skeletons/12720

We're anxious to see you get back to your laser activities... get well soon. -- David

 

[dkj4linux]

A little more progress...

Took a break to watch football today but still made a little progress...

Cut a new bottom plate to resize and relocate the needle guide hole to a better position below the crankpin...



Threaded the inflation needle guide into the new bottom plate, glued up the assembly, and then printed and attached a quick-change mount to the back...







Mounted the motor and we're almost there...



I'll fab and install a needle, add a cotton-wad oiler/stabiizer, hook up the ESC, servo tester, and power...



And it should be ready to go cut some foam -- David

 

[x33]

Hi David,
what kind of material did you use underneath the ply for laser cutting...may be imortant for "cutting threw"?

.................
A small video from the desktop...
http://www.jokr.de/cutter/cutting_shocky_sim.mp4
...showing the " "NC Corrector" verifying the GCode for the needle cutter.

I hope, we will have some success using the real machine the afternoon

Joachim

 

[dkj4linux]

Hi David,
what kind of material did you use underneath the ply for laser cutting...may be imortant for "cutting threw"?

.................
A small video from the desktop...
http://www.jokr.de/cutter/cutting_shocky_sim.mp4
...showing the " "NC Corrector" verifying the GCode for the needle cutter.

I hope, we will have some success using the real machine the afternoon

Joachim

Joachim,

I just use an old scrap of 3/4" (19mm) plywood underneath... as a spoilboard. You can screw small edge clips directly to it... to hold down thin pieces that don't want to lay flat. -- David

 

[RAGII]

Thanks for all the get well wishes. I was able to pass my Kidney Stone around 1:00 a.m. Still sore but at least the stone is out and it was a short time. Doctor originally stated it might be several days to work its way through.

Plan on working on the laser tonight when I get home. Quick question for you guys, I noticed in the $100 laser write up that 18 AWG (1 mm2 for the metric guys) was the minimum recommended wire size. The JST leads I ordered were advertised as 18 AWG but sure look more like 22 AWG. The wires on the laser diode don't look 18 AWG either which is why I am questioning this. Are you running the larger wire size?

Thanks,

Rob

 

[dkj4linux]

Thanks for all the get well wishes. I was able to pass my Kidney Stone around 1:00 a.m. Still sore but at least the stone is out and it was a short time. Doctor originally stated it might be several days to work its way through.

Plan on working on the laser tonight when I get home. Quick question for you guys, I noticed in the $100 laser write up that 18 AWG (1 mm2 for the metric guys) was the minimum recommended wire size. The JST leads I ordered were advertised as 18 AWG but sure look more like 22 AWG. The wires on the laser diode don't look 18 AWG either which is why I am questioning this. Are you running the larger wire size?

Thanks,
le
Rob

Rob,

Congrats on passing that stone

I generally take a cue from any wires already attached at the "factory"... and try to make sure I'm using at least that size wire for short-ish runs. For longer runs, I try to size up a bit if it is for power or high-current. The wire itself can handle substantially higher-than-recommended current before it is in danger of "fusing"... touch it and if it isn't warm/hot you're probably okay. Watch the connections/connectors though.. they shouldn't get hot. For signal leads, like the TTL leads, I wouldn't worry too much... there's no real current flowing in those. It is also possible you'll need to re-route and/or use shielded-cable for signal leads that are sensitive to nearby AC... air compressors, and such.

Hope this helps. -- David

 

[x33]

laser - honeycomb bed

...I just use an old scrap of 3/4" (19mm) plywood underneath...-- David

May be that a honeycomb bed will help to cut through more easy??? Because you do not have to heat up the material underneath during the last cutting pass - only an idea
http://www.cutlasercut.com/resources/tips-and-advice/burn-heat-marks-and-how-we-prevent-them

 

[x33]

Fist "real world" success with the needle

Having tested the GCode virtally, we loaded the code into the mill...and had a real, nice success!







the hole is 3mm


I tested some improvements on/with my first prototype

The small wooden blocks between the needle guide and the ball bearings are preventing the thin needle to flex or to resonate. The needle is 0,5mm

The new needle guide is a migmac welding tip (0,8mm)


with a pressed in short tube. This tube is a part from a bigger hollow injection needle (the type for refilling printer catriges) and fits very tightly.


There was no heating up while cutting all parts...

 

[GremlinRC]

Having tested the GCode virtally, we loaded the code into the mill...and had a real, nice success!

That is an excellent result Joachim. Incredibly clean. I have some questions. What feed speed did you run at? Also do you have any paper covered foamboard for a little test. I would like to see how it performs. I find breaking the paper is the hard part. I will probably cheat and make a copy of your variation and see how I get on. Hope you approve.

Regards,

Dave. (in strangely mild Dublin. (9C - 48F))

 

[GremlinRC]

Hi David,
what kind of material did you use underneath the ply for laser cutting...may be imortant for "cutting threw"?

I don't use anything. I just rest the edges on some stepped clamp risers. I find that leaving it down on wood or metal allows the smoke to creep underneath and stain a lot. I don't get that if I keep it "off the floor".

Speaking of lasers, here's a little frivolous project I carried out over the weekend with the help of my niece. She's 11 and I taught her how to use Cambam and generate GCODE. Of course I totally supervised and controlled the laser parts, but I still let her push the buttons.



She's Nicole, Lauren is her little sister.

Regards,

Dave.