Cutting foam sheets... with a needle!

[CMS_1961]

David,

Nice work! Looks great. I may have to build one of these low riders . I just have to make room.....too many hobbies/projects going on...anyone looking for an LS1 engine and 4L60E transmission?? LOL It takes up so much space.

My MPCNC is working great and takes up a lot of garage space as well, but that low rider looks like it would be a great project with all the upgrades/improvements you have made.

Thanks for all the work you have done,
Chalie

 

[edojr]

Here is my cutter.

 

[dkj4linux]

Here is my cutter.
View attachment 129773 View attachment 129774

I've not used that particular cutter design -- though many do -- and I see a couple of things of note...

There doesn't appear to be any counter-weighting to offset the weight of the eccentric bearing and its hardware; i.e. it's not a balanced system. I would expect vibration to be a problem and get worse as you increase the cutter's rpms. Is vibration why you've been running at so low rpms? I'd recommend printing a better flywheel... one that has enough holes provided directly across from the bearing for adding counter-weight. I know this flywheel looks a bit clunky -- but ran smoothly -- and note all the counter-weight to offset the needle bearing and hardware...

Another thing... note how your needle shaft comes off the loops at a tangent... and the needle hangs from the 6 o'clock position while the bearing is at 4:30? When the bearing and needle are at 9 o'clock, the needle is experiencing a greater flex than when at the 3 o'clock position. Take a look at at your needle "blur"... it probably looks like it's not centered over the guides. it should look "symmetric" above its entry point into the guides below, to minimize friction and the entry angle into the guides... similar to this

You can correct it by putting one more bend -- using round-nose pliers -- so that the needle exits the loops in line with the center of the bearing, like this...

Possibly you could minimize your needle breakage by insuring the direction of motor rotation is clock-wise (face on view), so that when the needle bearing is at 3 o'clock, it is on the DOWN-stroke. But bending the needle to get a symmetric needle blur (equal flex both sides) is, I think, the better fix.

"Tuning" a needle cutter to run and cut smoothly can really be a fiddly procedure. I'd start with these things and see the effect, if any. Then we can go from there.

-- David

EDIT: Another thing that occurs to me this morning... does the outer race of that bearing roll freely, without dragging on anything? It looks quite close to the face of the flywheel in your 2nd photo... can't quite tell but it looks as though the outer race might have grooved the plastic behind it at some point? You could also probably stand to put another loop in you needle as well... looks to be less than 1 turn.

 

[edojr]

Thanks, I'll make the changes tonight and give it a try.

 

[edojr]

I put another loop in the needle and removed the bearing and placed a washer behind it. After close inspection, I did see any grooving but added the washer anyway. I had some counter wait in the back that the photo doesn't show. I had in the front, but the needle was making contact with it. However, I did add an extra screw with one at the 1 o'clock position and the other at 11 with the needle mounted at the 6 o'clock. I also added the bend so the needle comes straight down from the bearing If the flywheel above is on thingaverse, I'm gong to trying it.

I can see that consistent needle making is a big deal. I ran the motor at about 5800 and 6000 rpm and 400 mm/min. My first needle broke because It was too long. I was able to cut out quite a bit of stuff with my second needle. (oh I also put a drop of super glue to hold the needle to the bearing.)

For the most part I was pleased since this was the most I've been able to cut without a break; however, I have a new problem. The cut looks great from the the top, nice a clean. Not so from underneath; it wasn't a continuous cut and I still had to use an xacto knife to cut the parts free. The needle is definitely going all the way through, but there were places were I could see individual pin holes instead of a continuous cut. Given the settings above, I can't believe I have the cutter moving to fast.

The only thing I can think of is the needle is still too long and it may be deflecting slightly and not going straight down. My needle goes through a welding tip and probably extends abut 15mm at full extension.

Or could this be a needle sharpness issue? I have to admit that I may not have the sharpest point and sharping a .025 piece of wire may be a skill I haven't yet acquired.

Edit: Found the flywheel on thingaverse and your installation instructions at #1431. I really like this since I don't have to coil the wire. This is my weekend upgrade. Thanks dkj4linux.

 

[datamichael]

I put another loop in the needle and removed the bearing and placed a washer behind it. After close inspection, I did see any grooving but added the washer anyway. I had some counter wait in the back that the photo doesn't show. I had in the front, but the needle was making contact with it. However, I did add an extra screw with one at the 1 o'clock position and the other at 11 with the needle mounted at the 6 o'clock. I also added the bend so the needle comes straight down from the bearing If the flywheel above is on thingaverse, I'm gong to trying it.

I can see that consistent needle making is a big deal. I ran the motor at about 5800 and 6000 rpm and 400 mm/min. My first needle broke because It was too long. I was able to cut out quite a bit of stuff with my second needle. (oh I also put a drop of super glue to hold the needle to the bearing.)

For the most part I was pleased since this was the most I've been able to cut without a break; however, I have a new problem. The cut looks great from the the top, nice a clean. Not so from underneath; it wasn't a continuous cut and I still had to use an xacto knife to cut the parts free. The needle is definitely going all the way through, but there were places were I could see individual pin holes instead of a continuous cut. Given the settings above, I can't believe I have the cutter moving to fast.

The only thing I can think of is the needle is still too long and it may be deflecting slightly and not going straight down. My needle goes through a welding tip and probably extends abut 15mm at full extension.

Or could this be a needle sharpness issue? I have to admit that I may not have the sharpest point and sharping a .025 piece of wire may be a skill I haven't yet acquired.

Edit: Found the flywheel on thingaverse and your installation instructions at #1431. I really like this since I don't have to coil the wire. This is my weekend upgrade. Thanks dkj4linux.

I'd be interested in seeing hi-res photos of completed cuts using this system. I've seen a few in person and was not impressed with the "resolution" compared to being cut with a knife or a router.

 

[dkj4linux]

I'd be interested in seeing hi-res photos of completed cuts using this system. I've seen a few in person and was not impressed with the "resolution" compared to being cut with a knife or a router.

Thread is full of them. Check back a few pages... post #2439, for example.

https://forum.flitetest.com/index.p...eets-with-a-needle.24251/page-122#post-466905

You mentioned the "resolution"... try cutting the crown

 

[edojr]

I'd be interested in seeing hi-res photos of completed cuts using this system. I've seen a few in person and was not impressed with the "resolution" compared to being cut with a knife or a router.

This thread is full of examples of what you can achieve with a needle cutter so feel free to browse. Whether it is better than using a knife depends on your skills. For me, I have never been able to achieve the percision with an xacto blade and metal ruler that I've been able to do using a cnc and needle cutter and I've been doing if for good number of years. Frustrated with poor results doing by hand so I moved to a CNC. I have a laser and router for it. So choosing between laser, router, drag knife or needle cutter really boils down to personal preference and what your building.

 

[dkj4linux]

...
For the most part I was pleased since this was the most I've been able to cut without a break; however, I have a new problem. The cut looks great from the the top, nice a clean. Not so from underneath; it wasn't a continuous cut and I still had to use an xacto knife to cut the parts free. The needle is definitely going all the way through, but there were places were I could see individual pin holes instead of a continuous cut. Given the settings above, I can't believe I have the cutter moving to fast.

The only thing I can think of is the needle is still too long and it may be deflecting slightly and not going straight down. My needle goes through a welding tip and probably extends abut 15mm at full extension.

Or could this be a needle sharpness issue? I have to admit that I may not have the sharpest point and sharping a .025 piece of wire may be a skill I haven't yet acquired.

Edit: Found the flywheel on thingaverse and your installation instructions at #1431. I really like this since I don't have to coil the wire. This is my weekend upgrade. Thanks dkj4linux.

Botttom side can look pretty bad for several reasons...

Check your welding tip... I had 0.035 and 0.025 tips... choose the 0.025 for 0.025 music wire. A word of explanation... the welding tips are sized for the wire they are designed to handle... not the OD of the hole through its middle. There is a lot less slop, needle in guide, with the smaller tip and the needle motion is much more stable... had this exact issue with the FoamRipper needle setup just a couple of weeks ago.

Also, make sure the foamboard you are cutting is held reasonably flat and firmly supported. I had some pretty chewed-up styrofoam backing initially... and the bottom-side looked really rough. When I put the vacuum pad down and placed the workpiece on the pad, papered side to papered side ... the cuts looked as in post #2439.

15mm needle extension is probably a bit much... I'd cut a few millimeters off the needle. Again, had to do that with the FoamRipper setup just a couple of weeks ago. It's best if you can get the tip of the needle guide (welding tip) down as close as practical to the work surface to provide best needle support.

A short conical tip (like a freshly-sharpened wooden pencil, only blunter...) is pretty easy to grind... twirl the needle between fingers while lightly holding the tip against the side of fine grinding wheel (or Dremel cutoff wheel) at a 30-45 degree angle. Even though the tip will dull with use, the symmetry of the tip remains intact and it should still cut foam cleanly.

Practice, practice, practice...

-- David

 

[edojr]

I expected the back to be chewed up a bit so that doesn't bother me. It was having to use an xacto knife to cut it loose. If I tried to "punch" it out, I was tearing the paper from the foam. So reducing the size of the needle should help. I did get the .030 inch welding tip as the .025 was out of stock. But they are back in and I will have them this weekend. I was using a file to sharpen kind of like using a sharping stone on my kitchen knives, but think I have a cutoff wheel for my Dremel which I will try. I can't thank you enough for your help and quick responses.

 

[bigALUSMC]

Hey David what do you think the cost would be to do the ripper? I had wanted to do something similar as it would cut down on movement and the need for so many cut's of tubing. It seems sleek and a simple design. I was looking at getting the lowrider bundle but they are always out of the flat pieces. Love your work sir! Also hat's off to all those who have the time and knowledge to share with those of us who do not have those skills.

 

[dkj4linux]

Hey David what do you think the cost would be to do the ripper? I had wanted to do something similar as it would cut down on movement and the need for so many cut's of tubing. It seems sleek and a simple design. I was looking at getting the lowrider bundle but they are always out of the flat pieces. Love your work sir! Also hat's off to all those who have the time and knowledge to share with those of us who do not have those skills.

BigAl,

Thanks for the kind words.

First, if you haven't seen them already, I think these links to Moebeast's Foam Ripper information may answer a few of your questions...

https://www.thingiverse.com/thing:2520214

https://www.flitetest.com/articles/another-cnc-foam-board-cutter

It is indeed a considerably simpler machine than MPCNC and LR2... using one less stepper, about half the bearings, and much less conduit, hardware, and printed plastic. I didn't really figure the $$$ cost of mine as I had so many appropriate bits and pieces on hand already... but I should think maybe half the cost of an MPCNC? I also built it, initially, staying pretty true to Mark's design... and then started playing around with it. I first switched it over to LinuxCNC from Marlin -- pretty much for nostalgic reasons, as LinuxCNC is what I started with -- and then I did the alternative carriage/Z-axis and compact needle cutter with slip-on flywheel, my first Onshape designs. The vacuum pad is a nice addition as well.

You will still have to fabricate a couple of flat end pieces but they're reasonably simple... and there are only two of them. I did mine on an MPCNC, with Dewalt router, but they can also be done reasonably well with jigsaw and drill press... and Mark provides the DXF files on his Foam Ripper Thingiverse page.

In honesty, this is IMO a nicer foam-cutting setup than either MPCNC or LowRider... but they are, of course, much more flexible, with all the available tooling and far larger user community. But for laser, dragknife, pen/marker, and needle cutter... this would probably be the tool I would use most. My build, and most of the mods I made to it. are all documented in this thread.

Please let us know how I/we might further help.

-- David

 

[bigALUSMC]

I think I can piece everything together... my only worry is the programing. I have a heck of a time even with openTX lol... that may be the only draw back for me. I was looking at getting a plotter and just cutting it out by hand which are running about 250.00 buck... but then the nerve damage in my hand from my military service... reminds me why I may need to build one of these to cut down on the hand work. Thank you again and will be picking your brain when I get this started.

**UPDATE**... WOW... thank you for the FT article link... that is outstanding and cheaper to make than buying a Plotter and would save my hands lol. THANK YOU SIR!

 

[dkj4linux]

BigAl,

Should you want to check the details of my Foam Ripper build, from its beginnings, it starts with this post

https://forum.flitetest.com/index.p...eets-with-a-needle.24251/page-110#post-427171

-- David

 

[bigALUSMC]

A work of art.... hope I can get mine done by years end.... just had my pc crash. Hate win 10.

 

[Michael9865]

A work of art.... hope I can get mine done by years end.... just had my pc crash. Hate win 10.

That is why I installed Linux Mint 19.1 and Universal Gcode Sender V 2.0 on my Dell Optiplex 745 tower that controls my MPCNC.

 

[Verris]

I've got a rpi v3 mounted to the bottom of my mpcnc, with cncjs running on it. Setup a local dns entry to send http://mp.cnc to it and do everything remotely. Works really well.

 

[jhitesma]

Dusted off the MPCNC yesterday to help my daughter with a project for her girl scout troop. They're having a big yard sale to raise money for a trip they want to take next year - we aren't available to work the sale but volunteered to make signs. She kept wanting to make them in crayon or with light pastel colored paints on white - and I had to keep explaining that they need to be visible and legible for people driving by in their cars on a 45mph street.

So....she asked if I could just draw up a design and use "my machine" to draw it out then she could color it in. Sure...no problem. But then she asked "If you're going to use the machine anyway can't you just cut out the letters? Then I could paint them and glue them down?" Well...yeah I can do that.

But after cutting out the first sheet I found a sheet of black DTFB and realized we could skip the painting entirely. And If I picked up a few more sheets of black and cut some out of that we could get two signs out of each sheet by using the "waste" as a second sign.

So up to dollar tree we went to get a few more sheets of black. Only to find they didn't have any But they did have green poster board which is a nicer girl scout color anyway and only $0.50 a sheet. And I can cut poster board with the laser on the MPCNC faster than I can cut DTFB with the needle so should let us make more signs even faster!

Except apparently the green color of the posterboard and my blue laser don't get along. I could have made it work but it would have been even slower than the needle. And my 40w CO2 laser can't do things this big (yet).

So...let's try an experiment. Got out some 3M 77 spray adhesive and glued the posterboard to the DTFB. Sure enough needle cutter handles it no problem! So we've got our signs:

Nice, high contrast with big letters easy to read from a moving car! She insisted on gluing the letters down herself without a guide or straight edge on the "positive" versions so they're a bit more "Handmade" looking. The arrows on them aren't attached yet so they can be re-positioned based on where the signs go. The "negative" signs the arrows aren't adjustable obviously. And I hadn't finished adding all of the loose bits when I snapped this.

I'm a little worried about readability out in the sun due to shadows from the 3D effect....but I think they'll work

Not too shabby for 10 minutes of inkscape, and 20 minutes of cutting per sign. Slowest part was her gluing the letters down which took her the better part of 30 minutes per sign. If she had done it my way using the negative as a frame probably would have gone a lot quicker

 

[Snow-B1]

Here is the tool settings I use. I use mm/min since that is what will be in the Marlin file. You can also use the "Replace" tool in NotePad to change feed rates in your gcode files.
View attachment 128948
I ran your project with this tool setting and generated this file.

I just wanted to thank you for your help, my mpcnc is now up and running (thanks to your suggestions) and I have cut out my first successful plane.

 

[Snow-B1]

Okay...

Finally started messing with the vacuum pad again. Didn't have any of the repositionable glue so decided Elmer's school stick glue (goes on purple!) from the dollar store would probably work fine for what we're doing here.

Glued the two slotted layers together and weighted them down while they dried... at Jason's suggestion and while I watched the golf tournament. They seemed reasonably flat, after golf, so cut the 5 ports to receive the 5 ends of Mark's plenum. I really wasn't sure I needed to glue the hole grid sheet and decided to try without glue... it's also the spoilboard, remember, so it'll eventually be replaced with a new sheet at some point down the road. Also decided to forego a frame of any sort at this point... I'd like this to be the minimalist version.

So, here it is in action. Spotted the hairy gorilla in the yard and called him in to help out... he did better, with supervision, but he's still a crappy actor. Go Navy!

$3 worth of foam board and a printed vacuum fitting... and it sucks! Hopefully the shop vac -- a small 2.5 gallon unit -- will not overheat with the restricted air flow in the time it takes to cut a sheet. I guess that's the next on the agenda for testing... actually cut a plane and see how it does. Since Jason is fond of the FT MIni-Scout... maybe that would be a good one to try

-- David

David,
I am impressed with your vacuum table, would you be wiling to share your plans for the DTFB slot and hole pattern? It would be most appreciated.