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So if you’ve check the FT thread you’ll know that I’ve been making great progress on my new and improved needle cutter:


I’m getting great results with it. I switched to a 0.62mm needle with a .030″ MIG tip as a guide. It also has four bearings to pre-gide the needle and straighten the motion. Oh, and I switched to a 2212 850kv motor that lets me run on higher voltages and still maintain RPM control. The motor is crazy overkill, a smaller motor would be perfectly fine…and in fact probably better since you could run something like a 2204 (or maybe even an 1806) since the motor doesn’t need a lot of power. (Brushless motor numbers generally indicate the size of the armature in mm. So a 2212 motor is 22mm diameter and 12mm tall while a 2204 is 22mm diameter but only 4mm tall) a shorter motor lets you make the cutter itself shorter which could potentially give more accuracy…though I have zero complaints about accuracy on the new cutter.

My only complaint is that the MIG tip still gets a bit warmer than I’d hoped even with an oiled cotton ball in the hole in the PLA above it to lubricate the needle. I was hoping to eliminate the wooden insulator that the guide mounts to – but seems it’s still necessary. If I printed the cutter in PLA or ABS it may be able to handle the temps…after 30 minutes of running I can hold my finger against the mig tip but it’s warm enough I don’t want to hold my finger there very long.

With the balanced flywheel this new cutter runs MUCH quieter and smoother than my old crank style cutter. I can actually stand to be in the room with it without using my hearing protection now:

Short video showing off the new setup:

And longer video showing a full cut:

I’ve actually been talking to another user and looking at my gcode found that I’m not cutting nearly as fast as I should be able to either. I had increased my feed rate in estlcam from 9mm/s to 20mm/s … or at least I thought I had. The gcode is still coming out at 9mm/s. When I manually edited and re-ran the code I was able to reduce the 27minute cut down to 17 minutes. I haven’t tried it on actual foam yet but the other person I’ve been talking to is using a similar cutter at that speed with no issues so I have every expectation it will work.

I hit DT today and didn’t see any actual “Magic Erasers” just these:


Which I hope/assume are the same thing. When I do our grocery shopping later today I’ll check for actual magic erasers and see how they compare.

I only have my needle setup for a 8mm deep cut max right now….actually it can probably do closer to 10 right now because I still need to trim the needle a bit more. With the flywheel setup the way it currently is I get 14mm of stroke. But there are holes that will give 22mm and 30mm of stroke. 3/4″ is about 19mm so that middle 22mm stroke hole should work to cut full thickness….but I’m not in a rush to modify my flywheel to try a deeper cut since it’s working so well for my needs right now 😉

So instead I sliced off a thinner piece of the foam and ran a bit of gcode from this puzzle:


Since it was the most recent thing I had cut 🙂 I didn’t bother to try and line it up to keep the parts on the foam or anything, just wanted to see how it cut – worked great! Even better than the DTFB I usually cut since with no paper on either side it was much quieter:


The torn bit is just where I tore it apart to separate the cut part since I didn’t try to line the cuts up on the piece.

Here’s a closeup:


The cut was super smooth and effortless. With my 0.62mm needle the cut was totally invisible but the parts came right apart. Didn’t quite “fall” apart but didn’t really give any resistance like there were uncut bits either. Just the friction of the foam against itself held the cut parts in place.

I’ll be posting the files for the revised cutter and flywheel on thingiverse later today now that I know it’s working.

The one very minor complaint I still have with it is that the guide vibrates a bit – doesn’t seem to affect accuracy but I’d like to eliminate it. I may have gone too far with removing the sides and bottom of the body as the back is nice and vibration free. One of these days I’ll try printing a version with a solid base or sides and see how it compares….but I’m really not in a rush since it’s working 🙂

Oh, and I can fairly easily adapt it to the new default 525 mount…in fact…I’ll probably work up a version for that before I post the files. Since I may get lazy and take a few days to do that here’s a link to the Onshape project so anyone can generate the STL’s themselves or copy it and make modifications:

The “B1” branch is my current working version with the latest tweaks.