I’ve tried my first cuts of XPS foam. It went better than I expected (the source SVG was a very quick and dirty trace of an image in inkscape). That said, the finish isn’t great compared to hot wire. I’m considering mounting a soldering iron to do the cut. Has anyone done this? Any ideas?
That all said, the main point of this post is: what lubricant should I use on the underside of the sled that will work with XPS foam?
The cut went well but the sled moved a bit and it’s hard to fix XPS to the frame. I’ve thought of attaching some batons to the waste board but the foam sheets aren’t strong and could easily bend or break.
the ‘right way’ to do this is to have two sleds with a hot wire between them go
down both sides of the foam, but that’s rather hard to arrange (I have plans in
the back of my mind to do this with my original maslow, get motors with shafts
on both sides and run two sets of chains, but so many plans, so little time
)
the big problem with single-ended hot wire setsups is that they will flex, and
not cut where you expect
It’s only 20mm thick. I plan to stack them and glue together. The total thickness in the end will be about 60mm attached to a curved surface (hence the 20mm thin sheet).
The thing about a soldering iron is that it’s rather wide and probably too hot. I might be able to take that into account in the gcode with some trial and error.
I did think of attaching a thick wire to the soldering iron but the cheap DC one that I bought isn’t right for that.
I think that I’ll mount the soldering iron in clay and let it harden. That will add weight and provide heat proofing.
You wouldn’t really have two M4s, more like very strong magnets. However that would only really work with a gantry style CNC.
The trouble with sleds is that they have to run on something. That prevents us using a two sided sled.
Indoor Outdoor Carpet tape might hold it down, even better when combined with a little bit of bracing on edges.
Could also use super thin pieces of material as clamps by putting them on the foam and screwing into the waste board through them and the foam. the maslow hops over small bumps just fine, you just need to make sure none of these are in places where the maslow would bump them while the bit is descended.
I think you would find that the solder iron will not melt/cut as fast as you think. Using a marker in the maslow and then cutting it by hand with a hotwire would probably be the fastest.
I did think of cutting a bit into the XPS and then finishing it with hot wire.
I’d probably have to leave a bit of margin around the shape as the hot wire melts it a bit.
At least with a soldering iron it will do the cut in a single step (for 20mm thick at least).
I didn’t attempt to solve that issue, because the sled sticks to everything, technically, via friction. It’s generally just a matter of overcoming that friction with things to brace the material and, with thinner materials, making sure that bracing is sufficient to overcome that friction across the entire surface and hold it flat.
If it’s still damaging the surface of the foam through that friction and you can’t find a suitable lubricant solution, you may need to find a way to float the sled. I had some promising results testing with casters attached to the sled, but I didn’t like how I had them attached and haven’t rebuild the thing to re-attach to the sled and take pictures to share, yet.
I suppose if I could find a very thin material that I could cut thru and have the XPS underneath. I suppose that thick paper would do the job but it would probably rip.
3mm MDF is a bit too thick and I think that’s the thinnest that I’ve found at the hardware stores.
I’ve also experimented with using evenly placed slats to keep the sled lifted and do a two-stage cut on the material below between the slats, moving the slats to expose the areas they previously covered between each cut.
This has the advantage of not creating additional waste, you just need to build a frame for the slats and create a proper jig if you want it to be simpler to manage.
You wouldn’t really have two M4s, more like very strong magnets. However that would only really work with a gantry style CNC.
The trouble with sleds is that they have to run on something. That prevents us using a two sided sled.
What I’m looking at is cutting 2" thick foam, so I’m thinking stand it up on
edge with a sled on each side. The two sleds will do a fair job of preventing it
from tipping, but it may need some manual assistance.
I suppose if I could find a very thin material that I could cut thru and have the XPS underneath. I suppose that thick paper would do the job but it would probably rip.
3mm MDF is a bit too thick and I think that’s the thinnest that I’ve found at the hardware stores.
if you sandwidch the foam between two layers of thin plywood, it won’t flex,
just cut through the entire stack.
I think another consideration there begins to be the depth of cuts. The more material you are cutting through the longer the bit will need to be in order to make the cut without hitting the lower Z limit.
I don’t know if this will help or not, but I’ve been noodling with making an adapter that fits where the DeWalt is on my M4 that would hold this hot-wire cutter I got off AliExpress. I haven’t posted anything about it yet because I want to test it and show working cuts first, but in case this gives anyone an idea… ¯_(ツ)_/¯
I read that thread.
One idea that’s missing is to have a horizontal frame but to passively support the sled from the roof.
I just don’t think the M4 is cut out for carving. You have to do it in slices and glue it all together at the end. That’s fine for carving plywood but not for natural wood.
I think that I’ll move to a gantry some day. The trick is to make it cheap at the same time as fitting a 4x8. Maybe that will be the M5 one day.
That’s kinda what I was planning, it was just that a soldering iron was more available and I could find a cheap DC one. I’m running my spindle on DC, so I plan to reuse its power source.
Unfortunately the soldering iron isn’t the same as my AC one, so changing the head for a wire (my original plan) like yours isn’t possible. I just have to test and see how good the cuts will be and see much it will melt the XPS.
I haven’t had that much time to work on it but hopefully I’ll have more time soon.
I very much do not need to do it on separate pieces and glue them together. I’ve had success with multi step carving jobs and with the slat supports.
I don’t need to make it horizontal, and I’m eventually building a panel saw onto my frame in a way that will allow me to mount the maslow in the place of the saw and have that act as a float/gantry. Might be terrible, might be fine, I’m gonna find out.
I’m also building a MPCNC, but it would be nice to see the much larger maslow be able to do that kind of work.
I’m more and more convinced that a gantry is the way to go but all current versions are expensive hence the space for maslow.
@bar
I reckon that a cheap gantry that used the belts to pull it on the X axis and a simpler one for the Y would do the trick. The tricky part is calibration and there I would use a lidar and ultrasound. Both are cheap components but one is good for long distance, the other for short. I suppose that the inaccuracy when the gantry is near the max would be made up by the accuracy when it’s far from zero.
