Facilitating Carving Entire Surface of Work Piece

Projects
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I’d like to be able to make cuts/carve without being restricted to maintaining a flat surface (on the workpiece) for the sled to slide across. With the machine as-is, I would expect to be restricted to working on pieces no wider or longer than being just shy of the radius of the sled.

My first thought was a gantry that would attach to the sled and the vertical axis being under the belts while the horizontal axis was above them. Would have to modify frame and maslow itself, and it’d be a significant design/cost investment.

That made me consider taking advantage of the sled sliding and building a metal trough just slightly wider than the sled for it to slide up and down and putting it on rails attached above and below the mounting board, reducing the cost and making it so I can just pop the sled out of the trough and it’d be much easier to take the mechanism off the frame when it isn’t wanted.

My second thought was supporting the sled on slats resting above the workpiece and only cutting between the slats, while also doing the overall carve in 2 separate g code files where the first cuts where the slats aren’t, initially, and the second cuts where they used to be, after you slide them over to a now-safe area. Other than needing to make sure to provide contact points to keep the sled flat at all times, build frames for each carve, and losing the thickness of the slats from the max depth of your carve, this seems like a pretty solid path.

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A rough example of the idea/process:

  • build support frame around piece to cut for sled
  • carve exposed areas between supports
  • move supports
  • carve material that was previously under supports

Just grabbed a random file from SketchUp’s library to use for the “terrain” visual.
((will need to have wider supports on the outer edges, of course))

Thinking towards simplifying the process, I had an idea relative to how many people build tables for flattening slabs manually, with a wooden trough that acts as a gantry. If the same process was used as the slats idea, but only using 2 supports, and the cut was done a single stripe at a time, the jig, while needing updated more times per overall carve, becomes much easier to manage.

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2

Hi,

If you can find flat or easy to cut out and sand position in your carve, then you can add stubs into it with a Z=0. They need to be no more than 7 or 8 inches away so the sled does not fall. Once done with the carve, cut and sand…

You also have the benefit of going deeper without the frame

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That was something I considered, but will not be viable for some of the types of things I’d like to carve.

I had actually considered doing this (in stripes), then slats as support to cut the remainder using the cnc so it’s still carved in the same exact way as the rest, but I realized it would be better to not have to offset the gcode of the 2nd cut file.

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I once considered supporing the sled using long smooth carbon fiber rods for X and Y axis, where the X and Y rods edges slide along a linear rail just off the spoilboard edge, not sure if belts would get in the way but I am a bit concerned that this idea will have resonance that shows up in Z vibration and artifacts in carve.

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realistically, if you are going to the trouble of building a gantry, the
maslow-style of driving the machine is probobably not your best option.

The maslow style of movement has the advantage that it doesn’t need the gantry.

If you have a gantry, a more traditional movement system (cartesian or corexy)
will probably work better for you, and has the advantage that it’s supported by
lots of software and boards out of the box.

David Lang

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That’s one of the reasons I was thinking in other directions. At this point, it’s more of seeing how far I can push the maslow and keep expenses down on hardware. If I can get the maslow to pay for itself, I’d be planning on building a more traditional DIY CNC as well.

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Carson Barry wrote:

That’s one of the reasons I was thinking in other directions. At this point,
it’s more of seeing how far I can push the maslow and keep expenses down on
hardware. If I can get the maslow to pay for itself, I’d be planning on
building a more traditional DIY CNC as well.

Most of the complication in a traditional CNC is in the gantry, not the drive
mechanism/electronics

so to add a gantry to the maslow is ending up with the worst of both worlds.

David Lang

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Don’t know if this is a good idea, but it’s an idea. Start your carve by cutting down to final depth along a grid, with grid lines that are, say 1 inch wide separated by 6 inches of uncut material. Drop into the cuts a grid cut in the same pattern, only the lines are, say, 3/4 inches wide. Secure the grid at the edges. This grid would have temporary “bridges” tacked to it that span the 1" gaps, holding the top surface of your grid level with the uncut surface of your work piece. The grid would also have holes drilled into it, into which you glue dowels that reach down to the cut surface. Once the glue is dry, remove the bridges, and the grid will stand on the dowel legs to support the sled. Now cut down to the finished surface in each of the 6x6-inch cells. Finally remove the grid.

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This is what its all about. Sky is the limit. Its the journey we learn from regardless if it makes perfect sense we are better for walking it.

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Another thought: Add waste strips outside your part on one corner, maybe 12" long and 4" wide. Set up your file so that when you cut phase 1, it leaves pillars un-cut. Maybe 1" or so on a 6" pitch? These would leave a sliding surface for the Maslow. THEN, structure your final cut plan that removes the pillars to remove them starting on one corner and finishing on the waste strip corner.

Yes, you won’t be able to go back and work on something, but it might work for what you need!
Alternatively, you could raster or scan across your work, taking it to finish depth and then stepping over. Again, you would need the waste strips in the finish corner. Maybe add some weight to the finish corner side to improve guiding.

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How about something like this? A router flattening jig: it’s like an unpowered gantry with the belts controlling the movement.

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This seems like the slats idea with a lot more setup in cad/cam and also more work during the cut.

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That is essentially one of the things I described.

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An idea perhaps is to cut a (partial?) mirror image/split to fit upside down into any necessary cavities.

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That still seems like it’s adding a lot of extra to the process.

If I was worried about the support slats needing support I would have 2 sets of slats, one just as spacers that get support from the uncut workpiece under them, and the other with t nuts mounted on the bottom with bolts sticking out like levelers for tables, etc. Would stick some foam rubber on the heads of the bolts so they don’t damage the workpiece and have a bit of grip.

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I must be missing some bigger part of the story here, because I think you are making a mountain out of a mole hill.

My first and the best solution would be to buy or build a larger gantry machine, because that is what they are meant to do and it avoids the whole sled problem. Your example looks to be about 3x3, and you can buy a 4x4 gantry machine without making a massive investment (or look for a used one and save some money.

Alteratively, to take the challenge to the M4 (which I am assuming is your intent), you can look to the old machines like the classic or the M2, and use a 15 degree (not quite vertical) slant on your frame/wasteboard, and cut from the top of the piece to the bottom. The classic and M2 have bricks on the bottom of the sled for weight which will keep the sled on the uncut portion of the material as long as the cuts are moving down. Another option to keep it level is to add a quarter inch piece of plywood that can move down with the sled. You would of course have to set your z or your depth of cut to be 1/4" lower, but you can always pause the carve, turn off the router and move the piece to keep the sled surrounded. If you don’t want to have to babysit it and go through all of this, get a 4x4 sheet of 1/4" plywood and stick it to the sled using double-sided adhesive (your z difference will be more like 3/8", but the wood being larger than the workpiece will just act as a much larger sled.

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you could also use a larger sled :grin:

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I once built a jig for my classic maslow which could do what you want it to do. was a lot of work though,but fun. with some tinkering I think it could be used for the M4 as well.

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The example is just an example. I intend to use as much of the 4x8 of my mounting surface as possible.

As this is more experimental than anything else and I’m specifically trying to find the limits of the Maslow in this regard, building a different type of CNC would defeat the purpose of the exercise.

Ill be doing an MPCNC when I get the chance, but in the meantime I’ll be trying this with the Maslow using support jigs and potentially stealing ideas from the MPCNC to make inexpensive rails. If that doesn’t work out, I’ll be able to repurpose that for the actual MPCNC.

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Yea try it! Though making it rigid and able to withstand vibration chatter from resonance while cutting may be challenging.

But, that said, I could see it working and worthwhile for carving large XPS foam.

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