Union Stars

Ok everyone, I need some much needed help. Been carving Union Stars for about 2 mo. Recently though the results have ben less than satisfactory. A lot of the stars around the edges are not the same size as the inner field. Have email Julie from Inventables and have tried all of her suggestions. Checked the belts, pulleys, set screws, ACME screw. Jogged the Z Axis up and down 1" to if it actually moves 1". Waste board is flat. Replaced some V Wheels. The results are all the same.

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Can you share the file?

I would make sure that every star is set to cut the same (i.e. on path, outside or inside).

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What Brian said. Based on your picture there isn’t a “pattern” to the ones that aren’t right.

Are you doing a v-carve? I had a similar issue with the stars when making some unions. I ended up using a second software program to generate a height map of the work piece and then apply that height map to the g-code to get a consistent carve. Bit more work, but it gives really nice results when doing a v-carve.

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The clamping might be causing your stock to be lower on the edges. You might try super glue and tape if your stock is flat. If it’s not flat, then do what @EthanKinney said.

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Neil, I have changed my clamping set-up, still with no success…


Have you checked the dust boot? If its to to tight against the material it will raise the Z height a little. I wouldn’t know what else to tell you other than your material isn’t level but you tried that so maybe its what Ethan said.
Good Luck

Are you sure your board is perfectly flat? I have had a few that the board is slightly warped (high in the middle) I added an extra clamp through the center section to pull it down. To fix the one I had that way I re-cut the stars that were to small by setting my probe in the general area of the incorrect star and rerunning just the stars needed to correct.

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Try a 60 degree bit and limit depth of cut.
60 degree bit is more forgiving on uneven material height.

Ethan - would you mind providing more details on the 2nd software program and what you do to generate the height map and g-code?

@BrianSkinnell I usually use bCNC to do the “autoleveling” like this.

The boards are flat. I’ve tried using less clamps and always get the same result. In my mind, if I get the same type result on different size unions, it seems like it could be a coding issue.

Hi Brian,

I’m using https://github.com/martin2250/OpenCNCPilot to generate the height map. I build my own “probe” by gluing a momentary button onto the end of a bolt and attaching that to the probe pin of my arduino.

My steps would be to:

  1. Locate the correct x/y position in easel
  2. Export the g-code from easel
  3. Close easel (to open the COM port)
  4. Start OpenCNCPilot
  5. load the g-code and create a height map probing routing (in the software)
  6. zero the work piece and then run the probing routine
  7. apply the height map to the g-code and save
  8. close OpenCNCPilot and open easel
  9. import the g-code and run

It adds about ~10-15 minutes to my carves, but I’m usually carving pretty fine detail over very large pieces. So the extra time for a good quality carve is worth it for me.

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oooohhhh Looks like I need to add my homing switches to the machine so I can use this.

I understand your switch placed in spindle for probing the surface and creating the height map.
How do you set Z height after placing bit back into the spindle?

Zeroing the probe is only for generating the height map and applying it to the gcode. You will still need to re-zero your bit afterwards and run the gcode.

The video at github did not show probing for bit length after height map was created. And of coarse it was being done on a circuit board with bit already in the collet.

I’ll be doing a carve on Sunday, I’ll post a video of it