Getting Z accurate/Fusion CAM

LowRider CNC Advice
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I have been making first cuts with my Lowrider V4 and it’s working sort of well!

I have noticed when I do a part cut in estlCAM with the correct material depth, the machine will not cut all the way through, e.g. this crown took a few jobs to get all the way through with some gcode hacks (hence uneven edges)

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On closer inspection, z -12 seems to correspond to -7mm on the work when zeroed to the top surface. I did configure xyz offsets before starting, but perhaps z needs a closer look.

My controller is an SKR PRO 1.2 running V1CNC_SkrPro_DualLR_2209-2.1.1
Lead screws are 8mm T8 Lead Screw 2mm Pitch 4mm Lead With Nut, as specified in the BOM.

I fiddled with esteps/mm to try and make z more accurate.
Current values are: M92 X100.0000 Y100.0000 Z823.0000.

This brings me closer to correct values, but it’s still a bit off. With 3mm estlCAM DOC, this makes quite aggressive cuts of around 3.5mm, and shapes are not accurate probably due to deflection. The crown below was set to 3mm engraving and 9mm part cut around contour, and you can see evidence of deflection, particularly in the circle at the top. but it did cut all the way through in one job!

I managed to ruin each of these at the last hurdle by crashing the spindle into the surface, or filing off tabs and splitting the ply :frowning: but they’re just scraps…I still have lots to learn.

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Sidenote: estlCAM is good for basics, but I would really like to switch over to Fusion for my CAM workflow, as I do most of my designs in there and I have the paid version. I have seen some stuff about this on the forum but there’s surprisingly little info about it, and I think Fusion has updated to the point where this stuff is depricated and won’t work properly. I have designed in Fusion a lot but I am a total n00b to the manufacturing workspace. Any tips here?

My next steps:

  • get z accurate
  • fight fusion manufacturing workflow
  • cut permanent strut plates
  • cut XZ plates in alu (what grade is needed?)
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I suspect the steps for z should be 800 - this is dictated by the pitch of your lead screws. Double check all the grub screws on you z axis. Actually check them all, sneaky blinders that they are…

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I think Fusion has updated to the point where this stuff is depricated and won’t work properly.

The stuff at the link you provided will not work. Don has posted an updated beta that is reported to work (I’ve not personally tested it). You can find it here.

If you are running a Jackpot board, I have to wonder if any of the other Fusion 360 GRBL postprocessors would work as well.

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I set the Z steps to 800 and it’s working a lot better!

I’m getting the hang of estlCAM now so perhaps I’ll stick with it.

Latest results (before breaking the tabs)

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It went all the way through just fine. I could probably benefit from using a smaller endmill here - I’m currently using a 2.4mm but I notice it’s missing some of the intricate cavities of the geometry.

Thanks for the tips. Hopefully I can graduate to something more interesting than crowns soon.

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@robertbu, you are correct. If you are running a Jackpot board, people may be able to use a standard GRBL post processor with F360. Unfortunately, two issues will remain:

  1. Hobbyist users of F360 will be limited to No Rapid moves. My PP looks for cases where rapids can be safely restored and makes these changes (when the correct options are enabled).

  2. For standard v1e builds, I believe the Z-axis speed is still much less than X and Y. My PP provides options for scaling and limiting to ensure the Z axis is not overdriven, resulting in lost steps. Scaling Z is essential for 3D movements like V-carve engraving, where Z changes at the same time as X and Y.

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