Finger widths do not match Simulate inspection

[patrickCCA97]

This is my first test cut, and the actual cuts are not matching up with the expected results based on inspection the bodies after running simulate.

I sort of expected it not be perfect since they were equal (hence doing some tests).

But they are way off. What's the next step to troubleshooting?

Drawn in Fusion ( 2.0.9854, macOS 10.16.0)
Generated NC with Carbide 3D GRBL post processor ( ver 43182).

CNC: Carbide 3D ShapeOKO and CNCJS Desktop to control it.

Thanks so much!

[Steinwerks · Accepted solution]

I suspect you are experiencing a good amount of deflection. Although I'm not a woodworker I've seen plenty of folks suggest using a conventional cut to fight the issue in lightweight routers. Heavy cutting action can also cause stepper machines to miss steps and create mismatched geometry, and I've even seen some people with loose belts or gears which can be extremely mind bending to track down if one doesn't know whether to check all the components.

[patrickCCA97]

Probably should have put this information in the initial post:

Machine is a Shaepoko XL, with a Dewalt 611

Spindle at Dewalt #2 (18000rpm)
Bit: Amana Tool 46017-K 1/4 compression bit (new).

Material: 3/4" Baltic Birch plywood
Feed: 1/4" multiple passes
No ramp or lead-ins. My material was not much bigger than the pieces.

NC file and screen shot of tool setup are attached

Thanks for the reply Neal.

I measured all the fingers and thinking I'd see more random differences.
The slots and fingers vary by  .1-.3mm.

The fingers though are consistently 1.5mm thicker than the slots.

Does deflection manifest consistently like that?

[patrickCCA97]

In general, going shallower (2mm) and using a downcut instead of a compression bit yielded better results. There is a lengthy discussion in the Skapeoko forum for those who are interested in following along.

https://community.carbide3d.com/t/fingers-and-slots-off-from-expected/31349

[Steinwerks]

Glad you got it figured out! As I said I don't work with wood, just wanted to suggest where to get started looking for evidence of issues and where to test.