Second Toolpath is Offset -0.5" along X-Axis

[buohara (Ben)]

I bought a Shapeoko 3 XXL. Assembly and Hello World worked fine. I’m trying to cut two identical chair parts out of redwood stock with a #201 end mill (1/4"). There are two toolpaths. The first does a few pocket cuts and the second cuts the parts from the stock with a contour. No tool changes. The first toolpath cuts fine. If I pause and measure the positions of the pocket cuts, they’re accurate and match the design in CC.

The second toolpath, however, is offset -0.5" along the x-axis. The width/height of the part are correct, just shifted left. The feed rate is 60"/min, RPM is 18000, and plunge rate is 12"/min. There’s no vibration/wobbling/excessive noise while the machine is cutting.

The simulation in CC looks correct. I read some other troubleshooting steps to check that V wheels are tight, that set screws on the motors are tight, and that belts are tight. These all look fine.

Anyone have other ideas to try?

[WillAdams (William Adams (Carbide 3D))]

A couple of considerations here:

• cutting a slot as narrow as the endmill results in near constant 100% tooling engagement — best practice is to add geometry and cut as a pocket down to tab depth at least:
• leaving a roughing clearance and taking a finishing pass will help with final dimensions

Adding geometry to cut as a pocket with a finishing pass

One technique which is often suggested to avoid slotting is to add geometry around a part which one wishes to cut out and cut as a pocket down to tab depth — here’s one technique for that. In this case, the project is a bevel gauge which will be cut out of 0.0625" (~1.5mm) thick aluminum: [bevelgauge] Due to the narrowness of the angles, an 0.03125" endmill has to be used, so after importing and scaling the file (we will be cutting out one which is 3") we select the perimeter and offset it tw…

• if you haven’t calibrated for belt stretch, doing so will help with the evenness of parts:

https://docs.carbide3d.com/shapeoko-faq/how-to-calibrate-the-machine-for-belt-stretch/

[buohara (Ben)]

Thanks for the tips. I haven’t done belt stretch calibration, I’ll do this next. I’ll update my design to add an offset pocket, then a second cut. I’ll post back here with the results.

[Julien]

Also double-check that the machine does not hit the left or right rails during that final cutout, which would result in lost steps on the X axis, shifting the rest of the cut along X by the same amount.