Toolpath Problems

I’ve been trying to cut a saxophone shaped part and have been experiencing a problem that I don’t know how to solve. This has happened three different times, each time with a different version of an .nc file, but they all originated from the same design.

In MeshCAM I created a project that ONLY had a waterline path. I’m guessing that is how you should cut out a part from stock material.

Everything was moving along just fine, until the bit took an unexpected left turn and went way over to the edge of the stock, even going OUTSIDE the established machining region. The bit then returned to the correct path and continued. In four locations it made the same (unscheduled) trip to the left edge of the stock. As you can see from the toolpath above these are not planned.

So did I do something wrong? My previous projects used roughing passes and finishing passes, this is the first time I have just done a waterline only job. Is that how you are suppose to cut out a part?

ColdCoffee, it doesn’t look like you have done anything wrong. The MeshCAM toolpath screenshot does not show the excursions, so they should not be present in the gcode. You could verify that by looking through the gcode for any X coordinates of zero or lower (because the excursions are obviously traveling to the edge of the stock and possibly beyond).

To cut a part out of flat stock, you are correct in using waterline. But waterline uses a fixed step-down increment, and almost never will take a last pass at the bottom of the material due to internal rounding issues. Add a pencil cut with the same tool. Pencil will follow the bottom of the geometry–it’s kind of like a final waterline cut that is guaranteed to be at the bottom even though it is not an even depth increment down.

Not being too eager to point fingers, it may be a controller glitch. I don’t have a Nomad, but have been using MeshCAM for years and it always gives reliable output.

You might also want to add a few shallow supports around the bottom perimeter of the shape just to hold it in place during the last cutout. .010-.020" (.25-.50mm) would be plenty and you can hand-smooth them afterwards. Being at the bottom of the inlay you could even undercut the profile a little when you sand them, and it would not show in the finished piece.



I had something similar happen a few times (see my other posts), where the Nomad starts cutting in the wrong areas, or starts hacking the bit into the wood in areas where nothing is to be milled.
I also had one occurrence where the Nomad started milling outside its area, it drilled a hole in the length probe on the side closest to the stock tray. The probe still works but it is still scary that the Nomad allows drilling into itself, I dont trust leaving the Nomad by itself because of these issues.
The other issues I had also just came up towards the end of the carvings in longer carving ‘sessions’. My file in Meshcam and the simulator never showed the areas where it was carving wrongfully, so i do not think its a issue with Meshcam or the resulting file but more with either the CarbideMotion application or the controller board. One of those 2 must be the cause (especially since i can use the same .nc file and it works fine a different time it runs on the Nomad.

I really hope that issue can be resolved soon since i lost a lot of material (and time) due to these issues.

i had this happen once as well. wrote it off as my mistake and did not dig into the details. i will keep an eye out for this now.

We downloaded and installed Carbide Motion version 2 (beta), and the problem appears to have gone away… or maybe we’ve just lucky been lucky this weekend.

Results without errors

Can you tell me what version number you are using? I have been using 2.0.305 from 03/02/2015 on the Mac.


Windows Version 2.0.305, Build Date 2015-03-02