Adaptive path: tool breakage at end of pass

Here's the place for discussion related to CAM/CNC and the development of the Path module.
Chowderhead
Posts: 14
Joined: Sat May 14, 2016 6:01 pm

Adaptive path: tool breakage at end of pass

Postby Chowderhead » Fri May 24, 2019 2:54 pm

Disclaimer: I'm no machinist.

I've been using adaptive tool paths for milling aluminum for quite a while with generally good results. I have, however, noticed that tools tend to break at the end of a profiling operation and I have not been able to diagnose the issue. I've tried different feed rates, tool speeds and stepovers to no effect. It always occurs at the end of the pass as the tool begins to enter the previously cut region. I'm not running a proper mill, just a CNC router, albeit a fairly rigid, all metal machine; nonetheless, it could still be a rigidity issue, but wanted to check with experts.

Thanks!
RatonLaveur
Posts: 324
Joined: Wed Mar 27, 2019 10:45 am

Re: Adaptive path: tool breakage at end of pass

Postby RatonLaveur » Fri May 24, 2019 3:59 pm

I havr noderate experience machining and can say that ig your g-code looks good and you still have an issue of breakage at the end it could be due to machine jitter making the tool give an abrupt little twitch at the last bit of material, or unwanted spindle stop. In order to limit this effect there are several possibilities:
Rounding the last junction between segments prevents or limits jitters.
Adding an extension at the end of the last segment or a lead out would guid your tool away from material smoothly.
Rounding your corners even a tiny bit (0.1-0.2mm) generally helps with jitter issues and the machine dynamics are smoother.
Make sure you don't initiate a G0 rapid when still engaging material they are wicked jittery as generally the machines are tuned more loosely for rapids.
Make sur your spindle keeps going. That the program doesn't abruptly stop everything.
...i pass the baton to someone else to give better/complementary advice.
m0n5t3r
Posts: 51
Joined: Fri Feb 03, 2017 2:55 pm

Re: Adaptive path: tool breakage at end of pass

Postby m0n5t3r » Sat May 25, 2019 2:14 pm

I could see this happening with climb milling and a bit of flex in the system (the end of an adaptive pass will usually be a sharp ridge that will put extra strain on the cutter, possibly enough for a thin one to break); if you do climb, try conventional milling or bumping up the spindle speed if possible.