Since I am a new member to the forum, I can only post 1 image. I condensed the 5 images down into 1 and it’s posted and annotated at the bottom of this post. Right-click to open the image in a new tab to view it better.
I’m having a hard time with this project and I need some guidance and wisdom. I’m cutting a 4mm path into a 6mm piece of cast acrylic on a Shapeoko 4 XXL. I’m using the stock Nomad #201 1/4" end mill. The values I used were from a video by Winston at Carbide (https://youtu.be/a9qi6Z-CEP8) for cutting acrylic on a Shapeoko with a 1/4" endmill (starts around the 2:07 mark in the video).
Pocket toolpath is image [1].
The settings for the toolpath is [2].
The first time I ran the job, at cut the first small sections fine but when it got to a longer stretch like on the letter L on the far left, I ran into a problem. And by problem, I mean the wasteboard. It went completely through the material and well into the wasteboard. I immediately stopped the machine and what is found is [3].
Another shot from further back is [4].
Not quite sure what happened to have caused that but I started looking into my computer logs to see if there was a failure or hang with USB communications during the job but that didn’t appear to be the case since no critical/error logs were found regarding USB or serial communication during that time. I’ve used the CNC many, many times using the same computer and USB adapter and I’ve never had any issues, so I don’t think that is the case. This was also my first time working with acrylic, though.
I performed a dry run but redoing the job but taking out the bit and keeping the spindle off for the job and there were no problems. It ran perfectly. I paid extra attention and recorded a video when it got to the spot where it failed previously just to be sure. I feel confident that it wasn’t the comm path, the CNC, or the computer.
I reordered another piece of 6mm cast acrylic, thinking that it was just a transient issue. I ran the job again and kept an eye on it. It made it past the part where it failed the first time and I thought everything was good. Shortly afterwards, it did the same thing again but at a different spot. The result is [5].
When it gets to longer, straight-line runs, it makes a different noise, like something isn’t right. Can’t quite explain it but it keyed me in and got my attention so I was able to stop the machine before something spontaneously disassembled. The cut gets deeper leading up to it and eventually passes through the material entirely and then keeps going into the wasteboard where it gets completely trapped. It seems like the material is pulling the endmill and spindle down, treating the bit like an auger or screw rather than a cutter but I can’t be 100% sure that is what’s really going on.
I figured that since I used settings provided by Carbide in the video and verified it in other posts on the forum that they would be safe to use.
What am I doing wrong?
