[SamTaylor]

Every step of the way seems to have a little hiccup with CNC lol.

So Ive got my first completely nested project and all the tool paths set up. I have ran three sheets of plywood and the same thing keeps happening with different results. Here is whats happening.

We place the zero and start the file. It starts off working perfectly. I have it cutting the insides of all the pieces first. Then it goes right to the largest outlines. Every thing is accurate and it cuts the first couple of pieces just fine. About 15-30 minutes into the cut it just starts doing weird things. At one point it was attempting to cut a piece out of an empty spot that had already been cut. Or in another example, which I photographed, the second pass on the second arm was not even close to where it should have been to finish the piece.

Is this a user error some how? or could it be the Shop bot itself losing its place?

I have completely scratched the project file and re-done it to try and eliminate any odd issues.

The plywood sheet is nailed down to the spoil to prevent it from moving.

hope these photos help you understand!

https://i.imgur.com/0M6Kg4U.jpg
The top is right, the bottom... so weird.


https://i.imgur.com/ZgNpwI8.png
how the nesting looks.

[awerby]

It looks like your machine is losing position. This is commonly caused by over-tasking the stepper motors, which causes "lost steps". Since it's an open-loop system, there's no way for the Shopbot to compare commanded position with achieved position; it just keeps going, assuming it's in the right place. It could be that your rapids are too fast, that your acceleration is set too high, that you're taking too heavy a cut, or that there's a mechanical problem with your machine, like couplers slipping, debris in the racks and rails, or a failure of lubrication. Another thing to check is cooling and heat-sinking on the drives - problems that start out after the machine warms up often are due to electronics getting too hot.