So I am trying to make some coaster for a friend of mine dad, BUT having some major issues. This is happening in all the files I have created in the two weeks. 

 

A couple of board I am just milling 0.2 inches over four passes. After the third pass the bit just drive straight down....

 

 

So I created a new coaster file. 0.96 thick. 

 

Using Vcarve Desktop with UGS. For some reason I will be in the middle of a pocket and then the Z axis drives all through the depth. If someone could look at my paths

first is 0.2 pocket 1/4 endmill
second 0.96 1/4 endmill
Then 0.1 90 vbit but I can never get past the second 0.2 pocket.

I've included my files paths. Any assistance will be greatly appreaciated as I am lost to why this is happening.

 

Thank you!
 

Edited June 3, 20232 yr by KevTN

When a CNC does something unexpected that didn't show up in the preview of the toolpaths, that means something else is happening.

Are you using a shop vac / dust collector to follow the bit around?  Static discharge from a poorly grounded shop vac hose can interrupt the bit flow sequence just long enough for one or two G-code commands to be lost.  A stepper told to move down -Z that didn't receive the last instruction that told it what depth to stop at will appear as an unexpected plunge too deep.  

A poor data connection/loose cable connection can do the same. Vibrations from the CNC when running can jiggle cables enough to reveal weak solder joints or other bad connection points.   Check the whole path from PC to controller to stepper motors for loose cables.  

It also helps to understand G-code.  The G-code file is just a text file you can open in Notepad to examine. If you don't see any commands with a Z in them and a lower height value than any depth of your toolpaths would be then it isn't bad G-code. 

 

BTW the only thing I would change in your coaster file is to add tabs around the edges of the coasters. 3 on each would be enough to keep them connected/in place while being cut and are easy to break through/sand  or flush trim off after the CNC is done. 

4D

Thank you 4D! I appreciate the input. I spoke with tech support of my CNC and they made some suggestions to help troubleshoot as well. 

Glad to help Kevin.  One last thing to check is the router collet. I know from personal experience they can get packed with sawdust and eventually not tighten well enough on a bit to keep it from slipping out as it cuts.   Up cut bits will pull themselves down if they aren't snug in the collet.  When you change bits completely remove the collet and tap it on the CNC bed to knock out any debris stuck in it.   That may not be what is happening right now, but it is a good practice to use anyway. 

4D 

Yes sir….I saw a video of that happening and the amount of dust collected in there. Yikes!

One semester I had a brilliant student assistant assigned to help me with student CNC requests. She rarely had any questions for me except for how to do complex joinery cuts when they popped up.   One day she complained the bit had been slipping out of the router collet during a job she did.  As this was a recent development I unscrewed the collet on the router she'd been using and showed her  how packed it was.  She was a little shocked when I tapped it on the bed a few times and each time more debris shook out.  She adopted the clean collet each job rule and never complained about loose bits again.  

4D

Edited June 10, 20232 yr by 4DThinker