Blend causes machine chatter on cone shaped section

[allister_mcrae]

I have a blended toolpath that causes severe chatter on the machine for a section of a cone (rounded sides). This is using a setting for a 1/4" bit with 4 flutes (ball) at a desired 0.006

**RESOLVED: Power Issues. (I'm guessing after slowing things down) All of this only applies on 4 flutes.  Set to 2 flutese 0.006 cut, everything is smooth.  Is the machine just not capable of moving in two directions at that speed?  Or could it be a power thing or something else?

• This happens at any point on the table. 
• It happens with no bit in the machine.
• It happens at mostly random points - but there is one instance where it was jamming every second round within a couple mills.
• The stepover is 0.04 in.
• Linking is all set to 0.25
• It was happening on other toolpaths - these tests just demontsrate it.
• It does NOT happen with a contour. (ie. Contour works fine)
  
  • But I want to use blended because some of the shapes are like the one attached but with a notch in the side that would have to be done separately if using a contour command
• With the contour paths, the machine does appear to have variable movement speed depending on what part of the circle its at (not a smooth speed curve around the O shape. )
• It does NOT happen with a blended square using the same settings.
• It does NOT happen when I do a circle command within the CNC software
• I haven't been able to pinpoint whether its happening on the X or Y axis.  No errors occur when I do a box within the CNC software
• CNC Machine is a shopbot PRT Alpha
• CNC Software is shopbot cnc
• The CNC machine software takes a long time to do anything after the file has loaded. And sometimes pauses after a move for an extended period if we can get that far.
• I have removed and inspected all pinions

I'm reasonably convinced that it has something to do with blend doing a circle. What is the difference between a contour and a blended toolpath? I feel like it may be in the code.  It doesn't make much sense it happens in one but not the other.

Attached .txt files are actually .sbp files (shopbot machine files) that i had to rename to allow upload.

Anyone have any thoughts on this?  

Thanks so much!

[FrodoLoggins · Accepted solution]

Chatter or poor surface finish? You mention this issue happening without a tool in the spindle. Do you mean your machine shakes without a tool?

If so, sounds like your CNC controller can't read the code fast enough so it moves to a point and then stops for a second to figure out where to go next then moves to the next point over and over again.

Your code as a lot of lines, are you turning toolpath smoothing on? Smoothing will reduce the amount of points your machine needs to read and should give you smoother results.

[allister_mcrae]

Amazing!  One of those "Haven't used enough to remember it" things.  Works fantastically well. Thanks so much 🙂

[allister_mcrae]

Follow up question: Those still looks like a whole bunch of M3 commands (which may be a shopbot thing as I use that for moving X,Y,Z all at once), as opposed a bunch of G0 or G2 commands.  Is it still outputting a bunch of lines instead of arcs?  Just less defined than the original somehow?