Gerber Saber perfect circle problem

[Cmiller01]

Hi everyone,
We have a Gerber Saber and have been running into a very strange issue with our machine. We cannot route a perfect circle on it without it leaving a "divot" on either the stop or starting point. We have tried bringing in files from Cad, Illustrator, and Corel Draw, and they all do the same thing. We have also tried adding more nodes to the circle, 8 instead of 4 for instance, but not difference. Has anyone else ran into this problem with their machine? Any suggested fixes or is this the nature of the beast? We have noticed it on other curved surfaces as well,and have minimized it by adjusting the start and stop point, but circles still elude us. Thanks!
Also, to my knowledge, it has always been this way. We just figured we would post and see if there are any solutions to the issue.

 

[J Hill Designs]

show a picture of the divot. some routing software does 'overcuts' (finish point past starting point)

or if its a concave divot, is the material moving on you during the last part of the cut?

 

[Cmiller01]

See attached photo. The material is not moving while cutting....

 

[MikeD]

not sure about the Gerber model, but most cutters have internal test / adjustment sfor origin and end points meeting up. If the values are wrong, the problem shows up in large circles more often than any other shape in my experience

 

[johnnysigns]

Ours has always done that to some degree or another... I find softer materials do this much more often leading me to believe the bit is "scavenging" more material as it enters slowly. I just play with the Z axis speed when it's an issue.

 

[Techman]

You cannot stop deflection. It will happen no matter what.

 

[J Hill Designs]

Only way I can see to overcome that is to make a second pass offset by .01 inches or so IN

 

[darrell]

Vacuum... is the piece moving at the end of the cut?
One technique is to make one pass first without going all the way through
try leaving .010 in. make a the second pass and go all the way through
This reduces the resistance and makes it less likely to move
Are there lots of circles try covering the areas cut to prevent vacuum loss
I've never used a Gerber hope this technique translates

 

[skyhigh]

First off....nice pic. It doesn't look too terrible. Can you notice the piece shift when it finishes the cut? evidently not, as you feel its in the software.

You had my curiosity up, and being I was just cutting some 1" acrylic, I tried the circle test myself. If I look really really hard.....nah, no divot. My circle is 6" round, using a 1/4" bit.

You say "its always been this way"? Did you buy the machine new? How long have you owned it? I'm thinking the "mechanics" are getting worn & sloppy, or the vacuum isn't doing its job too well.

This white acrylic is hard to photograph (esp. on a cell phone). I had to throw a piece of vinyl on the one side.