Gerber Sabre Quality Problem...Chatter?

[SignworksUnlimited]

We have a Gerber Sabre 408 router that has started to produce rough edges on routed pvc. We are using Enroute4. We have also noticed that the gantry is loose and we can move it by hand about a 1/16" in both directions when the table is idle. Has anyone had issues with "chatter" in the gantry causing quality issues on harder substrates? I should add that we do not see the problem with softer materials, such as HDU.
We replaced the bearing bushings and that helped a little but think it may have more to do with the connection to the lead screw under the table. Any help or recommends will be appreciated!
Thanks!

 

[Techman]

chatter is usually deflection at the cutter. IS the cutter sharp?

 

[SignworksUnlimited]

Tools Is Sharp!

The collet and bit are fine. Today I routed a DiBond sign with a 1/2" circle in the center. The hole did not rout as a circle...it was a square-circle mixed shape?? I wonder if the Enroute software is dropping info when it sends the G-code to the Sabre router...
I also get flat spots in letters that I rout...usually "O's".
"Chatter" is a bit-related term. I should have said the quality issues make me think the gantry or something is loose and cant deliver the precision it used to.??!!??

 

[J Hill Designs]

I would find a way to tighten the gantry first and foremost

 

[johnnysigns]

Is the lead screw bright and shiny on the Y axis? If it is you may be in for a lead screw replacement. X & Y axis lead screws ran us $4k+ in the last 6 months. That was our 1st major service call for the machine in approximately 8yrs. I find that our machine does not like heavier lubrication on those lead screws either. Our tech seems to like sprayable lithium grease, but I use something much lighter and it works well for our cutting needs. Our Sabre has run approximately 5.5-6hrs a day on average over the last 3yrs.

 

[ridefst]

The lead screw has a two part, spring loaded nut that is supposed to take up any slop in the nut/screw assembly.
I've seen that nut get dirty and not spin freely, so it doesn't self adjust anymore (the spring isn't very strong)
Sometimes also helps to unhook the spring and twist it a little bit tighter as well.

As Johnnysigns mentioned, if the lead screw is a shiny silver color in areas, that means the factory teflon coating has worn off and you're probably about due for a new assembly.

The screw is a Kerk product, I've bought them directly in the past for cheaper than Gerber's price.
It's been a while, so I don't have a part # anymore unfortunately. http://www.haydonkerkexpress.com/ecatalog/lead-screws/en
I believe I needed to get the ends of the screw turned down at a local machine shop when I did that though.