Technician in Brisbane, Australia?

[Shane]

Well this is going to be the short version as the long version of this post got lost when I was just about to post it.

Anyway, I need to find an expert or CNC technician that knows about the PRS Shopbot and can come around and fix my machine. It has vertical chatter and I've tried everything but it still appears. I'm more than willing to pay as this downtime is costing me money.

Regards,
Shane.

[knight_toolworks]

is the pic what you are talking about? if so that looks pretty normal. if not what are you talking about?

[kubotaman]

Right now I have the same problem. If I climp cut and make sure that there is no vibration what so ever the chatter would disappear. I also have to feed at a slow speed, 1-1.5 IPS. It is slow but the results are very good. Just make sure that the cutter is very sharp.

[Shane]

is the pic what you are talking about? if so that looks pretty normal. if not what are you talking about?

The chatter is worse than it looks from the photo. I mainly cut 18mm thick MDF wooden letters using 1/4 inch bits due to the small spaces between the letters. I have tried with 3/8th bit and the chatter still occurs. All bits are brand new Onsrud or Whiteside. Downcut spiral or compression, ranging from single flute through to 3 flute.

I never had this issue with my old CNC Shark Pro and would of thought a machine like the Shopbot should have a lot better and smoother cuts.

Is this vertical chatter normal for other shopbot users? Slowing down the feedrate doesn't really make any difference. It seems to be worse on the X axis. Would increasing the rpm help reduce chatter or does it make it worse? I've tried from 10k-16k. Feed rates from 20mm-100mm/sec.

I've tested for slop in the axis and tightened the steppers against the rails. Retightened the lower oblong guide wheels on the Y axis gantry.

I do my cuts using climb passes and change to a conventional pass for the final. Even tried using a 1mm allowance offset on the climb pass but makes no difference.

Shane.

[Shane]

Right now I have the same problem. If I climp cut and make sure that there is no vibration what so ever the chatter would disappear. I also have to feed at a slow speed, 1-1.5 IPS. It is slow but the results are very good. Just make sure that the cutter is very sharp.

So Daryl to eliminate your chatter do you climb cut only? How do you handle horizontal tool pass marks? Or is that single pass cutting?

Shane.

[jzarski1]

I had this same issue with my bot a few months ago. Well I realized that I had the wrong pinion gears. They where the right tooth count but wrong gear. Not sure how old your bot is but if you changed pinions then make sure they are the right ones. I guess there where two different kinds of rack. Not sure when they changed but I got sent the newer pinions and I had the old rack. I was getting the exact results you see and I also cut only MDF. Shopbot sent me the right pinions and cuts are perfect. I cut at 3.8ips with 1/4 downsprial and they are perfect ready to finish parts. Hope this helps.

John

[kubotaman]

Shane, I am forced to make multiple cuts to get the depth that I am required to do which is 1.5 inches deep. I am cutting VG Fir which is stringly and has lots of soft and hard spots. I also have to climb cut otherwise the grain pulls out making the part useless. To be rid of the multiple horizontal cut marks I have to do a clean up pass, .007 deep, to be rid of the poor looking maching marks. The clean up cut is required to be done in two passes. If I don't do the above steps then the parts don't come out very good at all and would require sanding. I opted to do it this way since I hate sanding. I admit this process is slow but it is the only way I have found to do these particular parts I am required to cut. I would think with MDF cutting in either direction would be okay since it has no grain to it.

[Bob Eustace]

Hi Shane

Could you tell us the Shopbot model please? Are you perchance using Australian made cutters by Carbitool or Carbatec? Spindle or router?

Bob in Melbourne

[Shane]

Hi Shane

Could you tell us the Shopbot model please? Are you perchance using Australian made cutters by Carbitool or Carbatec? Spindle or router?

Bob in Melbourne

Bob, It's the latest PRS 96x48 Shopbot. 2.5hp Spindle. I only use Onsrud or Whiteside bit purchased from America.

The only thing that isn't new is the Y axis stepper motor which was a replacement for the dead on arrival motor. But they sent the wrong model motor and it is an older PRT motor. I was advised by Shopbot support to change some settings in the control box for that driver to make it compatible. Could it have the wrong gear on the end for my rack?

Shane.

[jzarski1]

Bob, It's the latest PRS 96x48 Shopbot. 2.5hp Spindle. I only use Onsrud or Whiteside bit purchased from America.

The only thing that isn't new is the Y axis stepper motor which was a replacement for the dead on arrival motor. But they sent the wrong model motor and it is an older PRT motor. I was advised by Shopbot support to change some settings in the control box for that driver to make it compatible. Could it have the wrong gear on the end for my rack?

Shane.

I would get with Shopbot and find out what gear was on it. The number of teeth could be right but it's the pitch that was the issue for me. I messed with ths issue for weeks before realizing it. I hope it that simple fix.

John