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

[Shane]

I just rechecked the gear and I'm fairly sure they only sent the PRT motor and I had to take the old gear off and put it onto the PRT. So that pretty much rules out the gear being the issue.

Shane.

[jerry_stanek]

Call Shopbot and see if they will send you the correct motor.

[Rick W]

Shane,

I have the same thing, I have a 48" buddy (4' x 4' table) and a porter cable router. I purchased about a year and a half ago (maybe 50 hours on it).
The picture is 3/4" low density polyetheline, pass depth .0625, feed 1.5 inch/sec, plunge .5, 1.5" smooth ramp. Brand new 1/4" 2 flute solid carbide straight bit. Just went through "puzzled about why usb hubs help" thread, think that might have helped a bit with chatter with the exception of where I put tabs.
Like yours, the chatter is a lot worse than what it appears to be in the picture.
I don't really have an answer to your chatter problem, if I find anything out I will let you know. I am looking myself.

Thanks Rik

[davidp]

Shane,

Get your Y motor and pinion checked first,

Second try a Carbitool TSPL08S for a down cut or TSPR08S for an upcut, both single flute spirals, at approx 15000 rpm around 65mm /sec two passes leave approx 1.5mm depth and an offset of 0.4mm then final cut full depth no offset. The chatter is more often than not caused by the part moving resonating with the cutter. You will also achieve better cut quality by leaving a bigger space between parts. This reduces the movement of the parts.

Also Laminex MR Craftwood is a bit dearer but it produces better cut quality.

If you do not get it sorted I have a couple of people I can refer you to who may be able to help.

David
Sydney

[davidp]

Shane,

There used to be a bloke on the forum from somewhere near Nambour I think, who used to build and repair CNC he knew a bit about shopbots. Search the forum archives around 2008?


Send me a pm if you need further help.


David
Sydney

[Shane]

Thanks everyone for your replies. I think I solved the issue. It was the replacement PRT motor they sent me. I swapped it over with the normal PRS motor that was on the Z axis and now the chatter has gone.

The only thing is now there is a slight vibration in the Z axis. I phoned Shopbot support and they suggested to change the run setting in the driver from 6 to 4 (PRS motor normally run at 9). I think that has helped but with it being the Z axis at least it shouldn't be causing too many issues unlike the x or y.

I'm in two minds whether to request a new stepper motor from Shopbot. My PRS is brand new and the y axis motor didn't work from day one. The replacement they sent me looks like a refurbished PRT motor. Should I be happy with accepting a PRT motor for a PRS machine. Shopbot support never asked for the old PRS motor to be sent back. Maybe I should get the original PRS motor looked at by a professional to see if it can be fixed.

Shane.

[Shane]

Shane,

Get your Y motor and pinion checked first,

Second try a Carbitool TSPL08S for a down cut or TSPR08S for an upcut, both single flute spirals, at approx 15000 rpm around 65mm /sec two passes leave approx 1.5mm depth and an offset of 0.4mm then final cut full depth no offset. The chatter is more often than not caused by the part moving resonating with the cutter. You will also achieve better cut quality by leaving a bigger space between parts. This reduces the movement of the parts.

Also Laminex MR Craftwood is a bit dearer but it produces better cut quality.

If you do not get it sorted I have a couple of people I can refer you to who may be able to help.

David
Sydney

I was looking at trying the moisture resistant MDF. But the price was $54 for a sheet compared to $35 for the normal MDF. I mainly cut out letters and words so leaving more space between parts can be difficult.

I had been using 12k RPM at 76mm/sec for the first 8mm climb pass and the final was 13k RPM at 40mm/sec for the remaining 10mm conventional. I was getting a crosshatch pattern when having the final pass at 12k RPM. At 13k it seems to eliminate that issue. I'll do some test cuts at the higher RPM and see how that affects the finish.

Shane.

[Simops]

Thanks everyone for your replies. I think I solved the issue. It was the replacement PRT motor they sent me. I swapped it over with the normal PRS motor that was on the Z axis and now the chatter has gone.

The only thing is now there is a slight vibration in the Z axis. I phoned Shopbot support and they suggested to change the run setting in the driver from 6 to 4 (PRS motor normally run at 9). I think that has helped but with it being the Z axis at least it shouldn't be causing too many issues unlike the x or y.

I'm in two minds whether to request a new stepper motor from Shopbot. My PRS is brand new and the y axis motor didn't work from day one. The replacement they sent me looks like a refurbished PRT motor. Should I be happy with accepting a PRT motor for a PRS machine. Shopbot support never asked for the old PRS motor to be sent back. Maybe I should get the original PRS motor looked at by a professional to see if it can be fixed.

Shane.

Shane, as said in the other thread, I believe that you should get onto shopbot pronto and ask, as you are entitled to, for a new replacement part, especially in light of the fact that it is brand new and the fault was there on delivery. They may want the two servos back which is fine, once you get your deserved replacement.

Good luck....
Mike

[frank]

New motor was sent out yesterday.

[myxpykalix]

you can always count on Shopbot to do the right thing. They sent me the wrong size carriage when i bought my bot. I called them and i got a new one delivered the next day.

[Shane]

Thanks to Frank and Shopbot support they are sending out the correct motor. Great to see a fantastic level of support from Shopbot.

Shane.

[Simops]

As expected! That's why I bought a Shopbot.....Great old fashioned service!

Cheers

MT