Bad stalling suddenly occuring...

[jeffreymcgrew]

Hey everyone. Got a big problem (right in the middle of a big push natch).

We just upgraded to the 4g driver board, and so far it was great. Cut a number of jobs no problems. Now, however, suddenly we've got issues. We're getting a bad stall, where the table will be in the middle of a move or a jog, and will appear to 'stick' in place while one of the steppers seems to make a loud buzzing sound. While it does this the control software still thinks the table is moving. After about three seconds or so of this stall, the table will suddenly 'unstick' and keep moving with a way-off register. It seems to happen both in X and Y.

So I called Shopbot this morning, and they said to reload the firmware to the 'bot (which I hadn't done when I upgraded to the 4g stupid me) and to use a USB 2 connection instead. So I swapped to a nicer laptop (P4 3.0 Ghz, 1 gig ram, USB 2) and tried it. It ran the rest of that job, no problems.

Now, however, when I try to run the same job over again, I'm getting this bad stall, and being on the West Coast Shopbot is now closed...

So while I'm e-mailing into them the issue, I need to get this worked out ASAP so any help y'all got would be very appreciated.

[Brady Watson]

Hey Jeff,
Feel free to e-mail me the SBP & I will air cut it on my 4G to see if it happens on my machine. This would certainly rule out the controller, if it is somehow something to do with the toolpath.

Question: When you upgraded to the 4G, what voltage did you set your PRT power supply to? It is *possible* that the power supply could be overheating or 'clipping' if it is set too high. So while it may not show up the 1st few minutes, it may show up after it warms up. You won't hurt anything by pulling the voltage down to 48v, instead of the 50-some that SB originally recommended. I think they have since reduced the recommended voltage to 48v.

-Brady

[jeffreymcgrew]

Brady, thanks a ton. I'll send you the file right away. It's for a 4x8 sheet of plywood, 0,0 in the lower left corner, and it's got a big pocket, some drilling and some profiling.

I'll double check on the voltage thing. I did set it to 48 if I remember correctly, but I'll double check that. Thanks for the tip and the help!

[br928]

At what speeds are you trying jog? I can't reliably jog at more than 14 IPS with my PRT upgrade. Since it is a little colder I have reduced it to 10IPS. Try holding on to the carriage during a jog and see how much torque it is developing. Mine would 'strip' easily at around 16IPS.

[jeffreymcgrew]

I was jogging at 12-10 IPS, and when doing so it appears that the Shopbot has plenty of torque when I do give the carriage some resistance. I even slowed it down to 8 ips, and still had the bad stall/lock happening.

[zeykr]

Adding some fans to my control box with 4g upgrade seemed to reduce the stalling from happening - Maybe due to keeping a marginal powersupply cooler, but I still keep jog down to 10ips or lower and have had stall happen once recently anyway while jogging using keyboard. If I try to jog over 10ips the stall will happen fairly often.

I'm running USB 2.0. I understood from talking with shopbot or somewhere this is a sympton of bot moving faster that CPU can keep data flowing to it.

Keeping jog under 10ips is an acceptable solution for me and I'm very happy with the upgrade, but it would be nice to find the solution and be able to use the 4g to it's absolute fullest potential.

[rob_bell]

Hey Jeffrey-

I've had slightly similar issues from time to time - but I've never actually lost registration during a file. I've had sudden hiccups which while alarming didn't affect the cut. I've had the software 'think' it's moving the bot in keypad mode when it wasn't resulting in lost registration. And I've had random communication faults - generally first thing in the day which is odd. But nothing quite like you describe. I have an Alpha.

I'm not far off if you need a hand.

-Rob

[jeffreymcgrew]

problem is that it's stalling when cutting too. And it's not a stall as in 'it's lost power' its much more like a sudden 'lock and stick' accompanied by a loud buzzing sound. Not Good. Looking at it closer this morning...

(the voltage thing didn't seem to make a difference, for it was set at 48v too...)

[Brady Watson]

"...accompanied by a loud buzzing sound."

This is a clear sign to me that the motors are stalling. Everytime I have heard this noise, it was because there wasn't enough communication speed from the PC to the control box.

Slow things down to: 4 IPS on moves & 6 IPS on jogs and see if the problem crops up at those speeds. If it doesn't repeat the condition, then you'll have to look into improving communication on your PC. Make sure the ShopBot USB is hanging off of the 'enhanced' USB root. You may need a 2.0 hub (ideally a 2.0 port) to do this in the device manager.

-B

[jeffreymcgrew]

you know, I went over the 'bot this morning, checking every connection, cleaning out every nook and cranny, and checking tightness of things and such. I double checked that the voltage was set to 48v. And then I ran a number of tests and jobs, and so far it seems back to normal. I'm going to add some fans to the controller box, and hope that the issue doesn't come up. It seems fine again for now. If it does hit again, I'll slow it down more, and see if it keeps happening.

Thanks everyone for all the help!

[jeffreymcgrew]

Got it figured out 100% I think. I hope.

Anyways, the problem started back up again this morning, and we tracked it down to the USB bridge of the computer hooked to the Shopbot. It was conflicting with something else that was using that USB bridge internally to the laptop (it's got a webcam built into it) and the two from time to time were conflicting. Once that internal item was disabled, it was smooth sailing.

So watch out using Laptops to feed jobs to the 'bot. It's pretty common for Laptops to tie all kinds of hardware onto the same bridge as an external USB port, which could cause hiccups, or worse, bad stalling...