Stalling Steppers

[mrscheider]

Hi all,
Okay, so after working through a few initial problems with my new Taig mill I was smooth sailing. Brimming with confidence, I strapped on a piece of stock, set it up and ran a new project.
After the first couple hundred lines of code, I left the mill to do its thing...too cold in the shop to babysit it. Came back a half hour later and found the Y motor stalled out.
This is a brand new Taig DSDL 3000 with 200 oz-in stepper motors running on WInXP Pro, controlled with Mach3.
Instead of taking every shot in the dark with the dozens of variables and wasting all the stock and tools, I thought maybe you fine folks could post some of the most common reasons why motors stall on these benchtop systems. In the first instance, it was only the Y motor that stalled.
In the second attempt, the Y failed again. I changed the program to a simpler part to cut, a part I had cut earlier that day with relative success. Came back and now both the X and Y were stalled. It wasn't an issue with a limit or home switch either because DRO's were still happilly moving through the Gcode.
Any suggestions would be great.
Thanks!

Michael

[tpworks]

I had something similar happen and it was my drivers over-heating, put some fans on them and fixed the problem. Mine is an X2 with kit drivers but anything is possible with thes controllers.

[Pres]

Try keeping the screws/nuts and slides "wet" with lube.

Mobil 1 0W-20 synthetic has excellent wicking action.
(lasts longer, but still do it, at least, every 4hrs of machining)

hth,
Pres

[MonroePoteet]

I think Pres has it right: lube the ways and screws. I put a few small squirts of lube on the ways and screws before each job, and do a full lube before and after each day's work. If I don't do this, it'll miss steps, although it's mostly my Z axis that loses it.

I noticed in your previous post you're using WD-40 as way lube. I'm not an expert, but that doesn't sound like a good idea to me. The instructions for my Taig suggested Automatic Transmission Fluid, and now I'm trying Vactra to avoid the ATF smell (per another thread here).

BTW, after re-zeroing the axes, you can have Mach3 start the job from where it failed. I usually backtrack to the last application of the cutter (Z goes negative), use the "Set Next Line" and "Start From Here" to have Mach3 develop a setup move. Make sure the coolant is on and the "start spindle" button is checked, though!

mTp

[mrscheider]

Hi Guys,
Thanks for the replies. It's definitly not a heat issue. It was 15 degrees in my garage last night! The motors were barely warm. I could go along with lubriacation. Does the machine seriously need to be lubriated that often? I have allot to learn!
A also suspect I was pushing all my rates too fast. Feed, cut, approach, plunge... everything was like 40, 50 even had an 80 feed rate. After hours of researching "stalled Motor" threads, I realized these rates were a little high for the Taig... even in wood. So that could be a contributing factor as well as lubrication. I oiled it real good the previous day but not yesterday. I just didn't think it needed to do it again until I saw syptoms.
I'll try both possibilities and see if I can get more reliability from the system.
Thanks again for taking the time!

Michael

[Pres]

Originally Posted by mrscheider .... I changed the program to a simpler part to cut, a part I had cut earlier that day with relative success.....

Apparently, you neglected to mention that you had upped the feedrate?

Most of the suggestions were assuming you were running the same setup/params that you had used successfully before.

If that was actually the case, then about the only "variables" are cutter sharpness and bearing/slide lube.

The faster you go with stepper drives the more likely you are to lose pulses/position.

Pres

[mrscheider]

Hey Pres,
No, I didn't up the rates... those were the orignal rates I generated with the tool paths. Those ran the first time... it just never re-ran without stalling.
Incidentally, the lowered feedrates and the lubrication did the trick. I was able to get through a rough pass, a pre finish and a finish pass last night with no failures. Parts came out perfecto!
I was psyched! I dunno why the job ran the first time with the 80 feedrate.. but It was much more reliable at 40 so I'll stick around there for a while.
Thank you very much for the help though!

Michael

[tsalaf]

At 15 degrees your lube may have become too thick to lubricate properly, thus causing some sticktion.

You should also check all the wiring inside the control box to make sure everything is secure. Wiring terminals can loosen from vibration and from the screws compressing the wires over a period of time. This can cause intermittent loss of connection with the computer or power supply, resulting in stalled steppers.

My understanding of the Taig DSDL 3000 system is that it should stop all movement if the steppers stall, thus saving your material. If the DROs do not stop when the table stops moving, you might want to check the encoder signals or the Mach3 configuration.

[mrscheider]

I'll bet thats why the XML file came with MACHs Limit switches enabled. The Taig doesn't actually have limit or home switches, but having limit switches enabled, they would trigger, even while doing slow jogs. I tried adjusting the debouce signal inputs but it didn't help, maybe because that requires actual switches. In any event, yes, when the limits are triggered, the whole system stops. Momentum would usually throw the system off by .0005-ish so resuming wasn't always successful either.
Disabling the limit switches lets the system run more reliably but doesn't stop due to a stall and thus loses every step in that stalled axis until a reset. Bummer.
Anyway, Leaving off limits and feeding slowly, the system worked last night very well. I will have it try again tonight on a diff project. I agree with the viscosity of the oil too... it's thick until the system is warmed up a bit. I wiped it down, jogged it around a bit and lubricated with a room temp oil can prior to running a job and that worked out good. Hope it stays that way!
Thank for the replies!

Michael

[mrscheider]

Alright, to re-visit this sticktion theory. It's cold again in east PA tonight.. the oil thickening makes sense. Tonight I got home, I powered up all the equipment. I have a small ceramic heater out there... I turned it on for about 15 minutes. Wiped the machine, oiled it.. moved the tables about a little, strapped on the stock and ran a new code I generated tonight.
The Y stalled 500 lines in. I flipped the stock, zero'd, restarted.
The Y stalled a few hundred lines in again.
That time the stock was barely cut so I just restarted it.
Y stalled 1000 lines or so in.
WTF?
I thought maybe it was this new code.. I loaded last nights code and it seemed to work. Weird. Okay, I got a new piece of stock. Loaded the new program again and ran it. I just checked and its running fine.
Could it be that the machines ways and motors just have to come up to temperature? Should I run some ghost code just to get it all warmed up before starting any cuts?
What do you think?

Michael

[tpworks]

I would definitely run a few air runs before messing up too much stock, where in east PA are you, I used to live in the tri-state area and built Homes in the Poconos, Hemlock Farms area

[MIKE JEFFERS]

a warm up program is a good move :-)