ok fellas, i got something going on that has me completely stumped......my z-axis home position is drifting on me. ther are no missed steps, no coupler slippage, nothing like that. even running the axis slowly, the position creeps....its not like alot, i just notice it happening. the longer the run time the more it drifts. i tried running different voltages, changing step modes.....man i really donno on this one....any input will be more than welcomed. randy.

 

Hummmm mine does this too. I thought it was just some missed steps ( how do you really tell if it misses a few steps here or there with the Dremel running? ) so I deal with it. I re-home the Z axis every now and then, and all is well. It used to be a lot worse, but seems to have gotten better over time.
I know my Z won't hold up to the rapid tabbing shown on the new MII demo.

 

rcav8r, i test axis movements with dremel off. im starting to think its a precision setting in sketchup?

 

gotcha... I'm too lazy to do that ... I just re-set home, and "print". I should do that and try it just to see. I'll let you know what I find...if I remember to do this...

As far as precision setting in SU? DO you mean it doesn't always generate the code properly? A quick look at the code should show if the numbers are the same. I know on mine the bit pops thought the foam w/ maybe 1/16" above the foam. And if I set the tab/center line/fold at 50% it is almost through the foam, so I adjust accordingly. Just thought it was the way I was setting home on my Z.
FWIW I set my Z like this: I put a straight edge across the roller and the top of the cabinet at the front. Then adjust so the bit is about a credit card width away from the straight edge.

 

man, i have the couplers set-screwed to the screw and stepper shaft. got them both buryed. its not slippin, its something else. anyone know what that decay voltage setting really do?

 

hmmmm, shot in the dark here,, is the bit tight? :?:

 

t-bird, all the testing i am doing right now is with the dremel not running....it seem as to drift lower and lower. its not a large amount thou. im wondering if something in mach-3 got corrupted or something now....man its weird, its just on the z-axis....

 

dennis, i didnt think of that, thanks, i will check that out....maybe that 300ipm rapid is doin exactly what your talking about. also i can probally slow the accell rate to see if that helps. thanks man. randy.

 

dennis, the dremel is not moving.....i set the jog mode to single step, with a value of .010in. set my indicator on a 1/8 dia. blank i got chucked up. i jogged down a few times....then back up, and set zero on the indicator. when i jog down one value, it moves .009in that tells me i got a .001 of backlash....aint no biggie to me.......but when i jog up then down a few times, i can see the axis drifting lower and lower, like a .001 at a time.....i checked the tightness of the nut and everything is all good.....man im so confused now....it repeats good as it drifts down thou. also the jog moves were set, way, way slow.....all i can think now its ether the mach-3 or something on the z-axis part of the control board. man i have no clue how to troubleshoot this problem i have found. randy.

 

Well I did a dry run ( Dremel not running ) on some ply parts I was going to cut. Defiantly no missed steps on the Z. I then set the X/Y axis down to 12IPM ( you 400IPM folks are probably laughing now )and loaded some 1/8" ply. I generated the code using 1/8" as the material thickness in SU. The z axis was homed as I described above.
I then watched the machine as it cut. All Z axis plunges and un-plunges had the same values as the G-Code was rolling by. I'm fairly certain the SU plug in just fine. During cutting the bit was just poking through the ply.
I did notice as it was cutting the last piece the bit was no longer poking through the ply... It was leaving a thin skin where the cut was. I thought maybe the ply was warped, so I pressed down on the wood. No change.
I don't have the tools to measure like rjarois, but I'm guessing it's something mechanical in the setup (backlash?). This is the only axis that has gravity working against/for it. I'm using the stock all thread/metal nut for the Z as I haven't had the time/guts to tear it down and switch to acme thread and a UHMW nut. I don't think that the hardware/firmware is doing it as we would see it on the different axes since this the board is just 3 duplicates of one circuit; or is it?. Just my $0.02

 

FWIW, I am using a different stepper for my Z. The Stepper has a HUGE amount of torque, but no speed. When I had it in my Y axis I could hold the Y/Z gantry and it would move the cabinet across my work bench. I was only able to get about 12ipm (it would skip steps when not even connected to the rod) so I moved it to the Z.

I don't know how that is related to holding power, but if it is, I don't think that is my issue. If it's not, then you may be on to something.

 

rcav8r, i have a 260in oz stepper installed on the x and y axis. the y-axis is fine, its just the z im having troubles with. randy.

 

Yep... But Flash was mentioning holding power of the Z due to the weight of the Dremel... My X and Y are just fine too and they have the stock steppers.

 

ok fellas, its hard to decribe what the axis is doing...so here is a video of it. i have messed with the voltages both v-ref and decay, step modes, everything i can think of....the nut and coupler are tight, monkey tight...ther not moving. man im at my witts end. the axis works great, except for the zero drift. it drifts at even 5ipm feed. man im completely stumped on this. randy.

 

I would think it is the accurateness ofthe Z calculation setup in mach3. You only have 1"-2" to setup the distance calc. To be very accurate you need more distance to work with. I thaught I was loosing steps also after a lot of plunges or tabs. I will have to look to see what my #'s are? I know I changed the Z # from the setup #'s that Mark gave. I think he even states this fact in the TUT. Videos.

EDIT: After watching the video now I'm not so sure because I see that you are moving it very little and still loseing a thou. for every 5 up/downs. ?



Cheers,

E-T

 

Flash,

What is your calabration # for the Z I can't look at mine now. I'm at work but, wondering how close they are to mine and The ghetto foam cutting monkey's or did rjarois change out his Z allthread?

cheers
E-T

 

evil, i am using a acme screw...the calibration value wont be the same. randy.

 

ok fellas, after spending the day googling and serching the cnc zone i finally figured what was wrong...call me a bonehead, idiot, or like the fella on the cnc zone called himself.....well i cant tell ya what he called himself. they must have a more relaxed postong rules, lmao. ok after i slapped a new cpu in the pc a few weeks ago, i figured i bump up the kernel speed......well thats the wrong answer....as soon as i switched back to the 25000mhz setting, the axis is working perfectly now. repeating dead nutz now. man oh man, pullin my monkey butt hair out over this. want to thank all who tried to help the village idiot. peace, randy.