Why is my Z axis stalling all the time?


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Thread: Why is my Z axis stalling all the time?

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    Default Why is my Z axis stalling all the time?

    I haven't done much of anything with this stupid machine but today I had enough energy to try and engrave some wood for a friend. So far the Z axis has ruined the first 2 nice pieces of wood because the Z axis just randomly stalls and loses position, usually driving the cutter way too deep. When jogging the Z up and down it is fine and smooth 90% of the time then suddenly it doesn't move even though the motor is whining, like it's stuck. It happens going up and going down and seems to be random. I played with the acceleration setting ranging from 50 to 10 and it doesn't seem to matter. What can I do to troubleshoot this problem and fix it. I am so beyond sick of this worthless machine.

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    Change the two right settings higher in motor tuning, forget the name of them. Mine are 5. Acceleration to 5 for now also



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    Thanks B-Rad.

    Do you mean "Step Pulse" and "Dir Pulse"? Mine are currently 2 for both settings.



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    Yes, its the length of the pulse.



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    Interestingly, I changed the two settings from 2 to 5 and then did an air cut. The Z didn't stall at all but I think it's too soon to tell because it doesn't happen that frequently. I'll try more cutting tomorrow to see.

    So now my question is, what do those settings control and why would it affect the Z axis stalling?



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    Length of pulse, depending on your setup it will help. I'm using sherline mode so my pulses are really really long, but I still use 5 in those settings, I think that actually puts me at 25... Lol



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    Default Z axis stalling

    If the Z axis stepper motor is still whining than It is still turning but your ball screw is not. The coupler from the motor shaft to the screw is probably loose and you need to check the keeper nut at the bottom of the ball screw also.

    - - - Updated - - -

    If the Z axis stepper motor is still whining than It is still turning but your ball screw is not. The coupler from the motor shaft to the screw is probably loose and you need to check the keeper nut at the bottom of the ball screw also.



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    I tried using the machine again last night to cut some text into wood again. It would go along fine but then randomly and out of nowhere the Z would make a funny stall sound on a retract then the next thing I know the cutter is plunged way too far into the wood when it comes back down. It is trying to move and the computer thinks it has moved when it actually hasn't, throwing my Z position way off. I've ruined another 2 good pieces of wood after a long engraving routine.

    So I would pause the program and try jogging the Z up and down and it would still stall in both directions, then it wouldn't move at all. Mach still showed it moving but the the LEDs on the back of the Z axis driver quit flickering when I try to move it. The X and Y axes work fine. If I switch to manual mode the Z would work again and sound fine with no stalling, then if I switch back to Mach it would also work again for a while until the same thing would happen.

    What is the problem here? I don't think it's the motor since it works in manual just fine. I don't know if it is the driver since, again the manual mode seems to work ok. It's almost as if the driver is getting mixed signals then no signal. I'm just trying to identify where in the stream the problem is originating from and it seems to me it is up stream from the at least the motor and maybe the driver.

    This is so frustrating, the one time in forever someone is counting on me to make something for them in a soft material that the spindle motor can handle it still craps out. I can't even make one part without ruining it.

    Should I just scrap the whole system and get all new electronics at this point?

    edit: Ok I don't know if I can exactly afford to replace the whole system right now, but If I can do something to fix the Z stalling issue for now that would be ideal in this situation. Would a new Keling driver even be a plug and play part or would that necessitate other devices to be replaced like the breakout board too?

    Also does anyone with the integrated Mikini computer know if the ethernet jack still works after you pick out the black silicone caulk they put in there? I'm think if I go ape and redo the whole freaking machine I may want to add an ethernet smooth stepper.

    Last edited by SWATH; 05-30-2013 at 03:44 PM. Reason: Update


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    Swath, I feel for you. I wonder if the Z thing is a noise or software issue... For the noise thing...try this....After you home the machine, load a job that isn't to big to hit the limits switches. Then disconnect your limit switches from the rear board. If the job still has a problem, move on to your home switches. The home and limit proximity switches are only 5 volt. This low voltage makes them kinda noisy. I originally thought they were 12 volt, but, mine were not.

    If it's software related, you may have a corrupt xml file or Mach has to be reloaded. (I already suffered a corrupt tool library, so I threw the software thing in there

    pete


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    Pete,
    I'll try changing the stepper motor drivers tonight and cut air to see what happens. In the meantime I have pretty well decided to get a smooth stepper. I hear good things about the ethernet version over the USB version so I am thinking about this one from Warp9.

    Also If I wanted to get a more powerful stepper for the Z axis what is the best one I should get? It has a NEMA34 850oz/in currently and a 72v power supply. I don't know if the Mikini driver is digital but I would be willing to replace the driver with a better one if needs be but I don't want to if I don't need to right now.

    Last edited by SWATH; 06-04-2013 at 02:21 PM.


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    The ethernet smoothstepper is really nice. I've been using it for some time. You can't go wrong with buying it from either warp or cnc4pc. Although the warp guys are the ones who designed the smoothstepper. As for the stepper, the 850 should be no problem. I would hold off changing it until you have tried switching the drivers.

    Another thing you may want to look at is how many lines of code Mach reads ahead. I believe the default is 20 lines of code..maybe bump it up to 100 lines.

    pete


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    Thanks Pete,
    I wasn't going to change the motor yet but I need to preload these things in my head in case I need to replace it quickly. I wondered about the look ahead but hadn't changed anything with it. It is set to 20, what impact will it have if I bump it up to 100? Why not do 200 or 1000 or 10,000? What is the trade off, more CPU load? If that is the case wouldn't a smooth stepper help that as well. I think the smooth stepper will help at least with piece of mind as I need to run long programs and walk away from the machine without thinking I'm going to come back to a broken endmill, a gouged vice or table, and a smoking spindle. Right now I don't feel comfortable taking my hand off the e-stop.



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    I am curious about the effects of the lookahead setting as well... Anyone have some real world experience/impacts?

    CAD, CAM, Scanning, Modelling, Machining...


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    "-General Configuration (LookaHead____ Lines)
    Only applicable in CV mode. This determines how far “down the road” Mach-3's motion
    planner is looking. Setting this to a low number is like driving your car while being very
    nearsighted. A high setting is like 20/20 vision and using binoculars when necessary to
    see far down the road. This allows the software to better able to adapt to sudden changes
    in the motion path. It is recommended to keep this at around 200 for most cases. The
    maximum value is 1000, and setting this high may cause problems depending on the
    speed of your computer."

    And:

    "LookAhead determines the number of lines of GCode that the interpreter can buffer for execution. It
    does not normally require tuning."

    I found a post from 2008 that says the max you can set it is 1000...

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    I'll try bumping up the look ahead after I swap drives and cut air. I don't want to induce too many confounding fixes at one time.

    Another development I forgot to mention was while cutting wood last night the spindle motor and light tower would blink off for a split second then back on every so often. It did not hurt anything since it was wood but had it been steel, I would have lost and endmill and got a spindle halt. It literally turned off for about half a second. Does not make me feel confident. I also noticed that during this time even though the program specified S3300 (my spindle max), it actually read 5250 both in Mach and on the Mikini LCD but the actual RPM was 3300. The motor sounded different. In Mach the increment scaling changed from 100 to 250 so once I changed it back it worked. I don't know what's going on here but it's dodgy.



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    I switched the Z and Y motor drivers and ran a particularly jittery program with lots of rapid Z retracts for 45min. When it returned it was within .001 of where it started. I don't know if that tells me anything yet. I need to run it again and maybe a few times before I get a stall. I also ran it with the spindle off, so maybe I'll try it with the spindle on as well. I'm also a little bummed that there doesn't seem to be an aux 5v supply of of the board for the smooth stepper, maybe I'm wrong about that though, no big deal. I assume the 5v PW going to the display is for the backlighting of the LCD.

    The Mikini breakout board is weird as it seems to be broken into two parts, one in the chassis and the other behind the display. What I also don't get is that the parallel port is a 25 pin db25 but the header going into the front panel is 20 pins. How is anyone to know the pin outs for this, do I really need to get a continuity tester out and track down what each pin is? Also is such a cable even made (26 pin to 20 pin)?

    How have you had yours hooked up Pete? I'm just trying to figure out how to wire it so I know what cables to get and where everything would go.

    Last edited by SWATH; 06-05-2013 at 12:18 AM.


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    With my USB version, I just unplugged the parallel cable from the computer and plugged it in to the SS. Then plugged USB from the computer to the SS. You should not need to mess with anything on the Mikini. I would think/hope the ethernet version is the same way (exchange USB with ethernet cable)! The "other" end of the parallel cable takes care of where each pin goes on the Mikini side.

    Also, you may be able to source 5V from a USB cable, or at worst from the power supply in your computer (tap in using a Molex connector) - you won't need to get a power supply for 5V. Very worst case you can use a 7805 chip to regulate down to 5V from any 12V source you have available.

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    I kind of figured it out. I can just reuse the parallel cable from the PC and connect it to the ESS as you said but I need to get a LPH26-to-DB25 ribbon cable to make the connection since the ESS does not have a DB25 connector on it. The 5v power supply I'm still a little confused about (should be 5v 1A supply) but I'll figure it out. Can I just wire in to the 5v going to the front LCD and have both devices powered from the same supply?



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    Swath, I'll put the cable ( lph26 to db25) I had in the box. As for the 5 volt dc, check the breakout board in the back of the machine..the one with the relays....I believe it's on the top left side of the board...you would probably have to splice it in. There's also another voltage output on the top right hand side of the same board. But, I don't know the voltage. I'll check it tonight when i get home from work.

    pete


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    It is in the PDF SWQTH posted for me here: http://www.cnczone.com/forums/mikini....html#poststop . On the Mikini CNC Interface Board, J2 is 5VDC OUT (this is the wire that runs to the LCD that was mentioned) - should be very easy to tap in to that.

    I think the LPH to DB is normally included with the SS? They are available "for cheap" from Warp9: http://www.warp9td.com/index.php/order

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Why is my Z axis stalling all the time?

Why is my Z axis stalling all the time?