Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: ozymax on January 23, 2014, 08:51:49 PM

Title: Z Axis loosing steps in the up direction only.
Post by: ozymax on January 23, 2014, 08:51:49 PM
As the title states, my trusty router has developed a problem with it's Z axis motor loosing steps in the ^UP^ direction only.
This started after I gave mach3 a command to GOTOZ whilst doing some rotary carving on my 4th axis. It was a very stupid command to give, as that drove the cutter all the way into the job and ruined it. ::) I have the Z zero alinged with the center of my part and I've only just started experimenting with the 4th axis. Lesson learnt. :-[

Seeing that my project was ruined, I decided to complete the run and confirm that the job was going to turn out as I'd liked. This is when all my dramas started.
While running the rest of the code the Z axis started making strange noises and proceeded to drive deeper into the job.

I decided that I must have damaged the axis somehow, so I pulled it apart expecting to find a rough bearing or ball screw, but everything looked fine. I then ran the stepper without it being connected to the ball screw and found that jogging in the down direction the motor runs perfectly, but jogging in the up direction the motor jerks and moans and looses steps. Sometimes it even runs the wrong direction. The DRO appears to cycle as per normal and the soft limits were still working as they should.

I have changed motors and driver boards around and the problem still exists only in the Z axis UP direction. I have checked all my motor tuning settings and every other setting that I can think of and they are all set as they have been for years. So nothing has changed in the program that I can see.

My machine is running Probotix BOB and stepper drives, as well as their motors and power supply.
I've been running X Y & Z on 1/4 steps without a problem, and the rotary axis is running 1/8th stepping.
Could I have a bad BOB or parallel port pin? I have had the computer mother board go bad before and that made me suspect the BOB, but with some help from Probotix I was able to diagnose that the mother board had failed. The current board has been running fine for the last year or so.

Could anyone please help shine some light on the possible cause of my problem as I've run out of ideas?
Title: Re: Z Axis loosing steps in the up direction only.
Post by: Hood on January 24, 2014, 03:15:13 AM
Reduce your Accel and Vel for the Z by maybe 20% and see if that helps.
Check all your wiring is secure.
If you attach your xml I will have a look through that to see if there is a problem with it.
Hood
Title: Re: Z Axis loosing steps in the up direction only.
Post by: ozymax on January 24, 2014, 03:39:17 AM
Thanks for your thoughts Hood.
I've played around with Acc and Vel, going from one extreme to another and all points in between with no change.
I have looked at all my wiring terminals and came up empty handed.
There are IDE cables running between the BOB and driver boards. I have changed them all around, but still no change.
I've changed key boards over. No change.
I have the same result when jogging with the Mach3 pendant callout.

I have the hard drive out of the computer at the moment as I'm seeing if I can sustitute it to another PC. I'll post up the XML as soon as I can.

I was going to try fitting a PCI parallel port card to my PC and see if the mother boards port is at fault.
Do you think that would be worth a try? They are pretty cheap and if they work, then that may be a better way to go rather than replacing the mother board.
Unfortunatly we have a public holiday here this weekend, so all the shops will be shut. >:(

Thanks again.
Title: Re: Z Axis loosing steps in the up direction only.
Post by: magicniner on January 25, 2014, 04:43:58 AM
Ideally you'd want to isolate the fault before tearing down a system and PC, swapping steppers to alternate drivers, drivers to alternate break out board outputs and so on can allow you to identify the common component or connections present on the axis displaying faults.
Trying to solve an unidentified fault using untested parts is a recipe for an extended headache, it might just work first time though ;-)

 - Nick
Title: Re: Z Axis loosing steps in the up direction only.
Post by: Tweakie.CNC on January 25, 2014, 05:16:52 AM
Quote
I then ran the stepper without it being connected to the ball screw and found that jogging in the down direction the motor runs perfectly, but jogging in the up direction the motor jerks and moans and looses steps. Sometimes it even runs the wrong direction.

Assuming all electrical wiring is indeed correctly connected...
Try selecting Sherline 1/2 Pulse Mode, apply, then do a Mach3 restart and just see if that cures this issue.
If it does not then it could either be the Z axis direction pin is faulty on your LPT parallel port (or BoB) or the Z axis motor driver is faulty. You may be able to swap pin numbers for Z axis direction signal and rule out one possibility.

Tweakie.
Title: Re: Z Axis loosing steps in the up direction only.
Post by: ozymax on January 26, 2014, 06:44:41 AM
Ideally you'd want to isolate the fault before tearing down a system and PC, swapping steppers to alternate drivers, drivers to alternate break out board outputs and so on can allow you to identify the common component or connections present on the axis displaying faults.
Trying to solve an unidentified fault using untested parts is a recipe for an extended headache, it might just work first time though ;-)

 - Nick
I have 4x driver boards and 4 motors in my set up and I've swapped them all around and covered all combinations.
The only board I don't have a spare, is the BOB.
I have narrowed it down as much as I can to either the BOB or a problem with the parallel port.
I have just been given another PC with the correct ports, so I'll try that and see what I get.
Title: Re: Z Axis loosing steps in the up direction only.
Post by: ozymax on January 26, 2014, 06:50:54 AM
Quote
I then ran the stepper without it being connected to the ball screw and found that jogging in the down direction the motor runs perfectly, but jogging in the up direction the motor jerks and moans and looses steps. Sometimes it even runs the wrong direction.

Assuming all electrical wiring is indeed correctly connected...
Try selecting Sherline 1/2 Pulse Mode, apply, then do a Mach3 restart and just see if that cures this issue.
If it does not then it could either be the Z axis direction pin is faulty on your LPT parallel port (or BoB) or the Z axis motor driver is faulty. You may be able to swap pin numbers for Z axis direction signal and rule out one possibility.

Tweakie.

I didn't think I could swap pin numbers. I have pin #6 for Z step and #7 for Z direction. What pins would I be able to use other than these?
But bear in mind that the machine was running perfectly ok till I told it to drive through the job. Changing pins around seems to be an odd thing to do, but I guess it could help narrow down a possible faulty pin in the parallel port.
Title: Re: Z Axis loosing steps in the up direction only.
Post by: ozymax on January 27, 2014, 05:00:42 AM
I tried a few more things today with absolutely no change.
Tried Sherline 1/2 pulse. No difference after restart so changed it back.
Played around with pin numbers but couldn't get anything to work.
Here is my XML file if anyone would be so kind to look at it.

Thanks for all the suggestions.
I have a PCI/parallel port card coming and maybe that will solve my issue.
Failing that I'll see if I can get my other comp to work.
Title: Re: Z Axis loosing steps in the up direction only.
Post by: Hood on January 27, 2014, 05:16:04 AM
That is not the correct  xml as it has no config in it at all.
Hood
Title: Re: Z Axis loosing steps in the up direction only.
Post by: ozymax on January 27, 2014, 05:21:53 AM
That is not the correct  xml as it has no config in it at all.
Hood

Oh!
I've never had to use that type of file, so I simply looked for a file of that name in my Mach folder. I'll have another look around. If I open the xml file, what should I be able to see?
Title: Re: Z Axis loosing steps in the up direction only.
Post by: Hood on January 27, 2014, 05:30:07 AM
Open Mach and look at the name of the profile you are using, you can then look in the main Mach3 folder for a file of that name with a xml extension, not the xml backup folder just in case that was where you looked.
Hood
Title: Re: Z Axis loosing steps in the up direction only.
Post by: ozymax on January 27, 2014, 05:55:50 AM
I did look in the back up folder and assumed that was the one. ::)
Do I have the correct one this time?
Title: Re: Z Axis loosing steps in the up direction only.
Post by: Hood on January 27, 2014, 06:11:40 AM
Ok that looks better :)
Dont see anything glaring wrong with it so thinking it is not the xml at fault.
Hood
Title: Re: Z Axis loosing steps in the up direction only.
Post by: ozymax on January 27, 2014, 06:27:05 AM
Ok that looks better :)
Dont see anything glaring wrong with it so thinking it is not the xml at fault.
Hood

Ok thanks for looking and I learnt where to find the xml in the process.
Title: Re: Z Axis loosing steps in the up direction only.
Post by: stirling on January 27, 2014, 08:18:19 AM
Everything you've said suggests a dodgy Z DIR signal either on your BOB, your PP cable or the PP itself.

Try using a different pin for your Z DIR. In ports n pins I'd suggest you disable your A axis for a moment and set the Z DIR pin to 9. Then of course connect what's labeled on your BOB as the A DIR pin to your Z drivers DIR.

Title: Re: Z Axis loosing steps in the up direction only.
Post by: ozymax on February 13, 2014, 04:19:12 AM
Ok, I've just inserted my new PCI card to the computer.
Assigned a new address for the card in Mach3.
Changed over all the port numbers in ports&pins to the new card.
Tested all the limit switches and tool zeroing plate and checked their operation in the diagnostic screen and they all worked ok.
Powered up each axis one at a time and tested all the motors. All motors worked fine, so I homed the machine. All ok.

So it looks like I had a fault with my mother boards parallel port, but I still have a problem and that is, I can't get the E stop to work.
I have changed the E stop over to the new card but can't get it to work. I've toggled the active setting and still no go.
Everything else simply changed over without issue, so why not the E stop??

I'm now using #2 port with an address of A400 and I have un-checked the port #1 box.

Can anyone shine some light on my problem ???
Thanks.
Title: Re: Z Axis loosing steps in the up direction only.
Post by: Hood on February 13, 2014, 07:27:30 AM
Without seeing your xml it would be hard to even guess the problem.
One question however, why are you using port 2? why  not just set up as port 1?
Hood
Title: Re: Z Axis loosing steps in the up direction only.
Post by: ozymax on February 28, 2014, 07:08:30 PM
Ok heres a follow up of my issue so as to possibly help someone else chasing the same problem.
After doing some more playing around like re-installing drivers etc, I decided to make a late night (my time) call to Probotix and explained my issue. They were very helpful and ran through a couple of things for me to try.
When I first got my router up and running my e-stop switch wasn't working correctly and I had to fit a resistor across the terminals of the BOB to get the system to work.
After talking to the Probotix tech, it was suggested, amoung other things, to remove the resistor and see what happens.

Well my e-stop is working as it should now, so I'm a happy routerer again.
For some reason the PCI card wants to see a different voltage at terminal #15. Any way, I'm up and running again.
Thanks to all the people that have tried helping me with the problem.
Cheers.