Please help - missing steps ... Mach3

I have no more ideas for my problem ... http://www.cnczone.com/forums/images/smilies/frown.gif PLEASE HELP !!!

What I want to eliminate .... When I moving Y axis by JOG ... after 10 - 20 or 30 cm of movement ... and when I hold the stepper motor by hand .. I fill strange, fast, single motor stall for very small period of time . This is as losing steps ..... When add dial indicator to the axe after some movements .... I lose 0.1 mm linear accuracy ... for 1-2 and more hours will be about 5 mm ....http://www.cnczone.com/forums/images/smilies/frown.gif maybe

The sound is like a little, fast "knock" ....

What I did to eliminate the problem, noise .. losing steps ...
I tried many combinations

- 2 PC with Mach3 + LPT to the drivers. ( Acer 2 GB, 3 GHz.... Win XP .. ) and Cel 2.4 GHz, 256 MB ... Win XP
- 2 types of drivers - DQ860MA + Purelogic driver PLD8220-G2
- 2 power supplies ...
- 3 types of stepper motors - nema 23 - and 34 x 2...
- long shielded cables .. and short ...ones .
- Ground pipe in earth with cable to all shields .... cases ....
- tried all BIOS LPT modes EPP etc ..
- kernel mode - 25 and one level up KHz
- LPT direct cable to driver and thru BOB PCB card ....

With single G code - Y500 F500 .. after some mm I fill the same issue ...

When unattached motor is on the table ... the problem is the same ...

I have single phase 220 AC voltage ....

If someone have any ideas ... wiring drawings - please send it ... THANK YOU !!

Emil

With all the different hardware options you've tried without resolving the issue I'd guess that something may be amiss in your motor tuning, you can have problems with too fast or too slow and if acceleration is too high or too low.

- Nick

I had this problem a long time ago and it was caused by running the all-in-one system3 driver/Bob board at 30V. Dropped to 27V fixed the problem.
But you are using good seperate drivers so should be ok. What Bob are you using and what voltage is going to the drivers? Is it overheating?
Also tighten all screw terminals

Hello,

Problem is not resolved ... But I have one more issue to check .. this evening .... :)

My motors acts like - http://www.woodworkforums.com/showthread.php?t=167883
( only on 200 .. 300 mm of movement .. not on every rotation .. )

I have XP optimisation.txt file with step by step guide how to setup PC before Mach3 installation ... but maybe I miss this step for switching to standard PC .... and this cause this signal spikes on LPT - missing steps and stalling for small periods ...

So, I will check and if this is a problem will post the results .....

I have 2 core CPU and I hope switching to Standard PC ... will fix the problem ....

THANKS TO ALL OF YOU !!!

Emil

Hello,

Problem not resolved :(

What I did ....

1. Reinstalled XP PRO ...

2. Applied all steps from XP optimization.txt ....

3. Installed Mach3 + licence file

Started, but the same problem ... on every 200 - 300 mm movement motor 'knock' for a less than a second ... maybe 0.1 s ... :( I can feel the 'knocking' by my hand .....

Attached Win XP device manager screens - why I have 2 standard PC in my device manager .... is it normal ???

Any ideas .. ? Please help

Emil

What voltage do you have coimng out of the PP.? This problem sounds very much like PP is low power probably 3V type. This will cause the problem you are having because there isn't enough voltage difference between HIGH/LOW.

Also one more thing that can cause this and in some way related to the above is if your Step pulse is on the wrong edge of the pulse. ie: On the down slope(falling edge) when the controller is pulsing on the up slope (rising edge). This affectively puts the timing out and you'll loose one step with every direction change.
To test this for each Axis just write some G-code which moves the axis Back n forth small amounts but 1000's of times very fast.
ie:
G0 x10
x0
x10
x0

Copy and paste into a file to make several 100 lines. Make a Mark before starting and run the file. It should return and if it doesn't then you are on the wrong edge of the pulse.

Some drives will let you select the rising or falling edge, Some won't. To Force or change the edge just toggle the Active Low in Motor outputs. This will reverse the motor direction. So goto Homing and Limits and Click Reversed for that axis.

Try and let us know.?

Or better still do your self and machine a favor Dump the PP and get your self a external motion controller.!! . . . You won't regret it.

My understanding of the operation of the drivers is that the direction pulse should overlap the step pulse at both ends, so whether direction is set one way or the other, High Low, 0v 5v whatever it should be in a settled state before the step pulse, then whether it is a positive going pulse or negative one, both the leading and trailing edges are within the direction state. I would imagine that if different protocols are used for step and direction then results would be unpredictable. As would happen when the timing of pulses is in error, then direction would not be properly set. - Hence missing steps.
JAZZ - correct me if I am being Naive :unconscious:

It's more to do with the Controller issuing the step pulse on the rising edge and the drive set to process it on the falling edge there becomes a timing issue so when a direction change occurs the step is in front of the Dir and a step or MS is lost on each change of direction.

Having the wires on the drive wrong way around will also cause this. So Step + being connected to Step- on BOB. Also a BOB with slow Opto's could cause this but seen has the OP tried direct to drives I reckon not.!

Emil,
is this happening only to the Y axis?
And I didn't see what drivers you are using.

P.S. Saw the drivers in the first post.

Quote:

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Originally Posted by JAZZCNC

It's more to do with the Controller issuing the step pulse on the rising edge and the drive set to process it on the falling edge there becomes a timing issue so when a direction change occurs the step is in front of the Dir and a step or MS is lost on each change of direction.

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I think that is what I said i.e direction not settled before step.

Quote:

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Originally Posted by cropwell

I think that is what I said i.e direction not settled before step.

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I didn't read it that way at first but reading again then yes same thing really.!! Time is shortened and next signal comes along before gets chance to complete last thing so something gets dropped at each direction change.! . . . . . I've eaten since then so my brains fired up again. . Lol

Hello,

THANK YOU for all of You.

Problem is not resolved ... :(

Yesterday i tried with LinuxCNC live DVD . 2.7.

It is easy to try but the problem is the same !

I moved only one ( Y ) axe because I want to fix the problem.

I moved only in one direction .... from Y = 0 to Y = 600 ....

When I moved Y ... after 200 mm ...300 mm I am receiving that motor knock ...

In Linuxcnc - the same situation ... I tried many configurations .... for STEP pulses, driver setup ( I mean microstepping modes ... )

A little bit better on slow speeds ..... and 400 steps per / rev .... but that is not good idea ..

I have to check LPT voltage .. Also will try to drive the drivers by arduino .. to change speed and to prove driver quality ...

Any ideas are welcome ....

Thank you in advance,

Emil

Well first of all you seem to be jumping all over the place and not concentrating on trying to sort the problem out in a logical way. It is no use just trying random changes. So take it one step at a time giving clear and concise feedback.
.
Some good pictures of the machine would help, are you using ball screws or screwed rod etc? You have already been asked to check the pp voltage out put. ie is it 3.3V or 5V but you have not answered. This might just be a simple pp and bob problem.
.
Sorry to be a bit harsh. ..Clive

Get an external motion controller. The parallel ports on Acer and Asus motherboards are not great, I have tried both of them and know. If you do not want to afford a motion controller, get a second PCI parallel port and see what you get but chances are you will still be having issues.

Regards

George

Quote:

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When I moved Y ... after 200 mm ...300 mm I am receiving that motor knock ...

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Does it happen at different points when you apply different speed or steps per mm?
If at the same point then check the mechanics.

I had a knock on my X axis today when changing direction sometimes, turns out the grub screws holding the pulley on the stepper shaft were loose and slipping. I'd put one jnto the stepper shaft keyway and thar was rattling back and forward....until it too slipped.

Hello,

Clive, maybe you are right ... I have free time just to check LPT voltage - it is 3.3v on both PCs ...

I didn't check it before, because using one of the PCs with my bigger CNC machine I didn't have any problems for years !! ...
The same drivers on all machines !! ..

But when using it in another place / room I received the problem with both PCs -

So .....

Machanics is not an isuue ... motors knock on the table :) .. not connected to the machine ...

My plan - to add 6N137 fast opto - as opto and also as logic level 'converter' .. :)

( also I have them on 'stock' :) )

When I finish will write here the results ....

Thank you all of You !!

Emil

Quote:

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... I have free time just to check LPT voltage - it is 3.3v on both PCs ...

I didn't check it before, because using one of the PCs with my bigger CNC machine I didn't have any problems for years !! ...
The same drivers on all machines !! ..

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Ah but was you using the same BOB. The better BOB's level shift the 3.3V back up to the 5V and then generally all is well. Good luck with the investigation . Clive

EdingCNC is quite a nice controller. Also affordable. Will work witout issues in Ethernet or USB. This takes little setup and works good.

Hi,

Problem solved. :) Thank you for all your help.

The PC LPT port generate strange pulses .... from 4000 ns to 300 000 ns.... ( based on linuxcnc tests .. )

Why I not saw the problem ..

I tested all the electronics with my another PC ... ( also with the same problem .... but a little bit better !!! ), I used another PC with CNC machine for manu years, but just for some small cuts .. with perfect shape ... )

So, I suppose my first PC is OK .... with both PC s .. the problem exists .... so the problem is in the electronics ....

But when I tested it with NE555 generator .. motors are fine !!! So ... I became almost with no idea what to do ..

I grounded all, used 74HCT245 ... 6N137 ... to change the logic voltage levels .... and finally on the last started the linuxcnc
for N-th time and saw strange situation ....

After start i have 4000 ns step period ... and after a while ... 1 second ... it increased to 300 000 ns.....
after reset statistics button .... the same situation ...

Mach3 doesn't see the wrong signals .... message is "System excellent" !!! :(

I didn't investigate to check signals by scope in time period ... I have no time for that ...

So, please fine attached first cut picture - 4 mm carbide tool in wood ..... Sorry I am not woodmaker ... it is just a test

Have a nice day to all of you,

Emil

Please do not be offended by this:

You are wasting your time the parallel port! You should seriously consider buying a motion control board like we have all suggested previously.

[QUOTE=JAZZCNC;72299]It's more to do with the Controller issuing the step pulse on the rising edge and the drive set to process it on the falling edge there becomes a timing issue so when a direction change occurs the step is in front of the Dir and a step or MS is lost on each change of direction.

Just a thank you for this, I changed the settings in ports and pins and no more missing steps, round circles and pockets that are clean, I am hugely grateful