Re: [Emc-users] Steppers losing position

[Gregg Eshelman]

On 9/4/2014 9:07 AM, Viesturs Lācis wrote:
> Hello!
>
> I have a strange situation:
> Stepper motor of Z axis on a cnc router is losing it's position -
> doing a series of numerous holes in material will end up with various
> depths of holes.

Just thought of this, have you tried homing the Z axis up before 
drilling each hole? That would reset the position so the control will 
always start from the same known position each time.


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Re: [Emc-users] Steppers losing position

[Gregg Eshelman]

On 9/4/2014 9:07 AM, Viesturs Lācis wrote:
> Hello!
>
> I have a strange situation:
> Stepper motor of Z axis on a cnc router is losing it's position -
> doing a series of numerous holes in material will end up with various
> depths of holes.
>
> The strange part is:
> 1) for each time, when machine is running, it will lose position only
> in one direction; if holes are getting deeper, then they only get
> deeper, not the other way;
> 2) the direction of "drift" will change randomly as machine is
> restarted and only then; simply running another g-code file will not
> change the direction of "drift";

First thing I'd look at is your spindle speed and feed rate.

If the bit is pulling itself into the work faster than the control is 
commanding, it can force the motor to 'run ahead' of the commanded steps.

If the control is trying to push the bit in faster than it can cut, the 
effect is a 'push back' where the step signals go to the motor but it 
doesn't actually move.

Combine either or both with a slight variance in density of the material 
and you'll get randomness.

If tweaking the speed and feed doesn't completely cure it there are 
hardware solutions.

Were this my machine I'd find a way to put a scale (magnetic type, crud 
and fluids don't mess them up and can be cut to length) or rotary 
encoder on so the control always knows where the axis is.

Another possibility is more power. Put on a larger stepper with more 
torque so it can't be pulled ahead of or pushed behind the stream of 
step signals.

Another cause of it might be variability of chip loading in the bit. 
What do you have for keeping the bit clear? For material that can't take 
liquids use an air nozzle and vacuum.

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Re: [Emc-users] Steppers losing position

[John Prentice (FS)]

Greetings

>-Original Message-
>From: Viesturs Lācis [mailto:viesturs.la...@gmail.com] 
>2014-09-04 18:16 GMT+03:00 alex chiosso :
>> If the holes are deeper doesn't it means that the motor is making "more"
>> steps and not "less" ?
>> Is it possible that you have extra steps due to noises or bad 
>> connections PC ---> BoB ---> Gecko Drive ?

>Yes, as I said, motor is "drifting" in particular direction, which may
change (not always), if system is restarted, but the direction of drift does
not change, once the >system is running - if it gradually goes up, then it
does so; if down, then it keeps getting deeper.

>There is no BoB, step/dir signals go directly from 5i23 to Gecko.

Two thoughts - sadly neither addressing the "direction of drift constant for
a given boot" symptom:

(a) It is not possible to infer if steps are being lost or gained from a
series of holes. Noise might give additional steps - but IMO this is unusual
-  but this might be when going down when holes get deeper or going up when
holes get shallower.

(b) It might be worth checking that the 5i23 pullups are set to 5volt for
the connector you are using. The 5i20 manual says that, with 3v3 pullups,
optos connected to a 5 volt rail may not fully turn off.

John Prentice




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Re: [Emc-users] Steppers losing position

[andy pugh]

On 4 September 2014 16:07, Viesturs Lācis  wrote:

> There is Nema23 stepper motor and Gecko stepper driver.

A vaguely recall hearing of one channel of the G540 going "bad" and
then also that inverting the step signals makes it good again.
It certainly seems that it might be worth at least attempting an
inversion of the step pin. (both the parport and Mesa drivers allow an
output pin to be inverted)

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Re: [Emc-users] Steppers losing position

[alex chiosso]

This seems to be an electrical problem .
Have you tried to perform the machine cycle (i.e the holes drilling) in
"dry mode" (no material) and with a reduced feed rate ?
Just to understand if is related to the step frequency and torque .

Alex


On Thu, Sep 4, 2014 at 5:37 PM, Viesturs Lācis 
wrote:

> 2014-09-04 18:32 GMT+03:00 alex chiosso :
> >
> > Means that the "drift" in is both directions. But the axis (motor) is
> > always making more space than expected , isn't it ?
>
> Yes, "drift" can be in any direction, but the change of direction
> happens only on system restart.
>
> Viesturs
>
>
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Re: [Emc-users] Steppers losing position

[Viesturs Lācis]

2014-09-04 18:32 GMT+03:00 alex chiosso :
>
> Means that the "drift" in is both directions. But the axis (motor) is
> always making more space than expected , isn't it ?

Yes, "drift" can be in any direction, but the change of direction
happens only on system restart.

Viesturs

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Re: [Emc-users] Steppers losing position

[Viesturs Lācis]

2014-09-04 18:29 GMT+03:00 alex chiosso :
> A question for you ... the router is brand new (I mean that you have
> finished the setup) or is a "already working" machine ?

I built that machine 3 years ago.

Viesturs

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Re: [Emc-users] Steppers losing position

[alex chiosso]

As you sad :
"Yes, as I said, motor is "drifting" in particular direction, which may
change (not always), if system is restarted, but the direction of
drift does not change, once the system is running - if it gradually
goes up, then it does so; if down, then it keeps getting deeper."

Means that the "drift" in is both directions. But the axis (motor) is
always making more space than expected , isn't it ?

Alex


On Thu, Sep 4, 2014 at 5:29 PM, alex chiosso  wrote:

> As Gene is suggesting , here
> 
> is a discussion on the forum regarding problems with "steps" and Gecko
> Drive .
> A question for you ... the router is brand new (I mean that you have
> finished the setup) or is a "already working" machine ?
> This question is to understand if the machine was working fine before and
> later start with the problem you are mentioning.
>
> Alex
>
>
> On Thu, Sep 4, 2014 at 5:21 PM, Gene Heskett  wrote:
>
>> On Thursday 04 September 2014 11:07:07 Viesturs Lācis did opine
>> And Gene did reply:
>> > Hello!
>> >
>> > I have a strange situation:
>> > Stepper motor of Z axis on a cnc router is losing it's position -
>> > doing a series of numerous holes in material will end up with various
>> > depths of holes.
>> >
>> > The strange part is:
>> > 1) for each time, when machine is running, it will lose position only
>> > in one direction; if holes are getting deeper, then they only get
>> > deeper, not the other way;
>> > 2) the direction of "drift" will change randomly as machine is
>> > restarted and only then; simply running another g-code file will not
>> > change the direction of "drift";
>> >
>> > There is Nema23 stepper motor and Gecko stepper driver.
>> > Motor cable is checked for loose contact, step/dir signal lines are
>> > checked for loose contact, ballscrew and linear rails are checked for
>> > any damage to cause extra resistance in particular direction, the
>> > clutch between motor and ballscrew is checked not to slip.
>> >
>> > I am totally out of ideas, where to look. Has anyone ever experienced
>> > anything like that? What puzzles me most is the consistency to
>> > maintain direction of "drift" and yet randomly change, when whole
>> > system is restarted, so any suggestions will be appreciated.
>> >
>> > Viesturs
>>
>> Can we assume you have lengthened the dirsetup and dirhold settings?
>>
>> I don't have any gecko's, but this sure seems to be an ongoing problem
>> with them.
>>
>> From previous messages, it seems a trip to gecko for repairs fixes it, but
>> a random direction fixed at machine boot?  Thats weird, and I've no clue.
>>
>> Cheers, Gene Heskett
>> --
>> "There are four boxes to be used in defense of liberty:
>>  soap, ballot, jury, and ammo. Please use in that order."
>> -Ed Howdershelt (Author)
>> Genes Web page 
>> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS
>>
>>
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Re: [Emc-users] Steppers losing position

[alex chiosso]

As Gene is suggesting , here

is a discussion on the forum regarding problems with "steps" and Gecko
Drive .
A question for you ... the router is brand new (I mean that you have
finished the setup) or is a "already working" machine ?
This question is to understand if the machine was working fine before and
later start with the problem you are mentioning.

Alex


On Thu, Sep 4, 2014 at 5:21 PM, Gene Heskett  wrote:

> On Thursday 04 September 2014 11:07:07 Viesturs Lācis did opine
> And Gene did reply:
> > Hello!
> >
> > I have a strange situation:
> > Stepper motor of Z axis on a cnc router is losing it's position -
> > doing a series of numerous holes in material will end up with various
> > depths of holes.
> >
> > The strange part is:
> > 1) for each time, when machine is running, it will lose position only
> > in one direction; if holes are getting deeper, then they only get
> > deeper, not the other way;
> > 2) the direction of "drift" will change randomly as machine is
> > restarted and only then; simply running another g-code file will not
> > change the direction of "drift";
> >
> > There is Nema23 stepper motor and Gecko stepper driver.
> > Motor cable is checked for loose contact, step/dir signal lines are
> > checked for loose contact, ballscrew and linear rails are checked for
> > any damage to cause extra resistance in particular direction, the
> > clutch between motor and ballscrew is checked not to slip.
> >
> > I am totally out of ideas, where to look. Has anyone ever experienced
> > anything like that? What puzzles me most is the consistency to
> > maintain direction of "drift" and yet randomly change, when whole
> > system is restarted, so any suggestions will be appreciated.
> >
> > Viesturs
>
> Can we assume you have lengthened the dirsetup and dirhold settings?
>
> I don't have any gecko's, but this sure seems to be an ongoing problem
> with them.
>
> From previous messages, it seems a trip to gecko for repairs fixes it, but
> a random direction fixed at machine boot?  Thats weird, and I've no clue.
>
> Cheers, Gene Heskett
> --
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> Genes Web page 
> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS
>
>
> --
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Re: [Emc-users] Steppers losing position

[Viesturs Lācis]

2014-09-04 18:16 GMT+03:00 alex chiosso :
> If the holes are deeper doesn't it means that the motor is making "more"
> steps and not "less" ?
> Is it possible that you have extra steps due to noises or bad connections
> PC ---> BoB ---> Gecko Drive ?

Yes, as I said, motor is "drifting" in particular direction, which may
change (not always), if system is restarted, but the direction of
drift does not change, once the system is running - if it gradually
goes up, then it does so; if down, then it keeps getting deeper.

There is no BoB, step/dir signals go directly from 5i23 to Gecko.

Viesturs

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Re: [Emc-users] Steppers losing position

[Gene Heskett]

On Thursday 04 September 2014 11:07:07 Viesturs Lācis did opine
And Gene did reply:
> Hello!
> 
> I have a strange situation:
> Stepper motor of Z axis on a cnc router is losing it's position -
> doing a series of numerous holes in material will end up with various
> depths of holes.
> 
> The strange part is:
> 1) for each time, when machine is running, it will lose position only
> in one direction; if holes are getting deeper, then they only get
> deeper, not the other way;
> 2) the direction of "drift" will change randomly as machine is
> restarted and only then; simply running another g-code file will not
> change the direction of "drift";
> 
> There is Nema23 stepper motor and Gecko stepper driver.
> Motor cable is checked for loose contact, step/dir signal lines are
> checked for loose contact, ballscrew and linear rails are checked for
> any damage to cause extra resistance in particular direction, the
> clutch between motor and ballscrew is checked not to slip.
> 
> I am totally out of ideas, where to look. Has anyone ever experienced
> anything like that? What puzzles me most is the consistency to
> maintain direction of "drift" and yet randomly change, when whole
> system is restarted, so any suggestions will be appreciated.
> 
> Viesturs

Can we assume you have lengthened the dirsetup and dirhold settings?

I don't have any gecko's, but this sure seems to be an ongoing problem 
with them.

From previous messages, it seems a trip to gecko for repairs fixes it, but 
a random direction fixed at machine boot?  Thats weird, and I've no clue.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 
US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS

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Re: [Emc-users] Steppers losing position

[alex chiosso]

If the holes are deeper doesn't it means that the motor is making "more"
steps and not "less" ?
Is it possible that you have extra steps due to noises or bad connections
PC ---> BoB ---> Gecko Drive ?

Alex


On Thu, Sep 4, 2014 at 5:07 PM, Viesturs Lācis 
wrote:

> Hello!
>
> I have a strange situation:
> Stepper motor of Z axis on a cnc router is losing it's position -
> doing a series of numerous holes in material will end up with various
> depths of holes.
>
> The strange part is:
> 1) for each time, when machine is running, it will lose position only
> in one direction; if holes are getting deeper, then they only get
> deeper, not the other way;
> 2) the direction of "drift" will change randomly as machine is
> restarted and only then; simply running another g-code file will not
> change the direction of "drift";
>
> There is Nema23 stepper motor and Gecko stepper driver.
> Motor cable is checked for loose contact, step/dir signal lines are
> checked for loose contact, ballscrew and linear rails are checked for
> any damage to cause extra resistance in particular direction, the
> clutch between motor and ballscrew is checked not to slip.
>
> I am totally out of ideas, where to look. Has anyone ever experienced
> anything like that? What puzzles me most is the consistency to
> maintain direction of "drift" and yet randomly change, when whole
> system is restarted, so any suggestions will be appreciated.
>
> Viesturs
>
>
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[Emc-users] Steppers losing position

[Viesturs Lācis]

Hello!

I have a strange situation:
Stepper motor of Z axis on a cnc router is losing it's position -
doing a series of numerous holes in material will end up with various
depths of holes.

The strange part is:
1) for each time, when machine is running, it will lose position only
in one direction; if holes are getting deeper, then they only get
deeper, not the other way;
2) the direction of "drift" will change randomly as machine is
restarted and only then; simply running another g-code file will not
change the direction of "drift";

There is Nema23 stepper motor and Gecko stepper driver.
Motor cable is checked for loose contact, step/dir signal lines are
checked for loose contact, ballscrew and linear rails are checked for
any damage to cause extra resistance in particular direction, the
clutch between motor and ballscrew is checked not to slip.

I am totally out of ideas, where to look. Has anyone ever experienced
anything like that? What puzzles me most is the consistency to
maintain direction of "drift" and yet randomly change, when whole
system is restarted, so any suggestions will be appreciated.

Viesturs

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