[Emc-users] Closed loop stepping system

[Tomaz T .]

Does anyone have any experiences using this this system with linuxcnc?


http://www.fastech.co.kr/bbs/eng/product.php?mode=view1&uid=1#

As far as I understand, there would be only one feedback signal from driver to 
linuxcnc, telling that stepper is in position or not...

In my case might be interesting as I'm already using servos for all linear 
axis, except rotary axes where I still have steppers, as it is in my case a bit 
difficult to switch on servos, but with this system I could simply change 
motors (same size, same specs...), and would also be reliable about accuracy 
and no loosing steps in any case... 
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Re: [Emc-users] Closed loop stepping system

[andy pugh]

On 9 April 2013 10:11, Tomaz T.  wrote:

> http://www.fastech.co.kr/bbs/eng/product.php?mode=view1&uid=1#

It isn't immediately clear what advantage it gives over normal
steppers other than stall-detection. I guess it should also be able to
recover from a stall too, so perhaps there would be the option of
using adaptive-feed to slow other axes to allow it to catch up.

It would be interesting to see how it worked out.

-- 
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Re: [Emc-users] Closed loop stepping system

[Tomaz T .]

The whole point is that I don't have any feedback from steppers at this stage, 
and as I said, the "cheapest" solution would be to simply change the existing 
one with the one with closed loop "future" (and also drivers). So the basic 
idea might be to use In-Position signal (output) from stepper driver and when 
this goes fault, it triggers "following error" in linuxcnc.
Could this work?

Anyone using this stepper system from kelinginc?

http://www.automationtechnologiesinc.com/products-page/nema23-closed-loop-stepper-motor-system-hybrid-servo-kit/hybrid-servo-drive-kl-5080h



>
> It isn't immediately clear what advantage it gives over normal
> steppers other than stall-detection. I guess it should also be able to
> recover from a stall too, so perhaps there would be the option of
> using adaptive-feed to slow other axes to allow it to catch up.
>
> It would be interesting to see how it worked out.
> 
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Re: [Emc-users] Closed loop stepping system

[Viesturs Lācis]

2013/4/10 Tomaz T. 

> The whole point is that I don't have any feedback from steppers at this
> stage, and as I said, the "cheapest" solution would be to simply change the
> existing one with the one with closed loop "future" (and also drivers). So
> the basic idea might be to use In-Position signal (output) from stepper
> driver and when this goes fault, it triggers "following error" in linuxcnc.
> Could this work?
>

So why don't You put encoders on stepper motors and link encoder position
to axis.n.motor-pos-fb pin and let LinuxCNC track actual motor position and
it definitely will trigger following error, once it has been reached. This
way there are no fancy stepper drives and motors are required.



> Anyone using this stepper system from kelinginc?
>
>
> http://www.automationtechnologiesinc.com/products-page/nema23-closed-loop-stepper-motor-system-hybrid-servo-kit/hybrid-servo-drive-kl-5080h


No tuning of feedback loop? Well, then I do not see, how does this system
achieve its goal and correct for motor's position error.

-- 
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Re: [Emc-users] Closed loop stepping system

[Javier Ros]

This system

http://www.automationtechnologiesinc
.com/products-page/nema23-closed-loop-stepper-motor-system-hybrid-servo-kit/hybrid-servo-drive-kl-5080h

Is apparently a stepper motor that is controlled as a brushless.
Essentially a stepper is a brushless. This needs a encoder, probably one
with a index pulse correctly positioned,
so that the electronics can compute the switching accurately.

This means, even if the control of the drive looks like a STEP DIR control,
internally there are position and current loops, theoretically such a drive
could offer, velocity and
current control (I've not checked for the above reference). This means
essentially that, the motor runs cooler, because only the required
intensity is flowing in the motor, and not
the maximum required intensity (the one that is controlled with the typical
potentiometer in typical stepper drives). This means as well that the motor
runs smoother, this must
 be most noticeable at low velocities, and finally that the positioning can
be as precise as the encoder is.

I regard of precision, note that a stepper, is not as precise as
3600/steps_per_revolution/microsteps, because microsteps don need to be
equally spaced, even steps  are not precise due to manufacturing (magnetic
field)
do not have to be equally spaced. In addition to this forces make that the
motor is not centered at the center of the microstep. In comparison a
brushless type encoder based drive for steeper can be as precise
as the encoder, you know the actual position with the encoder position,
although the position can be different of the commanded position, but you
know the difference.

The only limitations seem to be related to control at hih rpms, performance
degrades in comparison with brushless. I would say that this is related to
the higher pole count of the steeper,and the inherent dificulty to
stablish intensity at high pole conmutation frecuency due to impedance,
something that con be alleviated increaing voltage as much as possible..

In regard to this the error position, it can be even smaller in this
brushless system because, as it runs cooler, you can allow for small
duration current higher than the nominal. For a steeper
you can not surpass the nominal value, not for the motor not for the
electronics.

I've never run a system of this type, but I would love to use one of the
MESA cards and brushless firmwares to test a such a setup (I'm interested
in current control) if somebody with more experience thinks/knowns this is
possible and not too difficult. Just using a double shaft stepper and a
cheap encoder. I would love, to identify stepper cogging, and to software
compensate for it.

This said, if the proposed system works as theoretically expected, it looks
to me it has a pretty reasonable price.

Regard,

Javier





On Wed, Apr 10, 2013 at 6:45 AM, Viesturs Lācis wrote:

> 2013/4/10 Tomaz T. 
>
> > The whole point is that I don't have any feedback from steppers at this
> > stage, and as I said, the "cheapest" solution would be to simply change
> the
> > existing one with the one with closed loop "future" (and also drivers).
> So
> > the basic idea might be to use In-Position signal (output) from stepper
> > driver and when this goes fault, it triggers "following error" in
> linuxcnc.
> > Could this work?
> >
>
> So why don't You put encoders on stepper motors and link encoder position
> to axis.n.motor-pos-fb pin and let LinuxCNC track actual motor position and
> it definitely will trigger following error, once it has been reached. This
> way there are no fancy stepper drives and motors are required.
>
>
>
> > Anyone using this stepper system from kelinginc?
> >
> >
> >
> http://www.automationtechnologiesinc.com/products-page/nema23-closed-loop-stepper-motor-system-hybrid-servo-kit/hybrid-servo-drive-kl-5080h
>
>
> No tuning of feedback loop? Well, then I do not see, how does this system
> achieve its goal and correct for motor's position error.
>
> --
> Viesturs
>
> If you can't fix it, you don't own it.
> http://www.ifixit.com/Manifesto
>
> --
> Precog is a next-generation analytics platform capable of advanced
> analytics on semi-structured data. The platform includes APIs for building
> apps and a phenomenal toolset for data science. Developers can use
> our toolset for easy data analysis & visualization. Get a free account!
> http://www2.precog.com/precogplatform/slashdotnewsletter
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>
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Re: [Emc-users] Closed loop stepping system

[andy pugh]

On 10 April 2013 12:18, Javier Ros  wrote:

> Is apparently a stepper motor that is controlled as a brushless.
> Essentially a stepper is a brushless. This needs a encoder, probably one
> with a index pulse correctly positioned,
> so that the electronics can compute the switching accurately.

The Mesa 7i32 does this too. Note that this is _not_ a Hostmot2
device, it needs to be controlled by SoftDMC and there is (As far as I
know) no official LinuxCNC support, though there is a component
http://wiki.linuxcnc.org/cgi-bin/wiki.pl?ContributedComponents#Mesa_7i32_micro_stepping_motor_driver


-- 
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If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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Re: [Emc-users] Closed loop stepping system

[Gene Heskett]

On Wednesday 10 April 2013 13:01:29 Javier Ros did opine:

> This system
> 
> http://www.automationtechnologiesinc
> .com/products-page/nema23-closed-loop-stepper-motor-system-hybrid-servo-
> kit/hybrid-servo-drive-kl-5080h
> 
> Is apparently a stepper motor that is controlled as a brushless.
> Essentially a stepper is a brushless. This needs a encoder, probably one
> with a index pulse correctly positioned,
> so that the electronics can compute the switching accurately.
> 
> This means, even if the control of the drive looks like a STEP DIR
> control, internally there are position and current loops, theoretically
> such a drive could offer, velocity and
> current control (I've not checked for the above reference). This means
> essentially that, the motor runs cooler, because only the required
> intensity is flowing in the motor, and not
> the maximum required intensity (the one that is controlled with the
> typical potentiometer in typical stepper drives). This means as well
> that the motor runs smoother, this must
>  be most noticeable at low velocities, and finally that the positioning
> can be as precise as the encoder is.
> 
> I regard of precision, note that a stepper, is not as precise as
> 3600/steps_per_revolution/microsteps, because microsteps don need to be
> equally spaced, even steps  are not precise due to manufacturing
> (magnetic field)
> do not have to be equally spaced. In addition to this forces make that
> the motor is not centered at the center of the microstep.

Let me fine tune this by pointing out that the stepper motor maker can, 
with access to the maps the controller uses to adjust its currents when 
microstepping, could be fine tuned such that at light loading, the 
microsteps can be pretty accurate.  This of course means the motor and the 
controller must be calibrated to each other.  That will be the makers job 
since few if any of us have the tools to do that, and it sure wouldn't be 
feasible economically for everyone to own their own stuff to do that. 

More just plain old comment:

The noise would likely go down a bit, but since we aren't also throttling 
the current in many drivers (mine does after about a second of no motion, 
so mine only heat about 15F when idle), the motor is still going to run 
hot. The ideal situation would be by adjusting the overall currents to keep 
the motor within say 20%/microstep of the ideal microstepped position, but 
again this would require a high precision encoder, or some sort of 
magnetically detected feedback to detect the error in real time & only use 
enough current to achieve that. But at that point, you may as well spend 
the money on a servo system, which may well be what this outfit is doing.  
Net cost will be similar.  My current stepper setup, using 425oz motors on 
the lathe, was just under $100/axis.  This is only a 252oz motor and costs 
USD 210/axis.  I can't seem to justify the extra sheckel's for me.

> In comparison
> a brushless type encoder based drive for steeper can be as precise as
> the encoder, you know the actual position with the encoder position,
> although the position can be different of the commanded position, but
> you know the difference.
> 
> The only limitations seem to be related to control at hih rpms,
> performance degrades in comparison with brushless. I would say that
> this is related to the higher pole count of the steeper,and the
> inherent dificulty to stablish intensity at high pole conmutation
> frecuency due to impedance, something that con be alleviated increaing
> voltage as much as possible..
> 
> In regard to this the error position, it can be even smaller in this
> brushless system because, as it runs cooler, you can allow for small
> duration current higher than the nominal. For a steeper
> you can not surpass the nominal value, not for the motor not for the
> electronics.

Theoretically true.  The motor can be banged with considerable overcurrent 
when it is lightly loaded and essentially exactly in position, but if half 
s step off or more due to heavy loading, then the rotor's magnetism could 
be effected, permanently damaging the motor.
 
> I've never run a system of this type, but I would love to use one of the
> MESA cards and brushless firmwares to test a such a setup (I'm
> interested in current control) if somebody with more experience
> thinks/knowns this is possible and not too difficult. Just using a
> double shaft stepper and a cheap encoder. I would love, to identify
> stepper cogging, and to software compensate for it.

A moot point IMO when the gearing is such that 1 microstep is a fraction of 
a micron without resorting to a doubling of cost per axis.

I haven't actually checked, as my step accuracy is the same on both axis's 
of the lathe, the x is a 2.5mm/turn screw, the z is 5, but the z is also 
geared down 2/1.  On my .0001 dial indicator, I can't see the individual 
steps.
 
> This said, if the proposed system works as theoretically expected, it
> looks to me i

Re: [Emc-users] Closed loop stepping system

[cogoman]

On 04/10/2013 07:18 AM, Javier Ros wrote:
> Is apparently a stepper motor that is controlled as a brushless.
> Essentially a stepper is a brushless. This needs a encoder, probably one
> with a index pulse correctly positioned,
> so that the electronics can compute the switching accurately.
>
> This means, even if the control of the drive looks like a STEP DIR control,
> internally there are position and current loops, theoretically such a drive
> could offer, velocity and
> current control (I've not checked for the above reference).
>
> The only limitations seem to be related to control at hih rpms, performance
> degrades in comparison with brushless. I would say that this is related to
> the higher pole count of the steeper,
If you were to design one of these from the ground up, since position 
would be verified from a 10,000 step encoder, and the stepper would be 
run as a type of servo motor, the stepper driver would function much 
differently.  It would generate commutation from the encoder, then it 
would drive a current into one coil to draw the motor towards the 
commanded position.  PID would decide how hard to hit the motor by the 
difference between commanded position and current encoder position.  
Since this works like a servo and not a stepper with feedback, the 
stepper motor could be designed with less steps per rev. less steps per 
revolution would require less soil current reversals, and would allow 
the motor to step faster. If a 1mH coil standard stepper could be driven 
to 3000 RPM,  one with 100 steps per rev instead of 200 could be driven 
at 6000 RPM. One with 50 steps per rev could be driven at 12000 RPM. The 
control circuit would have to do some tricky math to keep cogging to a 
minimum, but it's likely possible to make a very fast but still accurate 
stepper system this way.

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Re: [Emc-users] Closed loop stepping system

[Gene Heskett]

On Thursday 11 April 2013 00:58:10 cogoman did opine:

> On 04/10/2013 07:18 AM, Javier Ros wrote:
> > Is apparently a stepper motor that is controlled as a brushless.
> > Essentially a stepper is a brushless. This needs a encoder, probably
> > one with a index pulse correctly positioned,
> > so that the electronics can compute the switching accurately.
> > 
> > This means, even if the control of the drive looks like a STEP DIR
> > control, internally there are position and current loops,
> > theoretically such a drive could offer, velocity and
> > current control (I've not checked for the above reference).
> > 
> > The only limitations seem to be related to control at hih rpms,
> > performance degrades in comparison with brushless. I would say that
> > this is related to the higher pole count of the steeper,
> 
> If you were to design one of these from the ground up, since position
> would be verified from a 10,000 step encoder, and the stepper would be
> run as a type of servo motor, the stepper driver would function much
> differently.  It would generate commutation from the encoder, then it
> would drive a current into one coil to draw the motor towards the
> commanded position.  PID would decide how hard to hit the motor by the
> difference between commanded position and current encoder position.
> Since this works like a servo and not a stepper with feedback, the
> stepper motor could be designed with less steps per rev. less steps per
> revolution would require less soil current reversals, and would allow
> the motor to step faster. If a 1mH coil standard stepper could be driven
> to 3000 RPM,  one with 100 steps per rev instead of 200 could be driven
> at 6000 RPM. One with 50 steps per rev could be driven at 12000 RPM. The
> control circuit would have to do some tricky math to keep cogging to a
> minimum, but it's likely possible to make a very fast but still accurate
> stepper system this way.
> 
Somebody thinking "outside the box", and making perfect sense.  The only 
fly in the soup is the 10,000 step encoder, and servicing it at 200 rpS to 
get that 12,000 rpms, which would need to be able, if software, to do the 
whole control loop at a 2 megacycle rate.  The best we've been able to do 
in software is less than 100 kilohertz at the relatively simple job of just 
issuing steps to the motor.  These atom boards can do 50, but are hugely 
more comfortable running at about 47 kilohertz. 

To do the whole control loop at 2 megahertz to get that 12,000 rpm would 
need dedicated hardware that could do this in much less than .5 
microseconds.

I won't say its impossible, but I don't believe we have the 'state of the 
art', nor do "we" represent a sufficient economic incentive to do that as a 
chip design.  At least not in the next calendar year.

Cheers, Gene
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Re: [Emc-users] Closed loop stepping system

[Gregg Eshelman]

Search for Leadshine closed loop stepper on YouTube. Looks like some very 
smooth and quiet operation from steppers.

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Re: [Emc-users] Closed loop stepping system

[Tomaz T .]

That's nice presentation, and exactly what I'm looking for to improve my two 
rotary axes with steppers...
 
>
> Search for Leadshine closed loop stepper on YouTube. Looks like some very 
> smooth and quiet operation from steppers.
> 
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Re: [Emc-users] Closed loop stepping system

[Javier Ros]

Thanks Gene, this has been a very enriching discussion.

No plans still for the Hubles's mirror :).

Cheers,

Javier


On Wed, Apr 10, 2013 at 7:37 PM, Gene Heskett  wrote:

> On Wednesday 10 April 2013 13:01:29 Javier Ros did opine:
>
> > This system
> >
> > http://www.automationtechnologiesinc
> > .com/products-page/nema23-closed-loop-stepper-motor-system-hybrid-servo-
> > kit/hybrid-servo-drive-kl-5080h
> >
> > Is apparently a stepper motor that is controlled as a brushless.
> > Essentially a stepper is a brushless. This needs a encoder, probably one
> > with a index pulse correctly positioned,
> > so that the electronics can compute the switching accurately.
> >
> > This means, even if the control of the drive looks like a STEP DIR
> > control, internally there are position and current loops, theoretically
> > such a drive could offer, velocity and
> > current control (I've not checked for the above reference). This means
> > essentially that, the motor runs cooler, because only the required
> > intensity is flowing in the motor, and not
> > the maximum required intensity (the one that is controlled with the
> > typical potentiometer in typical stepper drives). This means as well
> > that the motor runs smoother, this must
> >  be most noticeable at low velocities, and finally that the positioning
> > can be as precise as the encoder is.
> >
> > I regard of precision, note that a stepper, is not as precise as
> > 3600/steps_per_revolution/microsteps, because microsteps don need to be
> > equally spaced, even steps  are not precise due to manufacturing
> > (magnetic field)
> > do not have to be equally spaced. In addition to this forces make that
> > the motor is not centered at the center of the microstep.
>
> Let me fine tune this by pointing out that the stepper motor maker can,
> with access to the maps the controller uses to adjust its currents when
> microstepping, could be fine tuned such that at light loading, the
> microsteps can be pretty accurate.  This of course means the motor and the
> controller must be calibrated to each other.  That will be the makers job
> since few if any of us have the tools to do that, and it sure wouldn't be
> feasible economically for everyone to own their own stuff to do that.
>
> More just plain old comment:
>
> The noise would likely go down a bit, but since we aren't also throttling
> the current in many drivers (mine does after about a second of no motion,
> so mine only heat about 15F when idle), the motor is still going to run
> hot. The ideal situation would be by adjusting the overall currents to keep
> the motor within say 20%/microstep of the ideal microstepped position, but
> again this would require a high precision encoder, or some sort of
> magnetically detected feedback to detect the error in real time & only use
> enough current to achieve that. But at that point, you may as well spend
> the money on a servo system, which may well be what this outfit is doing.
> Net cost will be similar.  My current stepper setup, using 425oz motors on
> the lathe, was just under $100/axis.  This is only a 252oz motor and costs
> USD 210/axis.  I can't seem to justify the extra sheckel's for me.
>
> > In comparison
> > a brushless type encoder based drive for steeper can be as precise as
> > the encoder, you know the actual position with the encoder position,
> > although the position can be different of the commanded position, but
> > you know the difference.
> >
> > The only limitations seem to be related to control at hih rpms,
> > performance degrades in comparison with brushless. I would say that
> > this is related to the higher pole count of the steeper,and the
> > inherent dificulty to stablish intensity at high pole conmutation
> > frecuency due to impedance, something that con be alleviated increaing
> > voltage as much as possible..
> >
> > In regard to this the error position, it can be even smaller in this
> > brushless system because, as it runs cooler, you can allow for small
> > duration current higher than the nominal. For a steeper
> > you can not surpass the nominal value, not for the motor not for the
> > electronics.
>
> Theoretically true.  The motor can be banged with considerable overcurrent
> when it is lightly loaded and essentially exactly in position, but if half
> s step off or more due to heavy loading, then the rotor's magnetism could
> be effected, permanently damaging the motor.
>
> > I've never run a system of this type, but I would love to use one of the
> > MESA cards and brushless firmwares to test a such a setup (I'm
> > interested in current control) if somebody with more experience
> > thinks/knowns this is possible and not too difficult. Just using a
> > double shaft stepper and a cheap encoder. I would love, to identify
> > stepper cogging, and to software compensate for it.
>
> A moot point IMO when the gearing is such that 1 microstep is a fraction of
> a micron without resorting to a doubling of cost per axis.
>
> I hav

Re: [Emc-users] Closed loop stepping system

[Jon Elson]

Gene Heskett wrote:
>
> Somebody thinking "outside the box", and making perfect sense.  The only 
> fly in the soup is the 10,000 step encoder, and servicing it at 200 rpS to 
> get that 12,000 rpms
If you run a stepper motor at 12,000 RPM, it will burn up in minutes.  You
can spin a typical stepper with the spindle motor, and above 1000 RPM it 
will
get very hot with no current at all in the windings.  That is all iron loss.
12,000 RPM will require insane voltages be applied to the drive, several
hundred Volts.  A typical stepper may generate 50 V at 1000 RPM, so
that would require a 600 V supply just to equal the back EMF at 12K.

Oh, but then cogoman said :

 "the stepper motor could be designed with less steps per rev. "

Yes, then why make it a stepper at all?  How about an 8-pole
brushless servo motor?  These work GREAT, used by Fanuc
since the late 1980's, and now available from many sources.
I make affordable servo amps for brushless motors, and
have one on my minimill.  You do need to get rotor position
info from the motor, most small ones have Hall sensors that
you connect to the servo amp.  I use 500 cycle/rev encoders
on mine, that is quite satisfactory.

Jon


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Re: [Emc-users] Closed loop stepping system

[Peter C. Wallace]

On Thu, 11 Apr 2013, Jon Elson wrote:

> Date: Thu, 11 Apr 2013 11:32:55 -0500
> From: Jon Elson 
> Reply-To: "Enhanced Machine Controller (EMC)"
> 
> To: "Enhanced Machine Controller (EMC)" 
> Subject: Re: [Emc-users] Closed loop stepping system
> 
> Gene Heskett wrote:
>>
>> Somebody thinking "outside the box", and making perfect sense.  The only
>> fly in the soup is the 10,000 step encoder, and servicing it at 200 rpS to
>> get that 12,000 rpms
> If you run a stepper motor at 12,000 RPM, it will burn up in minutes.  You
> can spin a typical stepper with the spindle motor, and above 1000 RPM it
> will
> get very hot with no current at all in the windings.  That is all iron loss.
> 12,000 RPM will require insane voltages be applied to the drive, several
> hundred Volts.  A typical stepper may generate 50 V at 1000 RPM, so
> that would require a 600 V supply just to equal the back EMF at 12K.
>
> Oh, but then cogoman said :
>
> "the stepper motor could be designed with less steps per rev. "
>
> Yes, then why make it a stepper at all?  How about an 8-pole
> brushless servo motor?  These work GREAT, used by Fanuc
> since the late 1980's, and now available from many sources.
> I make affordable servo amps for brushless motors, and
> have one on my minimill.  You do need to get rotor position
> info from the motor, most small ones have Hall sensors that
> you connect to the servo amp.  I use 500 cycle/rev encoders
> on mine, that is quite satisfactory.
>
> Jon


The Leadshine closed loop step motors actually do have some advantages. 
because of the high number of poles (50 typically), when run in step motor 
mode the torque vs displacement curve is much steeper than a normal brushless 
motor which allows a clever hack when stationary. When staionary the motor can 
be run in step motor mode (radial pull vs tangential pull) with reduced 
current. This eliminates the +- a count or so jitter that full servo systems 
have when stationary (especially with static load)

You still have the torque vs speed limits because of the number of poles
and stepmotors even run as servos are not as efficent or as high performance 
as normal brushless motors but in the size ranges that make sense, closed loop 
stepper systems are very nice.


>
>
> --
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> analytics on semi-structured data. The platform includes APIs for building
> apps and a phenomenal toolset for data science. Developers can use
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Peter Wallace
Mesa Electronics

(\__/)
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(")_(") signature to help him gain world domination.


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Re: [Emc-users] Closed loop stepping system

[Gene Heskett]

On Thursday 11 April 2013 22:13:10 Jon Elson did opine:

> Gene Heskett wrote:
> > Somebody thinking "outside the box", and making perfect sense.  The
> > only fly in the soup is the 10,000 step encoder, and servicing it at
> > 200 rpS to get that 12,000 rpms
> 
> If you run a stepper motor at 12,000 RPM, it will burn up in minutes. 
> You can spin a typical stepper with the spindle motor, and above 1000
> RPM it will
> get very hot with no current at all in the windings.  That is all iron
> loss. 12,000 RPM will require insane voltages be applied to the drive,
> several hundred Volts.  A typical stepper may generate 50 V at 1000
> RPM, so that would require a 600 V supply just to equal the back EMF at
> 12K.

And I never considered the iron loses Jon, but you are dead on.
 
> Oh, but then cogoman said :
> 
>  "the stepper motor could be designed with less steps per rev. "
> 
> Yes, then why make it a stepper at all?  How about an 8-pole
> brushless servo motor?  These work GREAT, used by Fanuc
> since the late 1980's, and now available from many sources.
> I make affordable servo amps for brushless motors, and
> have one on my minimill.  You do need to get rotor position
> info from the motor, most small ones have Hall sensors that
> you connect to the servo amp.  I use 500 cycle/rev encoders
> on mine, that is quite satisfactory.
> 
> Jon

That also makes great sense as long as its economical enough to do.

Cheers, Gene
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Re: [Emc-users] Closed loop stepping system

[Jon Elson]

Gene Heskett wrote:
> And I never considered the iron loses Jon, but you are dead on.
>   
Mariss Freimanis of Gecko describes some torture tests he did years ago
and reported this.
>  
>   
>> I make affordable servo amps for brushless motors, and
>> have one on my minimill.  You do need to get rotor position
>> info from the motor, most small ones have Hall sensors that
>> you connect to the servo amp.  I use 500 cycle/rev encoders
>> on mine, that is quite satisfactory.
>>
>> Jon
>> 
>
> That also makes great sense as long as its economical enough to do.
>
>   
The Gecko 201 series sells for $114, my brushless servo amp sells
for $150, for 20 A at 120 V.  Not vastly more expensive than a
good stepper drive.  Of course you need a PWM generator to run my
servo amp, but then you need a hardware step generator to get
full performance out of a microstepped stepper motor, too.

Jon

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Re: [Emc-users] Closed loop stepping system

[Gene Heskett]

On Friday 12 April 2013 00:56:36 Jon Elson did opine:

> Gene Heskett wrote:
> > And I never considered the iron loses Jon, but you are dead on.
> 
> Mariss Freimanis of Gecko describes some torture tests he did years ago
> and reported this.

Humm, now that you mention that, I read something similar on the net a few 
years agom from somebody at Gecko.  Could have been the same person I'd 
have to assume.
 
> >> I make affordable servo amps for brushless motors, and
> >> have one on my minimill.  You do need to get rotor position
> >> info from the motor, most small ones have Hall sensors that
> >> you connect to the servo amp.  I use 500 cycle/rev encoders
> >> on mine, that is quite satisfactory.
> >> 
> >> Jon
> > 
> > That also makes great sense as long as its economical enough to do.
> 
> The Gecko 201 series sells for $114, my brushless servo amp sells
> for $150, for 20 A at 120 V.

Which is 17 amps more than my lathe spindle has.  I wonder if that could 
make me a REAL variable speed spindle.  This one runs out of steam when the 
steel is above 5/8" in diameter.  Supposedly a 250 watt motor, older 7zx12.  
I'd like to take it up to shaving 1.75" to 2" stock.  Could that reverse 
w/o needing to toggle a 4pdt relay? 

> Not vastly more expensive than a
> good stepper drive.  Of course you need a PWM generator to run my
> servo amp, but then you need a hardware step generator to get
> full performance out of a microstepped stepper motor, too.

True, if you can find the voltage for the motors.  I hate paying 150-200 
for a big linear when I can cobble something up out of the surplus catalogs 
for 1/3rd of that.

Unforch, suitable transformers seem to be getting rarer as time goes by.

The gears are turning on that spindle idea though.  :)

> Jon

Cheers, Gene
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Re: [Emc-users] Closed loop stepping system

[Jon Elson]

Gene Heskett wrote:
>
>
> Humm, now that you mention that, I read something similar on the net a few 
> years agom from somebody at Gecko.  Could have been the same person I'd 
> have to assume.
>  
>   
Mariss is the designer and owner of Gecko, and an awesome engineer.
> Which is 17 amps more than my lathe spindle has.  I wonder if that could 
> make me a REAL variable speed spindle.  This one runs out of steam when the 
> steel is above 5/8" in diameter.  Supposedly a 250 watt motor, older 7zx12.  
> I'd like to take it up to shaving 1.75" to 2" stock.  Could that reverse 
> w/o needing to toggle a 4pdt relay? 
>
>   
Yes.  I use one of my servo amps to run the spindle of my minimill, and 
it does
reversing under computer control when rigid tapping.  If you have some
kind of spindle speed sensing or spindle encoder, then you could have 
closed-
loop spindle speed control.

Jon


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Re: [Emc-users] Closed loop stepping system

[Gene Heskett]

On Friday 12 April 2013 13:36:59 Jon Elson did opine:

> Gene Heskett wrote:
> > Humm, now that you mention that, I read something similar on the net a
> > few years agom from somebody at Gecko.  Could have been the same
> > person I'd have to assume.
> 
> Mariss is the designer and owner of Gecko, and an awesome engineer.
> 
> > Which is 17 amps more than my lathe spindle has.  I wonder if that
> > could make me a REAL variable speed spindle.  This one runs out of
> > steam when the steel is above 5/8" in diameter.  Supposedly a 250
> > watt motor, older 7zx12. I'd like to take it up to shaving 1.75" to
> > 2" stock.  Could that reverse w/o needing to toggle a 4pdt relay?
> 
> Yes.  I use one of my servo amps to run the spindle of my minimill, and
> it does
> reversing under computer control when rigid tapping.  If you have some
> kind of spindle speed sensing or spindle encoder, then you could have
> closed-
> loop spindle speed control.
> 
> Jon

I don't have that on the mill, very limited space to install, and a very 
dirty environment inside the gear case.  Lots of flying grease.  Which 
doesn't help, and may hinder because grease deteriorates some plastics, 
I've lost the hubs out of 2 of those "nylon" gears now.
 
Just one of the reasons why that mill may yet get replaced to a grizzly 
go704.
> 
> 
> -- Precog is a next-generation analytics platform capable of
> advanced analytics on semi-structured data. The platform includes APIs
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Cheers, Gene
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Re: [Emc-users] Closed loop stepping system

[andy pugh]

On 12 April 2013 18:40, Gene Heskett  wrote:

> I don't have that on the mill, very limited space to install, and a very
> dirty environment inside the gear case.  Lots of flying grease.  Which
> doesn't help, and may hinder because grease deteriorates some plastics,
> I've lost the hubs out of 2 of those "nylon" gears now.

Steel replacements exist:
http://www.littlemachineshop.com/products/product_view.php?ProductID=3453&category=

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Re: [Emc-users] Closed loop stepping system

[Gene Heskett]

On Friday 12 April 2013 14:43:55 andy pugh did opine:

> On 12 April 2013 18:40, Gene Heskett  wrote:
> > I don't have that on the mill, very limited space to install, and a
> > very dirty environment inside the gear case.  Lots of flying grease. 
> > Which doesn't help, and may hinder because grease deteriorates some
> > plastics, I've lost the hubs out of 2 of those "nylon" gears now.
> 
> Steel replacements exist:
> http://www.littlemachineshop.com/products/product_view.php?ProductID=345
> 3&category=

That is for the next bigger mill, this things original carcass was the 
micro-mill from Harbor Freight.  I have talked about that with Chris at 
LMS, and it for sure doesn't fit my head.  Darnit.

Cheers, Gene
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Re: [Emc-users] Closed loop stepping system

[andy pugh]

On 12 April 2013 19:45, Gene Heskett  wrote:

>> Steel replacements exist:
>> http://www.littlemachineshop.com/products/product_view.php?ProductID=345
>> 3&category=
>
> That is for the next bigger mill,

Some of us have hobbing equipment and can make gears.

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Re: [Emc-users] Closed loop stepping system

[Gene Heskett]

On Friday 12 April 2013 18:45:02 andy pugh did opine:

> On 12 April 2013 19:45, Gene Heskett  wrote:
> >> Steel replacements exist:
> >> http://www.littlemachineshop.com/products/product_view.php?ProductID=
> >> 345 3&category=
> > 
> > That is for the next bigger mill,
> 
> Some of us have hobbing equipment and can make gears.

Maybe, but thats a lot of work for someone with little return & no noise 
reduction.

I've had my name on Chris's list for the belt drive 3 speed conversion, IF 
the guy that made them 10 years ago ever makes any more of them.  

OTOH, I just did my taxes today, so a G0704 might follow me home from the 
Grizzly store in Muncy PA before the summer gets full blown.  I am hearing 
rumors of Dee wanting to go see her sister, near Ithaca NY which will make 
a good excuse to detour from Williamsport PA on over to Muncy as we go by 
that neck of the woods going one way or the other.  At nominally 400 lbs by 
the time I throw in some tools, methinks the Toy might be able to handle 
that.

Cheers, Gene
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Re: [Emc-users] Closed loop stepping system

[andy pugh]

On 12 April 2013 23:55, Gene Heskett  wrote:

>> Some of us have hobbing equipment and can make gears.
>
> Maybe, but thats a lot of work for someone with little return & no noise
> reduction.

I do it for fun. But you will be appalled at the noise increase.
Belt drive probably is the way to go.
Did I mention I can make belt pulleys too?
http://youtu.be/ltmZrDrt6pQ

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Re: [Emc-users] Closed loop stepping system

[Gene Heskett]

On Friday 12 April 2013 21:26:22 andy pugh did opine:

> On 12 April 2013 23:55, Gene Heskett  wrote:
> >> Some of us have hobbing equipment and can make gears.
> > 
> > Maybe, but thats a lot of work for someone with little return & no
> > noise reduction.
> 
> I do it for fun. But you will be appalled at the noise increase.

Its quite tiresome to these old ears now, not just the whine, but the 
rattling too.

> Belt drive probably is the way to go.
> Did I mention I can make belt pulleys too?
> http://youtu.be/ltmZrDrt6pQ

I see that.  I have an A table and its tailstock, but the tooth would have 
to be rather laboriously formed by a ball nosed, small mill.  And I would 
have to figure out the initial diameter needed to get x teeth per turn, 
which in gilmer belting, seems to be pretty critical else the belt would be 
obviously trying to climb out of the slot near the end of the wrap.  I 
would probably be farther ahead just to order the pulleys, and using a 5mm 
center hole as a locater, machine the holes to fit the shafting.  That also 
means a sliding mount for the motor so the belt could be flipped from pair 
to pair.  That whole box with its sliding cluster gear setup, needs to go, 
its way too big now that the controller has been removed and it gets in the 
way of the A axis, severely restricting table movement because of that in 
favor of a slightly taller but much more compact direct to the spindle from 
the motor belted design.  One with about 2x the low speed geardown 
available now, and the same 2x higher on the top end.  And my screws are 
wearing out, just another reason to go get the G0704 & put some real screws 
in it. 

There are other, heavier and more rigid machines available but that one is 
by far the most operating volume per dollar spent.

Cheers, Gene
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Re: [Emc-users] Closed loop stepping system

[Jon Elson]

Gene Heskett wrote:
> I don't have that on the mill, very limited space to install, and a very 
> dirty environment inside the gear case.  Lots of flying grease.  Which 
> doesn't help, and may hinder because grease deteriorates some plastics, 
> I've lost the hubs out of 2 of those "nylon" gears now.
>  
> Just one of the reasons why that mill may yet get replaced to a grizzly 
> go704.
>   
Well, I used some gear tooth sensors that are made to go inside a
car transmission, so they are heat and lube-resistant.  Of course,
they need ferrous gears.  On my mini-mill, I mounted the spindle
encoder outside the head, see the last picture here :
http://pico-systems.com/minimill.html

As for the Bridgeport encoder contraption, see
http://pico-systems.com/bridge_spindle.html
for a description of the gear tooth sensors and how I installed
them.

Jon

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Re: [Emc-users] Closed loop stepping system

[Gene Heskett]

On Saturday 13 April 2013 00:13:15 Jon Elson did opine:

> Gene Heskett wrote:
> > I don't have that on the mill, very limited space to install, and a
> > very dirty environment inside the gear case.  Lots of flying grease. 
> > Which doesn't help, and may hinder because grease deteriorates some
> > plastics, I've lost the hubs out of 2 of those "nylon" gears now.
> > 
> > Just one of the reasons why that mill may yet get replaced to a
> > grizzly go704.
> 
> Well, I used some gear tooth sensors that are made to go inside a
> car transmission, so they are heat and lube-resistant.  Of course,
> they need ferrous gears.

Of which, this toy has none.  All nylon.  For your encoder hanging 
outboard, is is a problem to access the drawbolt for tool changing?


> On my mini-mill, I mounted the spindle
> encoder outside the head, see the last picture here :
> http://pico-systems.com/minimill.html
> 
> As for the Bridgeport encoder contraption, see
> http://pico-systems.com/bridge_spindle.html
> for a description of the gear tooth sensors and how I installed
> them.
> 
> Jon

Cheers, Gene
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Re: [Emc-users] Closed loop stepping system

[andy pugh]

On 13 April 2013 04:11, Jon Elson  wrote:

> On my mini-mill, I mounted the spindle
> encoder outside the head, see the last picture here :
> http://pico-systems.com/minimill.html

An alternative:
https://plus.google.com/photos/108164504656404380542/albums/5747722155741347649/5866287005551819154?banner=pwa


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Re: [Emc-users] Closed loop stepping system

[Gene Heskett]

On Saturday 13 April 2013 09:59:47 andy pugh did opine:

> On 13 April 2013 04:11, Jon Elson  wrote:
> > On my mini-mill, I mounted the spindle
> > encoder outside the head, see the last picture here :
> > http://pico-systems.com/minimill.html
> 
> An alternative:
> https://plus.google.com/photos/108164504656404380542/albums/574772215574
> 1347649/5866287005551819154?banner=pwa

The bearing nut that is retaining that disk in the same manner I did use to 
put one on the lathe, is below those nylon gears in the micro head.  The 
amount of shaft sticking up isn't sufficient to allow anything above it.  
The draw bolts shoulder bottom is actually about 3/16" below the top of the 
gearbox cover.

The nose of the spindle sticking out of the bottom is only a fat CM long, 
and has the 6mm hole pair for sticking a tommy bar in to hold it while the 
draw bolt is tightened or loosened in it, so theres little if any usable 
room there either.  All of the ~10 CM above the spindles top bearing is 
occupied by the two drive gears, and the shift gears on their countershaft 
occupy the space between them.

About the only way would be an extension, pin locked to the spindle, to 
bring it above the upper cover.

That would involve making new draw bolts another inch longer.  Which 
wouldn't be a bad idea as the #2 collets I have now are bored an oversized 
3/8-18, and the bolt I got from Chris that fits them, is probably a good 10 
thou undersized.  I am amazed that I haven't stripped the 1/4 collet, its 
very poorly fitted and to reliably hold a 1/4 mill, it has to be pulled at 
least 3/4 turn past "tight".  The only OEM #2 spud that actually "fits" 
that spindle is the one on the drill chuck that came with it.  That uses 
the OEM metric draw bolt, which goes from loose to plenty tight in about 30 
degrees rotation of the draw bolt.  IOW, all of the US made after-market 
stuff is very sloppily built.  But if tightened enough, it gets the job 
done.

All the more reason to go get a G0704.  I've put enough sheckles in this 
sows ear of a mill.

Cheers, Gene
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
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Re: [Emc-users] Closed loop stepping system

[andy pugh]

On 13 April 2013 15:33, Gene Heskett  wrote:

> The bearing nut that is retaining that disk in the same manner I did use to
> put one on the lathe, is below those nylon gears in the micro head.  The
> amount of shaft sticking up isn't sufficient to allow anything above it.
> The draw bolts shoulder bottom is actually about 3/16" below the top of the
> gearbox cover.

This is the case with mine too, that encoder disc is actually a very
thin-walled top-hat.

> All the more reason to go get a G0704.  I've put enough sheckles in this
> sows ear of a mill.

I reached the same conclusion. But I decided if I was going to upgrade
I was going to get something made in Yorkshire, not China.

-- 
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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Re: [Emc-users] Closed loop stepping system

[jeremy youngs]

I reached the same conclusion. But I decided if I was going to upgrade
I was going to get something made in Yorkshire, not China.


me likes me some empirialism :)
thats why i converted a 1947 matson, but it is large :)


On Sat, Apr 13, 2013 at 4:40 PM, andy pugh  wrote:

> On 13 April 2013 15:33, Gene Heskett  wrote:
>
> > The bearing nut that is retaining that disk in the same manner I did use
> to
> > put one on the lathe, is below those nylon gears in the micro head.  The
> > amount of shaft sticking up isn't sufficient to allow anything above it.
> > The draw bolts shoulder bottom is actually about 3/16" below the top of
> the
> > gearbox cover.
>
> This is the case with mine too, that encoder disc is actually a very
> thin-walled top-hat.
>
> > All the more reason to go get a G0704.  I've put enough sheckles in this
> > sows ear of a mill.
>
> I reached the same conclusion. But I decided if I was going to upgrade
> I was going to get something made in Yorkshire, not China.
>
> --
> atp
> If you can't fix it, you don't own it.
> http://www.ifixit.com/Manifesto
>
>
> --
> Precog is a next-generation analytics platform capable of advanced
> analytics on semi-structured data. The platform includes APIs for building
> apps and a phenomenal toolset for data science. Developers can use
> our toolset for easy data analysis & visualization. Get a free account!
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> ___
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>



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Re: [Emc-users] Closed loop stepping system

[Jon Elson]

Gene Heskett wrote:
> Of which, this toy has none.  All nylon.  For your encoder hanging 
> outboard, is is a problem to access the drawbolt for tool changing?
>
>   
Not at all!  You do have to be careful with wrenches not to not break
the pulleys, but there is a big
preload nut for the spindle bearings that sits above the top of the 
head, I just
glued a bored-out pulley to it.  That turned out to be too fragile, so I put
a piece of PC board stock under the nut and glued the pulley to that, 
figuring
a glass-epoxy board would be good for adhering more epoxy to, and it has 
held
for years.
  So, the pulley is close, but not actually in the way at all, at least 
on my
machine, which I think is identical to the X2.

Jon

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Re: [Emc-users] Closed loop stepping system

[Gene Heskett]

On Saturday 13 April 2013 18:31:16 andy pugh did opine:

> On 13 April 2013 15:33, Gene Heskett  wrote:
> > The bearing nut that is retaining that disk in the same manner I did
> > use to put one on the lathe, is below those nylon gears in the micro
> > head.  The amount of shaft sticking up isn't sufficient to allow
> > anything above it. The draw bolts shoulder bottom is actually about
> > 3/16" below the top of the gearbox cover.
> 
> This is the case with mine too, that encoder disc is actually a very
> thin-walled top-hat.

I did not see that in the pix.  I'll go back and look again.
 
> > All the more reason to go get a G0704.  I've put enough sheckles in
> > this sows ear of a mill.
> 
> I reached the same conclusion. But I decided if I was going to upgrade
> I was going to get something made in Yorkshire, not China.

Link to candidate?

Cheers, Gene
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
My web page:  is up!
My views 

I want to see people using Perl to glue things together creatively, not
just technically but also socially.
-- Larry Wall in <199702111730.jaa28...@wall.org>
A pen in the hand of this president is far more
dangerous than a gun in the hands of 200 million
  law-abiding citizens.

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Re: [Emc-users] Closed loop stepping system

[Gene Heskett]

On Saturday 13 April 2013 18:34:55 Jon Elson did opine:

> Gene Heskett wrote:
> > Of which, this toy has none.  All nylon.  For your encoder hanging
> > outboard, is is a problem to access the drawbolt for tool changing?
> 
> Not at all!  You do have to be careful with wrenches not to not break
> the pulleys, but there is a big
> preload nut for the spindle bearings that sits above the top of the
> head, I just
> glued a bored-out pulley to it.  That turned out to be too fragile, so I
> put a piece of PC board stock under the nut and glued the pulley to
> that, figuring
> a glass-epoxy board would be good for adhering more epoxy to, and it has
> held
> for years.
>   So, the pulley is close, but not actually in the way at all, at least
> on my
> machine, which I think is identical to the X2.
> 
> Jon

The X1 (Micro-Mill) however, is a different critter.
 
> 
> -- Precog is a next-generation analytics platform capable of
> advanced analytics on semi-structured data. The platform includes APIs
> for building apps and a phenomenal toolset for data science. Developers
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Cheers, Gene
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
My web page:  is up!
My views 

I want to see people using Perl to glue things together creatively, not
just technically but also socially.
-- Larry Wall in <199702111730.jaa28...@wall.org>
A pen in the hand of this president is far more
dangerous than a gun in the hands of 200 million
  law-abiding citizens.

--
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Re: [Emc-users] Closed loop stepping system

[andy pugh]

On 13 April 2013 23:32, Gene Heskett  wrote:

>> I reached the same conclusion. But I decided if I was going to upgrade
>> I was going to get something made in Yorkshire, not China.
>
> Link to candidate?

Old but properly made:
http://www.ebay.co.uk/itm/Harrison-Milling-Machine-Vertical-attachment-and-clutch-/121092566051

-- 
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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Re: [Emc-users] Closed loop stepping system

[Lars Andersson]

> On 13 April 2013 23:32, Gene Heskett  wrote:
>
> Old but properly made:
> http://www.ebay.co.uk/itm/Harrison-Milling-Machine-Vertical-attachment-and-clutch-/121092566051
>
Gentlemen,
I recently bought a machine similar to that one, at scrap value. The 
rubber bellows for the knee screw is replaced in the picture.

http://forumbilder.se/CDVO4/fras

It has no power feed whatsoever but is not much worn and feels very 
sound. It is meant to be converted  to LinuxCNC as a hobby project.
I have not made anything this big before, wondering what drive torque on 
the feed screws to aim for?

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Re: [Emc-users] Closed loop stepping system

[andy pugh]

On 14 April 2013 11:20, Lars Andersson  wrote:

> http://forumbilder.se/CDVO4/fras
>
> It has no power feed whatsoever but is not much worn and feels very
> sound. It is meant to be converted  to LinuxCNC as a hobby project.
> I have not made anything this big before, wondering what drive torque on
> the feed screws to aim for?

I am using 750W servos with a 2Nm (7Nm peak) rating, with a 4:1 belt
ratio, and it seems to be about right.
I don't think I would want to go any lower on the Z, though it is
rather more than necessary on the Y.

I had to convert the Z to ball screw, the torque was inadequate with
the original leadscrew. So if you want to keep the Z as it is, then
you would need more.

I went for a rotating-nut arrangement on the Z to keep the motor
inside the machine. It isn't clear if you have access to that area in
yours.

-- 
atp
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Re: [Emc-users] Closed loop stepping system

[jeremy youngs]

i used 1600 oz in steppers pn my mill and am looking for more but still
need ballscrews and i want to try some way friction reduction. i get 60 ipm
wuth a @200 lb table, i havent powered the knee yet just the spindle head i
will need ballscrew for the z and am planning to coumterbalace the knee .
my drives will handle 80 volts and im currently at 48 i plan to step this
up soon


On Sun, Apr 14, 2013 at 6:20 AM, Lars Andersson wrote:

>
> > On 13 April 2013 23:32, Gene Heskett  wrote:
> >
> > Old but properly made:
> >
> http://www.ebay.co.uk/itm/Harrison-Milling-Machine-Vertical-attachment-and-clutch-/121092566051
> >
> Gentlemen,
> I recently bought a machine similar to that one, at scrap value. The
> rubber bellows for the knee screw is replaced in the picture.
>
> http://forumbilder.se/CDVO4/fras
>
> It has no power feed whatsoever but is not much worn and feels very
> sound. It is meant to be converted  to LinuxCNC as a hobby project.
> I have not made anything this big before, wondering what drive torque on
> the feed screws to aim for?
>
>
> --
> Precog is a next-generation analytics platform capable of advanced
> analytics on semi-structured data. The platform includes APIs for building
> apps and a phenomenal toolset for data science. Developers can use
> our toolset for easy data analysis & visualization. Get a free account!
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>



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