Servos and drive recomendation
28 Jan 2014 23:50 #43277
by clkeck1
Servos and drive recomendation was created by clkeck1
I'm about to purchase a Gear hobber and plan on bringing it into the 21st century.
I need to automate the Z and B axis
X is the height of the hob
Y is the hob cross feed
Z is the feed of the hob thru the gear
B is the rotation of the hob
C is the spindle axis
B will rotate off a scalar of C
Z will feed off of a scalar of B
For the servos, drives, and encoders what do you recommend? I have always just used what was in place on the machine.
Thanks
Cory
I need to automate the Z and B axis
X is the height of the hob
Y is the hob cross feed
Z is the feed of the hob thru the gear
B is the rotation of the hob
C is the spindle axis
B will rotate off a scalar of C
Z will feed off of a scalar of B
For the servos, drives, and encoders what do you recommend? I have always just used what was in place on the machine.
Thanks
Cory
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29 Jan 2014 20:51 #43294
by andypugh
It rather depends on the size of the machine. You are going to have to know what the required torques and speeds are.
I rather like resolvers as there is no chance at all off cumulative count errors messing up the gears, but interfacing them to LinuxCNC is not cheap.
My gear hobber (Actually a specific setup of a horizontal milling machine) has a resolver on the spindle and XYZ axes, but the rotary stage has an encoder on the motor.
Replied by andypugh on topic Servos and drive recomendation
For the servos, drives, and encoders what do you recommend?
It rather depends on the size of the machine. You are going to have to know what the required torques and speeds are.
I rather like resolvers as there is no chance at all off cumulative count errors messing up the gears, but interfacing them to LinuxCNC is not cheap.
My gear hobber (Actually a specific setup of a horizontal milling machine) has a resolver on the spindle and XYZ axes, but the rotary stage has an encoder on the motor.
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31 Jan 2014 00:57 #43341
by jmelson
Replied by jmelson on topic Servos and drive recomendation
If what are in place are good, then no need to change. But, nowadays, it
is possible to get much higher resolution encoders inexpensively, so
if you have to change them, then go for a higher resolution, it will
make movement smoother.
Are the servo amps in good shape? If very old, decrepit looking, etc.
then best to just change them now, and not have to deal with
breakdowns, later.
Pico Systems (that's me) has packages for brush and brushless
motors using our own servo amps and controllers, or an analog
output system for use with analog velocity servo amps such as
AMC and Copley.
Jon
is possible to get much higher resolution encoders inexpensively, so
if you have to change them, then go for a higher resolution, it will
make movement smoother.
Are the servo amps in good shape? If very old, decrepit looking, etc.
then best to just change them now, and not have to deal with
breakdowns, later.
Pico Systems (that's me) has packages for brush and brushless
motors using our own servo amps and controllers, or an analog
output system for use with analog velocity servo amps such as
AMC and Copley.
Jon
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31 Jan 2014 22:42 #43372
by clkeck1
Replied by clkeck1 on topic Servos and drive recomendation
Currently the machine is all manual and uses change gears and a single motor drive.
I was thinking about using 5S fanuc servos and a06b-6050 drives for the work spindle and feed.
Speed will be 50-300 rpm.
are there newer aftermarket motors and drives that are more compact and cheaper?
Thanks
Cory
I was thinking about using 5S fanuc servos and a06b-6050 drives for the work spindle and feed.
Speed will be 50-300 rpm.
are there newer aftermarket motors and drives that are more compact and cheaper?
Thanks
Cory
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01 Feb 2014 01:23 #43381
by jmelson
I have the PWM controller, which generates digital control signals
for my brushless servo amps. The servo amps need standard
commutation signals, so we have a converter that produces
these from the proprietary Fanuc encoder signals.
Jon
Replied by jmelson on topic Servos and drive recomendation
Yes, I have a system to run S series Fanuc motors with LinuxCNC.Currently the machine is all manual and uses change gears and a single motor drive.
I was thinking about using 5S fanuc servos and a06b-6050 drives for the work spindle and feed.
Speed will be 50-300 rpm.
are there newer aftermarket motors and drives that are more compact and cheaper?
Thanks
Cory
I have the PWM controller, which generates digital control signals
for my brushless servo amps. The servo amps need standard
commutation signals, so we have a converter that produces
these from the proprietary Fanuc encoder signals.
Jon
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01 Feb 2014 01:56 #43382
by andypugh
I would suggest keeping the existing spindle motor. It is there, it works, and is presumably appropriately-sized.
All you need to do is add an encoder to the hobbing spindle, then slave the A-axis to that.
Given that the A-axis is going to rotate fairly slowly you might want to look for a harmonic drive for it. In an ideal world you would also have a very-high count, very-high quality encoder directly mounted on the gear blank spindle. The quality of your gears will depend crucially on the accuracy with which you measure the gear blank angle.
So, if you have a harmonic drive and it is not perfect, any error in the harmonic drive will be reproduced in every gear you make. (In just the same way as any error in the existing train gears will be reproduced in every gear made).
Something like www.heidenhain.com/en_US/products-and-ap...ring/product-search/ would be ideal, if you can find one at a lot less than list price.
There are some on eBay for $X,000 but I know someone who picked one up for <£100.
I was looking at writing an interface for these: www.renishaw.com/en/resolute-rotary-angl...coder-options--10939 and Renishaw sent me a sample to work with, but it got lost in the post :-(
Replied by andypugh on topic Servos and drive recomendation
I was thinking about using 5S fanuc servos and a06b-6050 drives for the work spindle and feed.
Speed will be 50-300 rpm.
I would suggest keeping the existing spindle motor. It is there, it works, and is presumably appropriately-sized.
All you need to do is add an encoder to the hobbing spindle, then slave the A-axis to that.
Given that the A-axis is going to rotate fairly slowly you might want to look for a harmonic drive for it. In an ideal world you would also have a very-high count, very-high quality encoder directly mounted on the gear blank spindle. The quality of your gears will depend crucially on the accuracy with which you measure the gear blank angle.
So, if you have a harmonic drive and it is not perfect, any error in the harmonic drive will be reproduced in every gear you make. (In just the same way as any error in the existing train gears will be reproduced in every gear made).
Something like www.heidenhain.com/en_US/products-and-ap...ring/product-search/ would be ideal, if you can find one at a lot less than list price.
There are some on eBay for $X,000 but I know someone who picked one up for <£100.
I was looking at writing an interface for these: www.renishaw.com/en/resolute-rotary-angl...coder-options--10939 and Renishaw sent me a sample to work with, but it got lost in the post :-(
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01 Feb 2014 03:40 #43383
by clkeck1
Replied by clkeck1 on topic Servos and drive recomendation
I plan to keep the existing spindle motor (3Hp) to drive the hob spindle. A VFD may be added to allow for hob speed changes.
There is a 30:1 worm drive gearbox on the work spindle that I plan to retain. I will keep an eye out for an angle encoder to attach directly to the work spindle. A 2500 ppr motor encoder only gets me to an angular measurement of 3" which is probably a little coarse.
The 2nd servo will be for feed parallel to the work spindle.
There is a 30:1 worm drive gearbox on the work spindle that I plan to retain. I will keep an eye out for an angle encoder to attach directly to the work spindle. A 2500 ppr motor encoder only gets me to an angular measurement of 3" which is probably a little coarse.
The 2nd servo will be for feed parallel to the work spindle.
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01 Feb 2014 04:04 #43384
by andypugh
Something free of backlash (toothed belt or harmonic drive) might be preferable.
Having said that, my setup uses a cheap dividing head with a worm that has inconsistent backlash, yours is probably better.
This is pretty though: www.ebay.com/itm/Yaskawa-Servo-Harmonic-...&hash=item19c91d1f9a
Replied by andypugh on topic Servos and drive recomendation
There is a 30:1 worm drive gearbox on the work spindle that I plan to retain.
Something free of backlash (toothed belt or harmonic drive) might be preferable.
Having said that, my setup uses a cheap dividing head with a worm that has inconsistent backlash, yours is probably better.
This is pretty though: www.ebay.com/itm/Yaskawa-Servo-Harmonic-...&hash=item19c91d1f9a
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