Mill Upgrade Options - Reuse existing DC Brush amps and servos?

[Marty_Escarcega]

Since I'm getting a Centroid T-400 equipped lathe, and the more I read up on Ajax/Centroid, I am wondering about upgrading my knee mill. Its like new, it had a Mitutoyo MillstarIII control on it. I was originally planning on upgrading it using the Viper Step 2 Linear boards to send the 0-10VDC analog signal to the Glentek Amps.

The servo amps are Glentek 7115 DC Brush Servo Amps with Glentek GMA4020 DC Brush servo motors on XY&Z. There is an encoder on Z (Spindle) The Millstar control used standard Mitutoyo AT102 glass scales on the X & Y axis. I sold off the control console but kept the servo amp cabinet and the DC Brush servos they are all like brand new and obviously tuned to each other.

My questions for upgrade options:
1. Can I reuse the AT102 Glass Scales for feedback input for X&Y
2. Can I reuse the Glentek DC Brush Amplifiers, and if so, which AJAX solution is best? (Or do I have to scrap the servo amps and use the the All in one DC control?)
3. Since its a traditional Bridgeport head design, they are a little difficult to add spindle encoders to.


Any other considerations/suggestions?

Here is a link to a few pictures of the mill and control: https://goo.gl/photos/jVozzx3apV4NKmTM6

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[Al_The_Man]

Usually when using scales the motors also have encoder feedback for a dual FB system and these often hard to tune, also if the Glentek amps use velocity feedback in the form of tach F.B. this has now been replaced by Torque mode control amps where the tach is no longer used.
There is a an instructional video on the Galil site by Dr Jacob Tal about the different F.B. systems and also one on tuning the PID on dual F.B. scale/encoder systems
I am not all that familiar with the Ajax/Centroid system.
Al.

[cnckeith]

Marty,

1.) Yes
2.) yes..but i wouldn't do it. the allin1dc cnc control board has a 15 amp per axis digital autotuning 3 axis dc servo drive built right into the cnc control board. specifically made to replace older analog servo drives and eliminate the difficult tuning and unreliable operation. here is a link to the allin1dc hardware overview video.
3.) Elrod Machine Home Page has a nice spindle encoder adapter for manual bridgeport heads.

[Marty_Escarcega]

Hi Al,
No, in this case, the Millstar control used the glass scales for encoder feedback but there are tachometers in the X/Y axis feeding back to the Glentek 7115's.
Thanks for the feedback Al. I don't want to make the control conversion any harder than it has to be.
Marty

[Marty_Escarcega]

Marty,

1.) Yes
2.) yes..but i wouldn't do it. the allin1dc cnc control board has a 15 amp per axis digital autotuning 3 axis dc servo drive built right into the cnc control board. specifically made to replace older analog servo drives and eliminate the difficult tuning and unreliable operation. here is a link to the allin1dc hardware overview video.
3.) Elrod Machine Home Page has a nice spindle encoder adapter for manual bridgeport heads.

Keith,
I had just finished watching that video a few minutes ago. Well done. I agree. Using the All-in-One DC board is the way to go. It has the 6 encoder inputs. I can connect the X&Y axis glass scales to them for positioning feedback and ignore the tachometers in the existing Glentek motors. I would reuse the built in encoder on the Z axis servo motor. Much cleaner, and can use the Autotune feature of your software.

Thank you,
Marty

[cnckeith]

Marty,
Hello. when using scales for positioning (typically used to correct for a sloppy mechanical system) an encoder on the servo motor is still required by the control to run the servo motor properly. the encoder is used in the PID loop of the control to move the servo motor smoothly and position the machine using the scales as the final determining factor on position.
it will be pretty easy for you to replace the tack with a $175 encoder on the servo motors. here is a page showing the servo motor encoder upgrade process on a typical dc servo found on knee mills. DC Servo Motor Encoder Retrofit Upgrade, SEM, Baldor, Glentek

[Marty_Escarcega]

The original Millstar control really used the glass scales for positioning/feedback. Trouble is that the shaft on the end of one of my servo motors (would you believe it) was not made with a shaft to accept an encoder while the other was. The armature of the tach slips down over the shaft which appears too big in diameter for an encoder to slide over. The machine was fitted with balls screws. I think I could drill/ream the back of that servo motor shaft and press a pin into it for an encoder. It amazes me why Glentek did this, they did admit to doing some of the motors in this manner even though they are the same part number.

[Al_The_Man]

As in post #6 and my ref to the Galil video where it shows the division of the PID loop between the encoder and a linear scale, although it pertains to Galil, it is pretty universal when dual F.B. scale/encoder is used.
BTW I generally remove the brushes on the Tach when using torque mode drives, although they are not used, but just to eliminate any mechanical problem they may occur.
You could also machine off the rear shaft in your lathe if large dia etc, I have done this by removing the motor brushes and chuck up the shaft between chuck & tail stock and strap the stator down to avoid it turning etc.
Unless you just remove the armature.
Al.

[cnckeith]

yeah i agree with Al, removing the tach brushes is a good idea, makes the motor more reliable and actually increases the performance (less drag)
and turning down the shaft is a good option as well, just be careful and take your time.
whats the diameter of the shaft now? we can get encoders that accept 5/8" diameter shafts (1/2" is available as well) and on this price sheet is the sizes of encoders that we stock. http://www.centroidcnc.com/downloads...isualprice.jpg

[Marty_Escarcega]

yeah i agree with Al, removing the tach brushes is a good idea, makes the motor more reliable and actually increases the performance (less drag)
and turning down the shaft is a good option as well, just be careful and take your time.
whats the diameter of the shaft now? we can get encoders that accept 5/8" diameter shafts (1/2" is available as well) and on this price sheet is the sizes of encoders that we stock. http://www.centroidcnc.com/downloads...isualprice.jpg

They are Glentek GMA DC brush servos. The tach armature is on the end of the servo motor shaft.
I have a question, I have the opportunity to buy an MPU11 and GPIO kit that was held as a spare and never used. This hardware would work perfectly on my Mill upgrade allowing me to reuse the hardly used Glentek 7115 servo amps. Software is included but the seller states I'd have to buy the unlock codes from Ajax/Centroid. What is Centroid's position on something like this? Can I buy the software to run the knee mill and if so at what cost?
Thanks,
Marty

[cnckeith]

They are Glentek GMA DC brush servos. The tach armature is on the end of the servo motor shaft.
I have a question, I have the opportunity to buy an MPU11 and GPIO kit that was held as a spare and never used. This hardware would work perfectly on my Mill upgrade allowing me to reuse the hardly used Glentek 7115 servo amps. Software is included but the seller states I'd have to buy the unlock codes from Ajax/Centroid. What is Centroid's position on something like this? Can I buy the software to run the knee mill and if so at what cost?
Thanks,
Marty

Marty,
hello. please send me a photo of the mpu11, i'll be able to determine the serial number and from that we can figure out what optional software unlocks were purchased with the card. the centroid cnc software is included with all mpu11 cards so its just a matter of downloading a fresh copy and centroid will supply you with a copy of the original license key at no charge.
that being said, i'd seriously consider the allin1dc instead as the allin1dc is specifically designed for reusing the motors you have and makes it simple and easy to tune the servo motors with the built in digital dc servo drive and it is also a very reliable servo drive...

.. reusing the old glentek drive can be done but ..they are old analog drives and are quite fussy to get tuned up and running well. typically only experienced cnc installer have luck with this kind of install..most all diy cnc installers will fail at reusing old DC analog drives. the allindc is a sure thing and you have a support from centroid (and me) to get your questions answered during the install..if you use the glentek drives..you are on your own for servo tuning advice etc..

also... the mpu11 and the gpio4d have been combined into one new card called the "Oak CNC control board" here is a new video talking all about it.

[Marty_Escarcega]

Marty,
hello. please send me a photo of the mpu11, i'll be able to determine the serial number and from that we can figure out what optional software unlocks were purchased with the card. the centroid cnc software is included with all mpu11 cards so its just a matter of downloading a fresh copy and centroid will supply you with a copy of the original license key at no charge.
that being said, i'd seriously consider the allin1dc instead as the allin1dc is specifically designed for reusing the motors you have and makes it simple and easy to tune the servo motors with the built in digital dc servo drive and it is also a very reliable servo drive...

.. reusing the old glentek drive can be done but ..they are old analog drives and are quite fussy to get tuned up and running well. typically only experienced cnc installer have luck with this kind of install..most all diy cnc installers will fail at reusing old DC analog drives. the allindc is a sure thing and you have a support from centroid (and me) to get your questions answered during the install..if you use the glentek drives..you are on your own for servo tuning advice etc..

also... the mpu11 and the gpio4d have been combined into one new card called the "Oak CNC control board" here is a new video talking all about it.

Thanks Keith. I once again appreciate your response and advice. I think I will go with the All in One DC board. Makes sense and you get the latest hardware and software in the "kit"
Regards,
Marty

[Marty_Escarcega]

As in post #6 and my ref to the Galil video where it shows the division of the PID loop between the encoder and a linear scale, although it pertains to Galil, it is pretty universal when dual F.B. scale/encoder is used.
BTW I generally remove the brushes on the Tach when using torque mode drives, although they are not used, but just to eliminate any mechanical problem they may occur.
You could also machine off the rear shaft in your lathe if large dia etc, I have done this by removing the motor brushes and chuck up the shaft between chuck & tail stock and strap the stator down to avoid it turning etc.
Unless you just remove the armature.
Al.

All, I have Glentek Servos on the mill, XY are identical model numbers, both have tachs, but only one has the stub for an encoder and the other didn't. Spoke with Glentek about it and they admitted they did have a few of those that went out.
So, either I will drill/ream the end of the armature and press in a pin for the encoder or I will look at what you suggest, turning off the tach armature windings. I assume you left the armature in the motor housing and didn't take the motor apart? Or you have pulled them, turned it off and reassembled? As previously mentioned, the old Mitutoyo Millstar III used an old Galil motion controller, Z servo has both encoder and tach, XY servos used tachs for feedback to the Glentek 7115 servo amps but used Mitutoyo glass scales for feedback to the Galil motion controller.

[Al_The_Man]

It has been so long I cannot remember, but I believe I remove the armature and pressed off the tach.
Al.

[Marty_Escarcega]

It has been so long I cannot remember, but I believe I remove the armature and pressed off the tach.
Al.

If pressing them off is an option, I can go that route. Thanks Al
Marty