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Servo drive recommendations
« on: June 27, 2015, 10:27:21 AM »
I have been slowly starting a big mill retrofit. I got my ess issues all solved, at least in testing and design stages. Next is the servos. The current drives are 80vdc 15a. The actual voltage from the supply is 80v. I am looking for drive suggestions that will match or excide the original. The original analog drives have issues and it is t cost effective to use them. So a step/dir drive is what I was looking for. Currently I can run the full size knee mill at rapids of 250ipm. What are my options, greatly considering ease of tuning and support available.
Thanks
Don

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Re: Servo drive recommendations
« Reply #1 on: June 27, 2015, 10:54:46 AM »
What type of servos are they, and what are the ratings?
Gerry

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Re: Servo drive recommendations
« Reply #2 on: June 27, 2015, 11:49:18 AM »
Electrocraft e703
Max cont speed 1400rpm
Max peak torque 2000 oz-in
Max peak current 45a
Max control stall torque 427 oz-in
Max cont current 9.6a
Have the rest of the specs if needed.
Thanks
Don
Re: Servo drive recommendations
« Reply #3 on: June 27, 2015, 11:50:54 AM »
They are the he original servos and pwr supply to the machine. Hurco sm1-cnc mid 80's era

Don
« Last Edit: June 27, 2015, 11:53:27 AM by DonMarkey »
Re: Servo drive recommendations
« Reply #4 on: September 10, 2015, 04:46:00 PM »
Hi Don:
This post is a few months old, but I just read your questions. I have an older mill, with probably the same drives and the very same Electrocraft servo's. The driver/Amps were made by WestAmp, now out of business since I believe 1992. This type of control is Analog +/- 10v with encoder feedback. In the day, these were very good drives, and would hold position well.
The big problem is getting the drives repaired when they malfunction. Even though it might be a single resistor, easily replaced, finding exactly what is wrong can be very difficult without the proper electronic equipment. I have been able to find a few used drives on Ebay, but that is hit or miss.

The mill discussed now uses a dspmc controller by Vital Systems, and it runs the older drives perfectly. I did have to change the encoders to the AMT differential to work with the controller, but is runs better now than the original controller.

Since doing the retro-fit to the older controller, I have since learned of a newer type of Servo motor/drive that is far better than anything I have yet seen, and it uses step/dir for an absolutely solid, precise control.

If I did another machine, I would definitely use the Clearpath servo's by Teknic. There are Youtube videos showing these motor/servo's with Mach3.

John
 
Re: Servo drive recommendations
« Reply #5 on: December 28, 2015, 07:14:56 AM »
Thanks for the input I have been making slow progress on this. I did order one cnc drive and brake from Arturo at cnc4pc under his recommendation going with the larger drive to handle the regen of the heavy table to test with. Hopefully find out soon as I have the controller about 50% done.
Don
Re: Servo drive recommendations
« Reply #6 on: January 31, 2016, 10:52:08 AM »
Don
I'll share what I have encountered with my retrofit. My servo are rated at 150vdc 50amps. I started with the Gecko G320X drives. They work good are very smooth and quiet. Tuning is tricky but once you get the feel you can set them to a nice smooth run. The G320X is rated for a max of 80vdc at 20 amps which so far has ran the X and Y with no problems and plenty of power. I have been running this machine for 3 years in a fab shop so it see's a lot of work. The Z axis burns out the G320 after about 6 months. My mill is a bed mill with a large head and just needs more power than the Gecko can deliver. After losing a couple of the Geco's to this I stepped up to a Dugong 160 35 drive. As you can guess it is rated at 160vdc and 35 amps. This drive throws the Z axis around with no problems and can run much faster than I care to move that much weight. Now the draw back of this drive is that its noisy compared to the Gecko and the tuning is done through software. There is a scope in the software for pid tuning to see the effects of dampening which is very helpful in getting it right.
The specs of your motors are well within the specs of the Gecko and they would probably work good for you retrofit. If you use the Gecko drive be sure to put them on a good heat sink, they are very small and won't cool very good on their own. Something they don't mention in the paperwork provided with the drives.

Good luck hope this helps.

Steve
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Re: Servo drive recommendations
« Reply #7 on: January 31, 2016, 11:07:53 AM »
Thanks for the input Steve. I got it ready but the issue I have now is I can't get the dugong to tune. It is acting real strange. I think I actually have encoder issues or something in the feedback loop. I am using the original single ended encoders and one of their line drivers to change it to differential. Running the software I get a wield square wave type pattern on the scope and the motor moves the same amount no matter what I tell it to do. When I hook it up to the controller and let Mach tell it how far to go it moves the same amount regardless of the move commanded. I tried two different motors and their encoders. All of which work fine with the hurco controller. I think either something is really out of whack in the settings or I have a bad drive or differential converter. I need to order another of each an see as I am at a loss now for troubleshooting.
Don
Re: Servo drive recommendations
« Reply #8 on: February 01, 2016, 10:51:50 AM »
Try reversing the polarity of the motor, sounds like the encoder is reading reverse of the travel which will move a small amount that the drive is set for as out of position then stops. The loop is closed between the drive and motor so it will act the same regardless of where the command comes from. If this works but is backwards from the command you can change the direction in the Mach software to correct that.
« Last Edit: February 01, 2016, 10:54:07 AM by Machinehead57 »
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