Viper Servo Drives

[japcas]

Any of you guys using Viper dc servomotor drives on anything? I bought a Tree Journeyman 310 milling machine that I'm thinking of trying these on but would like to hear from someone who has used them before I take the plunge.

I've built a stepper based system before but I have no experience with servomotors. I know they have to be tuned and the vipers use a special cable hooked to the computer to tune them. You use the hyperterminal to do it from what I understand.

I hope to reuse the original servo motors but I haven't checked the wiring on one of them yet to see what kind of encoders are on them. It looks like I would have to use the Viper 100 as the servo is rated for 40.3 peak amps and 43 volts at peak torque. They are 2200 oz. in torque peak and 418 oz. in. continuous.

I'm doing a lot of research before I buy anything so any info would be greatly appreciated. Any recommendations would certainly be appreicated also. Breakout boards, power supply info, anything. This will all be ran with mach3 as I already have a computer with this installed.

[kf2qd]

Have you looked at brushless servos? it looks like those Vipers are rtated at just ove 160 watts which seems a little small for the Tree. I would have to see specs from the original.

Brushless servos would give you a servo system that can be set up for analog or stepper interface. They also have no brushes so there is little maintenance. They also have excellent torque characteristics at low RPMs.

I have worked with Yaskawa and a lot of the setup can be done from the front of the drive, and most of the time you don't need a computer.

Another source is Automation Direct. I have not worked with their drives, but the price is good.

Brushless drives will also let you replace the encoders as the drives produce those signals, and they can be adjusted so you get whatever encoder counts you need. They come from the factory with either 1000 or 2000 cts per rev and you 2 settings that are a fraction to scale the counts to what you need. For tuning you turn on the Auto Tune switch and cyle the drive a few time, then turn off the auto tune switch and run it.

[japcas]

I would really like to keep the original servos if at all possible. One being cost and the other is I really don't want to modify the mounts if I can help it.

I just ran out to the shop and took a few pics of the encoder as I wasn't really sure what was on it. It has 8 wires going to the encoder and 4 wires go to the motor itself. I couldn't even remember if it was a brushed motor but there was 4 brushes around the body of the motor.

I had heard of A and B channels but what is the Z channel? Can you shed some light on that for me? Like I said, I'm a total newby when it comes to servos.


http://i32.photobucket.com/albums/d39/japcas/IMG_0582.jpg

http://i32.photobucket.com/albums/d39/japcas/IMG_0588.jpg

http://i32.photobucket.com/albums/d39/japcas/IMG_0589.jpg

[macona]

http://www.thecubestudio.com/ServoDriveReview.htm

From this review I would skip the Vipers and go with the Dugong. http://www.cncdrives.com

Z channel is an index. It gives one pulse per rev. What you can do with this is use it to get a super accurate home reference. You use it with the home switch to get an exact home every time never having to worry about microswitch repeatability.

Basically after it hits the home switch it starts looking for the index pulse.

You have 500 line encoders.

[japcas]

Thanks for the info Macona. Does the Dugong drives support the z channel like you are talking about? I can see where this would be very accurate. Have you ever bought anything from them? I see the price is listed in some kind of foreign currency that I don't understand. Also, I'm posting a spec sheet that the servo manufacturer emailed me. Am I misunderstanding it because it says the encoder line count is 1000? Can you help me decipher it?

http://i32.photobucket.com/albums/d39/japcas/servospecs.jpg

[macona]

No drives support the Z channel. It has nothing to do with the operation of the drive, just homing. the encoder count wont matter for setting up the motor and drive. Either way you will have the same resolution as the original so it will be good enough. Usually the -500- part of the model number is the lines per rev. That will give you a servo motor with a resolution of 2000 steps per rev.

There was a guy that used to make a board that handled the Z channel for homing for mach but they are no longer available. Might be possible with some simple logic though.

The pricing is in Euros. These are pretty good sized servos on the machine. You could probably go with the Whale3 and not notice a difference as you would have to do some heavy, heavy cuts or very high acceleration to see these motors pull peak current. What are the old drives?

[Hood]

No drives support the Z channel. It has nothing to do with the operation of the drive, just homing.

Not strictly true, lots of drives themselves support homing to an index, mine do, but it is usually only the more Industrial orientated drives that support this feature.


The boards you were referring to were made by Ed Gilbert, he went by the name of CNC Building Blocks. He stopped producing them for several reasons, the main one I think he said was it would be too expensive for him to swap over to using surface mounts and the through hole components he was using were getting harder to get in numbers. He may still have some stock left so maybe getting in touch, I probably have his email address somewhere if you are wanting.

Hood

[japcas]

Guys, I really appreciate the information and the help. I am taking note of everything. When I built my stepper table last year I done a lot of research from one site to the other gathering info as I could. Finally, I bit the bullet and bought some components and wired them up. Low and behold they worked. Granted it was just a two axis system. Nonetheless I was very tickled.

Macona, this machine is supposed to be a 1987 model and has a Dynapath 10 control on it. The z axis drive card is dead in it right now. I have all of the info I need to get it repaired from a place up north who will guarantee it for 1 year but I really don't want to dump money into a system that old. It would be my luck I would get it repaired and one of the others would crap out or the power supply. I think your right about making these servos pull that much amps, with my hobby jobs I'd probably not be pushing it hard at all.

I will also probably wind up slowing the max speed down some too. This machine has 250 ipm rapids and I think that is a bit fast for a machine with a 44 inch table. I'll probably set it up for 125 to 150.

I checked the backlash on the machine under power and it seems to have about .0015 to .002. Can the ball nuts be adjusted to get some of this out?

[Hood]

Personally I would not go any slower than the original control pushed it along at, 100 to 150IPM will seem fast at first but you will soon find it extremely slow. My Bridgeport does 2500mm/min (100ipm) which was the same as original (stepper setup) but it crawls along, have just finished another mill which I have at 8,000mm/min which is the same as the original and that is much better :)
Quite a few people are using the Dugong drives now and so far have not heard any complaints although I prefer AC servos like macona.
Unlikely you will be able to adjust the ballscrews, you may find the backlash is in the bearings holding the screws in place, you can put a DTI on the end of the screw and slowly wind the table one way then the other and see if there is any end float, if there is you may be able to adjust this out. If its the balscrews themselves then you would probably need to reball them to try and reduce the backlash.

Hood

[macona]

Hood, I was referring to the hobby level drives, not your nice AB brushless servos!

If you have that guys email I would love to get ahold of him. Maybe I can rework the boards design to SMT.

Hmm. 1987 is pushing it... Thats tough.

Like Hood says keep the rapids up. Voltage is what determines the top speed of the motor, current is torque. Also listen to what Hood says about the backlash, its probably in the thrust bearings. And even at that .002 is workable. I put brand new thrust bearings in mine from Hardinge and I still cant get all of it out.

[japcas]

Hmm. 1987 is pushing it... Thats tough.

Like Hood says keep the rapids up. Voltage is what determines the top speed of the motor, current is torque. Also listen to what Hood says about the backlash, its probably in the thrust bearings. And even at that .002 is workable. I put brand new thrust bearings in mine from Hardinge and I still cant get all of it out.

The 1987 part is what is making me seriously consider this retrofit. I don't want to be a slave to Dynapath or this company that says they can fix the original board. The price for any of the boards we discussed is about half the price of repair for the one dead board I have now. So with a little more money I could have all new drives installed.

I don't know why I didn't consider the end play on the ball screw. I've been so consumed by these drives I think my brain is fried. I understand there will be a little backlash but I'd like to see it down to about .0005. Better if possible but I could live with that.

Probably good advice about the rapids too. Thanks for your help.

[japcas]

The price difference between the Whale3 and the Dugong is $105 and $168 respectively. For that amount of difference I don't believe I want to even try the Whale3 and find out it won't do the job.

The spindle is going to be controlled with a new Fuji GE 3 hp vfd that I picked up at the Cabin Fever show. I would like for the mach3 to control starting and stopping of the spindle motor for me and possibly the speed. I would like to set it up using the pulley system in mach3 to dial the varispeed head into a set speed and then use the vfd to vary a little above and below the set speed.

Can you guys make some recommendations as to what kind of breakout board and power supply you like? I can thumb through the web and search but I'd love to hear your suggestions.

[BobWarfield]

Homing with the index seems like an AND combination to me. You fire the home signal when you get the mechanical home switch AND the index pulse. Need some digitial whiz bang to design it, but I'll bet the circuit to do this with three axes would be really simple.

Cheers,

BW

[Hood]

My servo drives do the homing without Mach knowing and then just inform Mach that it has homed.
Eds boards did the homing differently in that Mach told the axis to home and when you hit the switch Eds board would not pass the signal back to Mach right away, it would wait until the encoders index was seen then it would tell Mach the switch was hit and Mach would reverse the axis and when a user configurable encoder count was seen Eds board would then tell Mach the switch had now closed.

macona, dont have Eds email here but hopefully I have it at home.

Hood