servo drive help?

[battwell]

sorry if ive posted in the wrong section, if anyone can recommend a better one let me know.
my problem: bought a really nice servo positioning unit on ebay, way under buy it now price but when i collected, the seller had lost the controller for it (it seems it had unbolted itself from its stand ho ho ha ha. anyway, i decided to take what he had, the controller isnt much good without the hardware its driving and vice versa was my thought.
the bits i have will make a great x axis for my cnc if i can find a suitable servo driver i can run the motor off in mach3.

the motor details are as follows:
brusatori dc powered 63 pc 213 conn
vdc 170
rpm 3000
amp 0.7
nm stall 0.44
watt 90
duty s1
ip44
made 13/11/98

the motor has just 2 wires and earth.
there is a seperate encoder driven off a gear on a seperate pinion
also has 2 dc brakes one on motor pinion, one on encoder pinion (was used for a digital positioning fence for a cross cut saw)

anyone know of a suitable drive either commercial or hobby type (i wont be working it hard)
any help would be appreciated

[H.O]

Hi,
At that voltage I know of four: The VSD-A from GraniteDevices, the HP-UHU, the Mammut from CNCDrive and Rutex. Personally I have experience with VSD-A, the HP-UHU and the Mammut. My advice is that if you want to get it going ASAP then look no further than the VSD-A, it's very feature rich and shoudln't have any problems running that motor (see note).

The HP-UHU is delivered in kit-form and has to be put together by you. If you have experience in electronics it's not that hard. If you don't it's still very much doable but you're in for a learning experience. The current draw of the motor is quite low so I'm not sure how well the HP-UHU (which is rated to ~25A or so) will do without changing the sense-resistors.

Note: If there's any backlash between the motorshaft and the encodershaft you might have a problem. May be best to move it to the motorshaft if that's the case.

HTH
/Henrik.

[Zappautomation]

I know this motor in its standard form, its a Siboni motor from italy.
The problem is the voltage, and if you want to get the speed of 3000 RPM, you will need a driver that takes 170V DC, and there are not a lot of drivers (Brushed drivers) that take clock and direction that have a DC bus voltage that high, unless you want to pay for it.
Do you need 3000 RPM? would you accept 1500 RPM? If you would accept the lower speed this opens things up quite a lot.

Originally Posted by battwell sorry if ive posted in the wrong section, if anyone can recommend a better one let me know. my problem: bought a really nice servo positioning unit on ebay, way under buy it now price but when i collected, the seller had lost the controller for it (it seems it had unbolted itself from its stand ho ho ha ha. anyway, i decided to take what he had, the controller isnt much good without the hardware its driving and vice versa was my thought. the bits i have will make a great x axis for my cnc if i can find a suitable servo driver i can run the motor off in mach3. the motor details are as follows: brusatori dc powered 63 pc 213 conn vdc 170 rpm 3000 amp 0.7 nm stall 0.44 watt 90 duty s1 ip44 made 13/11/98 the motor has just 2 wires and earth. there is a seperate encoder driven off a gear on a seperate pinion also has 2 dc brakes one on motor pinion, one on encoder pinion (was used for a digital positioning fence for a cross cut saw) anyone know of a suitable drive either commercial or hobby type (i wont be working it hard) any help would be appreciated

[battwell]

thank you guys for your responses. ive got no problem with electronics soldering etc.
re motor speeds. i havnt worked out speeds required yet. the motor looks to be quite a powerfull unit, being approx 80mm diameter 150mm length. it has an additional 90degree gearbox fitted ratio at 7.5:1 this is fixed to a direct pinion drive which runs on a 4metre long rack which is in turn mounted to the table. it looks like it would make a really good x axis especially for a long bed plasma cutter etc. the encoder is omron a, b, z output at 600 ppr. the amperage printed on the motor seems to be very low for a motor of this size?

the whole lot is mounted on a very sturdy carriage. i believe it was originally a bar feeder unit for a saw.

i also have some nice omron servos and drives which are already tested to be used on my design. im sure i can make this into a fast moving cnc when i get my design head on.
i was thinking along the lines of the chinese built steel tailor for plasma or similar to my biesse 321 for wood. the biesse has a rack and pinion x axis.

re the hp-uhu. where do i find more info on this? the other drives look good but i havnt found this info to compare yet apart from videos on u tube

[H.O]

Hi,
There's a forum section devoted on the UHU-chip and the various circuits developed around it here. Make sure you look at the HP-UHU and not one of the original designs - they are not up for the task at this voltage level.

I agree that the current seems low for a motor of that size, on the other hand a stall torque of 0.44Nm isn't that much so 0.7A is probably correct. Again, whatever drive you go for make sure it can handle such low current - usually you have drives that can't give enough current but in this case it seems to be the opposite....

[Zappautomation]

As mentioned the current is most likely correct, the current is low because the voltage is very high.
This motor is normally 24 or 48V.
Also you will need to get a driver with good current control or you will end up burning the motor.
The datasheet for the standard motor is here.
http://www.slidesandballscrews.com/p...rvo motors.pdf servo motors.pdf so it will give you a bit more information like the torque curves.
Also the right angle gearbox will most likely have quite a bit of backlash, because most worm gearboxes have over 1 degree of backlash.
It may be easier the get a new motor than using the existing motor due to the high voltage and low current.

Originally Posted by battwell thank you guys for your responses. ive got no problem with electronics soldering etc. re motor speeds. i havnt worked out speeds required yet. the motor looks to be quite a powerfull unit, being approx 80mm diameter 150mm length. it has an additional 90degree gearbox fitted ratio at 7.5:1 this is fixed to a direct pinion drive which runs on a 4metre long rack which is in turn mounted to the table. it looks like it would make a really good x axis especially for a long bed plasma cutter etc. the encoder is omron a, b, z output at 600 ppr. the amperage printed on the motor seems to be very low for a motor of this size? the whole lot is mounted on a very sturdy carriage. i believe it was originally a bar feeder unit for a saw. i also have some nice omron servos and drives which are already tested to be used on my design. im sure i can make this into a fast moving cnc when i get my design head on. i was thinking along the lines of the chinese built steel tailor for plasma or similar to my biesse 321 for wood. the biesse has a rack and pinion x axis. re the hp-uhu. where do i find more info on this? the other drives look good but i havnt found this info to compare yet apart from videos on u tube

[battwell]

thanks for your responses again guys. i was starting to think along those lines.
i have a good assortment of other motors here... damn ebay!

with drives like the gecko. have you had much knowledge of these? most info rates them highly.

i might just try linking one of the omron 200watt ac servos up to the carriage and have a play. i have 2 here so i could put one on each side if required

how do you rate rack/pinion drive? as i have 4.5metres of rack on this unit. my other choice may be a long belt. which im thinking should give zero backlash?

[Zappautomation]

For long stroke like 4.5M, the only way to go is Rack and pinion.
I have a customer who makes large plasma cutting machines and they use rack and pinoin for the long axis.

Originally Posted by battwell thanks for your responses again guys. i was starting to think along those lines. i have a good assortment of other motors here... damn ebay! with drives like the gecko. have you had much knowledge of these? most info rates them highly. i might just try linking one of the omron 200watt ac servos up to the carriage and have a play. i have 2 here so i could put one on each side if required how do you rate rack/pinion drive? as i have 4.5metres of rack on this unit. my other choice may be a long belt. which im thinking should give zero backlash?

[battwell]

maybe you can clarify this for me.
the pinion carriage has 2 gears, one from the motor, one to the encoder.
the motors gearbox has approx half a degree of backlash when checked.
the pinion for the encoder is direct drive off the rack at 600ppr

my commercial biesse uses a similar setup for the rack, where the encoder reads the rack position not the motor angle.

i presume this makes it way more accurate as the rack position is encoded so the backlash in the gearbox would be negated?

[H.O]

Hi,
Yes, it will make it more accurate by having the feedback device on the rack instead of the motor. BUT the problem is the way most servo drives used in the DIY-field work. When stationary they dither back and forth between two adjacent encoder counts. If there's backlash between the motor shaft and the encoder the motor will vibrate back and forth and "slam" against each side of the backlash. If the backlash is small it might work but the stiffer you tune the servo-loop the worse it will get.

For example, when you reverse direction the motor will start to move but the encoder won't so the drive "thinks" that the motor isn't moving and applies more torque in order for it "catch up". Suddenly the encoder gear engages and "bang" the motor is turning too fast so it overshoots due the extra torque applied....you get the idea.

Again, if the backlash is small it might work - YYMV.

/Henrik.

[Jason3]

Hi there,

0.44 Nm = 66 oz/in, that seems pretty light for a machine dealing with cutting forces and decent rapids - especially over 4.5 metres. Your Omron motors are probably a better choice...

If you're considering a belt drive, you might like to check out this thread: http://www.cnczone.com/forums/showthread.php?t=59570 for a very clever design that virtually eliminates belt stretch and reduces drivetrain inertia.

Best regards,

Jason

[protman16]

Originally Posted by H.O Hi, Personally I have experience with VSD-A, the HP-UHU and the Mammut.

Henrik,

Can you expand on your experiences with the Mammut drive?

Thanks,

Trevor