recurring problem - no holding torque

[sunward]

This problem I have has been going on for some time and I am at the point of throwing everything out and starting fresh with products (industrial, generally not for sale here). Everyone seems to say it is something else is causing the problem.

I am posting here as the unit showing a fault is the Gecko drive.

First, everyone I contacted has provided help.

I have a CNC lathe running under Turbo cnc. After about 30 minutes, one drive loses holding torque. If I reset the Gecko drive (one of the pins), the holding torque comes back. If I turn the power off to the drive/motor, I can use the system again after about 20 to 30 minutes. Will go through the same problem.

I have both drives running under G212. I have used 3 different drives on the axis and the same problem occurs.

I have a Keling NEMA34 SINGLE SHAFT STEPPER MOTOR 400 oz-in and an 1160 oz one on the problem axis. 4.2A/ phase.

Power supply is a 65 VDC 6ADC from Transformer Technology. I contacted them and the power supply should be good.

I have also changed the computer in use.

I contacted Gecko drive and the problem was the unit shutting down due to an overload. Suggested I change the motor.

I installed a 400 oz motor on the problem drive ( dual shaft as out of stock on single shaft).

The lathe worked like a dream!

For hours on end with no interruption or lose of holding torque.

Until this afternoon.

The same problem returned

I shut the system down to cool. No effect.

For the record, I was advised I needed a breakout board. I ordered one from Campbell Designs and was trying to install it but ran into problems. ( seems not easy for Turbocnc use). I did email back and forth with Bob Campbell but had to put this on hold until I had more time.

ANY suggestions?

[acondit]

Have you got heatsinks on the Gecko's?

Alan

[Crevice Reamer]

Formula for maximum motor voltage: Square root of motor inductance, times 32 = max.

Keling 400 oz N34 = 1.65 MH inductance. Sq. Rt. of 1.65 = 1.28. 1.28 X 32 = 41.

By my calculation, if these 400 oz motors are wired bipolar parallel, they should be run at no more than 41 volts. Sixty five volts must be overheating them terribly. Once a stepper gets TOO hot, it will lose magnetism and never run again.

You should only be running these 400 oz motors at 36 volts.

CR.

[sunward]

Originally Posted by acondit Have you got heatsinks on the Gecko's? Alan

They are mounted on an aluminum plate and have not gotten hot up to this point.

Originally Posted by Crevice Reamer ....You should only be running these 400 oz motors at 36 volts...

Amazing. I ordered the power supply based on the recommendations of the company.

Sent an email to Keling and waiting for a response.

Contacted Transformer Technology and they will custom build a 36V 8A system and I will send the current one back. Waiting for a price.

[Crevice Reamer]

The 1160 oz motor wired bipolar parallel could run at 80 V. The 400 oz motor wired in bipolar SERIAL (half the power and speed of B. P.) could run at 82 volts.

Perhaps you did not understand when Keling explained that the 400s had to be wired bipolar series to function.

Now you may need another 400 oz motor to replace the one that got cooked. If he did NOT explain to you how this motor had to be wired, then maybe he will replace it for you. The KL320-36 8.8 Amp power supply @ $59 would be adequate for two 6 amp motors if he had them in stock.

CR.

[sunward]

Originally Posted by Crevice Reamer The 1160 oz motor wired bipolar parallel could run at 80 V. ..

The specs for the motors were given to the power supply company and they made the recommendation.

IIRC, no mention of inductance was made at the time.

The motors are not fried.

[Crevice Reamer]

Originally Posted by sunward The specs for the motors were given to the power supply company and they made the recommendation. IIRC, no mention of inductance was made at the time. The motors are not fried.

Ahhh! So it was the PS company, not Keling. Well they got it HALF right.

WOW! If those 400 oz. motors have been running at 180% of their normal voltage, AND they are NOT fried--Those Keling motors must be some FANTASTICALLY GOOD MOTORS!

Glad to hear all will work out, and By the way:

Welcome to the Zone sunward!

CR.

[CoAMarcus]

Sunward,

From what I can gather from your first post, you had a 1160 oz motor that was giving you problems and you replaced it with a 400 oz motor and it worked for a little bit. Is that correct? I am just trying to sort it all out in my head so I can figure out exactly what is going on.

Marcus Freimanis

[sunward]

Originally Posted by CoAMarcus Sunward, From what I can gather from your first post, you had a 1160 oz motor that was giving you problems and you replaced it with a 400 oz motor and it worked for a little bit. Is that correct? I am just trying to sort it all out in my head so I can figure out exactly what is going on. Marcus Freimanis

Had a 400 and 1160 oz motor. Having the problem with the 1160oz motor. Replaced that one with another 400 motor. Worked great at first, then the same problem.

The other axis has never been a problem.

[CoAMarcus]

Sunward,

Have you tried swapping the motors from each axis, or swapping in a different motor aside from the 400 oz-in to see if the problem stays with the problem motor? I know you have already swapped, but try swapping it with a motor of comparable specs. Also, what is the size of your current set resistor?

Marcus Freimanis

[Crevice Reamer]

Upon re-reading your post, I notice that you were running two 6 amp motors on one 6 amp power supply. Those two motors would require at least 8.4 amps for best performance when both are running at the same time. I don't know if that caused a problem, but it's definitely not efficient.

CR.

[CoAMarcus]

Originally Posted by Crevice Reamer Upon re-reading your post, I notice that you were running two 6 amp motors on one 6 amp power supply. Those two motors would require at least 8.4 amps for best performance when both are running at the same time. I don't know if that caused a problem, but it's definitely not efficient. CR.

That is why I am very interested in his current set resistor size. I fear he may have a current set resistor on both of 4.2A, and with both running at full load they are stalling.

Marcus