Thread: Help on Z

Been testing all day.

Motion mode = cv
Distance mode = absolute
IJ mode = incremental

1) Velocity 1000 Accel 500 10,500 iterations: Z gained 1.6

2) Velocity 1000 Accel 500 10,500 iterations dropped feed speed by 50%: Z gained 1.55

Reset feed speed to 100%

Removed PSU to distant location to eliminate any possible electrical interference

3) Velocity 3000 Accel 500 5,000 iterations: Z gained 1.0

Changed Z BOB from pins 6 and 7 to pins 8 and 9

4) Velocity 3000 Accel 500 5,000 iterations: Z gained 0.8

Swapped driver for another Keling driver (4030)

5) Velocity 3000 Accel 500 5,000 iterations: Z gained 0.05

6) Velocity 3000 Accel 500 5,000 iterations: Z gained 0.1

7) Velocity 4000 Accel 1000 5,000 iterations: Z gained 0.2

It would appear to be beyond dispute that the problem lies with the driver(s). It is possible/probable that they are just not that accurate. There is still a degree of error but it would not worry somebody who was making a smaller machine.
I will see if I can sell them to somebody else.

I am now considering buying two more of the Gecko 203V drivers. I would rather not, because they are $150 each plus postage. The advantage of them is that I can then run all the drivers off the one PSU and that will be the 80 Volt one. I will also have three Keling 4030 drivers going spare then.

Comments?

Bob

Hey Bob how hard is it to check it on the 203 Driver besides being a total pain in the @#$.

Hmmmm

It really shouldn't be all that hard to check. I would need to plug the Z axis motor into the X axis plug and then tell Mach that it is using the X axis pins for Z.

Good idea Sean.

Bob

Hmmm, not quite as easy as I thought at first. There is one extra element that I didn't take into account and that is the amp limiting resistor. I should have changed that too.

As soon as I turned the machine on I could hear the extra power in the motor and after the 5000 iterations it was very hot and there was a small amount of burning smell in the air. Not enough to hurt anything but not something that should be done too often either.

The results were inconclusive because of the excess heating, so I will try again when I have a suitable resistor for the motor.

Bob

Latest results after putting the correct resistor on the Gecko 203V.

5000 iterations at 3000velocity and 500 acceleration Z gained / lost 0.000mm motor got too hot to touch for longer than 2 seconds

50,000 iterations as above Z gained / lost 0.000mm motor got too hot to touch for longer than 2 seconds so I clamped a couple of pieces of thick aluminium to the sides of the motor. No burning smell this time but the heat sinks got BL00DY hot.

I may need to rig up a fan for each motor if this is going to continue.

But all-in-all a great result. Thanks to everybody for their help in fixing this problem.

Now I need to decide whether I should buy two more 203V drivers or go for their cheaper brothers, the 201X. The 203s are close to $150each while the 201s are about $40 cheaper at about $110 each. Does any one have anything they could tell me about relative merits of these two drivers?

Bob

Bob

Glad you are seeing a better result.

Motors do get hot but not that hot.

What are the specs on the stepper? Amps and Inductance.

How much voltage are you feeding it?

Are you confident that you have the amps set correctly?

Greg

Hi Greg

I am using the 70 volt PSU on the motor. As that is what is attached to the Gecko driver.
The motor itself is a Kelinginc KL23H286-20-8B It is wired as bi-polar parallel and draws about 2.8 amps and has about 420 oz of holding torque in that configuration and draws about 4.17 volts to drive it. I put a 32k resistor in the Gecko to take the amperage down to the correct level.

As I understand it, these motors can handle about 80 volts.

Bob

Do you have an IR temp gun or temperature probe so you can measure the temperature of the motors.

Originally Posted by geckodrive.com

Q: How hot is too hot to run a stepper?

A: Stepper motors are designed to run hot. Most have class B insulation which means they can sustain temperatures up to 90 C without thermal breakdown occurring. This breakdown comes in the forms of insulation and winding failure.

Hi Ch4iS

No sorry, i don't have anything like that, but I could try cooking an egg on it.

Bob

I have just ordered two of the Gecko 203V drivers. I would have liked to order the cheaper drivers, but nobody suggested that it was a better way to go.

When I get them I may connect them to the 36 volt PSU as the 70 volts is making the motors REALLY hot. I hope the drivers provide the same accuracy at 36 volts as they do at 70 volts

The motor on the X axis is a lot bigger than the other two and can take the heat associated with the higher volts more easily.

Bob

Originally Posted by Bob Willson

I have just ordered two of the Gecko 203V drivers. I would have liked to order the cheaper drivers, but nobody suggested that it was a better way to go.

When I get them I may connect them to the 36 volt PSU as the 70 volts is making the motors REALLY hot. I hope the drivers provide the same accuracy at 36 volts as they do at 70 volts

The motor on the X axis is a lot bigger than the other two and can take the heat associated with the higher volts more easily.

Bob

Both drivers are basically the same in my eyes the G203V just has the additional protection features, I suggest the G203V to newbies over the G201X mostly because it has the extra features should they stuff up.

36V will work fine you will get the accuracy but not the speed, keling drivers must be faulty (Send em back)

With the 70V PSU to cut heat you can try a lower current setting, maybe 2.5A and see if that reduces it somewhat.

Thanks for that Ch4iS

I will try that,but I will first try setting up a small computer fan to blow over the motor and see if that is capable of keeping it all cool. If it works, then that would probably be the better option. That way I can retain the higher voltages with the concomitant benefits of enabling me to get rid of the extra PSU etc.

Bob

I took Chris' advice and have tried smaller current limiting resistors on the new Geckos.
They seem to keep the motors cooler but they also seem to slow them considerably as well.
Can anyone tell me if I can use an adjustable pot here instead?
What is the wattage that flows through the resistors?
If I can use these trim pots, then I can have an ifinitely adjustable driver amperage.
The pots are rated at 0.5 watts and the resistors are only 1/4 watt so they should work well.

Bob

I'm sure 0.5 watt will be fine. Not so sure about the infinitely variable idea though.

What about a miniature dip switch to select resistance. Say 2.5, 2.75 and 3 amp selections.

That way you will know for sure what amps you have selected and what motor tuning settings suit each selection.

Greg