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nikodell
04-29-2009, 05:42 PM
I offer no solution, but, like Bill Clinton, I feel your pain. I am running the Gecko540 with Keling 387 oz motors. I bought it as a package from Keling, so I (wrongly) assumed they were matched up. But my motors are running extremely hot also. I've been in contact with Marcus at Geckodrive, and he is suggesting that the PSU which came bundled with my package may be mismatched, meaning not big enough (wattage I assume). I'm still doing some testing, and won't lay the blame on Keling (yet). I, like you, used the recommended current limiting resistors, wire gauge, installed cooling fans etc. Followed instructions to the letter on putting together the electronics.

Hope you find a solution, as I'm probably looking to junk the PSU that came with the package and purchase a bigger one. (the wife is going to love hearing that, too) Good luck!!!

I would like to know before they send me my whole package.
Any word from kelling here?

G540 4 axis package (One G540 + Four
KL23H284-35-4B (1/4” Dual shaft with a flat) 387 oz-in + one KL-600-
48 48V/12.5A 115V /230Vpower supply): $624.95

KL-600-48 115/230 48V 12.5A Air-cooled 600 watt

ger21
04-29-2009, 05:54 PM
When you run steppers at their maximum recommended voltage, they'll get hot. Most steppers can run up to 180° without a problem. If you're not running the steppers as fast as they're capable of going, then a lower voltage supply may give you the same performance and much cooler motors.

nikodell
04-29-2009, 05:56 PM
So you could lower the power supply voltage and than keep the motors cooler

ger21
04-29-2009, 06:04 PM
Yes, but they won't be able to spin as fast with a lower voltage. Ideally, you want to use the lowest voltage that will give you the performance you need. However, determining what that voltage may be can be difficult, so most people use the highest voltage they can, and wonder why they have hot motors. :)

JeLC
04-30-2009, 07:43 AM
If I did the math correctly, the motors I bought should be able to handle a max voltage of about 74 volts. The PSU in the Keling bundle is 48 (I think, or maybe 50). Right now I'm running at about 47 volts. That's reading with an old cheap Volt Ohm Meter.

I'll go back and redo my math. Seems like the formula is something like the square root of the inductance times 32 or whatever. I'll find it and recalculate, just to make sure I'm not out on a limb with that number.

The thing I don't understand is that a power supply is just that. The load (resistance, right) on it is what determines how much power is delivered. So the motor is just pulling a certain amount of amperage based on the voltage supplied and the resistance of the load. A mismatched PSU shouldn't have anything to do with how the motor runs, as long as the PSU is able to supply the required amount of current at a certain voltage. I'm by no means an electronics expert, but I've always thought that a power supply has a maximum current capability at a certain voltage, and the load determines how much current is actually delivered.

Again, I haven't actually measured the temp of the motors, so I might just be creating a problem that isn't there. All I know is that they are way past warm. To the point of almost burning you if you accidentally touch them. I hope to come up with some type of measuring device today and get an answer. I'll post my results. This too will be an approximation, because I don't have the correct equipment to accurately measure the temp. Hopefully I can get close enough to get us an answer.

After reading your post a second time, I notice you are talking about a higher rated PSU than the one I'm using. Mine is rated at 7.5 amps. Don't know if it matters, but thought I should throw that in.

nikodell
04-30-2009, 07:49 AM
I see I thought you had that kit, LoL. I hope things work out with yours, what is your exat hardware?

Crevice Reamer
04-30-2009, 09:05 AM
If I did the math correctly, the motors I bought should be able to handle a max voltage of about 74 volts.

The Keling 387s USED to be rated at 4.1 mH inductance. That made them a 65V MAX motor. NOW I see the spec has changed to 2.8 mH. THAT, if correct, would make it a 54V MAX motor.


The thing I don't understand is that a power supply is just that. The load (resistance, right) on it is what determines how much power is delivered. So the motor is just pulling a certain amount of amperage based on the voltage supplied and the resistance of the load. A mismatched PSU shouldn't have anything to do with how the motor runs, as long as the PSU is able to supply the required amount of current at a certain voltage. I'm by no means an electronics expert, but I've always thought that a power supply has a maximum current capability at a certain voltage, and the load determines how much current is actually delivered.

Exactly True. The VOLTAGE does have an effect on how FAST the stepper motor coils can accept the current though, and THAT affects how fast the motor can turn.


Again, I haven't actually measured the temp of the motors, so I might just be creating a problem that isn't there. All I know is that they are way past warm. To the point of almost burning you if you accidentally touch them.

Touch them with a WET finger. If this does not sizzle, they are probably not too hot.


I hope to come up with some type of measuring device today and get an answer. I'll post my results. This too will be an approximation, because I don't have the correct equipment to accurately measure the temp. Hopefully I can get close enough to get us an answer.

Here is what you should use:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93983

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93984

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96451


After reading your post a second time, I notice you are talking about a higher rated PSU than the one I'm using. Mine is rated at 7.5 amps. Don't know if it matters, but thought I should throw that in.

It doesn't matter. The load determines how much current it will draw, not the PSU.

CR.

JeLC
04-30-2009, 03:13 PM
OK, I did some measurements this morning. Marcus at Geckodrive told me if I had nothing better, a meat thermometer would suffice. I had nothing better so that is what I used. I wrapped a cotton cloth around the motor tight enough to hold the business end of the meat thermometer close to the X motor. I'm still using the demo Mach3, so I couldn't run a really long program, but I designed a small area clear cut that equaled out to about 400 lines of g-code. It was a triangular cut so as to exercise the x motor pretty good. I ran this code 20 straight times, one right after the other. (I was not cutting anything either. I zeroed the Z Axis well above my table to make sure it never got into my spoil board.) So that was the equivalent of an 8000 line program. The motors moved continuously for about 90 minutes, which I feel was enough to get the motors up to their maximum temperature. The temperature of the meat probe was right at 200 degree when I stopped.

Too high, right? I'm not over driving the motors, meaning I have the PSU set at about 47 volts. My IPM rate on the x and y axis is about 30, but the g-code had it set for 20IPM rapids and 10 IPM cutting speed.

CR, I got no paperwork with the package from Keling, and I do mean no paperwork at all. no documentation on the motors, PSU or the Gecko. Not even a packing list. When I pulled down the specs on the motor from their website, the specs I pulled down said the inductance of the 387s were 4.1 mh, so that is what I used for my voltage setting. And according to your calculations, even at the lower inductance value, 47 volts is still within the operating range of the motor.

Now with all of that said, what can I or what should I do to lower the temp of the motors. Operating at that high temperature is surely going to do eventual damage to the motors, and, although I didn't measure all three, they all seem to be running at about the same temperature.

Crevice Reamer
04-30-2009, 03:39 PM
Ok. Get out your multimeter. Set to Ohms and 200K. Turn off the power. Remove The db9 cables and measure Ohms from pin 1 to pin 5. You should have 3.5K Ohm or less. Should NOT be more.

CR.

Crevice Reamer
04-30-2009, 03:45 PM
Here is all of the documentation that should have come with the G540:


http://geckodrive.com/upload/G540%20REV3%20MANUAL.pdf

http://geckodrive.com/upload/G540InitialSetup.pdf

CR.

Crevice Reamer
04-30-2009, 03:53 PM
If you don't already HAVE a digital multimeter--Spend the $5:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92020

You may also want to get a non-contact thermometer:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93983

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93984

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96451

CR.

JeLC
04-30-2009, 05:36 PM
That was my next step. I could not find 3.5K resistors here locally, so I ended up at the local Radio Shack buying 3.3K and 200 ohms and wiring them in series. The total resistance of the two measured around 3.6 K. I have a cheap VOM that I bought at Radio Shack several years ago. Before I retired as a computer geek in networking, I had a couple of nice Simpson digital meters and the one I'm using now is such a step down from that.

I have some 3.5K 1% resistors on order, just haven't received them yet. Hopefully that will help. And I found all the documentation on all the stuff I got easy enough. I just thought it was odd that a company would send out an order without any documentation. Guess that's what the Internet has done to us.

Thanks for all your help.

nikodell
04-30-2009, 06:20 PM
This is most likely your problem, I could be wrong but I think you would be better off with just the 3.3 if you intend to run the motors.

jalessi
04-30-2009, 06:43 PM
Have you tried applying some heat sink compound between the steppper motor and the mounting surface?

If your stepper mounting is made of aluminum it will heat sink or dissipate a lot of the heat away.

Jeff...

nikodell
04-30-2009, 07:15 PM
I think his Auto standby current is not working because the resistance is over 3.5K ohms. It is my understanding that it will not kick down if the resistor is above the 3.5 for a 3.5 motor.

Crevice Reamer
04-30-2009, 10:53 PM
I think his Auto standby current is not working because the resistance is over 3.5K ohms. It is my understanding that it will not kick down if the resistor is above the 3.5 for a 3.5 motor.

Yep!!!

CR.

rowbare
05-01-2009, 08:35 AM
While you are waiting for the 3.5k resistors simply remove the 200 ohm and run it at 3.3 amps. There is a minor loss in theoretical power (about 5 or 6 %) but you will likely not notice that in practice.

I have one of those on my Z axis and haven't had any overheating issues using a 3.47K 1% resistor.

JeLC
05-01-2009, 09:38 AM
The mention of auto stand by may be a key point, because I have noticed that when my machine is in idle mode for long periods of time (1 hour or so) I don't notice the motor temp going down at all. From all indications, the current limiting resistors seem to be my problem.

One problem too is that I built this thing as cheap as possible, and I'm not using metal motor mounts. Since I'm an long time woodworker, I have many wood scraps laying around, and not so much metal. My motor mounts are made out of oak. They are strong, but I know they don't dissipate too much heat away from the motors.

I've only had this thing up and running about a two weeks, so I realize there are many things I did wrong, because of my 'cheapness'. I wanted to get it up and running as cheaply as possible and then improve, rebuild, upgrade, etc. My table is built like the JPGO (I think that's the name) and there are a lot of areas where I'm not satisfied with. (like small inaccuracies in the bearing mounts, flexing of the gas pipe, etc) I'm in the process of designing another system. This time I'm going to use 8020 and a lot of the stuff from Fine LIne Automation, etc.

Thanks for everyone's input. That's why I'm so thankful for finding this forum. Lot of good people out here with a lot of good advice.

nikodell
05-07-2009, 10:08 PM
I got my steppers today and got it all setup ie: test bench no load and the steppers hardly even get to feel warm.

Larken
05-13-2009, 09:32 PM
How long does it take for the motors to get really hot ? If it takes only a few minutes then you have a problem.

Try reducing the current to about 1/2 the rated current. If they still get hot, then the voltage is too high.

edit: i didn't read the last page