[CAM_MAN]

:tired: Hopefully someone can help me with this. I have 3 Tormach steppers on a 48x96 router. Here are the motor specs:

Holding torque-Nm (oz/in) +/- 10% - 8.7 (1208)
Rated voltage - 2.7
Rated current per phase (amps DC) - 6.0
Resistance (Ohms) +/- 10% - 0.45
Induction (mH) +/- 20% typical - 5.1
Motor length (mm) - 118
Rotor inertia (g-cm^2) - 2700
Weight (kg) - 3.2

I am using a 60 Volt 12 Amp power supply with 3 Gecko 202's. Using a CNC4PC breakout board, charge pump and 5V/12V mini power supply. Geckos are sitting atop of very large heatsink fans which keep them vey cool. All my wiring is very neat with no power or motor cables near my step direction wires. All of my motor cables are shielded 18 AWG all my home and limit switches are 22AWG. My motor cables are about 22 FT. long. I am using Mach3 on a 650MHZ PC with 128 Meg Mem. I have Mach3 set at 35000khz and it displays a consistent 36152khz and I have used it at 25000khz and have not noticed any difference. With all that out of the way my problem is that I can run my router anywere from 20 to 80 ipm and it runs fine for about 15 minutes and then it starts missing steps. I notice that the motors start getting warm when this happens but by no means are they too hot to touch. Also the Gecko's get warm but just barely above room temp. I am checking them with a temp laser. And I had previously blew a couple of drives so I am being overly cautious and using 1 Amp fast blow fuses so I don't think I am drawing to much current. So anyhow I can let the machine sit for about 30 minutes and fire it back up and it will run fine for about 15 minutes and got to crap again. Mechanically the machine is very acccurate and will hold +/- .002 all day when not missing steps. All axis move easily with very little friction. I don't know if it matters but the programs I run are quite large and fairly intricate 3D. Anyhow I am just about at my wits end. Could someone please help me out. Hopefully Mariss will read this and bless me with some of his wisdom.
Thanks in advance.

[derekj308]

Hi CAM_MAN
As a double check, what is the value of your current limiting resistor. I did a quick calc and for 6A you would need a 282k ohm resistor based on the formula in the G202 manual

R (in k ohms) = 47 x I / (7 - I)

Make sure you using the high current range also. From the detail in your post I would expect you would have all this right but it doesn't hurt to double check.

I noticed also in the manual it says that the power supply needs to only be able to supply a maximum of 67% of the rated phase current of the motor. I can see the potential for misinterpretation of this in that someone may think that they need to set the current limiting resistor need to be set so that the output current of the drive is 67% of the rated phase current. The rated phase current, in your case since you run 4 wire bipolar motor, is 6A so you should set your current limiting resistor to achieve 6A. For those of you who run 6 wire or 8 wire as biploar use this site as a reference for what to set the current to.

http://www.orientalmotor.com/support...connection.htm

I hope you get your motors running right. That brain pain sure does hurt.

Cheers
derekj308

[CAM_MAN]

Thanks for the feedback. I have already done the resistor routine. I checked, double checked and triple checked the resistor before I even fired up the drives for the first time. I even bought a series of different size resistors to swap out to see if it would help my problem. No it had no effect. What do you mean "use the high current range"? Do you mean that I need to set my resistor for 6 amps and not 67% of 6 amps. I am setting my values for 6 amps if that is what you were wondering.Thanks again.

[derekj308]

Hi CAM_MAN

I don't own a Gecko so I'm only going on what I see in the manual, not from experience. 6A is right w.r.t. the 67% question.

"Using the high current range" refers to the jumper settings on the drive. In the manual on page 2 it says that if there are no jumpers on 1-5 or 2-6 that will set the drive to the low current range which is 0.3 to 2A as opposed to 1 to 7A. If I have interpreted the manual correctly, if you wanted 33% standby current ie when the drive is idle, you would have a jumper across 2-6. If you want full standby current then you would have a jumper across 1-5. Check that mid band compensation is on by checking there is no jumper between 3-7.

I would expect that you really only need one jumper present, a jumper between 2-6 to get 33% standby current or a jumper between 1-5 for full standby.

It sounds like your motors are 'just' working when cold and with a little temp increase they 'moo' and lose steps or stall completely. When I say 'just' working I thought of low current hence my suggestions for checking the drive settings. If you have no jumpers across 1-5 and 2-6 your current setting would be 1.7A for a 282k resistor.

Cheers
derekj308

[CAM_MAN]

I have the jumpering set right for the high current range. I checked that before I even installed the drives. Today I just changed my current set resistor way down to 5 amps and it seems to have helped. I think I will drop it down to 4 amps and see if it gets even better. I don't know why it is helping because they are 6 amp motors and the current set resistor is supposed to be set for that.

[H500]

Try changing to a bigger fuse. I wonder if the 1 amp one presents too much resistance.

[Joe Petro]

What kind of voltage do those motors see after 22 feet of cable?

Joe Petro

[jeffs555]

With a total of 44 feet of 18AWG, the resistance would only be .28 ohms, so at 6 amps, you would only drop 1.7 volts in the wire.

[ger21]

I believe that it was determined in another thread that the spindle was cauing the problem.

On a side note, I can't believe you can run Mach3 at 35Khz on a 650Mhz PC? Is your CPU usage at 100% al the time while running? Check with task manager.

[Jason Marsha]

As Gerry says the spindle may be causing the problem, is the power wire for the spindle(router) close to or touching any motor wires?

It may also be touching a metal part of the machine frame and with any break or weakness in the power cord insulation may cause problems with the steppers.

When I had this problem Gerry advised me to change my Debounce Interval setting to around 2000.

The spindle should also be powered from a different plug (seperate circuit)than the computer and cnc control box.

Just a question that I guess the more knowledgeable can answer, you have 3 motors rated at 6.0 amps per phase, you also said you do intricate 3D which would mean that all 3 motors will draw full power or close to that most of the time, can a 12 amp power supply provide enough power for these 3 motors ?

Jason

[derekj308]

Hi CAM_MAN
I think Gerry is on the right track with his question about whether or not your computer can output 35kHz running only a 650M processor. I have experienced different results in motor sound and performance just from swapping computers. If you get the chance hook it up to a fast PC and see what happens. I get the feeling it is 'dirty' pulses that cause the variation. Thank Mariss for bringing us the G-Rex and its 'clean' pulses.

I have an answer for Jason about the motor current. Even though CAM_MAN may be running all three axis at once the motors won't draw full current since during cutting the only forces required are frictional force of the system, which in a decent machine is low, and the force required to feed the cutter into the job which for hobby CNC is also low. The most current drawn is when the axis are accelerating during a rapid movement not feed movement. The current being drawn from the drives is limited via the current limit resistor setting to 6A not held constant at 6A. There is also the issue of duty cycle which is still low even for 3D machining. Also, roughing sequences are typically 2-1/2D. During a finishing pass or even pre-finishing pass the load on the motors is compatively low to current drawn during acceleration. If CAM_MAN is pulling high current during feed then he must have one hell of a powerful spindle (in hobby CNC terms anyway) and a rigid machine as well.

As a reference I can run 3 NEMA 34's to stall my 1kW router using one power supply that is rated to 2.7A continuous and 4A max. If it sees anything more than that it shuts down. I set my drives to 2A max.

Cheers
Derek

[CAM_MAN]

I believe that it was determined in another thread that the spindle was cauing the problem.

On a side note, I can't believe you can run Mach3 at 35Khz on a 650Mhz PC? Is your CPU usage at 100% al the time while running? Check with task manager.

Yes it seems like the router motor was the problem. I went ahead and rewired everthing in my control box so that my power supply is isolated in one area and my BOB and Charge Pump as far away from the transformer as possible and my drives isolated from those. I rerouted all my wires so that no power wires are anywhere near step,direction or BOB wires. I also set up a earth ground terminal which I grounded all my motor cables to. As far as the power cord going to the router motor I have it running about 1-1/2 away from the motor cables in the igus track. I have ran it several times for 30 minutes or longer and no more missed steps or stalling.

As far as the Mach3 running at 35Khz it was pegged out on the CPU so I backed it down to 25Khz. At that setting it is about 65% CPU usage.

Thanks for everybodys input.