G540 and 4 axis w/ dual X drives

[dsnellen]

Received my G540 yesterday. In all my research it never turned up that a G540 cannot be used on a 4 axis machine using dual X axis stepper motors. I have an A axis in addition to X, Y and Z. Because of the width, the X axis has dual motors. I called Gecko to discuss the resistor issue and discovered that the G540 cannot drive a dual X axis machine. According to him, people use the A axis to drive a second X motor or they buy two G540s. He said the 2.8 amp draw of each motor would exceed the output of a single driver. LSS G540 cannot be used this way. Very disappointed that the G540 cannot be used in a similar fashion.

However, I currently use a single Chinese CW250 to drive both motors. I checked my CW250 and it is set up to output 1.5 amps which drives the dual KL23H286-20-8Bs quite well. If it works on the CW250, why not on the G540? Why can't two of these steppers look like a single motor to the G540? Use a single 2.8K resistor and they should look like a single stepper. They would actually have more available amps than they do now.

Anyone have any thoughts? Otherwise, anyone need a new, unused G540?

[CoAMarcus]

If you run two motors on one drive you cannot take it above about 2 RPS or it will break out into violent oscillation because the motors must then be kept in their constant torque range. If two motors are being run from one drive they will draw a current that will vary with the load. This means that one motor would use up all the current and leave the other motor to stall out if it is taken above that speed. Step motors do not play well with each other. Consequently, one drive is meant for one motor.

What kind of motors do you have on all of your axes?

If you are unsatisfied with the G540 we have a 15 day no questions asked return policy, and we will gladly refund your drive and shipping costs if purchased directly from us.

Marcus

[grewgood]

May I recommend that you drive the second X-axis motor from the A axis and link the A axis to your X axis in the software. I did this in EMC2 and in WinCNC and I understand it can be done in Mach too. That way you get the ideal drive condition for each motor. Furthermore, if you software allows, you might even then be able to instantiate separate homing for each X axis motor, so that you can square up your axis using limit switches. (Thanks again for sorting my noise problem Marcus)

[CoAMarcus]

From what I understand in the original post he is trying to run a total of 5 motors. I believe he has a dual motor X axis and a single motor Y, Z, and A axis. If I am incorrect then there is not a problem running the machine as grewgood noted.

Marcus

[dsnellen]

Originally Posted by CoAMarcus From what I understand in the original post he is trying to run a total of 5 motors. I believe he has a dual motor X axis and a single motor Y, Z, and A axis. <snip> Marcus

Marcus, thanks for your reply. This is correct. I have five motors with two on the X axis. Unfortunately, I purchased it new from a vendor who will not accept a return. I have KL23H286-20-8Bs on all axis. I hear what you are saying about steppers not playing well together. But, it is set up with two steppers sharing one CW250 driver now and it works fine. Is there something about the CW250 that allows this? I stand corrected from the earlier post. The CW250 is outting 5.0 amps (not 1.5) which is being shared by the two X drives.

Grewgood, that could be done. I am using Mach3. However, I would lose the use of the A axis. Of course when using A, I am not using Y. Maybe a Mach3 setup would allow me to easily and simply switch the Y to the A when needed. This would require changing cables each time also. I like the idea of turning a 10.5" x 7 feet long log.

Anyone need a new, un-used G540?

Dave

[dsnellen]

Since I started this thread I thought I would summarize what I learned for others. The G540 is a surprising small, heavy device that appears very well built. There is a lot of information about the device on this site and on www.geckodrive.com. In every reference it is called and marketed as a 4 axis controller. It is not a 4 axis controller. It is a 4 MOTOR controller. Instead of labeling each DB-9 as axis X, Y, Z & A, they should be labeled as Motor 1, 2, 3 & 4. Now everyone in the world may have already known this, but this point never turned up in my research. I wanted a 4 AXIS controller, not a 4 MOTOR controller.

The resistor is necessary to establish the amp output of each driver. The amp output should match the Current/Phase of your motor. This was made very clear in the research. I became somewhat confused (my last electronics class was 35+ years ago) because my existing drivers did not require a resistor. Reason: while the G540 uses individual resistors for each motor, other drivers, like the CW250, use DIP switches on the driver itself to establish the amp output. Either way works fine.

In my original post, I made reference that I currently have two KL23H286-20-8Bs, each drawing 2.8 amps connected to a single CW250. This is correct, but the CW250 is outputting 5 amps (not 1.5 as originally stated) which are being shared by the two motors. I have not noticed any performance issue. I'm guessing this is because with two motors sharing the load, neither as a need for more than 2.5 amps.

In wrap up, the G540 is a neat device and if I had a need for a 4 motor controller, it would be at the top of my list. However, it will not work for a 4 axis machine with 5 motors.

I still have a brand new, never used G540 for sale. $250 obo plus shipping and it's yours.

Dave