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Mach3 4th axis question
« on: February 25, 2014, 10:37:25 PM »
Hello all,

I am in the process of learning Mach3 to eventually build a small desktop engraver. Right now I have only gone so far as to set up 4 stepper motors and drivers (X, Y, Z and A) on my bench. The X, Y, and Z motors appear to be running normally. I can jog in the +/- direction and everything looks normal. I can enter Gcode and everything seems to look normal.

The problem that I am having is that my A axis rotates in the same direction regardless of the jog direction that I choose. MDI Gcode also shows rotations in the same direction regardless of the sign convention that I use (i.e. A-36 or A36).

I've checked my wiring several times. I have set the A axis as "Angular" in the general configuration file and I have made sure that I have the correct pins selected in the pin and port configuration.

Could anyone tell me if there is something else that I should look at in the setup? Also I am new at this so please let me know what more information that I can provide to help with an answer.

Any help would be greatly appreciated.


Re: Mach3 4th axis question
« Reply #1 on: February 26, 2014, 07:58:47 AM »
Hi Randy,
  If you put a volt meter on the A Direction input terminal of the A drive, it should toggle HI / LOW as you attempt to jog one direction then the other.
Also check the PC output pin and the BoB input pin for the A Dir. voltage toggling.
Might help you to narrow it down.
Re: Mach3 4th axis question
« Reply #2 on: February 26, 2014, 06:35:53 PM »
Thank you very much for your suggestion. I checked the voltage of the DIR pin and there was no change when I toggled the on-screen A jog. I checked the other DIR terminals to make sure that I was doing that right and got the hi-lo voltages as I should.

I still need to check the BOB pins and the PC input pin. As embarrasing as this is to admit I'm going to have to do some searching to learn how to do that.

The breakout board that I got is a cheap $14 unit that I got off of e-bay. I bought that just for the learning aspect knowing that I would eventually set it aside for something better.

Again thank you very much for your help. I will let you know my results.

Re: Mach3 4th axis question
« Reply #3 on: February 28, 2014, 08:57:23 AM »
Hi again,

I measured the signal at pins 8 and 9 (A drive pins) at the parallel port and did not get any state change when selecting +/- on the A axis. I did the same thing for the X, Y and Z axis' and did see a change in state.

I am running Mach3 on a Windows XP 64 bit system. Could that be an issue?

Any help would be greatly appreciated.

Thanks again,


Offline Eli

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Re: Mach3 4th axis question
« Reply #4 on: March 02, 2014, 04:48:52 PM »
Open config Ports and pins go to Y and change the red X to a green check  then go to slave axis then make sure you click on A then OK make sure your Y and A are running at the same speed. Eli
Re: Mach3 4th axis question
« Reply #5 on: March 02, 2014, 06:02:44 PM »
Hi Eli,

Thanks for your response. I just found out this morning that it was the parallel cable that I was using all along. It was one that I had laying around. I do not know what it was used for but there is no connection going to pins 8 and 9 (I took it apart). I made my own cable and everything seems to be working normally now.

Thanks again for your time.