Centroid Community CNC Support Forum

Hi everyone, I have just in the last week began using and actually cutting metal on my new Acorn system. First part after being zeroed in was perfect size wise and I thought WOW all is good in the world but when I cut my 2nd,3rd and 4th part they were not the same as in they appeared to be getting progressively further away from their centre point (origin) even though I was using a jig and locating each part on an accurate dowel. I had conversations with Slodat here on the forum and he asked which way I had connected my servos to the acorn board to which my reply was direct to acorn board screw terminals. He had done extensive research and testing of the motors losing steps and suggested that I connect via a DB25 so I did that and low and behold the problem disappeared. I am using DMM servos and motors. I am as a proverbial pig in sh1t that now the parts are repeating as they should and hope to start to use the machine more and more. I will of course one day in the not too distant future post up on the success stories backed up with photos of my machine and some jobs done on it. Thanks to each and everyone on this forum who has taken the time and given me advice and helped me in getting all set up to run. I will no doubts be asking more questions as I progress with the learning curve of a new control system and for sure want to gain the knowledge of using the KP3 probe that I bought as it will assist me in the type of jobs that I want to be able of doing.

Cheers, Jeff

That's very interesting. Which DMM drives (DYN2 or DYN4) and which servo motors? Also, since the DB25 connector doesn't control the servos' Enable signal, how are you handling the Enable signal?

I may be wrong on this and I'm sure someone will correct me if I am.

The screw terminals are meant for inputs that use a higher voltage than the DB25 connector does. Some drives like mine say that they can use the screw terminals if you use an inline resistor. Maybe in theory but I was unsuccessful. I put it on the DB25 and all was well. I did some playing around with a test circuit and I'm of the opinion that the inline resistor does not work because you end up with a floating output.

Richards wrote: ↑Mon May 10, 2021 5:15 pm That's very interesting. Which DMM drives (DYN2 or DYN4) and which servo motors? Also, since the DB25 connector doesn't control the servos' Enable signal, how are you handling the Enable signal?

My drives are the DYN4 ones and the motors are DMM ,DHT 86M (0.75Kw) for X,Y & Z and I have a DST 640 (0.4Kw) for my rotary 4th axis. Pretty sure the enable signal is wired up to the acorn screw terminals (I didn't wire it, my friend did it for me as I am not electrically minded)

The Enable signal is what I was curious about. I'm just guessing out loud, but do you get the Step and Direction signals from the DB25 and the Enable signal from the Hx headers? I only have one DMM DYN4 driver and one 0.75 servo. They are in a box on a shelf for the time being. The DMM product worked very well, but because I only have one driver/servo and I have several Teknic ClearPath servos and because the DMM and ClearPath motors use different polarities for their Fault output, the DMM stuff is waiting its turn.

It's good to know that you found a solution to an unexpected problem. It looks like a good solution to me.