Machine moves by itself

Hello guys,

lt's the first time I make a machine with a parallel port.  The machine is all ready and working, but the machine is stopped, the spindle is off, it moves by itself slowly in the direction of X+, Y+ and Z-.  Has anyone ever experienced this?  Before she was half crazy with the spindle turned on, I isolated the power cable from the spindle and that problem solved….

sounds like floating ground voltage between servi drive inputs a pc output

Servo motors or stepper motors?
In case of servo, DC or AC servo?

I am using 220v DC servo motors

Hello Collins,

I made an improvement in the grounding of the control board and it seems that it solved, I did about 4 hours of tests and it didn't present this problem anymore.

At first solved thanks a lot for the help

Ingo

Hello friends,

I've been in battle since Thursday, because the problem is back….  I did the grounding and at first for a moment it resolved but now it came back worse with more force.  My question is related to transmission speed ( Feed x scale ), for example the encoder resolution is at 4000ppv, the machine speed is at 5000mm/min and the scale is at 400, is this related?

Do they move when LinuxCNC is not running?
Are you using a Mesa 7i77, meaning the drives are in velocity mode?
Do they move when LinuxCNC is on and enabled?

What hardware are you using to read the encoders, and interface with the servo drives?

When LinuxCNC is in normal automatic mode, but when it is stopped with the servo-on active, it starts to move by itself. I'm not using 7i77, a generic parport.

my machine will do the same thing, do you have the drive enable routed through the 7i77 ? if not, do that, almost all velocity mode drives tend to creep due to voltage fluctuating and ground voltage variances.


Mesa electronics does sell a galvanic isolation adapter for the db25 that should in theory solved this issue.

i have electrokraft 400 brushed motor drives. 

this is all very common, just run the drive enable control through the 7i77 on ENA + - on the tb connectors