i have a 3 axis eztrak that works beautifully except 2 things , when i reboot and home the axis my Y axis zero point changes usually .100 in plus or minua direction , the other problem is with the Zaxis sometimes the z zero point changes while the z axis drifts down and th z zero point changes while the machine is on.


thanks r brinttle

Y axis: move home switch "dog" so the switch makes .030 inches sooner. Your marker pulse and home switch coincide.
Does your Z axis motor have a rotary encoder? This means there are 2 cables coming from the motor, just like the X and y axis.

George

thanks , my z axis does not have an encoder , it has a glass scale to read z axis position ,

thanks

That is why Bridgeport mandated that the dealer retrofit these machines with a motor/encoder unit and the associated parts such that it DID not rely on the glass scale when in 3 axis mode. The glass scale would mis-read and the Z would adjust its position. Not good.

George

hi , what is involved with installing an encoder ? did or does bridgeport make a kit to install it on these machines ?

You need to contact Hardinge. Will they do anything for you is doubtful but you can try. The kit we used included a new motor, new AXSBOB board, cables, etc. It was not intended for the old style 3 axis with the ball screw on the left side of the head, but for the newer style with the Z ball screw in front of the quill. Like I said, a dealer may have dropped the ball here. But Bridgeport only paid us for about one hour of labor when we had travel expenses and the conversion took closer to 4. I can understand that other dealers did not want to do this.
You could make sure that the reader head is properly aligned to the scale and not loose. That may help you.

George

Make sure the coupling to the quill stop eye lug and encoder head is snug, as well as all other fasteners to the encoder scale mounting. I'd suspect any float in the Z encoder feedback verses actual position or hunting, should directly relate to poor mechanical rigidity from the quill to the encoder.

The cast arm that gripped the quill low could cause similar nonlinear tracking of commanded verses actual position also.

At least some possiblity among many.

DC