Threading Retro Fit Problem

[bouquina]

I work in a machine shop in Western New York. We have an old Poreba Engine Lathe that was retro-fitted CNC with an Analiam Series 1200 controller about 10 years ago. We recently were awared a contract were we have to thread some large parts with this machine. We built all the bracketry and installed it along with an encoder. For some reason the machine looses track of the timing between the rev's and the Z travel and doesn't start the thread in the same place when taking multiple steps at depth. If we take only one pass the thread is perfect but when we come back to take another pass it wipes out the threads. This machine is old and we don't have all the manuals for it. I did find something about using an encoder with a "zero-marker". I am not sure how to spec this out or where to purchase it from. Any help would be appreciated. Thanks

[FastBusa]

We have this same problem with our LeBlonde CNC laythes using Allen Bradley 9 series
controls. We never were able to figure out what is wrong so I to would be interested in
any ideas of where to start!!!!

[bouquina]

We also have a LeBlonde (Engine Lathe CNC Retro-Fitted) that used to thread with an Analiam Series 1200T control. We have since moved the machine a few times and the operator that used to run the machine left us and nobody else can figure it out. We have a tech here now and I will keep you posted. He has been talking about checking the voltage at the distribution board (whatever that is) and if a problem is found there we will have to upgrade the control to accept a new board because they don't make the board we have now anymore.