Linear Encoder

[ducati955]

I have a Southwestern Industries Prototrak MX3e system installed on a Knee Mill as a retrofit. I need to replace the liner encoder which reads the X axis movement. The original encoder is the Gage Wheel type and limits my travel in the Y Axis by a few inches because it fairly large. I would like to replace it with a glass scale type or a newall type. As far as I know the machine does not have encoders built onto the servos. I disconnected the gage wheel output to the control and of course no movement. My X axis travel is about 30 inches.
I was informed a Newall SHG-TT Linear Encoder would work but, I was also informed the encoder needs some sort of "mark" for the Prototrak system to read it. The Newall is pretty expensive and I am looking for something a lot less costly. Any ideas or experiences would be appreciated. My past experience is very limited. Usually I replace parts from the factory and it always cost a small fortune.
Thanks
Ken

[RICHARD ZASTROW]

We had excellent results with Newall Spherosyn round tube linear encoders. Solved our "lack of feedback" problem on large machines where the Heidenhain glass scales couldn't handle the vibrations. (30 ft. vertical boring mill converted to 4-axis CNC).

The scale and reader are enclosed in the "reader block" which cancels the vibration. Also, they function in the dirtiest environment.

Dick Z

[Zig]

I am using both glass transmissive scales from FRS (way before Heidenhain acquired them) and Adhesive reflective optical tape from Renishaw.

Both working nicely in their respective environments.

nishaw tape is applied directly to the machine frame and needs to be protected from envirnoment.

cost?? Cant remember the price of glass scales.. but renishaw product.. tape by the yard reader about 1200 dollars.