Thursday, March 13, 2014

My Fiber Optic Polishing Machine

I do research with lasers and fiber optics, and I needed a polishing machine customized to meet my needs.  I started with an old Fibertek machine, which could only polish standard fiber connectors.

 I need to be able to keep my parts perfectly vertical, and also have control over how hard the parts pressed on the polishing pad.  I made a guide using 4 hardened stainless posts with linear bearings. A dial indicator measures the polish depth, and counterweights in the rear control the pressure.

This circular cut was made on the mill using a rotary table. 

The accuracy of the rotary table cut approaches that of a lathe.  Here a lathe cut part fits inside with about 0.002" clearance.
 Here is a partially completed fixture that will hold 10 items in the polisher.   The pie shaped pieces will each hold a single part, and they can be removed without disturbing the other parts.  They are held by a single screw at the small end, and a dovetail at the big end.  All of the holes were done with the bolt hole function on my Shumatech DRO.  Here I did not use the rotary table at all, for it was much easier to program the Shumatech.

The outside diameters and the dovetails were cut on the lathe.  Then I cut the upper disc into the pie shaped pieces using a bandsaw, and then I milled the saw cut edges smooth.
 My high powered lathe has no trouble turning these diameters, even in steel.  However, it puts about 300% more stress on the drive belt pulley as does a 7x10 or 7x12 lathe.  The pulley finally failed, so I ordered a replacement from Little Machine Shop.   Here is a picture of how the belt connects to my gear reduction unit.   Someday I will make a metal replacement pulley.

I needed a way to hold an optical fiber connector, known as an MT connector, very accurately, and with no free play.  The MT's measure 3mm high x 6 mm wide.  Here is one in a rectangular hole I made with tolerances of 0.1mm

I began by milling a slot slightly smaller than the MT's dimensions.  Then I drove a rectangular punch I made from a hardened steel bolt into the slot.  Even though my method was crude - I drove the punch in with a ball pein hammer - I had good repeatability from one part to the next.


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