This project is an attempt to build a linear measuring machine. I am attempting to build this from surplus parts and a few custom made parts. The measuring machine will be build around a Hewlett Packard 5528A Laser Interferometer System. The HP 5528A is a collection of components from Hewlett Packard, which make up a laser interferometer. The components include; a laser head, two "Beam Bender" front face mirrors, two retroreflectors, an optical interferometer, optical reciever and the HP5508A Measurement Display. The laser interferometer will be fastened to a pair of movable slides, which are mounted on linear bearings and guide rails. Finally, the guide rails are mounted to a surplus milling machine T-slotted table.
Previously, I tried to build this project on a cheep aluminum slide rail and carriage. The rail was mounted on a square tubing which also held the stationary parts of the laser interferometer. That project did not live up to my expectations, and after being neglected for over a year, the parts were scavenged to build a CNC router.
Since then I've learned to program slightly better. I've been trying to figure out what quadrature encoders are, and how Phase Locked Loops work. I've also befriended a machine shop owner and a granite counter top shop owner.
As I move forward with this project, I intend to use a brute-force mentality for the moving parts and the measuring surfaces. The entire project is build on top of a 400 pound steel milling machine table. Running side to side on top of the T-slot table, two THK linear rails are bolted down to guide two movable steel slides. The slides will provide a place to mount the interferometer as well as providing measuring surfaces. The measuring surfaces are made from surplus granite straight edges. Two identical granite blocks will be mounted (one each) to the steel slides. The granite blocks are honed flat and will be mounted so that they are held vertically and horizontally parallel. After mounting on the slides, the granite faces will provide the measuring surface. A third granite measuring stone is fastened to the top of the T-slot table. The measuring stone is used as a flat reference surface for placing the object being measured upon. The measuring stone will lie under the other two granite parallels. All of this steel and granite are intended to provide a rigid, flat, and heavy working surface.
Finally, my hopes and dreams are to have a functional machine capable of measuring the length of gage blocks, check rods and inside micrometers. I dream of having a measuring range of about 40 inches, with a resolution of 10^(-6) inches and an uncertainty ±5*10^(-6) inches.