Grunting away at a mirror for extremely long periods of time is not only un-fun, but is not a good use of your time, nor is it tending to symmetry. A mirror making machine enables the optician to multitask as well as save their own bodies from the horrors of mirror making work, and is highly repetitive promising a better surface of revolution [hopefully]. Small mirrors can get just plain boring to push around, but large mirrors can be physically demanding and detrimental to your arms, back and attitude.
Here is a shot of Jeff Baldwin’s 40” project from around 2000. Erich Reichenbach, Leo Radcliff, Roger Radcliff and Jeff Baldwin are shown pooped out from curve-generating by hand. Yuck. Where’s a machine when you need one?
Here is a shot of Mike Lavieri polishing with Greg Wilhite’s machine in Jeff’s shop on his 32” f/3.6 mirror.
It’s a totally different thing.
Here’s Jeff fixed-post grinding on a 24” using Greg’s machine..
So, there are a few machine styles out there. In our shop we use fixed-post grinding and polishing, then parabolizing with an Elgin style system.
Fixed-post machine grinding is where the mirror is on a turntable rotating around, and a 75% tool is on top. They are already curve-generated. The tool is hanging over the mirror by 1/6 the diameter of the tool, or about 1/8 diameter of the mirror, and is fixed in this position. The motor turns the mirror and the differential rotation enables the grit and water to grind away at the mirror and tool neutrally, meaning the ROC isn’t changing. You go through the grits this way.
Fixed-post polishing is similar, only with a pitch lap rather than a grinding tool.
You may get zones, they can be polished and blended, but it’s fast and easy.
For parabolizing, there are a few methods out there. I use a combination from Robert Kestner and Carl Zambuto. Most other ATMers use Carl exclusively.
The summer of 2012 Greg Wilhite and Jeff Baldwin built Jeff’s new machine, Ol’ Yeller. It has a 40” turntable, but we are able to work up to 46” mirrors with it, possibly larger. 40” is as large as we intend to work unless special requests come our way.
Ol’ Yeller fits in the corner, lots of weights to put on the work. The turntable is 40” in diameter.
The voltage controllers allow the speeds of the eccentric and turntable to vary. I have a 120 vac circuit converting into 90 vdc feeding the 1 hp eccentric motor, and a 230 vac circuit converting into 180 vdc feeding the 1.5 hp turntable motor.
You can see the DC motors and gearboxes underneath as well as the skate wheels.
Top view shows the over-arms from the eccentric and the fixed station.
This machine no longer looks quite like this. I’ve added many features to it. I’ll post photos when I get a chance.
Click Me to watch the machine running at 31 PRM on a 25” f/3 meniscus mirror with a 19” stone tool at 500 grit.
Click Me to watch the machine running with a slower turntable speed and a short stroke polishing on a 12” quartz flat. This is no longer done this way in our shop, but the video is still here to demonstrate that I can have goofy programming on the machine.
Click Me to watch the machine running with a double stack of weights and short strokes polishing on a 12” quartz flat. Same thing, I don’t do this anymore.
Click Me to watch the machine running with a short stroke on another 12” quartz flat. Again, I don’t do this anymore.
Click Me to watch the machine polishing a 25” f/3.0 meniscus mirror sitting on a backer. The machine is different now, and I do NOT use this much weight while fixed-post polishing anymore.
Click Me to watch the machine grind the back of a 32” mirror flat.