- Why is this a manual process? Aren't there jigs or tools that can automate out the grinding and get a more precise result?
- Why does the mirror have to be made out of glass? Lens I can understand, but a mirror just needs to be sturdy enough and chemically compatible with the metal layer. Could a 3d printer produce a precise enough substrate?
Industrial lens and mirror making is surely not a purely manual process. The method described is clearly meant for use with minimal infrastructure. The lack of jigging and tooling then is actually a feature in this instance.
The substrate requires sufficient hardness and dimensional stability to hold its shape. While glass is certainly not the only material that fits the bill, it's probably the cheapest.
High-end (read Industrial) 3D printers can probably -not- get a precise enough substrate, at least as designed right now.
Partly it's a tradition handed down over the years. Many years ago it was much cheaper to get glass blanks and grind them yourself to get a good mirror than it was to buy the mirrors. So there are many documents from old astronomers telling how to grind a mirror. You learn a lot about lens terminology.
For smaller mirrors you don't really need jigs or automation.
For bigger mirrors there is plenty of automation.
As I understand it it's a self-calibrating process. The friction and movement of the tool create the shape, which is why they talk about moving the tool around a lot.
YouTube has some interesting videos of home made contraptions to polish rocks into spheres - you have 3 cones with a ring of abrasive, and some abrasive slurry, with a lump of rock in the middle of the cones, and you just spin the cones and end up with a nice sphere.
- Why is this a manual process? Aren't there jigs or tools that can automate out the grinding and get a more precise result?
- Why does the mirror have to be made out of glass? Lens I can understand, but a mirror just needs to be sturdy enough and chemically compatible with the metal layer. Could a 3d printer produce a precise enough substrate?