Making Candy Floss. Weeee!

[ImanCarrot]

I use single point diamond machining to make lenses. The swarf (chips) that come off looks just like candy floss!

here's some piccies!

Oh, that's just the front surface machined.. wait till the other one's done, they look dead nice.

(they go into helicopter weapons systems)

[Dr Pete]

Very nice!
We make lenses here the old fashioned way, grind with al203 grit and then polish with pitch.
We tried this once on our lathe using coolant chucked up a glass blank, didn't turn out half bad but takes too long.

Do you get that nice finish just using the diamond?
Does it have to be polished again?

[ImanCarrot]

Nope, no post polishing- that finish is straight off the lathe (it is acrylic though, not glass).

I used to polish glass using pitch- did it for years, very skilful and time consuming, especialy hand lapping to 1/20th of a wavelength! but very satisfying when you hold it in your hand and think "I made that, not a lot of people could have done that".

I tried diamond machining glass, but the results were horrible- even post polishing it didn't work so I stuck to aloxite 302, 302.5 and 303 then poished with pitch, water and Cerium Oxide (Cerox), which is better than rouge cos it don't stain everything red

[emd68]

Hi, Iman & Dr Pete
Great to see some other optics guys on this site. I spend most of my work days double side grinding and polishing of sapphire optics. Funny thing the
other day one of are great sales staff came back and asked if we had a
Diamond Turning Machine. We do not have one. You would think after 12
years he would have some clue. Who do you guys work for if you don't mind
me asking?

Take care
Ed DeMarco.........

[youngjim]

Nice! Found this while reading up on (really) high precision machining..
Quite likely the most accurate lathe anywhere

[ImanCarrot]

hehe, nice off axis paraboloids. I've made stuff that is suspicioulsy the same

Double sided grinding? do you mean twin lapping? as in you have the substrate rotating between two metal disk plates? I did that years ago and it is the only way to get very, very parallell windows. Second to none.

Can't recall the machine I used, but it had an outer horizontal cog and an inner one which you could vary the rotation on. The components were placed in a mylar holder which had teeth on the outer periphery (fitting the rotating cogs).

Aloxite water and suspension fluid was flowed through the top plate into the lapping zone.

I honestly didn't think anyone did that anymore! Memory lane here!

[Edit]Oh, saphire... you're working saphire (for UV work I take it), you have my deepest sympathies lol it is a BEITCH to work. You won't be using aloxite then.. prolly Hyprez or Engis diamond paste? which in itself is another pain in the derier. It gets blinking everywhere![/Edit]

[ImanCarrot]

Finished the first design today.. here's some pics. That was the most complicated lens, got another 3 different type to do. Then they got to be coated, have bits on the corners chopped off and black painted round the edges.

Should look good when they're done.

[emd68]

Hi Iman,
Double sided lapping twin lapping same thing. You would be surprised how much work is being done this way. The machines we use are from a company called PR Hoffman but there are many others including Engis you mentioned that build that type of machine. I just recently looked into pricing on one of Hoffman's bigger machines and was told that it would be February of 09 before I could get one along with the $350-$400 thousand dollar price tag. The sapphire we make has a huge range of application UV being one of them but also for medical, space, military. There was a time that we made allot of sapphire missile domes but most of that has been taken in house by the companies that make the missiles like Raytheon, we do at times still see some small quantities. I've seen some of your work in different threads around this site, very nice. It must be great to work with plastic very little wear on the tools, the diamond point in your case. Back some years ago I worked for Lens Crafters a one hour eye glass company here in the U.S. mostly CR-39 and Polycarb. The CR-39 cut great but the Polycarb could get a little stringy at times but also not to bad to work with. Very low precision compared to what you are working with I assume. What kind of tolerances do you normally work with for radius and center thickness?

Take Care
Ed DeMarco.......