Flame polishing

I'm sure that some will know this, but this is like a black art. Flame polishing of DELRIN (acetal copolymer) can be flame polished after machining to bring back that factory finish (highly polished sheen look)
After machining, take a propane torch and just wave the flame ovet the matl. breifly. (not too much) It comes out great. Good luck too all.

A customer of mine that made stuff from Plexi used a hydrogen torch to flame polish.
Any other fuel contains carbon which can condense out of the flame and leave black
particles embedded in the surface which can't be removed. They were working with transparent stuff making store fixtures.

A heat gun would also work on thin stuff but is not really hot enough so it tends to melt the piece before the haze clears itself up.
The hydrogen flame would just be flashed quickly over the edges and it was as clear as rest of the sheet.

On another note Guy Lautard mentions in one of his books, can't remember which, something called vanishing oil, which is used to machine transparent plastics. It evaporates completly very quickly and leaves perfectly clear machined surfaces. I've never seen it used so I can't vouch for it.

I haven't tried this myself, but our supplier of acrylic (perspex) says it pays to rout the edges first, then flame, otherwise you can still see the saw cuts. Also said you can wipe with methylene chloride - its not very effective, but it is used to clear edges (maybe has something to do with gluing too?)

They have a special machine with a opposed belts that grabs the piece and mills the edges perfectly flat. Then they flame it.
Its not a router but a custom built machine that uses a cutter that looks like a small circular saw mounted on a die grinder arbor but cuts by feeding the edge over the flat side so it hits the edge twice with every pass. In other words, its cutting with the set of the teeth. It spins at high speed and does a nice job.

I think they used methylene chloride for solvent welding. They would clamp up the pieces dry with weights on top and then use a syringe to apply solvent to the joint which would pull in by capillary action, soften the edges, and then evaporate. when they took off the weights about a minute later they had a perfectly clear joint. The
joints were pretty strong too.

[This message has been edited by yf (edited 12-02-2002).]

With the info above, you now know more than many of the places doing plexi work in my area.