Re: Machining Lexan +

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Gary Weaver" <gary350-at-earthlink-dot-net> 

Lexan polycarbonate cuts very smooth with a brand NEW end mill.  Be sure the
end mill has never been used to cut anything at all.  Climb cut on the final
pass and it will smooth up very nice.  I like to sand the sharp edge with
400 grit paper.  Put the sand paper on a block of wood and sand only the
edge.  This also removed the very tiny chipped places caused by the plastic
chipping off as its being cut.  You can use an oxygen acetylene torch to
remove the sharp edge and make the cut edge smooth as glass.  Set the torch
so its not very hot you can always turn it up hotter if you need to.  It
takes a few minutes of practice.  Pass the torch back and forth along the
cut edge very fast slow down a little on each pass and when you reach the
correct speed you will see the frosted edge start to look clear.  The trick
is not to burn the edge.  Make sure the torch is not too hot and move the
torch along the edge at a steady speed.  Don't spend a lot of time on the
same edge the entire piece of plastic will become hot and melt.  It works
best if you have done it before an sorta know about how hot the torch needs
to be and how fast to move the torch along the edge.  When the plastic is
cold you can melt the edge of the plastic with the torch without melting the
entire piece of plastic.  Plastic has a very poor heat transfer rate so its
very easy to melt the edge without melting deep into the entire piece.  If
you make too may passes over the plastic with the torch the entire piece of
plastic becomes too hot to work.  Let it air cool about 15 minutes then try
again.  You can run some cold water on the plastic and work it again in
about 2 minutes.  Experement on the scrap pieces of plastic.

Gary Weaver




----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, January 02, 2004 3:57 PM
Subject: Re: Machining Lexan


 > Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
 >
 >
 > That offer was from me Mark.
 >
 > Dr. Resonance
 >
 > Resonance Research Corporation
 > E11870 Shadylane Rd.
 > Baraboo   WI   53913
 >  >
 >  > I have experimented fire polishing on spare pieces of Lexan, but was
 > unable
 >  > to get the relatively rough machined edges to clear up much.  While the
 >  > smaller scuff marks on all the Lexan parts cleared up nicely, the
deeper
 >  > gouges I found impossible to remove without burning the corners or
 >  > sub-surface bubbles forming.  The primary supports may polish up OK,
but I
 >  > worry about all the sharp corners getting burned.  I have had an offer
 >  > previously to have someone experienced fire polish it all with a
 >  > hydrogen-oxygen flame.  I may yet take that person up on their offer.
 >  >
 >  > I guess some descriptions are in order....
 >
 >