Machining plastics

[Brass_Machine]

So I am taking on a project for a family member. Looking to machine some plastic (of some sort)... Now I have worked with delrin and others, but nothing like he wants. Is the a plastic (or something) that is clear (IE tube or rod) that cam be machined and remain (or polished back) to clear. Like acrylic or polycarbonate? can that be machined?

Eric

[Brass_Machine]

Thanks Kenneth!

Did you give thought to my other question?

Eric

[Bogstandard]

Eric,

Acrylic and polycarbonate can easily be machined.

Keep the feeds and speeds fairly low, otherwise you will melt the material rather than cut.

If possible, use razor sharp new tooling for the job. I do a fair amount of it, and if you are careful, with a soft buff and a very fine polishing compound the edges can be brought back to a perfect finish. Again, you have to be very careful not to heat up the edges, otherwise they will burn and 'string'. You can polish back by hand using the finer grades of metal or silver polishes and soft cloth (old t-shirt).

The way commercial people get the smooth edge and shine back is either with a flame, or chemically, by feeding the edges thru the fumes of certain chemicals, of which I have know idea which ones they use.


John

[Spurry]

In one of Guy Lautard's books (No 3 page 66), he mentions Vanishing Oil to obtain a transparent finish when tapping and machining plastics. I wonder if anyone had any experience of its use, and if it was available in the UK.

Pete

[Brass_Machine]

...

If that wasn't the other question, let me know...

Your PMs 

[andyf]

Eric, I've machined a crude lens from acrylic (trade names Perspex etc over here; Lucite etc on your side of the pond). As others have said, sharp tools and moderate speeds - though it doesn't exactly melt, it can get a bit "gummy" with friction.

To make the lens, I turned a conical shape, rounded it with a file, then used progressively finer emery paper, metal polish and finally toothpaste for a final polish.  

If you need to stick bits of Perpex/Lucite together and can get hold of some ether (as in bygone anaesthetics), that will give a nice clear joint. Good ventilation prevents you sleeping on the job.

Andy

[Swarfing]

If it helps i just machined up some fibreglass block as an adapter for my chuck. The speed i used was on about 75-100 rpm. This stops the cutter from getting hot and i cut it dry. Suspending the item you want clear again in some acetone works with some plastics. Worth testing a bit first? I just oiled my fibreglass afterwards with wd40.

[rowbare]

If you are going to machine acrylic, try to find cast acrylic. It machines much better than extruded. ref: http://www.cnczone.com/forums/glass_plastic_stone/22982-melting_acrylic.html

Also acrylic and polycarbonate can be chemically polished: http://bbs.homeshopmachinist.net/showthread.php?t=34730

bob

[fixerup]

Greetings,
It machines quite well,  when drilling, I like to put a small radius on my tool to prevent the tool bit to grab and lift the part. Also when I'm cutting close to an edge I try to slow down my feed to not break that edge.  I've use a hand soap and water solution to machine and tapping operation  (1part soap 20 part water). 
Cheers!
Phil

[Brass_Machine]

Hi guys...

Thanks for the advice. I got some acrylic rod and made a prototype of the part. Came out quite nice! I haven't done much as far as polishing it up, but I did clean it up a bit. Will try the torch trick to see how that goes...


Eric