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View Full Version : Need Help! New to milling plastic



Shocker
02-27-2010, 05:21 PM
Hi,

I havent done much milling before, so i dont really know what i am talking about really.
Im a university student and i am building a robot. This robot is built using 5mm perspex that hopefully will be milled out. This is one piece of it (http://i195.photobucket.com/albums/z106/Shockerr87/upright.jpg) . The technician that over looks the operations done on the milling machine doesnt have a clue what his doing. So he has no idea what the setting should be for different materials and he refuses to put the coolant on.

Looking on the internet i cant find any details on the spindle rpm, feed rate and plunge rate at which the milling machine should be at for perspex.

May one of you please advise me on the spindle rpm, feed rate and plunge rate at which i should mill the perspex out please? Please bear in mind that there wont be any coolant on the tool. I think i need a slot drill to cut the perspex out, is this correct?

Thanks for any help in advance,

Rob

xerophiles
04-11-2010, 02:15 PM
Perspex is an extruded acrylic - correct? This search was effective: http://www.google.com/search?q=acrylic+spindle+feed+rates

xray34
04-11-2010, 02:31 PM
Hi.
feed rates and spindle speeds are important but tool preperation is also important.
I have found grinding a small flat at a negative rake along the cutting edge of a slot drill or an end mill on each flute will give a far superior finish for later polishing and leaves mimimum if any tooling marks.
It also reduces heat build up and vibration in thin sections in the perspex wich can lead to burnishing and dull polished finish.

Try if you can to at least have an intermittent mist sprayed onto the area being machined,
Hope this helps.

ImanCarrot
04-12-2010, 08:34 AM
Use a two fluted end mill (that lets the chips get out of the way). Use Climb Milling if you're going round the edge.

http://en.wikipedia.org/wiki/File:Climb_Milling_01.png

You can just use a spray mist for coolant (50% WD40/ 50% water) or you can just get away with air. If you have no access to either of these, coat the stuff in soap.

Watch out cleaning the stuff, acetone tends to melt it and it scratches dead easy so put tape on the front and back to stop it getting marked during machining.

Feeds and speeds I would experiment with. What machine is it?, someone else may know better than me for optimal cutting, but it does depend initialy on what dia of end mill you plan to use- generaly you can cut a depth of half the diameter of the tool you're using, but with acrylic you can go deeper- watch the chips as they're coming off that'll let you know if you're going too fast or slow.

Oh! you can dye acylic virtualy any colour lemme know if you want details how, we do it here all the time.

Ah, forgot: Cast Acrylic machines much better that Extruded.