Routing Plexiglass and Polycarbonate

[ear3]

Just a quick question about routing plexiglass or polycarbonate sheets (like Lexan) -- are there any concerns about this stuff going into the CT, given that the high speed of the router bit actually melts some of the chips?  I've done some flush/trim routing of this material in the past (before I got my Festool routers), but I didn't have a vac hooked up to the router.

 

[tjbnwi]

I've never had concern when routing plastics.

Tom

 

[rst]

If you are producing melted chips, you are feeding too slow.  Also, never use a shear bit.  The best bits are made specifically for plastics a have what is called an O flute.  It has different geometry for the cutting and clearance angle.  Plastics are best cut with a scraping action and that is the best way to smooth a finished cut, use a scraper or the ones sold for plastic fabrication that have V and half round profiles.  There are industrial machines that actually give a clear finished edge by trapping the work piece and dragging it along a fixed carbide or diamond blade.

 

[ear3]

Thanks.  Yeah, I was cutting it with a straight bit, so I'll switch over for this application.

If you are producing melted chips, you are feeding too slow.  Also, never use a shear bit.  The best bits are made specifically for plastics a have what is called an O flute.  It has different geometry for the cutting and clearance angle.  Plastics are best cut with a scraping action and that is the best way to smooth a finished cut, use a scraper or the ones sold for plastic fabrication that have V and half round profiles.  There are industrial machines that actually give a clear finished edge by trapping the work piece and dragging it along a fixed carbide or diamond blade.

 

[rst]

Actually the bit I meant to say not to use is a helix or slicing style bit.  A straight carbide bit should work fine.

 

[tbellemare]

While melting chips using a CNC router, one can increase the feed rate (to a degree) to minimize the dwelling that is causing the chips to melt after being cut.

Using a handheld router, most people have a comfortable feed rate and if the chips are melting, one can just turn down the speed of the bit.

It's the same thing if you're getting burning of the material - slow down the bit.

As always with cutting operations, it's a feed and speed thing... If your speed is too high for your feed, it causes dwelling, which causes excessive heat because the chips produced aren't removing the heat. In plastic, it will melt the chips and in wood, it will burn the work piece. It also causes premature dulling of the cutter.

Tom