Cutting Large Hole in Acrylic Sheet

[Mike Goetzke]

I'm making an enclosure for my laser engraver/cutter out of acrylic sheet.

First I need to bore a 4" diameter hole for the exhaust ventilation fan. I have seen some use a hole saw, and multitool. I was wondering if a template and router would be better. Looking for info from people with previous experience. -Thanks

I also have some smaller holes - maybe 1" in diameter. Would a Forstner bit be best? Step drill?

Thanks
Mike

 

[luvmytoolz]

Machining acrylic or polycarb is super easy with almost anything that has a reasonably sharp edge.

I do loads of both on the CNC, but if that's not practical or is a size I do a lot of, I usually make an MDF template and use that with a template guide on the router, or a flush trim router bit.

Treat it the same as machining wood, but don't dwell anywhere long enough to heat up the cut as the waste may stick behind the cut, although this is easy enough to remove anyway.

The only caveat is the thinner it is, the more likely to vibrate and lift under load. If doing really thin sheets, clamp a waste sheet of MDF to it and go through both to get perfect crisp edges with no breakage.

 

[tjbnwi]

Use your laser to cut it.

If it is a color issue with the acrylic, coat the acrylic with a cutable color.

Tom

 

[Mike Goetzke]

Use your laser to cut it.

If it is a color issue with the acrylic, coat the acrylic with a cutable color.

Tom

Wish I could. I have a diode laser and it only cuts black opaque well. Mine is a clear amber.

 

[Packard]

Regardless of which method you choose, flame polishing the cut edges is a fast, easy way to smooth out those edges.

This video shows a heat sink to prevent overheating the plastic, but once you’ve mastered flame control, all you need is the flame itself.

 

[Cheese]

Mike, if this were my experiment... [smile]...I'd start with the hole saw and then clean it up with a router if an absolutely pristine edge is desired...then to take it to the next level...flame polish it. [big grin]

 

[rst]

With 40 years of selling and tabbing plastic, I would drill with a hole saw, preferably on drill press clamped tightly, jog the bit in and out to clear the teeth.  If handheld, hold on tight as it will want to grab.  Having a Shaper, that is how I now make holes or diameters.  Also, industry recommends sanding all cut edges, even if flaming.  Sand to 320.

 

[Packard]

My experience with using a router to cut acrylic is that it wil easily melt the plastic.  For that reason you need a fairly fas feed rate.

 

[Mike Goetzke]

Thanks for all the replies. Have to see if I have a 4" hole saw. This hole doesn't need to be 100% clean since I'm adding a DC flange to it. But, for Christmas my son got us a wall clock that has stick on hour markers. I bought a piece of 1/2" thick acrylic to mount them on and had to radius the corners. I sanded the edge to 320 and then used my lathe buffer - surface is perfectly polished. (BTW - on a scrap piece I tried the torch and it clears it up but you can still see some saw marks.)

 

[Crazyraceguy]

[member=4518]Mike Goetzke[/member] Cutting acrylic is not that hard, you can do it with pretty much anything that you would use for wood. The exceptions are things like spade bits with those screw-type tips that help pull it in and regular metal twist bits. Those have a tendency to grab, especially when the material is thin.

Flame polishing is not a cure-all for a bad surface. You need to sand to at least 220, finer doesn't hurt.
The better the surface looks before you ever light the torch, improves the end result.

Personally, I get the best results with a single-flute router bit (O-flute) either with a regular router and a bushing, or Shaper Origin.