Bending and Sanding Cast Acrylic Rods

[ht403685]

I'm working on one of my first props project but I've hit a point where I'd like some thoughts and advice.

I need to bend a cast acrylic rod (1 1/2" in diameter) around a form without breaking it and hopefully maintaining the clarity of the plastic. I've heard that some people use heat tape, like around water pipes, but I can't imagine that would be hot enough. Any thoughts?

I also need to cut the rod and make the ends as clear as possible. I was playing with a sample piece that I have but the crosshatches of the sand paper always showed through. I tried using a heat gun but that just caused the acrylic to bubble and lose clarity. I'm really kind of stuck so anything helps!

Thank you!

 

[Culvan Van Li]

I'm not sure how long your acrylic rod needs to be. I've bent 1" acrylic by using my oven to heat it up.

1) heat oven to 200 degrees F.
2) put acrylic on cookie sheet in oven. (I put it on wax paper too, but that created some smoke.)
3) rotate every 2 minutes for 16-ish minutes.
4) Increase heat to 225 F. and continue to rotate every 2 minutes
5) Rod should get kinda floppy, but if it doesn't then bump up the oven to 250F. and keep rotating until it does. By Floppy I mean that when you pick it up to rotate it, it bends from gravity.
6) bend it around a wood form. I covered mine in felt to reduce marring.

Mine still had a polished surface, but I didn't want that so I hit it with some 1000 grit sandpaper so that light would shine out of it.

Theoretically you could use a heat gun on low heat to get the same results. I think the key was to rotate it often so you don't get a flat spot. Also I think it helps to heat it slowly. It can be a fiddly process so it probably wouldn't be a bad idea to plan to try it multiple times. Acrylic shows scratches really well, you'll need to use extremely fine sandpaper to get it down to a haze then find some way to get it polished. You probably should research the method that you feel most comfortable with: buffing, chemicals or blow torch. Personally I've used a creme brulee blow torch to reflow the surface, I thought it was the easiest.

Andy

 

[Brucelee42]

The biggest thing there is patience! a heat gun will work, but you have to keep the acrylic moving. Mount the heat gun in a vice pointing up. depending on where you want the bend keep moving the rod back and forth as well as rotating it. Don't get closer than 6" inches or so. It will take about 15-20 minutes. If you can stand to take longer, keep the distance to 8-10 inches. The bad thing about acrylic is that you wont get any warning that bubles are just about to happen, until they start.

Another thing that works well for localized bends is a single slice toaster. And if you can find one, a strip heater is best.

As for the sanding, just work your way up from 600 to 2000 grit sandpaper and then use a buffing wheel, or dremel tool with the puffing pad. (or by hand, with rubbing compound, may take longer but will work)

If your adventurous you can use flame to get rid of the fine scratches, but I would practice on scrap. Its an art...

Hope this helps!

 

[ht403685]

Thank you SO much! I really appreciate the thoroughness! I'm really excited to get started now and not nearly so hesitant to just go at it!

Btw, that umbrella handle is amazing!

 

[Majonaise]

Don't know if this is too old to be useful.

As for getting it glossy again, I know of two major approaches.

One is to flame polish using a gingerly applied blow torch. It'll make it glossy, but how smooth the end is depends on how finely you sanded it. You'll usually still get some striation.

The better option is buffing it. Sand down to about a 600 grit, then buff it with blue compound, and then an acrylic compound; it'll come to a perfectly mirror polish. You have to be really careful about burning acrylic while buffing it though. Don't jam on it with too much pressure for too long or it'll melt and gum up your buffing wheel and leave a poor finish.