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Cutting curves in Plexiglass

EricP's picture

Hello All,


I need to cut out some letters in 1/8 plexiglass for an art project at my church.  I've tries several different blades in a jigsaw at several different speeds but the plexiglass always seems to crack.  Anyone have any thoughts on a way to proceed. 


As always, thanks!


Eric

(post #84475, reply #1 of 18)

I haven't actually done it myself, but, you might try a roto zip

(post #84475, reply #2 of 18)

Plexi sucks, use Lexan.

Spheramid Enterprises Architectural Woodworks


Repairs, Remodeling, Restorations


 


They kill Prophets, for Profits.


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(post #84475, reply #3 of 18)

The sheet was given to me with the letters drawn on it.  Is Lexan substantially more expensive?  It would be easy enough to re-trace the letters on a new sheet of Lexan but I don't want to break the bank for a simple art project.


Eric


 

(post #84475, reply #4 of 18)

Well yeah it costs more, cuz it works!


With Plexi you need to either melt it, sandwich it btween other stuff ( like wood) , or highspeed ,low impact cutter, which..will..melt it.


Go for the Lex.


Spheramid Enterprises Architectural Woodworks


Repairs, Remodeling, Restorations


 


They kill Prophets, for Profits.


http://www.youtube.com/watch?v=Dj_oEx4-Mc4


 

www.richmondrenovationsandrestoration.com  

(post #84475, reply #10 of 18)

I wonder if you could somehow cool the workpiece with dry ice to prevent the melting. Or flood it with liquid CO2.


Conscience is the still, small voice which tells a candidate that what he is doing is likely to lose him votes. --Anonymous


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #84475, reply #13 of 18)

Just made a few zero clearance throat plates of 1/4" Plexi ( I am out of enough Lex) and I bandsawed them just fine, it was the beltsander that was hard, it does melt easy..which is good and bad.


Applying a torch to a fresh cut edge, brings back the gloss, I think Iceing it would make a thermal shock crack or induce a shrink/distortion factor.


Spheramid Enterprises Architectural Woodworks


Repairs, Remodeling, Restorations


 


They kill Prophets, for Profits.


http://www.youtube.com/watch?v=Dj_oEx4-Mc4


 

www.richmondrenovationsandrestoration.com  

(post #84475, reply #17 of 18)

Ex-wife worked for Rohm & Hass. I use to have a ton of plexiglass. For cleaning up the edges I found that an back of an old hacksaw blade made an excellent scraper. A couple of strokes with 220 and then 400 grit sandpaper would have it ready for a glue up. For a polished edge I would use the same steps then wipe the edge with a Q-tip dipped in the glue.


I'll have to pick up a small piece of Lexan and see how it bends on my strip heater for plexi.

(post #84475, reply #18 of 18)

Picked up a sheet of Lexan today and will try it over the weekend.  I'd do it in the evening but spent all day putting up 28 ft 2x10 rafters and I'm worn out.


Thanks!


Eric


 

(post #84475, reply #5 of 18)

I used a rotozip to cut out a new backboard for a basketball net.  Get the right bit, and GO SLOW.


 


Oh, and clamp the livin bejeezus out of it - if it flaps even slightly, you're toast.


Edited 11/4/2008 8:04 pm ET by HammerHarry

(post #84475, reply #6 of 18)

Was that plexiglass or Lexan you used.  What bit did you use on the rotozip?

(post #84475, reply #7 of 18)

I've only worked with 1/4" Plexiglass but I do know that it melts easily and that tends to seal up the cut. The solution to that is to go slow -- so slow that it doesn't melt. Often I would chisel off the melted stuff that I could and re-cut the "welded" sections.


For drilling, the drill bit has a tendency to break through and grab and form a crater. Perhaps drilling halfway through and then finish from the other side.


Maybe you could try an old-fashioned coping saw or maybe a scroll saw.


~Peter


It's all Osama's fault. [You heard it first here folks and us Trotskyites can't spell right or maybe tell the difference.]

(post #84475, reply #8 of 18)

Bandsaw works well on acrylic sheet. The long loop of blade stays much cooler than a saber saw blade.

Bill

(post #84475, reply #9 of 18)

Scroll saw at low speed works well too. I think the support the table gives it is as important anything else. For drilling I purchase the p-glass bits. They have a very long tapered point and a longer twist on the cuting flutes than a standard twist bit.


Hey Sphere, how about bending Lexan or glueing it up? I have never used Lexan, so would like to know b4 I lay out any $$  for it.

(post #84475, reply #12 of 18)

I have not bent lammed it , but made scores of guitar jigs with itm cuz it won't explode near cutters. All I got is try it, suprglue works well.


Spheramid Enterprises Architectural Woodworks


Repairs, Remodeling, Restorations


 


They kill Prophets, for Profits.


http://www.youtube.com/watch?v=Dj_oEx4-Mc4


 

www.richmondrenovationsandrestoration.com  

(post #84475, reply #11 of 18)

My father had a sign business for many years... bandsaw

(post #84475, reply #14 of 18)

I've cut a lot of plexiglass and I've found that what works best and cleanest for me is a small router or laminate trimmer. I've mostly used a template and bearing-guided bit. That might be tricky if you're trying to do letters.

(post #84475, reply #15 of 18)

The thin stuff can sometimes be polystyrene rather than acrylic (Plexiglass).  That stuff is an absolute bear to cut by any method- especially if it's old and has seen any UV exposure.


Polycarbonate (Lexan) is the cat's @ss- way more fracture resistant and easier to work with.  Well worth the extra cost.  Works very much like wood, except tougher and way more flexible!


DON'T cool any of these materials with dry ice- you'll embrittle them and make it even more likely to crack!


1/4" acrylic can be cut with a jigsaw using a new, sharp blade, slow speed, and a little oil or wax to lubricate the cut.  Take your time and don't feed too fast.  The blade needs to have lots of set to the teeth so there's a clearance between the sides of the blade and the material immediately behind the teeth.  You need an anti-chip film on the top AND bottom- masking tape will do if the polyethylene anti-scratch film it comes with has already been removed.  1/8" is going to be tougher, since you generally want more than one tooth per thickness of the material just like when you're sawing metal.  The metal-cutting jigsaw blades tend to give you a lot of friction and hence melt more than they cut.


The bandsaw's a good option as it does stay cool better, but will only do for the exterior cuts.  You still need something to do the interiors of closed letters.


Routers work well.   If you can cut them with a router with a template guide, it's a fair bit of work but should work out.  Try not to plunge cut when you don't need to- cut from the outside edge inward.  For closed letters like D etc., it's probably better to cut the inside out first. 

(post #84475, reply #16 of 18)

Been cutting thin plexi with scroll saws for years. 


Use a blade with  at least 15 teeth per inch.   Too many teeth per inch and  a real thin blade may cause the plexi to melt and weld  behind the blade.   Too few teeth will crack the Plexi.    Try a few different blades.


Run a thin sheet of masonite or plywood (maybe 12" x 15")  into the blade to about mid point of the sheet, and clamp it to the saw table. This gives the saw a zero clearance throat and a good surface to move the plexi on.


Hold the plexi down firmly.  You'll have to keep your fingers close to the blade, so be careful not to turn the plexi so fast that it catches and jumps.


If you have a multi speed saw, try different speeds till you find what works best.  The speed you feed the material into the blade will affect it too.   Experiment.  


My current saw is a cheap, single speed, but I can cut curves easily as long as I take my time and hold the material tight to the table.

oldfred