bending acrylic

anyone have experience bending sheets of acrylic? I’m thinking of using a heated pipe. don’t have any $$ for fancy equipment… this is just a personal project. not for school.

I don’t want any “bubbling” to form…

I think the problem youd have with a heated pipe would be getting a consistent heat output along its length. Probably not so mush of an issue if your doing small (less than 30cm) bends.

If you can find a way around that you should be fine, though.

Check out computer modding sites like www.bit-tech.net
They have a lot of cases made out of bent acrylic. The method I’ve seen most often is using a heat gun, a vice grip, and a pipe.

What about cutting it… is a cnc router enough or is laser more effective? sounds like it might melt become all distorted if too much heat is applied… i understand laser is very precise, but i don’t want the edges to become warbled… i have a few ideas that require lots of cutting before it’s bent to final shape… making some napkin holders for xmas…

The laser cutter would be the way to go. Have someone with experience suggest how powerful it should be set in order to keep the edges clean and crisp. How thick is the acrylic you’re bending?

The acrylic will only bubble if you have it heated up for too long. I suggest doing a test run since the size is pretty small so you can time how long it takes for bubbles to form. Make sure you allow the same amount of warm up time for the pipe in both the test run and the final bend. Good luck!

I’ve used these before:

http://www.tapplastics.com/shop/product.php?pid=169&

you can control bubbling by how close the plastic is to the element…

I’ve bent a bit of Acrylic, PVC, and ABS sheet material over the years…

The cheapest tool in my kit is an Ace Hardware Hot Air gun; it has two temperature settings (warm and hot) hot delivers 1200 watts. I think I paid $25 for it. But it’s only useful for material up to about 3/16", it’s a pain in the ass to keep running the gun up and down the length of the bend to get it hot enough. Any thicker than 3/16 and the material at one end of the bend is trying to cool at about the same rate as the end you are heating.

For really good results you’re going to need a strip heater. They’re not too expensive, depending on where you look $35-65. Look at it this way, if you’re going to be “designing” as a career, it’s a tool to have in your box. If you’re going to try to do thicker than say, 1/4" you’ll need a controller to keep the temp down so you can heat the material slowly. If you use high temp the exterior of the material (closest to the heater elelment) will over heat and blister/bubble before in interior of the sheet becomes soft enough to bend. Low and slow for material between 1/4" - 3/8". Over 3/8" and you’re getting into “serious” territory, you won’t have much luck with this strip heater.

Plastic strip heater element $65; this one is sold by TAP Plastics. There are others (see below)
http://www.tapplastics.com/shop/category.php?bid=11&

Others:
http://www.moddersmart.com/index.php?target=products&product_id=30282
http://catalog.pitsco.com/store/detail.aspx?KeyWords=strip%20heater&by=20&ID=2731&c=0&t=0&l=0

Spend some time at TAP’s website; it’s time well spent. [Disclaimer: I have no affiliation whatsoever with TAP]

And you’ll need a frame for it … easy, and cheap to do; and you can take it apart to store it too if you want to.

What is not shown are two strips of metal that lay (screwed down) parallel to the length of the strip heater element, one on each side. The diameter of the bend is determined by the width of the area you heat, and that width is determined by the distance you set the two metal strips apart. Maybe easier to conceptualize if you think of these strips as heat shields. If the two metal strips are close together the heat hitting the acrylic is be radiated onto a narrow strip, and the resulting bend radius will be tight; farther apart and a larger area will be heated enabling a larger bend radius. Your plastic stock is supported over the heater using whatever you can find. The heat shields are not necessary, but they do make for well controlled, crisp bends, without distorting adjacent material.

Watch this DIY build video

Cutting…

A laser… …??? Dude!!! Yer killen’ me… … I thought you "don’t have any $$ for fancy equipment… " By all means, if you know someone that has one USE IT!!! And don’t worry too much about the edge; laser cuts are generally clean, and burr free. Worse case scenario; a little clean up with sandpaper and you’re ready to bend.

But if you don’t have access to a laser . … .

straight lines - use a plastic cutter to score the material and then snap it along the the cut.

coping saw for intricate work

or a band saw with a 14 Tooth/inch blade; blade width determined by what kind of line you are cutting blade; 1/8" for intricate curves … wider for straighter cuts.

or jig saw >

but you’ll get a lot of kick-back with a jig saw.

Stripping and cutting blanks, use a table saw - use 10" dia. x 60 Tooth (minimum) blade; 72 or 80 is better. Anything less than 60 teeth and you’re going to be “exploding” a lot of plastic. And you will want to raise the blade quite high so the teeth are coming down as close to vertical as possible (in other words the blade should not be just barely above the surface of the material (yeah, scary stuff with that blade so far above the table, make sure you use a push stick)).

A router would do okay (the speeds are rather high and tend to burn acrylic if you feed too fast), and you have to secure the stock to a work surface to really be in control, not to mention eating a lot of chips.

ya got in on me pdog.

Thanks LMO & Pdog.

LMO: that’s a lot of very useful information. thanks especially for the pics… I’m a visual learner so diagrams, videos and photos really make a big diff whether I understand something or not.

With respect to laser cutting, I’m having a laser cutting company nearby do the cutting for me. They have cnc laser… unfortunately the cuts I’m making are far too complex to do without one. The thickness I’m using is 1/8"… Does that sound like it’d be too thin to work with?

I’m going to get one of those strip heaters… how can you live without one… seems to get the job done well and quickly too. I can see how using a heat gun might be a pain… What if you used a metal pipe that stayed hot long rather than a plastic one? Would that be smart or stupid?

1/8" material heats very quickly, relatively speaking. Keep your eye on it. If you’re using the strip heater with the heat shield close together, say 1/2" or so you’ll be able to get very high bend radii. But try to make your bend radii appropriate for the material thickness; i.e.don’t bend 1/8" over a sharp edge. It will bend to that radius, but will be prone to breaking later.

Not sure if a heated pipe will radiate sufficiently, I’ve never tried it. But metal does radiate heat quicker than plastic. How do yu intend to heat the pipe (plastic or metal)?

The strip heater is the trick in my opinion.

Time and distance is a good thing to keep in mind, it’s interchangeable; closer to the heater = quicker heating (and easier to blister); farther away = slower heating (less likely to blister).

It’s a learning curve for sure. Be prepared to “waste” some stock. But think of it this way, you’re not really wasting it because you’re learning the process.

If you can afford the heat contoller you’ll have much more “useable” tool when it come to extremes of material (say .060" on one end of the scale to 5/16"-3/8" on the other.)

There is also such a thing as a heat blanket. I’ve seen it used many times for large bends. You get even heat/softness. The key here is simply knowing the limits of your material. Yes, 1/8" will heat quickly and you only get bubbles after its been overheated (also note, that’s when all the toxins come out so wear a respirator if you’re doing that.)

Lmo seems to have the best solution with limited resources.

thanks again Lmo and Nurb. I think I’m just going to dig up $65 and get the heating strip. i plan to use it for some time to come. acrylic seems versatile enough.

While we’re on the subject of this material, can acrylic be screwed together? What’s the best way to fasten (for example) two .5" pieces together so that they can be easily assembled/disassembled?

If its .5" thick, you can drill and tap it.

um, no. I have to disagree, a laser cutter would not be the way to go for bending. For cutting definitely. (I have lots of experience with the universal laser systems x-660). There is such a thing as an acrylic bender. The ones I know are about 3.5-4 feet long, and look a bit like a florescent light. You turn it on, let it heat up, and lay the area you want to bend right over it. Then give it a second then slowly bend it! You can use a form if you want. if you do not have that Id either get a head gun and some leather gloves, or go to a place that dose acrylic work and pay them a few dollars (under the table is best) to bend it. Be really specific if you go the later route.

I have had good success a couple of ways but avoiding bubbling is largely down to not overheating the acrylic and not heating it too quickly. Plastic is a natural insulator of heat hence it takes time for the heat to get all the way through.

I found good results on smaller pieces by holding the piece over a ceramic hob element - you do need heat proof gloves though and also need to practice on scrap to get a feel for distance away.

Even better, if you can measure the temperature accurately in an oven and its reasonably stable with no major hot spots, about 120 degress centigrade in the oven and it comes out (with gloves) floppy - you can even cut it with shears! But this way you would need something to form it over - ie a pipe for a curved bend / box section etc for a sharper right angle. But be very careful that you chekc progress every couple of minutes as it cna still bubble if left in too long, and this is risky if you dont check your temperture carefully or leave it un-attended.