HOW TO: Bending Plastic with a Strip Heater (Blaster Parts)

[ZeroRoom[TK]]

After having some of my blaster parts laser cut in acrylic I needed to jump on the strip heater to bend them into shape. It's a nifty device with an infinite variety of practical uses when manipulating plastic so I thought I'd share a quick "How To" for anyone unfamiliar with the magic of a strip heater.

 

A strip heater is pretty much a long heating element (similar to the kind you would find in a toaster or electric home heater) that has an adjustable cover made of thick steel. This adjustable cover lets you expose just a "strip" (hence the name) of heat source at your desired width, which allows you heat specific sections of you plastic piece without affecting the rest of it. Unlike a heat gun or an oven you can heat very precise lines and very small areas individually, which allows for bends, sharp turns and shaping in only certain areas of the plastic. Think of taking a flat piece of any thermo plastic and bending it into an L shaped bracket for example.

 

Of course, in my infinite wisdom it didn't occur to me to actually take a picture of the strip heater as I was working the parts, but basically they look like this:

 

 

 

And work like this:

 

 

It's an incredibly simple machine, and although it takes a little practice and care to get used to the plastic your working with, the heating times and the cooling times etc you can do some pretty nifty stuff very easily with this bad boy.

 

So where do we start? First adjust your gap to the width that will suit the sharpness of the bend you are looking for. Obviously the wider the gap, the larger the area of plastic that will become flexible, so a small gap will make sharper turns, while a large gap will make larger softer curves.

 

If necessary place some additional blockers to shorten the strip length wise as well, and place you piece of plastic on the bars, with the area you wish to bend directly above the exposed portion of the element. Here I am doing it with the flat cut out of the folding stock butt template:

 

 

The length of heating time depends on the material and the thickness of that material - this 3mm acrylic took about 10 minutes to become fully pliable. You will know when it's ready as the plastic in that area stops being smooth and takes on a strange almost wavy appearance, as seen here:

 

 

Don't worry - it's much easier to see in real life than it is in a photograph.

 

At this point the plastic will take on the consistency of a stiff rubber. Remove the plastic from the heater and simply use your hands to bend the shape you want:

 

 

The smaller the strip the more the plastic will naturally bend toward the intended crease. If you heat a wider area you must be careful to get the curve exactly where you want it.

 

You have to work quite fast here as the plastic stops being flexible much faster than it seems to cool. (ie; it can still seem very hot to the touch long after it has lost it's flex and gone hard again) If you keep applying pressure too long it's likely you will crack the plastic. Much like working with a heat gun, It also helps to push a little further than your intended shape as there will be a little spring back. Once you've got the position right, hold it until the plastic has no more movement in it to ensure it stays where you want it. This is hard, as at this point the hot plastic will be burning your fingers, so don't wuss out here...

 

The great thing is that once you've done one part, the strip heater will heat the next part while protecting the bit you just worked on from reheating and losing shape. Thus you can do one part at a time. This is my butt (oh ha ha - grow up <_< ) after heating and bending two sides:

 

 

With a wider strip setting you can heat a bigger portion of plastic and bend softer curves like this:

 

 

Of course this requires more holding and shaping with your fingers than a simple bend so you are really, really gonna burn your fingers doing this (if anyone says why didn't you wear gloves, it's because I'm really tough )

 

I also found that the smart thing to do was have a score line in your plastic where you want tight folds.

 

 

It not only helps line up the piece on the strip heater, but it will bend more naturally where you want it to:

 

 

(See the state of my hands? I repeat: your fingers will suffer and hate you - ignore them. They don't understand how cool it is to blend plastic to your will...)

 

Now we understand the principle here's a quick series of photos showing it in action to make the arms for the folding stock:

 

 

 

 

 

 

Rough test fit of the parts:

 

 

 

You'll note the underside of the butt piece is a touch flatter than is accurate. I should have (and will soon) given that a slight curve by placing it underside down on a wider setting on the strip heater.

 

All in all this a great piece of kit. It's much less strenuous than working with metal bending and using plastic allows for much more precision in shape. It would be ideal for making inner drop boxes too, or getting a better fit on your crotch tab.

 

If you don't have access to a strip heater they are actually really quite easy to make (and let's face it: no workshop should be without one).

 

They cost about $300-$500 but there's a great tutorial on how to build one for under $30 here:

 

http://www.mp3car.com/fabrication/111936-how-to-build-a-heater-strip-to-bend-acrylic-for-30-bucks-or-less.html

 

I hope this encourages other to give it a shot - if only because it's so much fun!

 

Zero Over and out

[Spectre]

Wow that's awesome as, great work mate.

You're just a little too tough man, you're scaring us.

[gazmosis[501st]]

You should make a run of parts once you've ironed things out. Can you find me a tutorial on how to make a laser cutter for $30??

[dashrazor]

that is too cool! i mean hot need to get me one of those rigs..

[ZeroRoom[TK]]

Can you find me a tutorial on how to make a laser cutter for $30??

No - but I can find you a tutorial on how to make one for under a grand:

 

http://www.buildlog.net/cnc_laser/index.php

 

[Marv]

These are wicked toys, used to make photo holders in school with them.

[TKCaleb]

that is awesome man!! a whole new way of building a blaster, out of plastic!!!

[ZeroRoom[TK]]

that is awesome man!! a whole new way of building a blaster, out of plastic!!!

 

I am indeed working on an all plastic E-11 build (partly because I have no metal working knowledge and partly because of the laws regarding replica firearms here).

 

I've found plastic pipe with accurate outside diameter and wall thickness:

 

http://forum.whitearmor.net/index.php?showtopic=17455

 

which is much better than 40mm PVC pipe IMHO.

 

I'm using a resin grip cast and a resin scope but the rest will be acrylic, which means I can use plastic weld to keep it extra durable.

 

Thanks to the precision of the laser cutter I've even been able to build a working trigger mechanism that will allow the bolt to be cocked and fired (single shot only). I've been working on it tonight and it's coming together well so I'll keep everyone posted with pics.

[Spectre]

Sooooo cooool. Also the polycarbonate tube was a great find! I'll be using that for my next blaster build I reckon.

[TKCaleb]

Any more progress with the build? I'm eager to see what you have so far!

Edited December 30, 2011 by TKCaleb

[darthcue[TK]]

I am indeed working on an all plastic E-11 build (partly because I have no metal working knowledge and partly because of the laws regarding replica firearms here).

 

I've found plastic pipe with accurate outside diameter and wall thickness:

 

http://forum.whitearmor.net/index.php?showtopic=17455

 

which is much better than 40mm PVC pipe IMHO.

 

I'm using a resin grip cast and a resin scope but the rest will be acrylic, which means I can use plastic weld to keep it extra durable.

 

Thanks to the precision of the laser cutter I've even been able to build a working trigger mechanism that will allow the bolt to be cocked and fired (single shot only). I've been working on it tonight and it's coming together well so I'll keep everyone posted with pics.

hey Lucas do you templates for building the working trigger mechanism?