Credit for the method goes to: Merryalycen / Kirakira Cosplay (on DeviantArt and on Facebook) and her fabulous Gaige the Mechromancer costume.

Also, feedback is welcome, this is my first Instructable.

I set out to make a Cyborg Arm for a costume piece. Turns out this is actually easier than I expected. Thanks to an internet search I found the Gaige cosplay (credited above). She referenced a technique of shaping Styrene plastic with a heat gun and using velcro to attach it to a lycra glove.

I took it from there and devised my own strategy for getting this done.

The four main steps are:
1) Design & transfer to the Styrene
2) Shaping the plastic with a heat gun
3) Painting the plastic & adding the Velcro
4) Creating the Lycra sleeve/shoulder & adding the Velcro

Materials:
- 1/16" (.060) Styrene - i got it from my local plastics store (8 sq ft for $18 at TapPlastics in Seattle)
- Black Lycra Glove - ~$22 for the pair from Amazon
- Approx 1/2 yard Black Lycra - purchased for $12/yard from my local fabrics store
- 2 yards of velcro
- Epoxy
- Spray Paint of Desired Color(s)
- Optional
* EL Wire
* Additional Texture items (copper wire, old computer parts)

Tools:
- Old T-Shirt (I used one that has been a shop rag for some time now)
- Permanent Pen
- Graph paper
- Scissors
- Utility Knife
- Heat Gun
- Heat sinks of varying sizes (2" iron pipe, 3/4" EMT, 1/2" EMT, 5/16" copper pipe)
- Sewing machine & needle/thread

Step 1: Design & Transferring Design to Styrene

I sketched out the design on paper just so I knew basicaly where each piece needed to go. I then took paper, lightly taped it to my arm and drew where I wanted the plastic to be. Cut the paper off, layed it on the styrene and traced the design i just drew with a permanent pen. The ink soaked through the paper and transferred the design to the styrene so i could cut it out.

I did this for each piece.
- shoulder
- bicep
- forearm
- back of hand
- 3 digit segments for each finger (15 in total)

I have a strong grip and was able to cut the 1/16" styrene with scissors and a little bit of work. I'm sure there are other tools you could use to make this easier (tin snips?).

Step 2: Shaping the Plastic With a Heat Gun

Probably the whole trick to this technique is having something you can heat up the plastic on and shape it. I used metal pipes which worked pretty well. I wasn't sure how hot the plastic would get so i wanted to use something that wouldn't melt.

The shoulder was the first one i did, and one i could easily cut out again if i messed it up. The key seemed to be constant heating of the entire surface, making sure that more than just the area you want bent is warmed. If you just heated the line you wanted bent, the rest of the rigid plastic would hold it into a weird shape.

The consistency of the plastic when warm is like thick Fruit Leather. Its kind of floppy and malleable but stiffens within 10-15 sec. I was able to touch even the hottest plastic for 2-3 seconds to shape it properly.

Step 3: Painting the Plastic & Adding the Velcro

Spray paint the plastic the color you'd like. Don't forget the underside that'll show, especially on the shoulder, etc.

Epoxy the evil-Hook-side of the Velcro to the bottom of the plastic. Don't spray paint the underside of the part where you're going to glue the velcro, I had a problem with it peeling off until i sanded the underside spray paint off.

For flare, i added a copper wire by drilling a hole in the plastic and just bending it on the other side.

Step 4: Creating the Lycra Sleeve/shoulder & Adding the Velcro

Similar to the idea of using the paper contoured to my body, i just took an old t-shirt i use as an oil rag normally and drew on it as i wore it. This became the template for the Lycra shoulder/chest cutout and what I sewed to the Lycra evening glove.

Sewing the velcro to the Lycra was done by sewing machine above the elbow, but i couldn't get it inside the glove... so it was all hand sewing for the forearm and the hand. EASILY the most tedious part of the entire costume. I almost debated cutting the glove open, sewing it with the machine and sewing the glove back up. But i figured that was a poor choice.

Once the sewing was done, you add the plastic + velcro to the Lycra + velcro... and voila!