I recently bought a 661 comp mtb helmet, and im trying to make a visor for it.
Ive cut out the shape and everything, got it right, but i need a way to bend the polycarb
anyone know how to do this with out burning it?
Thanks!
__________________
"We have nodded our heads at fear, now we must shake its filthy hand."
Go Fast!!!
Quote:
Originally Posted by vj922
Its obvious that kebbek and rayne are the same manufacuturer, but one is a sub company.
It sounds like you have a pretty thin piece of polycarbonate (less than 1/4" thick).
You could heat it in your oven - hang on, need to find a white paper to tell us what temperature...
What I'd do is set it up on a block of wood that is maybe 1/3 the total length of the polycarbonate piece... that way you can watch it, and when the ends start to sag, you know you have reached the temp you need to bend it.
Then, you remove it from your oven, and carefully bend it to your shape - it helps a lot if you have a buck of the shape you want that you can simply press the polycarbonate against. Make sure it isn't textured or wavy - if the polycarbonate gets too hot it could pick up a texture impression.
I'd use insulated leather gloves to handle it... home centers sell them by their fireplace accessories I believe. You could go high tech and buy kevlar gloves too... but no need for a one off project!
I've done a lot of thermoplastics forming (usually cast acrylic sheets), and never bought fancy gloves (of course I'm usually doing sharper bends with a strip heater anyway).
Here's a good "everything you need to know about thermoforming": http://www.spartech.com/plastics/vfmanual.pdf
...but no temperature tables. Hang on...
Here you are, sir - all about fabricating with polycarbonate (ignore the Lexan brand name): http://www.theplasticshop.co.uk/plas...sing_guide.pdf
Looks like around 200 degrees is good - do you have access to an oven that can run that low?
Check out particularly the note on drape-forming - that might be ideal for what you are looking to do. You might need to massage it a bit if you are bending in more than one direction.
I heat and bend my 1/32" lexan to fit my Azonics AZX. The 1/32" lexan is felexable to bend without heating but I have found when left in the heat at the top of the hill it wants to straighten out, so I heat shape them.
I do not remmove the protective coating before heating. I heat me over to about 225 and bake the shield for about 15 minutes.
TO get the proper bend in them I found I could use a 6x9" baking pan and place the ends of the cut shield in the bottom of the baking pan so the faceshield curves up. Do this on the 6" side.
When the shield is done, make sure the "curve" is in the right place and centered and find a good place to let them cool with the proper curve.
I have a couple ready to go and they can be replaced between race heats.
Heating and bending polycarb
Linear Mode
