Forming Lexan Sheet

I have some 3/16" Lexan sheet that I need to bend to make a windshield. Has anyone done this?
will I need to heat the bend area? Any help would be great!
Thanks, Randy

We bend in a break. Cold, leave lots of room, sometimes get slight stress lines at the bend. Heat is better. But you are trying to bend a bow? If so it is better to build a form and clamp the peice and heat in an oven and I can't remember if you need to anneal or just let cool. And I can't remember how hot for how long. I think you can heat the form and get a good result also.

What type of windshield? If this is in a car no bending is required. The Lexan is flexable enough to conform to the curve. I just did one on a car and used a flat sheet.

Randy, he is right about bending in a brake. I hope thats all you need because it's a pain to form lexan. If it needs to be curved when in the free state then your gonna have to thermoform it. Lexan requires a drying time in the oven at 250F for a time period of 1 hour for each 0.010 material thickness. 3/16 is going to need about 18 hours at 250F. If you omit this step, it will make a good shower door as it will be nothing but small bubbles from steam trying to escape. Forming temperature I believe is about 375F. You might want to check on that, my notes are at my shop. It will be like a sheet of rubber when ready. You need to work FAST, it goes hard fast, not like Plexiglass. Put a bunch of cutoffs in the drying oven and leave one out. Experiment on the scraps to find the right oven time. I remember something like 8 minutes for 1/8 lexan. Just for fun, cook up the scrap that wasn't dried. You will see why drying is important. Have fun. Bill

I use Lexan alot.

I made a motorcycle windshield for a Goldwing using nothing but a heat gun to get the proper curvature.

The trick is to keep the heatgun moving or you will form bubbles. We conformed it to the fairing and screwed it in place, once it cooled it was set and looked just like the origninal factory piece.

Have also had good success welding Lexan together using a hot air plastic welding gun and Lexan filler rods.

I've used a break to bend 1/4 and 1/2 inch Lexan but it seems that if you go much past a 45 degree bend that you'll get stress fractures. Bending to 90 is the cold limit, go past that and it'll break. Use a heat gun and you can tie it in a knot if you want.

Sev,

Let us know what works. I have some 1/4" Lexan I'd like to form into the driver's side window on my F350. Anybody know if 1/4" is enough to protect from small calibre (9mmP or .380) handgun fire at point blank? My main threat is "walk-ups" or "pedal-ups" to the driver's side when stopped in traffic.

John

where I worked we tested a piece of 1/4 lexan against a 22lr. pistol at about 8 feet. All it did was smudge the lexan. did'nt have a bigger gun to try.

A long time ago my eye doctor had a sample polycarbonate eyeglass lens of normal thickness (1/8 or 3/16). it had a 9mm bullet stuck in it. No cracks, no shatter, the bullet just stopped.

The lens maker passed these out to show how tough the lens was so that we shop people would know they were good enough for safety glasses.

Something as large as a truck window will fade back from the impact so the bullet probably won't penetrate at all.

Live in a Nasty Neighborhood, huh?

The windshield on my race car was formed in an oven over a mold, so that it slumped in place and cooled in the right shape. it is polycarbonate of some sort, but I asked and they said the same thing for lexan, just more expensive - probably due to the preheat mentioned earlier.

Remember that normal Lexan scratches and hazes really easily. You need to use special stuff for windows or replace them a lot.

Brian

Jim K,

Thanks for the info. I live in a peaceful area but work in one of the worst parts of Los Angeles where shootings are so commonplace they rarely make the evening news. The word is that the media spike the stories so as not to make the area look bad.

I bought the Lexan to make shields for my Rong Fu m/d as much to reduce slinging the coolant all over the place as to to hold back the chips, mounted them to the 1/2x13tpi holes on the vice jaws. Quick-n-dirty, but works well.

I have enough left over for a driver's side window.

John

Well , at that point, don't forget the door.....first thing I would do after the window didn't work is shoot the door. (if the ricochet didn't get me). I'd be one ticked gang member at that point if I were the guy at the window.

You'd be swiss cheese. The tempered silly putty used as metal these days wouldn't stop a determined knife.

Lexan is GE's brand name for polycarbonant.

one way to heat is to buy silicone rubber heater strip, these are available in all sorts of sizes and are fairly cheap. I used to have one 2 24 inches. just lay in on the surface with a weight like a wood strip. and plug it in. you can get by with out a thermostat if you watch it, but they are intended to be used with a controller. gives good contact and puts out alot of heat. you will get bubbles if you do not dry it first,

In California we have TAP Plastics (plastic supply retail store). A few years back I bought a heater strip from them. Just high resistance wire that is backed with a thin layer of glass cloth (about an inch wide). This was only a few bucks. I groved out a piece of 1/2 inch plywood and layed the heater strip in there back with several layers of heavy alum. foil to reflect the heat in outward direction. I just lay the material I want to bend over the strip for about 5 minutes , checking it every couple of minutes to see if it is getting flexible. Bends are easy with both Lexan and Plexiglas, but have not done anythng thicker than 1/8 inch.

http://www.tapplastics.com/

TMD

J Tiers,

You're right about the doors, but I wear my Kevlar even when commuting to and from work. It offers no protection from approx 4" under the arm and up, but its better than nothing.

I doubt that the second round fired would be thru the door - it takes time for the "WTF" factor to register. The 3rd most certainly would be through the door.

Also, in a carjacking scenario, they don't usually shoot the driver till he exits the vehicle. The Lexan window would give me an opportunity to stall the threat until I was ready to address it.

Been in this area two years and no problem yet. Most of the shootings are gang vs. gang.

Anyway, at least now I know that the Lexan isn't that difficult to form.

I have a removable hardtop for a '66 Chevy that the plexiglas has spidered. Might have to come back to this sometime and contemplate making a rear window. Wonder how hard the forms will be to make, to match the original.
15 years ago they wanted almost 400 dollars for the rear window.(if you could find one)
David from jax

Come on JTToner, I hope you are not saying Brea is bad. I live a mile from you and I am more worried about getting run over by a soccer mom in her SUV talking on her cell phone than getting shot.
Though you may get shot by that same soccer mom if you steal her parking space at the Brea Mall when Nordstrom's is having a sale.

Oops should have read further down the thread. There are places I wouldn't go in LA.
You should look at a spec sheet on Lexan and see if it degrades in sunlight. Some of the "bullet proof" plastics were less bullet proof when UV hit them for a while.
I have wondered if you could get Kevlar mats and just place them under the doors inside trim panels. If you can buy Kevlar mats.

Sandman, you got a form already, your old window. When I was 15 I worked at a machine shop/plastics fab shop. My boss was THE MAN. He retired from Rohm and Haas and was the guy that figured out how to form plexiglass. During 2nd WW he lived at the plant making all the plastic bubbles for the gun turrets on the bombers. The book they put out on forming plexiglass or lexan is everything I learned on. Sometimes I think he wrote it. He figured it all out. The guy was a genius. When they came out with fibreglass resin and cloth, he took a bunch home and built his son a duck boat for hunting. First glass boat in the world. R & H was wondering what they could use this stuff for. LOL. He retired because of a stroke. Mr Haas gave hime a honerary degree in chemical engineering that day. Not bad for a guy with a 6 grade education. He grew up in a rough time. He retired and started his own shop. Remember the Chess set Nixon sent to Russia? We built the plexiglass case for it. He is my hero forever. Also the best damn teacher I ever had. I could go on and on but lets get back to your windshield. Take your old windshild and lay it on a table with support under it. When the plastic is ready to form, lay it on top and pull it over tightly. When cool, trim it to the outline of your old one. Schrinkage will bring it so close to the original size, it will fit nicely. Cover your old windshield with flannel cloth before hand, reduces markoff. I wish I could remember all the tricks that Cookie tought me, I was sowing wild oats at the time. Many of them has made me good money over the years. By the way, if your gonna make a roll up window out of lexan, make sure it is hardcoated, lexan scrathes very easily and is next to impossible to polish.
Bill

Once again, it is amazing to see the experience of all here. All these ideas make you think about other things, too. Here in Texas, some people were wondering if a thin sheet of Lexan - if UV protected - would do for solar and hot water collectors. The issues were intense UV, summer heat, and transparency. It will occasionally hail - up to softball size. Sometimes debris will also hit the collectors from a windstorm or dust storm. A 40,000 foot tall sand wall cloud rolling in on you at 70mph is not unusual in Lubbock.

Jerry

Lee3

Brea is great. I can walk to Birch St.late at night without looking over my shoulder. The thing is I work So. Central, frequently evenings and weekends. Brea is a whole different world! BTW, I'm 3 blks east of Brea Blvd., north of Ash. Shoot me a note off-line.