blueovalz Posted December 26, 2003 Share Posted December 26, 2003 I would like to form some Lexan headlight covers for the BlueovalZ. After doing some small amount of research, I've determined a design for the box in which the forming will take place, and instead of using a vacuum to "draw" the Lexan into the mold (reminds me of a T-shirt I bought my boy when he was a kid that said "science never sucks" because there is no such thing as "suction", only positive pressure), I am going to use pressurized air to push it into a mold. I am stuck so far as in what material I will use for a mold that will be easily made, but also not change much under some heat. I've considered plaster for now. Anybody on this list have any experience in this kind of work. I've got everything but this nailed down. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted December 26, 2003 Share Posted December 26, 2003 Terry, I made a stationary (as in pens and pencils) tray way back when in school. We used negative (suction ) pressure. I made the form out of wood. Layed the form on the machine, then layed a sheet of plastic down, heated the plastic to just the right amount (I remember that this took several attampts to get the timing right), then hit the vaccuum. Hope that helps. Tim Quote Link to comment Share on other sites More sharing options...
innerware Posted December 26, 2003 Share Posted December 26, 2003 I am a model maker and prototyper. I have had experience with vacuum molding in the past. I don't know about using pressure to blow the mold on. Sucking the plex on to the mold is a tried and true method. It is easy to make a vacuum box and use your shop vac. You can also make your mold and have a shop do the forming. You can use lexan, plex, polycarb. They all bend at the same temp or around there, as far as I know. For a mold pretty much anything is good. As long as it is durrable enough like high density foam, or plaster. I can probably give you specifics and find out anything that you might need to know. I also have access to a good sixe vacuum former at my grad school. I am in a masters program at SFSU for industrial design. Let me know if I can help. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted December 26, 2003 Author Share Posted December 26, 2003 I'll keep that in mind. Thanks Quote Link to comment Share on other sites More sharing options...
Guest Aaron Posted December 29, 2003 Share Posted December 29, 2003 My company is working on a "blow molding" process to form synthetic posts, etc. I am not in engineering, however, so I do not know how it works, just that it works, and you can get some really nice detail in the finished product. They used wooden posts to make the original molds from, and on some of the prototypes I have seen, you can actually see the wood grain on the molded posts. Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted December 29, 2003 Share Posted December 29, 2003 Sounds like Innerwear is your man. Also, Aaron brought up a point that has bothered me in the contemplation of a similar project: how does one get the plastic to shape WITHOUT transferring mould marks/disturbing the inner surface of the lexan? I've considered a plaster of paris male mould/plug and using a hair dryer/heat gun to lay the plastic down (gravity deformation, no pressure of either polarity ), but what finish or release agent should be put on the mould? Is this a feasible procedure? Quote Link to comment Share on other sites More sharing options...
Guest Aaron Posted December 29, 2003 Share Posted December 29, 2003 I once saw a video of a company molding lexan windshields for drag racers. They cut out the shape of the window then placed it in an oven to heat it until it was soft. Then they simply slid the soft lexan out of the oven and onto a mold. The window fell into shape and was allowed to cool naturally. I am not sure if this process would work with headlight covers or something with a sharp bend or radius. Quote Link to comment Share on other sites More sharing options...
SpeedRacer Posted December 29, 2003 Share Posted December 29, 2003 Terry - Why don't you give our friend John Washington at Reaction Research http://www.reactionresearch.com/automotive.html a call since he makes Lexan headlight covers for his kits. I got mine from him and they are very high quality. Quote Link to comment Share on other sites More sharing options...
Guest dpiatkin Posted December 29, 2003 Share Posted December 29, 2003 or you can go to vitoriabritish.com and get plastic ones, not lexan and they run 60.00 plus shipping and come clear or tinted Quote Link to comment Share on other sites More sharing options...
Dan Juday Posted December 29, 2003 Share Posted December 29, 2003 or you can go to vitoriabritish.com and get plastic ones, not lexan and they run 60.00 plus shipping and come clear or tinted I'm gonna take a WAG and say those might not fit on Terry's car. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted December 29, 2003 Author Share Posted December 29, 2003 Good WAG Dan! Thanks all for the helpful suggestions. This gets me one more step closer. Quote Link to comment Share on other sites More sharing options...
dot Posted December 29, 2003 Share Posted December 29, 2003 Just out of curiosity at what temperature does Lexan become pliable enough to work with? I was thinking of using it for a rear window, but only if I could have the curve like the original glass. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 29, 2003 Share Posted December 29, 2003 Dot, I've heard stories of laying a sheet down on the original window and forming it with a heat gun, but I've never actually seen or done it myself. I'd be curious to know the answer too... Jon Quote Link to comment Share on other sites More sharing options...
blueovalz Posted December 29, 2003 Author Share Posted December 29, 2003 I believe it's about 350* but not sure as all my research is at work. The drying out of the lexan will be the big thing in my mind. I'm planning on 1 hour at a much lower temperature to dry it so that bubbles don't form. Quote Link to comment Share on other sites More sharing options...
dot Posted December 30, 2003 Share Posted December 30, 2003 I was in a plant last year that made skylights. They put the sheets into an oven like they where hanging towels. They brought them out, clamped them down and put compressed air under them forming the bubble. This got me thinking. My idea was to make a wooden box just large enough to fit my part. Then put a heat gun in the end of the box, heat it up to the specified temp and lay the plastic on the old window and hope it doesn’t crack. I never though to ask the guys at the skylight plant what the magic number was. Quote Link to comment Share on other sites More sharing options...
Dan Juday Posted December 30, 2003 Share Posted December 30, 2003 I've been told plexi softens enough to form at 180*. Couldn't tell you about Lexan. Quote Link to comment Share on other sites More sharing options...
innerware Posted December 30, 2003 Share Posted December 30, 2003 This is what I got on temps for you all. ABS (cheap, low forming temp [200ºF], not too strong) Vivak (low forming temp[250ºF], strong, cheap, slightly photo degradable) Lexan (High forming temp[350ºF], expensive, extremely strong and stable) A heat gun really sucks for propper heat distribution. It getts reall hot in small areas and is a pain to properly keep all areas the same temp. In order to get a good mold you want all the material to be around the same temp. Otherwise parts cool faster and you don't get a good shape. Things to use if you are to make your own heater is some kind of refelctor panel ( metal sheet) and electric oven elements. They heat up evenly and cover a wide area. Once the material sags evenly it can be formed. Any more questions I can find answers (hopefuly) Quote Link to comment Share on other sites More sharing options...
260DET Posted December 30, 2003 Share Posted December 30, 2003 Interesting. For a rear hatch replacement 'glass', what I'm thinking of is to lay the plexiglass sheet over the original glass resting on a concrete floor. Then build a brick enclosure around the glass and use a piece of cement building sheet over the top, leaving an access hole. The trick then would be to introduce sufficient heat into the enclosure, maybe use a domestic fan forced heater for that. Might have to insulate the enclosure but such an improvised oven would allow you to do large items at home. Quote Link to comment Share on other sites More sharing options...
Z-TARD Posted January 18, 2004 Share Posted January 18, 2004 On a somewhat related subject, here's a how to article on how to build your own heating oven. This one is meant for bake on finishes for rifles, but the concept could be applied to a larger oven for sheets of Lexan, etc.http://www272.pair.com/stevewag/heater/heater1.html Hope this gives you guys some ideas. Mike Quote Link to comment Share on other sites More sharing options...
Guest iamjackal Posted January 26, 2004 Share Posted January 26, 2004 Innerware is on spot with his temps, I work as an injection molding tech so I kind of have to know this stuff as well. We also use vacuum forming at work to form vinyl over a particle board substrate for Toyota vehicles. To answer a couple of questions blow molding may work best as opposed to vacuum for this. For vacuum molding air must actually be drawn through your mold,so the air channels will leave marks in your lexan. Commercial spray on mold release agents can be bought for 8-12 dollars per aerosol can or the do it yourselfer could try car wax if temperatures were kept reasonable. Quote Link to comment Share on other sites More sharing options...
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