I am thermal forming tail light lenses. I am wondering if it is possible probably using heat to press on the inner side of the lens to press in nipples and a reflector? Doing this would be easier because then the back tail light cup piece could take a simple look because you won't be able to see it.


http://members.dslextreme.com/users/mbk5/tp.jpg

http://members.dslextreme.com/users/mbk5/tlc.jpg




thanks

If you are using a female die for forming the lens, you could have better luck with forming prismatic sheet with the defuser texture already done. As long as the draw is not too deep, this should work ok. Screen masking off some areas to manipulate the heat toward the desired flow zones can help thinning and tearing. The negative here is the edge will include the prism surface.

Compression forming needs very precise die design and alignment to allow for material displacment and preventing a lock on as the material shrinks. I.E. all of the draft angles and facet directions in the defuser need to release easily. Die cartidge heaters can help to keep the dies from chilling off. As I recall the trick is to do this type of operation all at once when the sheet is up to working temp.

The former would need a huge amount of upper platen pressure based on the surface area to move that material. They do get near injection mold quality and great detail, but, rarely are these machines created with such things in mind. You can end up using an excessively oversized machine for a much smaller blank.

Lens and defuser options (http://www.alp-ltg.com/Download/Adobe/Lenses/ALP-52.pdf)

Just a few ideas from my stint of experience in the industry.

DC

The prismatic sheet Idea is great duh I should of thought of it... thanks for that bit. What I think I will do is thermal form the outer piece flat then bond to the back a clear prismatic sheet. The light cup will go through that to the red to give it a better look.

Do they make sheets of reflector in this grade

http://members.dslextreme.com/users/mbk5/rrs.jpg



thanks

There are suppliers out there that do offer metalized coatings, front, rear surface mirror and prismatic textures, but I do not know if they form all that well. At least a few years back the coating would not flow at the same rate the base material was drawn. That left tears in the mirror coating. Shallow drawing could work without tearing.

What may be tough is finding it in Polycarbonate. Very nice to work with compared to acrylics. You would be very lucky to trim acrylic after forming without chipping or cracking the stuff.

DC

The design that I am going with has flat edges so the forming will work better. Also I know in any round surface it will distort but I think I will be okay this route. I just need to find out where to get the diamond reflex reflecter sheets. Then the next step for me is metalizing the light cup to reflect light better. As for acrylic for the material that is up to debate depending on what works best.


let me know about the diamond sheets and the metalizing


thanks

You might want to Google it up to find what you are looking for. Depends on what the distributors in your area can offer.

Sterling Acrylics (http://www.piedmontplastics.com/static/literature/Acrylite%20Sterling%20Reflective%20Patterns.pdf)

Mirror sheet (http://www.americanacrylics.com/mirror.htm)

Plaskolite Products (http://www.plaskolite.com/productguide/25.pdf)

DC