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polycarbonate, and I believe they are molded.
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Can anyone tell me how the tail lights on modern cars formed and what material is used to create them. I have looked under red lexan......nope!
Mike
No greater love can a man have than this, that he give his life for a friend.
polycarbonate
Yep, injection molded.
I did not want to hear that! How do they get the transparent red or orange color in the poly? Are the poly beads already colored?
Second question. Could the rear lights be made via vacuum forming?
Mike
No greater love can a man have than this, that he give his life for a friend.
Yes, the beads are already colored before they get molten.
You will not be able to vacuum form them in polycarbonate, but PMMA ( acrylic ) is possible.
From which materials ar made molds for automotive tail light, head liigts (transparent ) and which finishing surface.
The outer skin is usually made from clear PMMA and it doesn't carry any optic.
The inner layers are made from PC and they form the optics which may be very complex now.
The reflector body is made from PC/ABS bayblend and it's metalized in High-vacuum chambers.
All the parts are assembled and glued together by mirror-welding or high-frequency (ultrasonic) welding.
The PC lenses may be clear or colored, depending on the needed final effect. Some colors are obtained by the combination of colored lenses together (dicroic filtering principle)
Mold surfaces are smoothly (mirror like) polished.
For prototyping or short-runs various techniques are used.
For single prototypes to few units, RP prototyping like stereolythography and synthering are ued as well as thermoforming.
To get the optics on a thermoformed part they often use flat molded batches (the required optics are obtained on simple flat molds which produce simple/cheap plates to be manually thermo-formed and cut on shapes) or (sometimes) they CNC cut clear plastic (usually PMMA) from stock.
The reflectors are usually made from RP (SLA or SLS) and then vacuum-cast in RTV molds. They're then metalized in the same high-vacuun chambers used for the production runs.
For short runs (I mean from as little as 20 units to several hundred units) Rapid-Tooling techniques are used.
I will not take in consideration the composite tooling techniques, but I will limit to the metal molds.
Injection molds may be made in as little as a few weeks or even days (depending on the complexity) machined out from Aluminium (new high grade AL alloys are now available which offer excellent results in term of strength and surface finishing) or from Steel.
For prototyping and short-run purposes, some compromises are usually accepted like no undercuts and no sharp edges (which would often require a wide use of EDM finishing).
Some undercuts may be easily obtained with free-releasing in-mold insert (not automatically linked, of course).
However, due to the increasingly demand of rapid tooling for short-runs, various technologies and production techniques have been set in order to obtain complex figures with undercuts, very detailed finishes and even multi-shot moldings (two colors, usually red/orange and clear lenses together, or black shields on clear lenses).
These molds usually take eight weeks to produce parts from the receiving of drawings. However, production time had been reduced sometimes to a couple of weeks, for a complete tail lamp including the reflector, some lenses and the outer skin (which means several molds).
The colored lenses were - usually - obtained by painting (with special pigments) the clear parts ( a lot of manual work was required for finishing, masking and painting), now the tendence is to mold colored parts from matching raw materials.
The main advantage of molding from AL or Steel injection molds is the capability of using the final materials which will be used in production runs.
Typically, standard RP processes involve SLA/SLS part, RTV moulds and Polyurethane/Epoxy casting.
These materials may produce excellent results, very attractive parts, perfectly detailed and finished but ...
they usually don't have the required optical characteristics and this make it impossible to use them for laboratory measurements and certification.
Also, when used for on-the-road trial tests, under severe environmental conditions, RP materials may react differently and this may result in lamps warping or opening due to the heath or to sudden temperature changes.
All these issues mean loss of time, high costs and some other disavantages.
And RP parts should be considered as batches of single (unique) units rather than lots of matching parts.
The production costs for RP molds are not very cheap and they usually produce only a few parts and then a new mold-set is usually required.
This makes the single unit cost very high and it will not lower over time.
On the contrary, metal molds may cost a bit more than the RP tools but can produce several hundred or even thousands parts.
The more parts are produced the lower the cost (like in production runs) and the final product can be used for certifications (shortening the homologation process by months) crash tests and trial tests.
Finally, these molds are often used as a test rig when further modifications are required on the final moulds.
Before touching the expensive production tools it's much easier and chaper to check the modification on the prototype.
I designed molds and programmed CNC paths for several tail lamps for European car manufacturers over the past three years, and we were very successful and competitive with the above mentioned techniques/process.
The most recent technology and design trends are leading the development of automotive lights into the LEDs and this involves a lot of new technologies and machining techniques. Nano-machining is now involved for micro-lenses which are almost impossible to machine with traditional methods.
In-mold decoration as well as multi-shot molding are also part of the development.
The most recent developments of the research for automotive lights are also positively reflecting on other fields of application (consumer goods, house-hold applications, leisure) and it's very exciting to see how fast some things are developing.
I hope I helped you in what you were asking for.
Paolo
If you are looking at making quick one-offs, or need to repair existing pieces, try
http://www.alumilite.com
Their products work great. And they are easy to use.
(And NO, I don't work for them or represent them, I just enjoy their products...)
pavel59: In which company you work and which city in italy you live.Can you attach some example that you work.Can you more explain about LEDs technology.
hey that alumilite stuff looks good. i've found that those types of products tend to be pretty expensive... has anyone tried any bulk "generic" rubber products for casting? the casting specific stuff doesn't seem particularly "special"...
james
I live and work in Udine which is located in the far north east of Italy, close to the borders with Austria and Slovenia.
I own my own design firm and as a consultant I often design molds for prototyping and short-runs in the automotive field.
I will later send you a link to some of my pages where you can see some examples of tail lamp parts we made.
Customers were the major European automotive manufacturers like Audi, BMW, Bugatti, Mercedes, Porsche, Volkswagen, Volvo, AlfaRomeo, Maserati.
About the LED technology, unfortunately I can't tell you too much since it's pretty new and a patented technology.
In the pictures you'll be able to see some LED applications in tail lamps from Bugatti and Volkswagen. However they're using standard high-power led.
The new technology I was speaking about, uses chip-LED technology (even smaller than SMD LEDs) combined with new patented optics which intensify the LED emission.
The optics are very small and require accurate machining with special tools to achieve the perfect finishing of the intricate geometry (imagine some kind of 3D fresnel not more than 0.10mm high at the edges and with a similar pitch).
Current RP technology isn't accurate enough for this application.
getting back to the main topic of this thread, I feel that Polyurethane casting offers excellent results in term of aestetic appearance but doesn't satisfy the optical requirements of a certified lamp.
In order to keep a good precision in the casting you should use a good Silicone rubber offering the best dimensional stability.
Paolo
Do you speak Slovenian or Croatian language.
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