The lights in modern cars do more than illuminate dark roads. They’ve become a design signature of many OEMs. Audi started this trend in 2004 with the LED daytime running lights fitted onto the A8, and lighting technology has advanced rapidly since then, making auto lamp mold production a critical part of automotive manufacturing. Today LED lights are commonplace in both the front and rear ends of the vehicle, active lighting is throwing light around corners, and even laser high beams are emerging.
Front and rear light clusters go through rapid design cycles as manufacturers make styling changes every few years. Producing these assemblies of injection molded plastic components requires complex mold tools and their long lead times can easily constrain or delay model facelifts. Inevitably, designers and die makers are under increasing pressure to accelerate auto lamp mold production.
Product development typically follows a pattern of: design; prototype; test and validate; freeze or modify design before it moves into scalable manufacturing. True design validation often calls for complex auto lamp mold production tools that might take weeks or months to finish, dragging out each iteration and risking a launch or program delay.
Advanced 3D computer modeling and ray tracing software lets designers conceive and evaluate more alternatives but there’s still no substitute for physical prototypes. The key is to reduce auto lamp mold production lead time so they can be made faster.
Why Prototype at All?
In the case of auto lamp mold production, physical prototypes are essential, for five reasons:
- Cost evaluation
- Fit assessment
- Prove-out of overmolding/insertions
- Material performance assessment
- Optical testing
1. Cost Evaluation
Only by molding parts is it possible to determine actual cycle times and actual yields. Lessons will be learned about the mold temperatures and pressures needed, cooling and shrinkage rates, distortion and so on. From these, tool modifications will be identified that bring down ultimate manufacturing costs.
2. Fit Assessment
After metalizing, molded reflectors are bonded to the clear or colored housings to create lamp clusters. Fitting together in the computer is no guarantee the actual parts will go together the same way, so prototypes are essential. The completed assemblies are then mounted on vehicle mock-ups and sculpted models for evaluation of fit and appearance under a range of lighting conditions and viewing angles.
3. Prove-Out of Overmolding/Co-Molding and Insertions
Many automotive lamp assemblies need different color plastics molded together, such as orange and clear or red, orange, and clear, and these are made by overmolding or co-molding. Male and female threaded inserts are needed for mounting in the vehicle as well as holding the bulbs and associated electrical components. Only by actually making the parts is it possible to verify the integrity of these overmolded and sometimes co-molded assemblies, and the insert bond strength and position.
4. Material Performance Assessment
Auto lamp assemblies are expected to last years in all kinds of environmental conditions without substantially diminished output. Plastics manufacturers continue to improve the grades available and prototyping lets development teams evaluate their performance under a wide range of conditions.
5. Optical Testing
Output, intensity, visibility, and beam shape are the subject of many regulations. Additionally, as manufacturers put greater efforts into adaptive lighting, it becomes even more important to track critical performance metrics. Regardless of how much modeling is done, only a functional prototype can ”bring to light” the actual performance achieved or delivered, validate the modeling, and demonstrate conformance to tighter regulations.
Tooling Lead Time Reduction
Production injection molding tools are typically machined from steel before hardening. Milling is slow and usually followed by hours of grinding to blend radii and surfaces. EDM can take hours to spark-erode complex pockets and cavities, after which more grinding is needed. The whole process, from design initiation to delivery, can take months.
Additive manufacturing methods using metal may one day reduce development time but today their chief contribution is producing SLA patterns as a basis for urethane molds. These allow pouring of liquid acrylics that take on the shape of the part needed, as described in this case study of an automotive tail lamp prototype, but aren’t directly usable in injection molding.
An alternative is to harness the speed and precision of modern CNC machine tools to shape molds from aluminum. Aluminum can be machined without slow grinding and EDM processes. Lifetime, measured in quantity of parts produced, will be less than that of steel tools, but that’s not a concern when making prototypes. In addition, the heat flow characteristics of aluminum can be of benefit when molding small quantities.
All About Speed
The lamp clusters used on modern cars have almost become fashion accessories and that means frequent design changes and intense pressure to get new designs to market. Computer modeling lets designers explore far more alternatives than was possible before but physical prototypes remain essential. Consequently, launching face-lifted car models depends on the speed of auto lamp mold production, which, in turn, depends on quality, time-sensitive prototyping.