Technical Tip: How to reduce materials in injection molded automotive parts
By Ken Fassett, RJG Inc.Automotive Canadian Plastics
The majority of injection molders are packing way more plastic into their auto parts than necessary.
We’re all feeling the pains of material supply issues as they ripple across the globe, especially those in the plastic injection molding industry. The answer is simpler than you might think: use less plastic. It sounds both obvious and difficult, but believe it or not, the majority of injection molders are packing way more plastic into their parts than necessary. This additional material leads to a slew of hidden costs, both on your finances and on the part’s performance.
Lighter automotive components, by contrast, put less load on the battery systems resulting in longer range for the vehicle – saving the final user money and frustration, increasing car sales, increasing your customer’s faith in you, which leads to long-term partnerships and more continuous revenue.
There are a lot of ways to reduce how much material is in your automotive parts—some easier than others. Here are nine of them:
1. SELECT MATERIAL TYPE WHEN DESIGNING THE PART
The material type should be decided upon and taken into consideration in tandem with designing the part. The type of material will greatly affect how it performs inside the mold and what features need to be present in the design in order to make it as efficient as possible.
2. USE GOOD MANUFACTURING PRACTICES DURING DESIGN
Design is key and can make or break the project before it even begins. Techniques such as coring out thick sections when applicable to reduce part weight should be taken into consideration. The runner and gate size and location are vital as well.
3. PERFORM MOLD SIMULATIONS
Mold simulations allow for inexpensive investigations into potential part designs before the mold is constructed. The risk of altering a part design is lowered when the process capability is simulated beforehand.
4. USE PROCESSING TECHNOLOGY
The utilization of a process control system and in-cavity pressure sensors allows you to see what’s happening inside of the mold before the part is ejected. That means you can create consistent processes that result in high quality parts again and again without the need to sort through scrap.
5. USE SEQUENTIALLY VALVE GATED HOT RUNNERS
A valve gated hot runner system, in most cases, removes the scrap of a cold runner system due to the gate located on the part surface. Eliminating this sprue from every part produced adds up very quickly.
6. TRAIN YOUR TEAM
Training gives processors knowledge to optimize the molding processes. This can result in avoiding costly processing strategies (or lack thereof) that needlessly increase part weight.
7. USE GAS ASSIST MOLDING
Gas assist is a process where nitrogen is injected into a thick part to hollow it out. This makes the part lighter by packing from the inside out, creating a hollow channel in the interior.
8. USE FOAMING AGENTS
Foaming agents are a category of chemical additives mixed into the plastic resin. When the resin or foaming agent is injected into the mold, the foam will expand and create hollow cellular structures inside the thicker regions of the part. This essentially packs the part from the inside out, resulting in much lighter parts. This process is also known as low pressure molding.
9. USE DECOUPLED MOLDING PROCESSING
Decoupled molding separates pack from hold in the injection molding process, eliminating the effects that viscosity shifts can have on the process and building consistency in part quality. It streamlines the process to make it as efficient as possible in all ways, including finding the perfect balance of material for each part.
Ken Fassett is director of global sales with RJG Inc., a Traverse City, Mich.-based training and consulting company that specializes in the injection molding industry. Visit www.rjginc.com for more.
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