Plastics Can Be Tougher than Metal (And Lower Cost)

It’s hard to break old habits—like using metal parts and metal products. However, there are three good reasons for changing from metal to plastic:

• Lower manufacturing cost
• Lighter weight
• Zero corrosion

What many manufacturers don’t know is that—when done properly—plastic parts can be injection-molded with the same tight tolerances and perform just as well (or even better) than their metal counterparts.

Careful design and planning, selection of appropriate materials, and use of scientific injection molding principles will control the main factors that affect precision, accuracy, and tight tolerances—these include material preparation, melt flow index, machine processing parameters, and most importantly, using sophisticated sensor technology to track what is happening inside the mold in real time. Making these kinds of high-performance plastic parts therefore also requires a robust quality system that can monitor every step of the injection-molding process.

When injection-molding vendors fail to meet tolerances consistently with plastic parts, this creates additional machining costs, quality costs to sort or even re-call parts, and possibly even litigation. (Source: Plastic Overmolding by Kaysun)

It only takes one bad experience with plastic parts to drive a company back to metal. But, with an experienced metal-to-plastic-conversion injection molder, there are some big advantages in going with plastic, such as:

Lower cost to produce
No secondary process to prevent oxidation
May be able to eliminate some assembly
Plastic is generally less expensive than metal
May be able to eliminate costly machining operations
Lighter weight means lower shipping charges
No painting needed, molded in color/graphics
Lighter weight
Less fatigue on a person if it is carried
Might make a product go faster

The key is to successful metal-to-plastic conversion is understanding the limitations of the process, materials, and tools are before committing to the project. Every part or product is not necessarily a good fit for metal-to-plastic conversion: important factors that must be carefully considered are the expected tolerances, materials, specific part design/configuration, and initial mold flow/analysis.