The decision of whether to use plastic vs. rubber molding is often encountered by manufacturers developing a new product. This is no simple “either/or” decision. If the wrong material is selected, designers could end up with components with inappropriate tolerances, low quality, and costly production. By considering a few details about the component in question, designers can make an informed, thoughtful decision that will save them time, money, and hassle.
PHB can help designers answer the question of “plastic molding or rubber molding?” with ease and surety. Consulting PHB on a component’s application, aesthetics, and cost will ensure that parts are produced with the optimal materials and under the best conditions.
How To Do It: Plastic Molding & Rubber Molding
To make an informed decision regarding whether to use plastic or rubber molding, designers and manufacturers need to understand the different molding processes.
Rubber Molding
The first step in rubber molding is choosing a suitable rubber! There are many applications for rubber molding, and it’s vital to select rubber with the correct chemical composition (nitrile, silicone, neoprene, custom blends) for each unique application (compression molding, transfer molding, over-molding, etc.).
After selecting the rubber, engineers and designers work together to develop the mold and determine the best process for pressing. Rubber is then transferred, compressed, or injected into the mold, and the appropriate pressure and heat are applied so that the rubber cures. Finally, the newly-pressed rubber piece is extracted from the mold.
Plastic Molding
Like rubber, material selection is crucial for plastic molding. Once the plastic with the appropriate attributes is selected, the molding process can begin.
Essentially, plastic molding is precisely what it sounds like: plastic is melted, the liquid plastic enters a custom mold, and then hardens in the shape of that mold. Plastic parts are produced via injection, compression, or extrusion. After molding, the components are left to cool.
Once cooled, the extraction of the plastic component can be more complex than rubber. Plastic pieces can accommodate much more intricate designs than rubber, but this can also require more sophisticated extraction from the mold.
Plastic parts must release from molds without breakage, sometimes requiring a draft angle to allow the component to stay intact. Designers and engineers should also consider the amount of shrinkage associated with the specific plastic and molding method selected.
Crucial Considerations: Plastic Molding vs. Rubber Molding
PHB engages every customer on the exact function of their planned component to ensure that the appropriate molding process and materials are used. Application of the molded part in its environment, plus its appearance, must be balanced with cost, volume requirements, and logistical constraints.
Application & Working Environment:
Different materials will perform differently depending on their application. For example, rubber molded components are perfect when the ability to withstand high temperatures, absorb vibration, or create seals is necessary. Conversely, in lightweight, moderate conditions, the clean, crisp chameleon-like abilities of plastic are more appropriate.
Appearance:
Depending on the industry that parts are molded for, the look of a product is as critical as its performance. Plastic is generally considered a more “attractive” material, as plastics can be pigmented before molding and take finishing textures well.
Cost:
Much of a molded component’s final price depends as much on the production volume as the material itself. Plastic is generally less expensive than rubber and typically has shorter production times. However, the time required to extract more complex plastic parts from their molds can drive up lead times. On the other hand, Rubber has inexpensive options, and the potential for high mold cavitation can make up for the longer cycle times.
Comparison: Molded Plastic vs. Molded Rubber
There are significant differences between plastic and rubber as materials, and naturally, these differences apply when the materials are being molded.
| Plastic | Rubber | |
| Weight | Lighter | Heavier |
| Flexibility | Varies; typically more brittle | Varies; typically more flexible |
| Recyclable | Yes | No |
| Cost | Lower | Higher |
| Tolerance | Capable of high tolerances | Lower tolerances |
| Production Time | Faster, but mold release can take time | Slower |
| Thickness | Complex to build thickness | Easily made thick |
| Mold Release | Can be difficult | Easy |
| Hardness | Medium to very hard | Varies; can be quite soft to very hard |
| Industries | Consumer products, medical, electronic, aerospace | Automotive, trucking |
Deciding on Plastic Molding vs. Robber Molding:
PHB Supports Customers
PHB’s extensive molding expertise means that customers get excellent guidance and advice when it comes to comparing plastic molding vs. rubber molding. Our range of rubbers, plastics, and thermoplastics can fit your design and budget. Contact us today and let us take your plastic or rubber molding project from prototyping to delivery.
