The Protolis guide to compression molding
In this guide, you will find comprehensive instructions for Compression Molding, a widely used method for crafting precise, high-quality rubber components.
Method Type
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Comparison with other technologies
• Compression molding vs. injection molding
Compression molding and injection molding are two prominent manufacturing techniques used to produce flexible parts. Here are five key differences between these methods:
- Material placement: In compression molding, the raw material is placed directly into the open mold cavity and then compressed. Injection molding, on the other hand, involves injecting molten material into a closed mold under high pressure.
- Tooling complexity: Compression molds are typically simpler and less expensive to produce compared to injection molds, which require complex designs to accommodate the injection and cooling systems.
- Cycle time: Compression molding typically has longer cycle times, as each phase (heating, pressing, cooling) must be managed sequentially. Injection molding benefits from faster cycle times due to its continuous and simultaneous processes.
- Waste management: Compression molding can lead to more material waste in the form of flash (excess material that oozes out of the mold), which must be trimmed. Injection molding usually produces less waste, as the excess material can often be reused immediately.
- Part consistency and detail: Injection molding enables higher detail precision and more consistent part quality across productions, thanks to controlled injection parameters and material flow. Compression molding may result in less uniformity in part consistency and detail, especially with more complex geometries.
- Costing: Compression molding typically involves lower initial tooling costs, making it an economical choice for low- to medium-volume production. However, the per-part cost can be higher due to slower cycle times. In contrast, injection molding has higher initial tooling costs but benefits from lower per-part costs due to its faster production rates and increased efficiency, making it a suitable choice for high-volume production.
| Feature | Compression Molding | Injection Molding |
| Material placement | Raw material is placed directly into the open mold cavity | Molten material is injected into a closed mold under pressure |
| Tooling complexity | Simpler and less expensive molds | Requires complex molds with more detailed designs |
| Cycle time | Longer due to sequential process phases | Shorter due to simultaneous processing steps |
| Waste management | More waste in the form of flash, which needs trimming | Less waste and excess can often be reused |
| Part consistency & detail | Less uniformity in part consistency and detail | Higher precision and consistency in details |
| Costing | Generally, initial tooling costs are lower, but the per-part cost is higher due to slower cycle times | Higher initial tooling costs but lower per part cost due to efficiency and faster production rates |
Understanding these differences helps manufacturers select the most appropriate method based on their specific needs. Each technique offers unique advantages that are suitable for different applications in the plastics and rubber manufacturing industries.
Continue your exploration of compression molding in other chapters:
How does compression molding work?
When to choose compression molding for prototypes and low volume manufacturing?
Benefits and limitations of compression molding