Foaming
⚙️ Operating principle
Plastic Injection Moulding (Structural Foam): Technical Guide
Structural foaming is the benchmark technology for manufacturing solid, ultra-stiff, and lightweight plastic parts, while reducing material and tooling costs.. This process allows for the creation of parts with a «sandwich» structure: a compact and solid outer skin surrounding a honeycomb core..
The Different Foaming Technologies
There are several methods for introducing the blowing agent into the polymer melt. :
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Addition of blowing agents (Chemical): Chemical additives are mixed with plastic granules; they decompose under heat to release gas..
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MuCell / Gas Injection Technologies (Physical): An inert gas (usually nitrogen) is injected directly into the molten polymer under high pressure before injection into the mould..
Pros & Cons
✅ Advantages
- Stiffness to Weight Ratio: Allows for a sandwich structure that is 3 to 4 times stiffer than a solid part of the same weight.
- Absence of shrinkage: The internal expansion of the gas compensates for thermal shrinkage, eliminating surface defects even on thicknesses greater than 10 mm.
- CAPEX Savings: With much lower injection pressures, less expensive aluminium moulds can be used.
- Dimensional stability: The process generates very little internal stress, which prevents any risk of warping.
⚠️ Limits
- Surface appearance: The presence of "streaking" or silver streaks is common, often necessitating paint for consumer hardware.
- Cycle time: Thick-walled cooling can lengthen the production cycle.
- Detail accuracy: This technique is less suited to ultra-fine textures or micro-details than standard high-pressure injection.
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