Slide 1
Injection moulding fills a cavity, then releases the set part
Injection moulding pushes softened material into a mould cavity. After it sets sufficiently, the tool opens and the part is ejected.
More to Read
The mould is a major investment, so the process is often attractive for repeated production. The economics differ from methods with low tooling cost but slower production of each individual part.
Slide 2
The gate determines where the flow begins
The gate controls where material enters the cavity. Flow paths influence filling, trapped air and where separate flow fronts meet.
More to Read
A meeting line can become a weaker or more visible region depending on conditions. Gate placement is therefore chosen with the part’s loading and appearance in mind, not only the shortest filling distance.
Slide 3
Cooling can shrink different regions differently
The material contracts as it cools, and different regions may shrink by different amounts. Tool dimensions account for the expected behaviour.
More to Read
Thick sections cool more slowly and can develop sink marks or internal voids. More uniform walls and suitable ribs can provide stiffness while reducing the problems of a large solid mass.
Slide 4
Release angles help the part leave the mould
Draft angles help a part leave the mould without excessive rubbing. Undercuts may require moving tool features or a different design.
More to Read
Adding a small feature can greatly complicate the mould if it prevents simple opening. Design review therefore considers the direction of tool movement alongside the final product’s function.
Slide 5
Consistent conditions matter beyond the cavity shape
Temperature, pressure, material condition and cooling time affect repeatability. A cavity alone does not guarantee identical good parts.
More to Read
Inspection can reveal drift as tools wear or material batches change. Stable production joins tool design with process monitoring, rather than treating the first successful part as proof of indefinite consistency.
Sources
- What Is Injection Moulding?
TWI
- Design for Manufacturing: Polymers
MIT OpenCourseWare