In household appliance mold processing, minimizing plastic shrinkage is crucial to meeting customer demands and optimizing production. DAYIN Plastics notes that shrinkage is typically more pronounced in thicker sections of injection-molded parts, such as ribs or protrusions, due to slower cooling in these areas. This slower cooling can lead to sink marks at the junctions, a defect that severely limits the design and molding of plastic products, particularly large, thick-walled items like TV cases and monitor housings.
For consumer electronics and other products where appearance is critical, eliminating sink marks is essential, whereas products with less stringent surface quality requirements, such as toys, may tolerate their presence. The formation of sink marks can be influenced by various factors, including processing methods, part geometry, material selection, and mold design. While part geometry and material selection are typically determined by the raw material supplier and are difficult to alter, there are still many adjustable factors within mold design, such as cooling channel layout, gate type, and size.
For example, the cooling speed of a tubular gate is typically faster than that of a conical gate. This rapid cooling can reduce the cavity fill time, thereby increasing the risk of sink marks. Molding technicians can address shrinkage issues by adjusting processing conditions, with fill pressure and time having a significant impact on shrinkage. During the filling phase, continuing to inject additional material to compensate for shrinkage is an effective strategy. However, a fill time that is too short may exacerbate shrinkage, leading to more pronounced sink marks.
DAYIN Plastic Products Co., Ltd. is a high-tech enterprise dedicated to product R&D, design, manufacturing, and sales services, offering one-stop manufacturing solutions. Founded in 1989, the company specializes in mold making, injection molding, post-processing, and electronic assembly. In addition to providing OEM services, DAYIN also develops its own products for customers to directly customize under private label production. With a 50,000-square-meter production base, 30 years of mold development experience, over 50 R&D personnel, and more than 100 injection molding machines, DAYIN is committed to delivering high-quality manufacturing services.
Minimizing Shrinkage in Appliance Molds: The Design Half
Shrinkage conversations usually start at the machine; the design half of the answer costs less:
| Design lever | How it minimizes shrinkage | Design-stage cost |
|---|---|---|
| Uniform wall strategy | Removes the thick-thin gradients | A review meeting |
| Core-out thick sections | Replaces mass with structure | Tooling detail only |
| Rib thickness discipline | Stops sink at rib roots | Percentages, not millimetres |
| Gate near last-to-fill mass | Packing reaches the thick zone | Simulation hours |
The rib row is the most frequent violation of the cheapest rule: ribs at eighty percent of the adjoining wall sink invisibly, ribs at sixty sink never, and the difference costs a percentage of thickness rather than a re-engineering program. The gate row closes the loop with the packing physics — pressure takes the shortest path, and a gate placed where the mass lives delivers packing where shrinkage would, while a gate placed for cosmetics leaves the thick zone to fend for itself. Design-stage shrinkage work is also the cheapest warranty against the variations that surface later in production, because steel remembers every shortcut; geometry reviewed once, honestly, is geometry that never appears in a defect meeting. The process-half answer is in shrinkage variation handling, and the gloss neighbour in gloss in appliance molds. Reference: shrinkage behaviour and dimensional control.