Material selection is one of the first decisions that affects an injection mould quotation. Resin choice changes shrinkage, flow length, cooling time, gate design, venting, polishing, steel selection, and sample acceptance. For food containers, cups, lids, and IML packaging, the buyer should confirm material requirements before the mould factory finalizes the tool design.
A practical RFQ should include the intended resin grade, melt flow index when available, food-contact or export requirements, target part weight, wall thickness, product use, filling temperature, color or transparency requirement, and expected production volume. These details help the mould supplier estimate whether the design can fill, cool, eject, and hold dimensions reliably.
Polypropylene is widely used for food containers, lids, thin-wall boxes, yogurt cups, and microwaveable packaging because it offers useful heat resistance, chemical resistance, and low weight. PP can work well in thin-wall moulding, but the mould needs strong filling balance, cooling control, and ejection design to avoid deformation.
PET, PS, PE, and other materials may be selected for specific packaging needs such as clarity, stiffness, impact resistance, or cost control. The right choice depends on product function. A lid that needs sealing flexibility has different priorities from a transparent cup or a rigid lunch box.
Every resin has its own shrinkage behavior and flow characteristics. Higher shrinkage can affect lid fit, stack height, clasp function, and anti-theft buckle accuracy. Low-flow material may need different gate size, runner layout, or injection machine capacity. Transparent or high-gloss products usually require stricter polish, venting, and surface protection.
Material also influences cooling and cycle time. A resin that needs longer cooling can reduce output even if the mould has many cavities. For thin-wall packaging, the buyer should discuss both part weight and cycle target because lightweighting can create filling and strength tradeoffs.
The mould steel should match the resin and production life. Standard PP packaging moulds may use common pre-hardened or hardened steels depending on output requirements, while corrosive, abrasive, transparent, or highly polished products may need stronger steel and surface-treatment planning.
If the resin includes additives, color masterbatch, recycled content, or fillers, the buyer should tell the mould supplier before quotation. These inputs can affect wear, vent buildup, polish life, and maintenance intervals. Hidden material changes after sampling are a common reason for production instability.
During sampling, buyers should inspect dimensions, part weight, shrinkage, warpage, surface marks, sealing fit, stacking performance, drop behavior, and cycle time using the agreed resin. If samples are made with a substitute material, the acceptance result may not represent future production.
For food packaging, check the real use condition where possible: hot filling, cold storage, transport stacking, lid assembly, label adhesion, and automatic packing. Material behavior under these conditions is often more important than a single visual sample.
Before ordering a mould, confirm the resin grade, supplier datasheet, target part weight, functional tests, export or food-contact standard, color or transparency requirement, and expected annual output. Ask the mould factory how the material affects steel choice, gate design, hot runner selection, cooling layout, and trial acceptance.
Good material selection protects the tooling investment. It gives the mould designer stable assumptions, helps the buyer compare quotations fairly, and reduces the risk of expensive correction after steel cutting.
Ningbo Hengqi Precision Mould Co., Ltd. is professional China Plastic Injection Mould Manufacturers and custom Plastic Injection Mould factory, engaged in the development and manufacture of thin-wall packaging moulds. Our company has complete manufacturing equipment, scientific quality management system, rich practical experience in mould and hot runner production, combined with professional system design, using high-precision high-speed machining centers to achieve mold processing high standards. Hengqi Mould is in the leading position in the field of thin-wall injection molds in China. It produces thousands of sets of PP lunch boxes, cups and in-mold labeling system molds with a wall thickness of 0.35-0.45MM each year, which are supplied to the domestic market and exported to overseas. Hengqi Mould adheres to the spirit of continuous innovation and development of precision moulds.
In 2012, Hengqi Mould Factory was established.
In 2016, Hengqi Enterprise established Tianjin factory.
In 2017, Hengqi officially changed from individual to company.
In 2019, Hengqi established Chengdu branch and Betterfork cutlery department.
In 2024, Hengqi continues to expand international markets.
