How to Select Injection Mold Components Based on Product Requirements

Based on four core dimensions—material characteristics, appearance precision requirements, structural complexity, and mass production scale—precise selection of injection mold components can be achieved layer by layer, balancing molding yield, mold life, and overall cost, adapting to customized needs in precision scenarios such as aerospace and automotive.

1. Determine the Basic Framework First: Mold Base Selection

The mold base is the load-bearing skeleton of the entire mold, directly determining the overall structural cost and operational stability. The core selection focuses on matching the gate type with the product's appearance requirements: Large-Gate Two-Plate Mold Base: Suitable for common injection methods such as side gates and submarine gates. It features a simple structure and low cost, prioritizing conventional plastic parts with low appearance requirements and simple structures, such as ordinary shells and general structural components. The CI/DI series conforming to the national standard GB/T 12555-2006 can meet most scenarios.

Three-plate mold base with fine gate: Supports automatic material cutting at the point gate, resulting in minimal gate marks. Suitable for appliance housings and precision electronic housings with extremely high appearance requirements and center-mounted injection. For multi-cavity molds with four or more cavities, the standard DA/DB type is preferred to ensure uniform injection.

Simplified fine gate mold base: Combines the advantages of point gates with cost control. Suitable for medium-complexity plastic parts with side sliders in the fixed mold and limited budgets, avoiding interference issues between guide pillars and side core pulls in standard three-plate molds.

Prioritize mainstream standard mold bases such as LKM and FUTABA. Non-standard mold bases are only customized when ultra-large plastic parts or special side-pulling structures cannot be accommodated, significantly shortening the manufacturing cycle and reducing the difficulty of later maintenance.

2. Core Molding Components: Cavity, Core, and Steel Selection

Directly determines product shape accuracy and mold life, perfectly matching product material and mass production scale:

For small to medium batch general ABS/PP/PC products: P20 and 718H pre-hardened steel are selected. No quenching is required, processing cycle is short, polishing performance is good, and mold repair is convenient, making it a cost-effective solution for conventional structural components.

For high-precision assemblies and flame-retardant/corrosive plastic products: NAK80 and S136 steel are selected. The steel has uniform hardness and minimal deformation. The rust and corrosion resistance of S136 prevents oxidation and carbon buildup in the cavity, ensuring excellent long-term mass production appearance and dimensional stability, suitable for aerospace precision electrical assembly housings and medical plastic parts applications.

For products with glass fiber/carbon fiber fillers and mass production exceeding one million cycles: H13 and SKD61 hot work mold steel are selected, achieving a hardness of HRC50-52 after quenching. This provides impact and wear resistance, resisting long-term erosion from glass fiber and preventing wear and collapse of ribs and edges. Suitable for automotive engine peripheral structural parts and heavy-duty industrial brackets.

For cavities with severe glass fiber wear, additional nitriding and TD coating treatments can be applied. The surface hardening layer can extend mold life by 10-20 times, significantly reducing mold repair costs during long-term mass production.

3. Gating System Component Selection

Matching product filling balance and production efficiency requirements:

For ordinary small to medium-sized parts and single/few-cavity molds: Side gates are selected, simplifying machining and facilitating mold repair, suitable for most conventional plastic parts.

For products with large projected area and multi-point injection requirements: Fan-shaped gates or multi-point gates are used. Mold flow analysis optimizes the runner layout, avoiding weld lines and short-fill defects, ensuring balanced melt flow speed.

High-volume production efficiency scenarios: Adding an in-mold hot-cutting system automatically cuts off the gate after pressure holding, saving 5-8 seconds per cycle, increasing production efficiency by 30%-50%, resulting in a smooth, stress-free gate end face and a yield rate increase of over 20%; for glass fiber reinforced systems, carbide cutters are preferred to avoid rapid wear of ordinary high-speed steel.

Hot runner molds: Regardless of the injection method, a two-plate mold base is always used to avoid interference and leakage between the three-plate mold structure and the hot runner system.

4. Ejection and guide component selection

Matching product structure and demolding requirements:

Standard appearance parts: Utilizing a standard SKD61 ejector pin layout, ejection points are evenly distributed in locations with good product rigidity, preventing whitening and concave deformation. Nitrided versions are suitable for high-wear-resistance mass production scenarios.

Deep-cavity, thin-walled, easily deformable products: Using a combination of push plates and ejector tubes for ejection, dispersing ejection force, ensuring a smooth demolding process without tearing, suitable for automotive door panels and deep-cavity housing parts.

High-precision, long-life molds: Utilizing 20Cr carburized and hardened guide pillars and bushings, coupled with high-precision locating pins, the mold closing repeatability is controlled within 0.005mm, ensuring no offset or flash during long-term mass production and maintaining stable precision for over 100,000 molding cycles.

5. Temperature control and venting component selection

Matching product cooling uniformity requirements and resolving warping and bubble defects: For products with uneven thickness and prone to warping: The water channels are evenly arranged following the product contour, achieving close-range, balanced, and full coverage, ensuring consistent cooling speed in all areas, significantly reducing the risk of internal stress deformation, and shortening the molding cycle by more than 30%.

For products with dense ribs and many holes: Precisely designed venting grooves are created at the parting surface and insert mating points, with a depth strictly controlled between 0.01-0.03mm, ensuring smooth venting without generating burrs, completely resolving defects such as scorching, short shots, and brittle weld lines.

6. Selection of Core-Pulling Auxiliary Components

Matching Special Structures such as Undercuts and Side Holes:

Shallow Undercuts, Inner Groove Structures: Utilizing a slanted ejector mechanism, this compact and low-cost design is suitable for the inner demolding needs of most small and medium-sized molds.

Large Outer Side Holes, Deep Undercut Structures: Employing a slider + hydraulic cylinder driven core-pulling mechanism, this mechanism allows for lateral movement to disengage from the undercut during mold opening and precise locking before mold closing. Suitable for complex structural components such as automotive bumpers and large interior panels, ensuring reliable movement and long service life.

Qingdao Xueyu Molding Products Co., Ltd. is mainly engaged in the design and manufacturing of injection molds, injection molding and secondary processing (spraying, pad printing, ultrasonic welding, stamping), etc. For more information about injection mold components, please contact us.

Website: www.xyzmould.com

Address: No.18 Henan Head Road, Henan Head Community, Jihongtan Street, Qingdao Industrial Park, Shandong Province, China

Email: wangmiaotian8@163.com