From Design to Molding: Unlocking the Core Logic of Insert Molding

2025-11-19

Discover Bost’s expertise in insert injection molding and the insert molding process. From design to molding, we unlock the core logic to ensure precision, durability, and efficiency in every project. Enhance your manufacturing with Bost’s innovative insert molding solutions.

In plastic part manufacturing, insert injection molding is a "1+1>2" technology—it combines inserts (such as copper pins, stainless steel nuts) made of metal, ceramics, etc., with plastic through injection molding, enabling parts to have both the light weight of plastic and the high strength of inserts. The implementation of this technology, however, relies on the precise planning of injection molding design and the strict control of insert molding process.

Injection molding design is the "blueprint" for insert injection molding. During design, it is necessary to consider not only the fluidity of plastic (to avoid material shortage caused by inserts blocking the material flow) but also the precise positioning of inserts: for example, inserts need to reserve a "wrapping allowance" of 0.1-0.2mm to ensure that plastic can tightly wrap the inserts; at the same time, the mold needs to be designed with insert fixing structures (such as positioning pins) to prevent inserts from shifting during injection. BOST is a professional injection mold company, and its design team uses simulation software to predict the material flow trajectory. For instance, it designs "annular gates" for insert injection parts of home appliance interfaces, allowing plastic to evenly wrap metal pins and avoiding bubbles or gaps.

Insert molding process is the "implementation manual" for realizing insert injection molding. The complete process is divided into four steps: first, pre-treat the inserts (clean oil stains, polish the surface to enhance the bonding force with plastic); then accurately install the inserts into the positioning structure of the mold; next, inject molten plastic, and at this time, the injection pressure needs to be controlled (usually 10%-15% lower than ordinary injection molding to prevent insert deformation); finally, cool and demold to obtain integrated insert injection parts. BOST is a professional injection mold company. For complex inserts (such as multi-pin connectors), it optimizes process parameters—for example, adopting "step-by-step injection molding": first inject a small amount of plastic to fix the inserts, then inject at full pressure, which greatly reduces the insert offset rate.

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The synergy of the three can solve the pain points of traditional assembly. For example, for the metal terminal of an automotive sensor, if the traditional method of first injecting the plastic base and then manually installing the terminal is used, not only is the efficiency low, but poor contact is also likely to occur; however, through determining the terminal position via injection molding design and achieving precise bonding through insert molding process, insert injection molding is finally completed, and the part qualification rate is increased from over 85% to over 99%. BOST is a professional injection mold company. For such automotive-grade parts, it will add "anti-leakage grooves" in the design stage and match a temperature monitoring system in the process to ensure that the bonding strength between inserts and plastic meets the automotive industry standards (tensile force ≥50N).

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FAQ

FAQs

What is the delivery lead time? Do you offer global logistics?

Standard products: 5–15 working days; custom modifications: 2–4 weeks. We support global air/sea freight and provide export customs clearance documents (including REACH/UL certifications).

How do I select the appropriate engineering plastic grade for my product?

Selection should be based on parameters such as load conditions (e.g., pressure/friction), temperature range, medium contact (e.g., oil/acid), and regulatory requirements (e.g., FDA/RoHS). Our engineers can provide free material selection consulting and sample testing.

What is the minimum order quantity (MOQ)? Do you support small-batch trial production?

The MOQ for standard products is ≥100kg. We support small-batch trial production (as low as 20kg) and provide mold testing reports and performance data feedback.

Can Bost customize modified plastics with special properties?

Yes! We offer modification services such as reinforcement, flame retardancy, conductivity, wear resistance, and UV resistance, for example:
• Adding carbon fiber to enhance stiffness
• Reducing the coefficient of friction through PTFE modification
• Customizing food-grade or medical-grade certified materials

What are the core advantages of Bost engineering plastics compared to ordinary plastics?

Bost engineering plastics feature ultra-high mechanical strength, high-temperature resistance (-50°C to 300°C), chemical corrosion resistance, and wear resistance. Compared to ordinary plastics, their service life is extended by 3 to 8 times, making them suitable for replacing metals in harsh environments.