Process

• The mold is typically made from hardened steel, aluminum, or other durable metals.
• It consists of core and cavity sections that shape the plastic part.
• During injection molding, molten plastic is injected into the mold, cooled, and ejected as a finished product.

Design: Firstly, according to the product’s shape, structure, and size requirements, designers use computer – aided design (CAD) software to create a 3D model of the mold. They consider factors like the parting line, gating system, and ejection mechanism to ensure smooth molding.

Material selection: Appropriate mold materials are chosen based on the product’s requirements and production volume. Common materials include alloy steel, P20 steel, and stainless steel.

Machining: The selected material is processed by various machining methods, such as CNC milling, turning, EDM (Electrical Discharge Machining), and grinding. These operations are used to form the cavity, core, and other components of the mold with high precision.

Assembly: After machining, the individual mold components are assembled. This involves precise alignment and connection of parts like the cavity and core, installation of the gating system, cooling channels, and ejection mechanism.

Testing and debugging: The assembled mold is installed on an injection molding machine for testing. Parameters such as injection pressure, temperature, and cooling time are adjusted to ensure that the mold can produce high – quality products.he Mold Making Process Includes:

Application

Injection mold making is widely used in the manufacturing of plastic products, such as automotive parts, electronic product housings, medical devices, and daily – use plastic items. It enables the mass production of complex – shaped plastic parts with high precision and efficiency.

Why It Matters:

Injection mold making ensures high repeatability, precision, and production efficiency, and is essential for industries such as automotive, electronics, and medical devices.

What Are Injection Molds?

Injection molds are precision tools used in the injection molding process to produce plastic parts in high volumes. The mold forms the shape of the part by allowing molten plastic to be injected, cooled, and solidified inside a cavity.

Main Components:

• Core and Cavity – Form the external and internal shapes of the plastic part.
• Runner System – Channels (sprue, runners, gates) that guide molten plastic into the cavity.
• Cooling System – Circulates water to quickly cool and solidify the part.
• Ejection System – Removes the finished part from the mold (ejector pins, plates).
• Vent System – Allows air to escape during injection to prevent defects.
• Guiding System – Ensures precise alignment between moving and fixed mold halves.

Mold Types:

• Hot runner mold – Uses heated nozzles to keep plastic molten; reduces material waste.
• Two-plate mold – Simple and common; parting line separates core and cavity.
• Three-plate mold – Includes a separate runner plate; used for more complex parts.

Applications:

Injection molds are widely used in industries such as:

• Automotive (interior parts, housings)
• Electronics (device enclosures, connectors)
• Medical (disposable instruments, cases)
• Consumer Products (toys, packaging, containers)

Classification of Injection Molds

Category	Mold Type	Description
By Structure	Two-plate mold	Most common type; simple design with one parting line between core and cavity.
	Three-plate mold	Includes a runner plate; suitable for pinpoint gating and automatic runner removal.
	Hot runner mold	Uses heated channels to keep plastic molten; eliminates runner waste.
By Ejection Method	Ejector pin demolding	Uses ejector pins to push the part out; widely used.
	Ejector plate demolding	Suitable for larger or complex-shaped parts; uses a plate to push the product.
	Angle pin / slide core demolding	For parts with undercuts or side holes; enables side core pulling.
By Cavity Quantity	Single-cavity mold	Produces one part per cycle; ideal for precision or low-volume production.
	Multi-cavity mold	Produces multiple parts per cycle; increases efficiency.
By Runner Type	Cold runner mold	Unheated runner system; runner is removed after molding.
	Hot runner mold	Runner remains molten; improves efficiency and saves material.
By Application	Standard injection mold	Used for general engineering plastic parts.
	Optical / transparent part mold	Designed for clear plastics like PC or PMMA; requires high-polish finish.
	Two-shot / multi-color mold	For molding multiple materials or colors in one cycle.

Injection Mold Materials & Their Suitable Applications

Material	Suitable Products	Key Features
P20	General plastic housings, consumer goods (e.g., remote shells, daily items)	Cost-effective, easy to machine, ideal for medium-volume molds
718 / 738	Appliance parts, automotive interior components	Good toughness, suitable for multi-cavity and precision molds
S136 / 420	Transparent products (lenses, cosmetic containers), medical devices	Excellent polishability and corrosion resistance, ideal for high-gloss and clear parts
2316	Parts molded from corrosive plastics (e.g., PVC, POM)	High corrosion resistance, suitable for humid or acidic environments
H13 / SKD61	High-temperature plastics, engineering parts, hot runner molds	Superior heat and wear resistance, long mold life, ideal for high-volume production
8407 (Enhanced H13)	Precision connectors, small complex parts	Improved toughness and thermal stability for demanding molds
ASP23 / S390	Ultra-durable molds, high-wear inserts and sliding components	Extremely high hardness and wear resistance, suitable for extreme conditions
7075 / QC-10 (Aluminum)	Prototypes, short-run plastic parts	Fast machining, excellent thermal conductivity, lower durability

Injection Mold Materials & Their Suitable Applications

Material	Suitable Products	Key Features
P20	General plastic housings, consumer goods (e.g., remote shells, daily items)	Cost-effective, easy to machine, ideal for medium-volume molds
718 / 738	Appliance parts, automotive interior components	Good toughness, suitable for multi-cavity and precision molds
S136 / 420	Transparent products (lenses, cosmetic containers), medical devices	Excellent polishability and corrosion resistance, ideal for high-gloss and clear parts
2316	Parts molded from corrosive plastics (e.g., PVC, POM)	High corrosion resistance, suitable for humid or acidic environments
H13 / SKD61	High-temperature plastics, engineering parts, hot runner molds	Superior heat and wear resistance, long mold life, ideal for high-volume production
8407 (Enhanced H13)	Precision connectors, small complex parts	Improved toughness and thermal stability for demanding molds
ASP23 / S390	Ultra-durable molds, high-wear inserts and sliding components	Extremely high hardness and wear resistance, suitable for extreme conditions
7075 / QC-10 (Aluminum)	Prototypes, short-run plastic parts	Fast machining, excellent thermal conductivity, lower durability

 Material Selection Tips

• For clear or polished parts, use S136 or 420 for optimal surface finish.
• For corrosive materials (e.g., PVC), select 2316 or H13 to ensure mold longevity.
• For prototypes or low-volume runs, aluminum molds offer fast turnaround and lower costs.

Common Materials for Injection Molds

Choosing the right mold material is critical to ensuring mold durability, processing efficiency, and part quality. Below are some of the most commonly used materials for injection molds, along with their key features and applications: P20 – Pre-hardened steel ideal for medium-volume production. It offers good machinability and cost-efficiency for general plastic products. 718 / 738 – Modified P20 steels with better toughness and wear resistance, suitable for multi-cavity molds and automotive or appliance parts. S136 / 420 – Corrosion-resistant stainless steels with excellent polishability. Commonly used for optical parts, transparent products, and medical components. 2316 – Highly corrosion-resistant steel, especially suited for molds processing aggressive materials like PVC or POM. H13 / SKD61 – Hardened hot work tool steels with excellent thermal fatigue resistance. Ideal for high-volume molds, hot runner systems, and engineering plastics. 8407 – An improved version of H13 with higher toughness and thermal stability for complex or high-precision components. ASP23 / S390 – Powdered high-speed steels offering extreme hardness and wear resistance, used in high-performance or ultra-long-life molds. 7075 / QC-10 (Aluminum) – Lightweight aluminum alloys suitable for prototyping or low-volume runs. Fast to machine, with excellent heat dissipation.

Injection Mold Summary

Injection molds are essential tools in modern plastic manufacturing, enabling the mass production of complex parts with high precision, consistency, and efficiency. The quality of a mold—determined by its design, material selection, and machining accuracy—directly affects the performance, appearance, and dimensional stability of the final product.

From automotive and electronics to medical devices and consumer goods, injection molds play a vital role in ensuring reliable and cost-effective production. Choosing the right mold type and material is key to achieving optimal product quality and long-term manufacturing success.