The processes require advanced machining techniques, high-quality materials, and strict complying with design drawing. Let us to have an overview of the steps for manufacturing plastic injection molding tools to everyone. 

1. Material Selection for Mold

The mold material must withstand high injection pressures and repeated thermal cycling. Tooling steel is the best choice, if low-volume or prototype molds. aluminum material is considered available. In general term, Steel Molds are durable and repeatable, they are used for high volume production. We suggest that the below material as your choice.

P20 Steel belongs to Pre-hardened steel, commonly used for injection molds.

H13 Steel is Air-hardening steel and has excellent toughness, used for high-pressure or high-temperature molds.

Stainless Steel is possiblely Used in molds that prevent corrosion resistance from some corrosive material like PVC.

Aluminum Molds are lighter, easier to be machined, and suitable for prototype molds or a low volume production.

2. Machining the Mold Components

After the design and material selection,according to the designed drawing of the mold, the mold components such as core, cavity, and supporting components are machined. These components are all high precision, and require cnc machining process to finish.

1. CNC Machining

Large portions of the mold are shaped using high precision CNC milling machines. the core and cavity of the mold will be formed here. The mold base holds the core and cavity and is machined to fit the mold components accurately.

2. Electrical Discharge Machining (EDM)

EDM (or spark erosion) is used to create complex geometries. It also create sharp corners, deep cavities, and intricate details of the cavity. By electricity spark, and achieve supper high precision process for the mold.

3. Gun Drilling

Cooling channels, which control the mold temperature during production. These cooling channels are made by through hole drilled on the mold using specialized deep-hole drilling machines. Through water and oil, cycle inside cooling channels, provide a quick even cooling when the part solidifying.

4. The Mold Surface Finish

To have a desired surface result on the plastic part, the surface of the core and cavity of the mold accept grinding and polishing, keep proper alignment and seamless halves closing of the mold and minimizing flash of the part line. The below includes two types surface finishes. For high-gloss parts, the mold surfaces are polished to achieve a mirror finish . This ehances the appearance of the final part and ensures smooth ejection from the mold. For parts that want to a matte or textured finish, Engineers can etch and sandblast the suface of the mold to create the desired texture.

5. Mold heat treatment

To enhance the wear resistance of the mold, the mold should be heated by quenching and increase hardness of the surface of the cores and cavities of the mold. This makes the sufaces more wear resistance and withstand more repeatable action frictions during fast cycle injection actions. And produce more high quality qualified plastic injection parts and reduce mold maitenance and repair cost in high volume quantity production.

6. Assembly of the Mold

When finishing all the components machined , we will assemble the mold. Mounting the core on the male half of the mold, fix the cavity on the female half of the mold, and install the mold on the chassis of plastic injection machine, and assemble relatant components like ejector pins, sleeves on the area of the mold, connect to cooling channel with pipe and screws, and built a cooling system. Then begin alignment with two halves of the mold, adjust them position unitl the mold can run smoothly.

7. Testing and Mold Trials

After assembly, the mold is tested in a process called mold trials to verify that it produces parts according to specifications. We should do the follow steps to verify the performance of the mold. The rapid prototyping testing is done. The mold mounted in an injection molding machine has a trial testing. Feeding some plastic into hopper, start the plastic injection machine, begin first injection plastic molding test. Based on the trial results, optimize the mold’s performance. It involves of modifying gate locations, adjusting cooling channels, or fine-tuning ejector systems. Once the mold consistently produces parts that meet the required standards, mass production is proceed.

8. Maintenances and Repairs

Passing mass manufacturing for some time , These injection molding tools require regular maintenance. Proper care and timely repairs can significantly extend the life of the mold and ensure to have a high manufacturability. When the plastic injection process has a break down, Technician will check these mold component wear and testing the injection process. Maybe find some trouble and hidden problem in mass production, such as cleaning the mold between production runs, checking for wear, and applying lubrication. These can prevent premature damage. If defects like scratches, cracks, or wear spots appear in the mold, similar with high precision casting dies repair and maintenance , such as re-polishing, welding, or replacing components.