Plastic Injection Molding Process

Once your plastic injection mold tools are ready, the molding process consists of the following basic steps:

Step 1. The plastic resin comes in raw pellets. These are dried to the right moisture content, and then if necessary they can be blended with pigments or master batch colorants.

Step 2. The dried pellets are poured into the hopper of the molding machine. A reciprocating screw inside the barrel of the machine will transport these pellets towards the mold.

Step 3. Within the barrel, the pellets are mixed and heated until fully molten, forming the liquid resin.

Step 4. The heated mold closes automatically and resin, under great pressure, is injected through a gate and into the mold cavity.

Step 5. The mold is cooled to solidify the part inside.

Step 6. The mold opens and the part is ejected to begin a new cycle.

Plastic Injection Molding Tolerances

All plastic material will expand and contract under the influence of heat and moisture. Our tolerance guide will give more general information on the characteristics of most common resin types for typical part features.

We will work closely with you to optimize your designs for manufacturing. We will indicate any areas where poor design may produce thermal stress, shrinkage, warping, etc. Consult our design guide for more information on common defects and how to avoid them.

Unless otherwise specified, we comply with the DIN 16742 standard tolerances for plastic injection moldings. Read about the visual quality standards that we apply to injection molded parts.

Plastic Injection Molding Materials

Mold Tools

We make injection molding tools and dies from Aluminum 7075, P20 and NAK80 semi-hardened steels and H13 fully-hardened steel. Additionally, we offer standard SPI finishes, EDM texturing and a range of etched textures.

Each of these material types will have distinct advantages for certain applications. Considerations include:

Cost of the raw material

Durability and resistance to corrosion or abrasion

Machinability

Ability to take a high surface polish

Time required for heat treatment

Expected tool life

Contact our technical specialists to learn more about which one is right for you.

Plastic Injected Parts

There are thousands of thermoforming and thermosetting plastics to choose from for your project. In addition, mechanical and chemical characteristics can also be enhanced with additives like glass fibers, UV stabilizers and lubricants. Our materials sheet will give you more detailed information about the standard types and the tolerances to expect with each.

Your choice of resins may depend upon one or more of the following considerations:

UV, chemical, abrasion and impact resistance

Cost of raw material

Mechanical strength

Weight and density

Flexibility

Transparency

Recyclability

Contact one of our technical specialists to learn more about material properties.