Custom Injection Molding
Creating Custom Plastic Parts
Plastic injection molding is the perfect solution for producing large quantities of identical or related parts with efficiency and precision. This versatile manufacturing process offers nearly limitless possibilities and is widely used across industries such as consumer electronics, automotive, medical devices, tools, toys, and packaging. Post-processing techniques can further refine parts, achieving specific finishes or textures to meet unique requirements. As a cost-effective method for mass production, plastic injection molding ensures consistency, quality, and value in every part produced.
Process Overview
How it works
Plastic injection molding is the process of making plastic parts using molten plastic and a metal mold. Pelletized plastic resins are melted and then forced into the metal mold. Molds are typically made of steel or aluminum and often have texture added to the surface of the mold to change the appearance of the parts. The molten plastic fills the cavity inside the mold, forming a custom plastic part and once cooled and re-solidified, the part is ejected from the injection mold.
KEy components
Injection Molding Machines (Presses): Melt and inject plastic into molds under high pressure.

Molds: Can be single or multiple part cavities, molds are designed with two halves that are pressed together in the injection molding machine and then separated to eject the part.
Steps in the process
- Pelletized plastic resin is melted and pushed into the mold.
- The mold stays clamped closed until the plastic solidifies.
- The mold separates and ejects the cooled part, and the cycle repeats.
Plastic Options
Plastic injection molding can be tailored to meet a wide range of needs, depending on the type of plastic used. Selecting the right material is critical, as plastics offer unique characteristics based on their chemical composition. Factors such as durability, flexibility, performance, texture, density, and color all play a role in determining the best fit for your project.
At Susquehanna Plastic Injection Molding, our experts can guide you in choosing the perfect plastic to match your part's application. We work with a wide variety of materials to ensure your project meets its specific requirements. Some of our plastics include but are not limited to:
- Acrylonitrile butadiene styrene (ABS)
- Acetal
- Acrylic
- Nylon
- Polycarbonate (PC)
- Polyethylene (PE)
- Polypropylene
- Polyphenylene
- Polysulfone
- Polystyrene
- Polyurethane
Plastic Injection Molds
Plastic injection molds can range from simple designs to highly complex systems. A basic mold consists of two halves that separate after the plastic is injected and cooled, allowing the part to be ejected.
For more intricate part designs, molds can incorporate advanced features like side-pull mechanisms or core pull. These actions allow the mold to create detailed features like undercuts and hollow parts with intricate features. At Susquehanna Plastic Injection Molding, we specialize in creating molds that meet even the most demanding design requirements.
Multiple-Cavity Molds and Family Molds
Plastic injection molds aren’t limited to producing just one part at a time. Molds can be designed to create multiple identical parts or multiple different parts related to the same product in a single production cycle. This flexibility allows for higher efficiency and faster production for larger quantities of parts.
Molding Trials
A molding trial ensures all parameters are set correctly for a new injection molding job. The process starts with minimal parameters and gradually increases to fill the mold. Injection rate and pressures are adjusted to achieve the correct part weight and eliminate defects like sink marks. Once optimized, the process is documented for consistent future production.
Cycle time, determined by time for material loading, injection, cooling, mold opening, and part ejection, is crucial for efficiency and cost. Modern presses have made plastic injection molding more sustainable and cost-effective.
At Susquehanna Plastic Injection Molding, we can bring your ideas to life, starting with just basic sketches or concepts for your project, component, or production part. Our team will guide you through the process ensuring you feel confident at every stage of development.
