Plastic Injection Molds

Plastic injection molding is the process used to produce high volumes of finished plastic parts for commercial and industrial use. From intricate surgical clips to automobile tires, the applications span a range of industries. In combination with digital design technology, molds for plastic injection are capable of producing complex plastic parts at high yields. MSI’s plastic experts look forward to working with you to produce a quality, cost-effective product that serves your operation’s unique requirements.

In-House Mold Builds

Our mold build area is staffed with experienced designers and machinists using the most modern software and CNC machinery. After all customer part designs are approved for manufacturing our team will design and build robust trouble free plastic injection molds for your production.

Molds For Plastic Injection

Receiving high-quality plastic parts starts with buying a quality built mold. We’ll work with you every step of the way to ensure you’re familiar with the different types of molds for plastic injection available, and we’ll make sure you’re informed before you buy.

Insert molds have a cavity side and core side insert that fit inside of a custom mold base here at MSI. They are a great way for us to offer customers economical tooling at very rapid lead times. The insert style design is great for small and medium size parts that require low quantity part orders or fast delivery of parts. Even though insert molds are low cost in basic design, they are made with the same high quality materials and components as free standing plastic injection molds and provide the same high quality defect free parts.

  • Low cost
  • 2 to 10 day lead times​
  • Good for small parts
  • Good for 1 cavity molds and small order quantities

Free standing molds, also known as stand-alone molds, provide an all-in-one design. They are built to include the mold base, inserts, and all components needed to be fully functional alone. A properly designed free-standing mold is built for production inside any SPI standard injection molding machine that is sized properly for the mold. Stand-alone molds have a higher cost, but they are a good choice for multi-cavity production and with high-quantity orders. A summary of the primary features of free-standing molds for plastic injection includes:

  • Higher cost
  • Lead times of one to eight weeks
  • Best method for parts that will not fit into insert molds
  • Best choice for multi-cavity molds to reduce part cost

Whatever type of injection molding you need, MSI’s digital technology provides the map for turning your vision into the product your operation needs.

plastic injection molds

Digital Technology

The use of digital design technology is responsible for many of the desirable features you have come to expect in plastic injection molding. Productivity is more efficient, which means higher yield, reduced cost and reduced labor intensity. MSI uses the latest computer-aided engineering technology to ensure our molds for plastic injection do the job you need them to do.


The first injection molding machine was created in 1872 for a billiard-ball manufacturer. Today, plastic injection molding is the industry standard for products in dozens of industries, including the following:

  • Aerospace
  • Machinery
  • Engineering
  • Electronics
  • Aviation
  • Marine
  • Home Appliances
  • Packaging
  • Entertainment
  • Recreation
  • Automotive

MSI strives to accommodate specified elements such as thermoplastic material and color pigmentation. While these and other aspects may differ depending on your product’s unique qualities, the basic process is consistent whether your product is for a hearing aid or a control-panel knob.

Injection Molding Process

Injection molding requires three primary components – an injection molding machine, a mold, and raw plastic material. Molds for plastic injection consist of pre-hardened steel formed into two halves that join inside the molding machine and form your product. The machine injects molten plastic into the mold, where it solidifies to become the final product. The four-step process cycle is fast, generally lasting no more than a few seconds to two minutes. The first step is preparing the mold.

Clamping – Before the injection takes place, the two halves of the injection mold are clamped together securely to minimize leakage of the liquid plastic. The injection molding machine is equipped with a hydraulic clamping unit that pushes the two molds for plastic injection together with the force required to seal them.

Injection – Raw plastic, generally in the form of small pellets, is loaded into the injection molding hopper. The plastic material heats up as a screw-type plunger advances it toward the mold. Once the plastic reaches the targeted temperature, the machine injects it into the mold, pushing it into the endpoints of the mold cavity. Injection is a quick process. The exact duration depends on the volume and temperature of the melted material as well as the injection power.

Cooling – As soon as it contacts the internal mold surfaces, the molten plastic begins to cool. The cooling process solidifies the shape and rigidity of the newly molded plastic part. Cooling time depends on the thermodynamic properties of the plastic and the maximum wall thickness of the part.

Ejection – Molds for plastic injection are designed to open once a specified cooling time has elapsed. Then, the ejection mechanism pushes the product out of the mold. Depending on the type of thermodynamic plastic used, a mold-release agent may be applied to the mold surface prior to injection. Once the new part is fully ejected, the mold is ready for use on the next part.

Before the final product can be packaged, it undergoes post-processing to remove bits of excess material. The excess can be recycled into the next batch, so the process creates minimal waste. Aside from this, no finishing is needed.

MSI is committed to staying current with developments in molds for plastic injection and plastics technology, in general. We always employ modern and technologically driven systems. We specialize in production runs of 100-100,000 units, and our plastic experts look forward to working with you to produce a quality, cost-effective product that serves your operation’s unique requirements.


High quality parts that'll meet your expectations.

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