Plastic Injection Molds

Plastic Injection Molds

After a custom plastic part has been designed, making a plastic injection mold is the first step in creating custom molded parts. In combination with skilled mold designers, software technology, and the use of expensive CNC machinery, MSI builds molds for plastic injection that are used to produce high quality molded plastic parts.

Your mold is not only the largest up front investment in your injection molding project, its construction is also the most significant factor in the quality of the parts it will produce. If you are searching for an injection molding company in the USA to work with it's important that you find a supplier with in-house mold manufacturing capabilities to insure that you have single source responsibility on the project timeline and quality of your parts.

Our injection molding experts look forward to working with you on your mold build project as the next step toward manufacturing your custom molded parts. If you’re looking for an injection mold supplier, we have you covered.

In-House Mold Builds

All of MSI customer molds are built right here inside of our Michigan manufacturing facility. Our mold build area is staffed with experienced designers and machinists using the most modern software and CNC machinery. After customer part designs are finalized and approved for manufacturing our team will design and build robust trouble free plastic injection molds for your production requirements.

If your company requires new tooling for your injection molding project, you should want single source responsibility for the quality of your injection mold tooling and your production parts. If your injection molding supplier doesn't build your tooling in-house you could face significant quality problems, lead time delays, and unforeseen costs to your budget.

If you are an engineer or buyer responsible for sourcing a plastic injection molding supplier let us help you with high quality parts and tooling.
Plastic Injection Mold

Lifetime Warranty

Whatever type of plastic injection mold you need, we understand that your injection mold purchase will become a significant asset to your business. For that reason, we warranty the production life of molds we build for our customers for the life of their production requirements.

We will help you better understand plastic injection mold construction and their cost. The quality of your custom plastic parts will first depend on the quality of your mold. Let us quote your next injection molding project and we will work closely with you to make your project a success!

Molds for Plastic Injection

High-quality plastic parts start with a quality built injection mold. The mold for your custom parts can be a big investment, so we’ll work with you every step of the way to ensure you’re familiar with the different types of molds for plastic injection that are available, and we’ll make sure you’re completely informed before you invest. Below we provide you with a valuable understanding of basic injection mold construction types and the benefits of each.

Insert Molds

  • Low cost
  • Average lead times from 5 to 15 days​
  • Good for small parts
  • Good for 1 cavity molds and small order quantities
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.

Free Standing Molds

  • Higher cost
  • Average lead times of 3 to 8 weeks
  • Best method for parts that will not fit into insert molds
  • Best choice for multi-cavity molds to reduce part cost
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.

Why Do Plastic Injection Molds Cost So Much?

People often ask why plastic injection molds cost so much? Here is the answer –

Producing high quality plastic parts can only be achieved by using a high quality built mold. Molds for plastic injection consist of precisely machined components made from various metals such as aircraft grade aluminum or hardened mold steels.

These molds are designed and made by highly skilled and well paid people categorically called “mold makers”. They have spent years and possibly even decades being trained in the mold making trade.

Additionally, mold makers need very expensive tools to perform their job, such as very expensive software, CNC machinery, tooling, and precision fixtures. The amount of time that mold makers need to finish a plastic injection mold can range from a few days to several weeks depending on the complexity and size of the end product.

Advantages of Molds Made in the USA

Having your custom molded plastic parts made in the United States can offer consistent quality and lower overall costs. Modern USA plastic injection molding companies use high-tech equipment and offer reliable technical expertise.
In addition, if you source your project to a reputable USA injection molding supplier they will consistently use high-quality materials unlike many offshore suppliers.
When you hire injection molding experts in the USA like MSI Mold, you significantly lower the transportation expenses and have readily available access to customer service and communication. Interaction with our molding experts throughout the process ensures the timely production of the best possible molded plastic parts.

Components of Injection Molds

A plastic injection mold consists of a series of metal plates along with intricate machined components on both the cavity-side and core-side of the mold. All mold components are manufactured with very close tolerances and the overall quality of the mold will directly affect the part quality and the mold's useful life expectancy.

Cavity Side

The cavity side mounts to the stationary side of the machine platen and houses the following elements:
  • Locating ring
  • Sprue bushing
  • Guide pins
  • Clamp plate
  • Cavity block

Core Side

The core side mounts to the moving platen and contains these components:
  • Core block
  • Leader pin bushings
  • Support pillars
  • Ejector pins
  • Return pins
  • Ejector retaining plate
  • Ejector plate
  • Clamp plate

Manufacturing Of Custom Plastic Molds

Building plastic injection molds involves two primary machining methods, EDM and CNC machining.

EDM Machining

This process involves using a copper or graphite electrode to electrically burn the specified mold shape into the mold component. EDM machining is slower and more costly than CNC machining, and it is only used for mold features that are not practical to cut with a CNC machine, such as sharp corners and very thin rib features. The steps of this method include:

  • CNC machining the electrodes in a high speed CNC machine
  • Submerging the mold component and electrode in dielectric fluid
  • Programming an electrical discharge machine to sink the electrode into the workpiece with a precisely controlled pace and amount of electricity

CNC Machining

CNC machining uses advanced computer technology to cut complex and precise surface shapes into the mold materials. Our mold designers create a 3D model with the required mechanical dimensions and shapes of the mold details using CAD software. Final mold designs that are ready for machining can take one or two weeks to complete.

The 3D CAD models within the final mold design are then used within our CAM software. Our CAM programmers can tell the software how to machine the raw metal into the final mold shape and the software creates the commands to execute in our CNC machines.

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