Custom Injection Molding

Custom Injection Molding

Our rich experience as a USA plastic injection molding company includes production capabilities for many different industries, plastic materials, and specialty add-ons for your custom plastic parts.

Our focus is on production runs of 100 to 100,000 units per order. We know every custom injection molding project is different, but every MSI Mold customer enjoys our key values:

  • High quality custom plastic injection molds and custom parts with reliable on-time deliveries
  • Outstanding attention to customer needs through advanced quality planning
  • Fast quotes and delay free communication
  • Friendly and knowledgeable customer service
custom injection molding

What Is a Custom Plastic Mold?

A custom plastic mold involves the creation of a specialized and unique mold that’s used to manufacture a specific product to meet a requirement. If you need to manufacture hundreds or thousands of quality custom parts, making a plastic mold that meets your exact requirements is essential.

As the first step in your process, a quality-built mold demands effective communication. Our design experts work with you each step of the way. We ensure you receive a top-quality mold that meets the specific conditions unique to the part you are manufacturing.

Custom plastic injection molding utilizes analytical tools, scientific approaches and consistent molding processes to achieve your project’s precise goals. Our injection molding experts communicate and work closely with our customers on advanced quality planning as a blueprint for making sure they get high-quality custom plastic parts.

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.

Custom plastic molds

Components of Injection Molds

An injection mold consists of a series of metal plates with intricate machined components on both the cavity-side and core-side insert.

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
custom plastic molds

Construction of Custom Plastic Molds

Creating custom molded plastic parts involves two primary 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 molds. Our mold designers define the mechanical dimensions and shapes of the mold details using CAD software, then translate those into manufacturing drawings.

These drawings and 3D CAD models 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.

Factory producing injection molded products

Do Plastic Injection Molds Wear Out or Have a Limited Production Life?

Plastic injection molds can wear out due to friction or repeated contact between parts over thousands of cycles. Wear primarily affects gates, slides, ejectors and other moving elements within the mold. When components slide or touch against each other, they eventually show signs of wear.

This is a standard expectation of plastic injection molds that require hundreds of thousands of parts or cycles across a project’s life expectancy. At MSI, we warranty the production life of the custom plastic molds we build for our clients.

If we build your mold and we run your production you will never see another tooling charge, and our in-house mold makers will perform all required maintenance on your mold for the life of your project.

Our focus on reliability and excellence makes us a clear choice for your custom plastic injection molding needs. We invest time and energy into communicating with our customers, ensuring you get the best, high-quality molded plastic parts possible. Contact us today to discuss how MSI can make your next mold build project a success.

How Does the Quality of the Mold Affect Part Quality?

Building a high-quality mold is the first step to receiving high-quality custom molded plastic parts. Although there are a few types of part defects that can be dealt with after the injection molding process is complete, the best way to ensure you receive good parts consistently from your injection molding supplier is to make sure they’re making a plastic mold that produces good parts without secondary handwork operations.

plastic molding company

Plastic Injection Molding Challenges

Two of the biggest hurdles of every plastic injection molding project are the cost and lead time.

At MSI Mold, we overcome these challenges by building all injection molds in-house. We have also developed rapid tooling systems that reduce costs and improve lead times without sacrificing quality.

Having your custom plastic mold and 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, 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.

logo of MSI mold, a U.S.-based plastic molded parts manufacturer

Mold & Part Costs

Target Cost Planning for Custom Injection Molding

The cost of custom plastic injection molding for long-term production varies greatly. Simple molds may range anywhere from $3,000 to $10,000. More complex, multi-cavity or high-production molds cost significantly more from tens of thousands to hundreds of thousands of dollars. Calculating injection mold prices involves assessing many factors, such as:

Factor #1

Part Complexity

Part design features such as sharp corners, thin ribs, or undercut features require more expensive tooling and, frequently, a secondary EDM machining process. During a quote consultation we will point out part design considerations that can reduce overall costs when possible.

Factor #2

Mold Construction

Of the two primary categories of injection molds, insert style molds will cost significantly less to create than free-standing molds. Insert style molds allow us to only make the mold components that are custom for each part shape, and there is no sacrifice of part quality, mold quality, or mold life.

Factor #3

Number of Mold Cavities

The lower the number of mold cavities, the fewer parts will be produced per machine cycle, meaning a higher cost per part. Though a one cavity mold will be less expensive, there is an inverse cost relationship between adding mold cavities and the cost of the parts.

Factor #4

Part Size

Simply put, the larger the part, the higher the costs will be for the injection mold and the parts. Small plastic parts only require small machinery to make molds and parts, and large parts require large machinery to produce the molds and parts. The machinery & equipment costs for injection molding companies are proportionate to the size of the equipment.

Factor #5

Material Choice & Part Weight

The plastic material chosen for a part not only affects the weight of the part, but it also impacts production rates, which is a considerable cost factor for custom injection molding. Heavy thick-walled parts will cost a lot more to produce than parts that are designed with weight reducing features. When choosing the material for your custom molding project, consider the part’s function, application and environment, as well as the following features of the raw plastic: -Flexibility for function -Impact strength against breakage during use -Environmental temperatures -Cost and availability -Recyclability requirements Your plastic material’s density is a vital element to consider as raw plastic material ranges from $1 to $25 per pound. In addition, different families of plastic materials can process faster or slower within injection molding applications which directly affects the long term cost of the parts.

Factor #6

Cycle Time

The length of time it takes a molding machine to finish a complete production cycle from mold closing through ejection of the parts is called cycle time. The cycle time (amount of time it takes to create a part) is the single largest cost factor in custom plastic molding aside from plastic material costs.

Factor #7

Extra Add-On Costs

Specialty packaging, secondary operations like pad printing and extra machining contribute to a higher cost for custom plastic parts. In very low order quantities these add-on costs can be very expensive.

Mold Cost Relationship to Mold Cavities and Part Cost Relationship to Mold Cavities

Selecting Materials for Your Custom Plastic Injection Mold

Since there is a wide variety of material options for custom plastic molding, it is most helpful for product engineers to focus on the primary function and working environment of their parts. This allows a narrowing down of the right material for your custom injection molding project.

At MSI Mold we are happy to provide consultation to help customers find the right plastic material choice for their custom molded parts.


Choosing the right material hardness depends upon the part’s intended use, environment, required abrasion resistance, and how a user will interact with it. Plastic hardness is measured and represented by number values on “shore 00”, “shore A” or “shore D” scales. For example, a gel shoe insole might have a hardness of “30 shore 00”, but a construction worker plastic hard hat might have a hardness of “80 shore D”.

Flexibility & Impact Resistance

Different from hardness, flexibility or stiffness indicates how much or little a material will resist stress. Impact resistance is another specification to consider for plastic materials that might see tough conditions across wide ranging temperatures.

Part Weight

The mass or density properties of plastics can vary widely. In turn, for any given part volume in cubic cm the part weight can vary widely simply by picking a different plastic material. Keeping in mind that plastic raw materials are sold by the pound, unnecessary costs can add up very quickly throughout a product life cycle if the wrong plastic material is chosen.

Material Cost

Fitness for the product application should be the primary concern when choosing the plastic type for a particular custom molded part. Cost per pound should only be considered where there is a choice of suitable materials.

Types of Plastic Materials Used

We use many thermoplastic materials for your custom plastic part needs. Many of the plastics listed here are always in stock and ready for production. If your product needs a custom color we can help!

  • ABS
    Acrylonitrile Butadiene Styrene
  • ASA
    Acrylonitrile Styrene Acrylate
  • HDPE
    High Density Polyethylene
  • LDPE
    Low Density Polyethylene
  • PA 6
    Nylon Type 6, Aliphatic Polyamide
  • PA 66
    Nylon Type 66, Aliphatic Polyamide
  • PC
  • PC/ABS
    Polycarbonate + Acrylonitrile Butadiene Styrene
  • PMMA
  • PP
  • POM
    Acetal, Polyoxymethylene
  • TPE
    Thermoplastic Elastomer
  • TPO
    Thermoplastic Polyolefin
  • TPU
    Thermoplastic Polyurethane

Equipment We Use

As a reputable plastic molding company, MSI Mold uses a variety of technologies for designing and manufacturing molds and custom plastic parts, including but not limited to:

Modern CAD Software

Computer-aided design software allows the manufacturer to take a simple 2D drawing and create an optimized 3D design for your parts and injection molds. Our knowledgeable and friendly technicians put their expertise to work on designing custom parts and molds for your manufacturing needs.

In-House CNC Machining

Computer numerical control is a technology that uses a software program to direct the manufacturing equipment in machining the part shape and features into the plastic injection mold. This process is how aluminum or tool steel is machined to form the custom injection mold for production. Our mold manufacturing processes are fast and produce high-quality injection molds in-house.

All-Electric Servo Injection Molding Machines

At MSI Mold, all of our injection molding machinery is modern all-electric servo driven. That means our machines use 50-70% less energy than traditional hydraulic pump motor driven molding machinery of the past. We are proud to say that in addition to being environmentally and workplace cleaner, our machinery is the most precise and repeatable that is available in our industry.

High quality parts that'll meet your expectations.