Injection molding is a great manufacturing technology that produces large amounts of parts repeatedly at a low cost. Plastic injection molding uses a combination of thermal principles and pressure to create the parts and components you need for your business.
During plastic injection molding, a plastic material is melted into a liquid state and then forced into a mold under high pressure. The part quickly cools and solidifies to create the unit.
Plastic injection molding offers a wide range of unique benefits. It allows companies to produce parts in complex shapes that would be too difficult or costly to machine otherwise, and it also allows many plastic parts to be created at the same time, making it ideal for high-volume applications.
Other key advantages include:
The injection molding process also produces very little waste, since the unused plastic scrap can be easily recycled and used in other molding products.
Choosing the right tooling is critical to cost, speed, and part quality
Tools can include automation, slides, multi-cavities, and/or family setups. Here are the different types of tools available:
This tooling option is used when companies need parts very fast for testing, prototyping, or production. Tolerances and the number of parts produced varies, and parts are also restricted by size and material. Rapid 3D printed tooling is typically ideal for small parts composed of low-temperature materials like TPU, ABS, PP, and PE.
This is a great option to get parts fast. Lead times are generally in as little as three weeks depending on size and complexity. Molds are usually good for 2,500 parts or less and can be created in single, family, or multi-cavities.
In the niche markets of today, all parts do not need big, expensive steel tools. Over the last 20 years, The Technology House (TTH) has worked with production aluminum tools and Master Unit Die (MUD) inserts that allow for shorter lead times and lower costs.
When tolerances are tight and volumes are high, the best option is steel tooling. Steel tooling gives you consistency from part to part at high volumes and is ideal for projects exceeding 20,000 parts.
Use these questions to determine the right tooling approach for your project
Pre-production projects typically use aluminum tooling for faster lead times and lower costs. Production projects require evaluating annual usage and lifecycle.
If the material requirement isn’t needed, see alternative RTV Molding and 3D Printing options.
Larger parts require standalone tools, while smaller parts can often use insert tooling for cost savings.
Insert tools are extremely popular for smaller components. Instead of paying the full price of a standalone tool, TTH can build an insert tool that fits into the (standard MUD) base unit on our press.
For example, if you have a small 3″x 2″x 1/2″ housing that needs to be produced via injection molding, TTH will build an insert tool out of aluminum or steel that fits into preexisting bases on our press instead of building a full standalone tool for the small part. This is an extremely economical, waste-minimizing method of producing smaller components. TTH offers insert sizes ranging from a 5″x 5″ all the way up to an 11″x 14″.
Low volumes typically use single cavity tools, while higher volumes benefit from multi-cavity tools.
When part quantities and the life of the project are unknown, or there is no solid forecast, single cavity tools are a good place to start. You can always consider building multi-cavity tools later on. Multi-cavity tools come with a little more upfront cost, but they can significantly lower part piece prices.
Yes—mild injection mold resins like polypropylene extend tool life, while harsher materials like glass-filled nylon increase wear. This can be a crucial deciding factor when your part has a life of 8,000-12,000 pieces, and you’re deciding between aluminum or steel tooling.
Yes—features like undercuts, cores, textures, and finishes all impact tooling decisions.
Aluminum tools: 2,000–10,000 parts, depending on type of aluminum, part material, and geometry.
Steel tools: 100,000+ parts, depending on material and geometry.
Most, if not all, tools will eventually require some degree of maintenance after being in production for some time.
Aluminum: 4-6 weeks for small parts and 6-10 weeks for larger parts.
Steel: 6-8 weeks for small parts and 8-12 weeks for larger parts.
Steel tooling typically costs 20–30% more than aluminum tooling.
A wide range of materials to meet performance and regulatory needs
One of the many positives associated with plastic injection molding is the wide variety of material options available to manufacturers and designers.
Some of the more common materials include:
Injection molded parts can be customized with a wide range of finishes, from high-gloss diamond buff finishes to textured and blasted surfaces.
The table on this page outlines SPI finish standards, including diamond, paper, stone, and dry blasted finishes—along with their roughness comparisons and applications.
Key design considerations for successful injection molding
Consistent wall thickness helps reduce warping, ensures proper filling, and minimizes shrink variability. Ideally, there should be no variation, but ribs should only be 60% at its base of the wall it intersects.
Parts must have a gate, or an opening that allows the plastic to be injected into the mold. Gates should enter the thickest part of the cavity and flow toward thinner areas. Placement should be on non-cosmetic surfaces when possible.
Radii, in particular fillet radii, should be applied at the base of all interior ribs and walls. In general, plastic doesn’t like sharp corners for a couple of reasons:
Sharp corners are stress risers that can cause part failure. The radii allow the molten plastic to navigate around the corners while reducing the molded stress and pressure to fill the tool.
Draft, when the side walls in the mold are tapered in the same direction that the mold opens, facilitates the removal of the part from the mold.
It’s important to note that different degrees of draft are required based on part geometry and surface texture. A tool should use at least one degree of draft for all vertical surfaces (two degrees works very well for most parts). TTH can add various textures to the tool.
Soft tooling uses aluminum for prototyping, usually only good for a couple thousand parts. Hard tooling uses steel for production and longer tool life. Usually, tools are created using steel for better tolerancing, repeatable cycles, reduced cycle times, and extended tool life.
Insert set tooling involves modular tools where the core and cavity are created in different sizes that fit into standard MUD bases, and can be aluminum or steel. Insert set tooling helps reduce cost, inventory space, build time, and setup by using interchangeable inserts.
This type of tooling is used for smaller- to medium-sized parts.
Hand loads and slides are pieces of tools that are needed to create features that are not in the line of the draw when trying to open a tool. In both cases, the tool sections must be removed from the tool before the tool can open.
With a hand load, the operator must physically remove the tool section to open and close a tool for molding. Hand loads should be easily handled and should not be too large or heavy. Using hand loads is a great way to reduce the upfront cost of a tool, but hand loads increase part cost and tool maintenance, and result in longer cycle times. They’re good options for prototypes, bridges, and low-volume tools for smaller- or medium-sized parts.
With a slide, the molding process is done automatically. Slides in tools increase the initial tool investment, though over time, it reduces costs by cutting cycle times and the risks associated with operator handling. Use slides in your tools when you want to reduce risk and piece prices or you want consistent high volumes.
A process where a material is molded “over” a substrate, typically a rigid plastic or metal part, that we then “overmold” with an elastomeric or rigid material to create multi-material parts.
An example of this would be rigid handles with soft grips. To do this, we would create two separate tools, one tool for the substrate and the other tool for the overmold. These can be in the same tool or different tools but must be separate cavities.
Best for high-volume production, repeatability, and low per-part cost when designs are finalized.
From prototype to production—all under one roof
Whether you need to move quickly through early-stage prototyping, bridge into production, or scale to high-volume manufacturing, TTH adapts to your timeline, volume, and complexity.
Your parts are produced using a wide range of materials and processes, with the flexibility to support everything from small, intricate components to large, high-volume production runs—up to 1,000,000 parts or more.
You’ll have access to the right equipment for your application, ensuring your parts are manufactured efficiently, consistently, and at the scale you need.
From initial design through tooling and production, your project is approached with a full-service mindset—so every decision is made with your end-use, cost, and performance goals in mind.
We provide domestic and international tooling options, including aluminum and steel tools, as well as MUD insert systems. We also conduct mold flow analysis and process validation to ensure optimal results.
We offer a full range of finishing options, including high-gloss, matte, textured surfaces, custom colors, painting, labeling, and more.
Efficiently create hundreds or thousands of custom parts in many shapes, sizes, and materials with aluminum and steel tooling tailored for your prototype, bridge, or production injection molding project.
Personalized quoting—no auto-quote. We offer a consultative and personalized approach for your project to determine the best result.