(Updated July 2021)

injection mold designed to optimize cycle times and reduce mold downtime.  

  1. Evaluate resources and technologies used to make injection molds
  2. Determine the injection mold classification your project requires
  3. Decide on injection mold type for your product.
  4. Research to choose the right molding partner

Thus, it is critically important to work closely with your injection mold builder from the beginning of your project to manage risk while helping keep the mold build on its timeline as well as on budget.

1. Evaluate resources and technologies to make injection molds

Tooling engineers utilize technologies to develop 2D and 3D computer generated files of injection molds and mold fill simulation software to create mold designs with proper actions, runners, gates, venting and cooling to achieve reliable and consistent plastic components.  From these 2D and 3D injection mold models detailed tool paths are created for specialized CNC machining. 

CNC high speed machining centers and EDM’s are using this software and other advanced technologies to help journeyman tool makers manufacture injection molds with enhanced accuracy, efficiency and precision. This provides an almost unlimited geometry which has become good news for the production of complex plastic components.

An injection mold building tool maker’s job requires advanced training to calculate the feeds and speeds required to make precise cuts with drills, end mills and other sophisticated CNC cutting tools - a job that requires a 4 to 5 year apprenticeship program, and significant on the job training. 

2.  Determine the injection mold type your project requires.

The Plastics Industry Association is responsible for establishing the customs and practices of the injection mold makers industry. This association classifies injection molds to help eliminate confusion and create uniformity between mold types in the mold quoting system, which increases customer satisfaction. These classifications are Class 101, 102, and 103 and are discussed below in more detail. It is essential to understand the differences between these three classes when sourcing tooling.

  • Class 101– is built for high production runs of over one million or more cycles. These molds are made with the highest quality materials, which makes them the more expensive molds. Mold base should be a minimum hardness of 280BHN, and molding surfaces (cavities and cores) must be hardened to a minimum of 48 RC. Steels moving against one another should be dissimilar and have a hardness differential of at least 4 Rockwell. Temperature control provisions are to be in cavities, cores, and slides wherever possible. 
  • Class 102– is built for medium to high production runs - not to exceed 1 million cycles. These molds are good for abrasive materials and/or parts requiring cost tolerances. Class 102 molds are fairly high-quality mold as well as being relatively high priced. This mold base should also be a minimum hardness of 280BHN, and molding surfaces (cavities and cores) will be hardened to a minimum of 48 RC. Temperature control provisions should be in cavities, cores, and slides wherever possible. 
  • Class 103 – is built for medium to low production runs of fewer than 500,000 cycles. The mold base should be a minimum hardness of 165 BHN and cavity and cores of 280BHN or higher.

3.  Decide on the injection mold type for your product

The selection of the type of injection mold needed depends entirely on the customer's requirements and product specifications; below is more detail on the various mold types. 

  • MUD units: these are standard frameworks for tools, allowing for custom machined inserts for specific components.
  • Unscrewing Molds: used when the plastic parts have details like threads or ridges that cannot be easily injected using the standard knockout methods. These parts are carefully unscrewed from the mold to avoid thread damage. To be cost-effective - these complex molds need to move at high speeds and clear previously molded parts efficiently to begin the next cycle. These types of molds are suitable for products like medical syringes, vials, caps, and connectors.
  • Action Molds: these molds have some mechanical action incorporated in the design to enable molding of complex parts and detailed geometry like a hole, slot, undercut or thread that is not perpendicular to the mold's parting line. 
  • Hot Runner Molds:  are typically more expensive to manufacture but allow savings by reducing material waste, cycle time, and labor costs. These molds can produce more complex components while providing a variety of gating options that improve part quality. 
  • Three plate Molds: these molds have a runner plate between a moving half and a fixed half. These molds have two parting lines and are picked for their gating location flexibility.
  • Family Molds: family molds are used when all the products being manufactured are from the same material. These help to eliminate color matching problems because the products are manufactured at the same time. It is crucial with these molds to have proper flow balance, runner shutoffs, and additional cooling circuit control.

4.  Research to find the right molding partner

There are many injection mold tooling partners to choose from, so it is imperative that you do your research to identify the right one! Below are a few topics to discuss with potential sourcing partners:

  • Tooling options and experience: look for a sourcing partner that offers a broad range of tooling options; the right sourcing partner will have extensive experience with the various tooling and material options available. Also, you need to partner with an injection molder, such as Crescent Industries, who has Design for Manufacturability expertise; this simply means the tool design and manufacturing teams are integrated to allow manufacturability. When issues are identified, than can be addressed during the design process instead of after the tool is fabricated – saving significant tooling development time and cost!
  • Materials: Many different materials can be used in the tooling process depending on the type of tool required and the timing required. The most common materials used in tooling include aluminum, steel, cast iron, carbides, and composites (REN). Certain supply partners specialize in the different material types, so learn the experience of a potential supplier.  
  • Volume Capabilities: To be cost-effective, make sure the injection mold is built based on the anticipated volume of parts the tooling needs to produce – not significantly more or less. If this rule of thumb is not adhered to, you will develop a tool that is not optimized for your volume needs, and you will likely pay too much for tooling, especially in the case of designing for too high a volume.
  • Quality and turnaround time: Finally, you need to understand the timeline for making tools – the fastest toolmaker is not always the right choice because, frequently, quality is sacrificed to make tools quickly. Take your time to find a sourcing partner that produces quality tools in a reasonable timeframe.

At Crescent Industries, we leverage our expertise as injection molders and our advanced technologies and equipment to produce quality injection molds for plastic components.  To get your project started right, go to the Steps for Launching an Injection Molded Project webinar.

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Topics: injection mold building