Precision injection molding ensures a molded component is repeatable every time, from lot to lot, regardless of the annual production volumes. However, not every molder provides the same level of experience/awareness or fully embraces the use of scientific molding principles in their pursuit of high-quality parts. There are several critical factors that need to be considered for success with an injection molding project, including choosing the right partner who: understands the entire development process, can participate in the part design & the material selection, and can properly manage the tool design.
Choosing the right manufacturing partner is an important first step in creating a quality part. Engaging with the right partner from the beginning will minimize potential issues through the commercialization process. It is crucial to find a manufacturer that specializes in precision molding with an in-depth knowledge of tooling and the entire molding process. This can help reduce development cost and prevent delays in product release. The right contract manufacturer will have experts in design, manufacturing, tooling, and quality.
Precision molding begins with good part design and the right partner will spend the time to review each part to ensure it is manufacturable. A knowledgeable manufacturer can assess manufacturability and make suggestions for how to revise the model to improve tooling conditions. Beyond the 3D geometry, the part drawing holds the key to success for the manufacturer.
Selecting the right resin is another critical factor for production of precision parts. A partner knowledgeable in the properties of all types of thermoplastics can facilitate the early selection of a material that is properly suited to each part/device.
- Expected service life – is the device reusable or disposable?
- Service environment – will it be exposed to chemicals, high stresses, or high temperatures?
- Sterilization method – will gamma radiation discolor the resin?
- Relation to other parts – are there moving parts or tight fits?
- Tolerances and form – will the material induce warp or changes in shrink rate?
A good manufacturing partner will consider the customer’s short- and long-term sales goals, and will recommend an appropriate tooling plan which may involve: true prototype tools to aide in part-design verification; bridge tools to allow fully qualified entry to the market without high capital costs; and/or multi-cavity tools to ensure production volumes or price targets can be met.
There are numerous factors the tool shop and the molder must consider to achieve optimal parts, such as ensuring good cooling and venting, proper ejection, and gate location/style/size to minimize warpage or cosmetic issues. The more complex the part, the more ‘action’ the tool will have, and the more considerations must be made for long-term wear and serviceability.
With proper tool design and solid craftsmanship, the process engineer will have the best opportunity to establish a robust molding process. Coupled with a good tool-maintenance program, the experienced CM will provide consistent part quality over long periods of time.
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