1.First, in order to begin evaluating plastic injection molding companies, it is important to know what you need them to mold for you. Specifically, you will need to have a fully defined 3D Model and engineering drawing of the plastic component you wish to have molded. Be sure to fully specify draft angles and surface textures in drawing.

2.Next, it is critical to realize that for most companies seeking an injection molding supplier, for right or wrong, the largest factor tends to be cost. Going oversees to places like China or Korea usually results in a lower piece cost than staying in the United States. However, this savings in cost per molded part can be offset by delays in getting the product to market.
Based on the project your company is working on, determine if there are absolute restrictions on price as this will be important to know.

3.Next, when evaluating a potential injection molding company, it is very important to learn about the history of the company and their capabilities. How long have they been in business and what industries do they typically mold parts for?
If you have a part that requires extremely tight tolerances, an injection molding company in the health or aeronautics industry may work out better than a company that molds toys.

4.After you learn about the background of the company, investigate their capabilities. What type of molding capabilities do they have? Do they have any specialties such as 2-shot molding or insert molding?
What type of presses do they use and how old are they? Are they able to handle the volumes or quantities that you require?
As alluded to earlier, lower molded component cost does not always translate to an overall savings. Depending on the quality control of the molder, their quality may be sub par resulting in delays in the schedule or worse...returned product from the customer.
Take some time to understand how the plastic injection molding company monitors and ensures quality. Do they do control charting? Are they ISO certified? Ask to see examples of quality records/documentation for some of their recent projects.
If some unacceptable product is found during an audit, what is their corrective action plan? Do they quarantine the last X hours of product?

5.Lastly, the location of the supplier can also be very important. Where are they located and how will this impact your working relationship? Having an injection molding supplier "right in your backyard" so to speak is great as it allows you to make day trips to the supplier when issues arise. Contrast this to going overseas to an Asian supplier where it will cost thousands of dollars per person per trip to visit.

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