Manufacturing – Plastic Injection Molding

Fourté’s capabilities include plastic injection-molding for thermoplastic materials. Our New Product Introduction (NPI) and Engineering staffs have years of experience on tooling complex injection molded parts. By understanding your design intent , we then design and fabricate molds to your product specifications.

Injection molds are used for high volume parts. Customer’s parts are created by making a mold for the part using tool steel. The mold is then placed into an Injection Molding machine for fabrication of the parts.

Injection molding is used to create many things such as wire spools, packaging, bottle caps, automotive dashboards, pocket combs, some musical instruments (and parts of them), one-piece chairs and small tables, storage containers, mechanical parts (including gears), and most other plastic products available today. Injection molding is the most common method of part manufacturing. It is ideal for producing high volumes of the same object. Some advantages of injection molding are high production rates, repeatable high tolerances, the ability to use a wide range of materials, low labor cost, minimal scrap losses, and little need to finish parts after molding. Some disadvantages of this process are expensive equipment investment, potentially high running costs, and the need to design moldable parts.

Mold or die are the common terms used to describe the tooling used to produce plastic parts in molding. Since molds have been expensive to manufacture, they were usually only used in mass production where thousands of parts were being produced. Typical molds are constructed from hardened steel, pre-hardened steel, aluminum, and/or beryllium-copper alloy. The choice of material to build a mold from is primarily one of economics; in general, steel molds cost more to construct, but their longer lifespan will offset the higher initial cost over a higher number of parts made before wearing out. Pre-hardened steel molds are less wear-resistant and are used for lower volume requirements or larger components. The typical steel hardness is 38–45 on the Rockwell-C scale. Hardened steel molds are heat treated after machining. These are by far the superior in terms of wear resistance and lifespan. Typical hardness ranges between 50 and 60 Rockwell-C (HRC). Aluminum molds can cost substantially less, and, when designed and machined with modern computerized equipment, can be economical for molding tens or even hundreds of thousands of parts. Beryllium copper is used in areas of the mold that require fast heat removal or areas that see the most shear heat generated. The molds can be manufactured either by CNC machining or by using electrical discharge machining processes.

Injection Molding Examples
• Pistol grip
• Communication enclosure
• Mounting brackets
• Cable organizers
• Tools that require low loads

Advantages
• High production rates
• Tight tolerances are repeatable
• Wide range of materials can be used
• Low labor cost
• Minimal scrap losses
• Little need to finish parts after molding

Accuracy and Repeatability of Process
Injection molding is a repeatable process; accuracy of the finished part is a function of a controlled machine process, environmental changes and the quality of the tool made to create the part.