Everything you need to know about injection molding

What is injection molding?

Injection molding is a manufacturing process for producing parts in large volumes. It is generally used in mass production processes where the same part is created thousands or even millions of times.

Why use injection molding:

The main advantage of injection molding is the ability to scale up mass production. Once the initial costs have been paid, the unit price during injection manufacturing is extremely low at qmolding. The price also tends to drop considerably as more parts are produced. The other benefits are:

Injection molding produces low reject rates compared to traditional manufacturing processes, such as CNC machining, which reduces the substantial percentages of an original plastic block or sheet. However, this can be negative compared to additive manufacturing processes like 3D printing which have even lower rejection rates. Note: Plastic waste from injection molding manufacturing generally comes from four areas: the core, guides, valve locations, and any overflow material that infiltrates into the part cavity a condition called shine.

A pour is simply the channel that guides the molten plastic from the nozzle of the injection molding machine to the entry point of the entire injection molding tool. It is a separate part of the molding tool itself. A shoe is a system of channels that meet the core, usually inside or as part of the mold tool, which guides the molten plastic into the cavities of the mold tool. There are two main categories of runners (hot and cold) that you can read here. Finally, the door is the part of the channel after the corridor that leads directly to the part cavity. After an injection molding cycle (usually only a few seconds), all of the molten plastic cools, leaving solid plastic in the core, sliders, valves, partial cavities, as well as some potentially overflowing edges of the parts (if the buffer is not 100% correct).

Thermosetting material, such as an epoxy resin that hardens after exposure to air, is a material that hardens and burns after hardening if an attempt is made to melt. Thermoplastic, on the other hand, is a plastic that can melt, cool and solidify, then melt again without burning. With thermoplastic materials, the material can be recycled and reused. Sometimes this happens directly in the factory. They correct the drinkers/corridors and any reject room. Then they add this material to the raw material that goes into the injection molding services.

This material is called “re-grinding”. As a general rule, the quality control services will limit the amount of grinding that can be reintroduced into the press. (Some performance properties of the plastic can degrade as it is molded over and over again.) Or, if they have a lot, a factory can sell this new mill to another factory that can use it. Generally, the crushed material is used for low-quality parts that do not require high-performance properties.

Injection molding is highly reproducible. In other words, the second part it produces will be practically identical to the first, etc. It’s a wonderful feature when it comes to producing brand consistency and parts reliability in high volume production.

What is the disadvantage of injection molding?

Initial costs tend to be very high due to design, testing, and tooling requirements. If you are going to produce parts in large quantities, you need to make sure you get the right design for the first time. It’s more complicated than you might think. Getting the right design includes:

  • Design and then prototype the part itself according to the specifications
  • The development of the initial prototype is usually completed on a 3D printer and often a different material (such as ABS plastic) on which the final part will be built.
  • Design of an injection molding tool for a first production cycle
  • Typically, the generation of 300 to 1000 injection molded prototypes in production equipment requires the development of an injection molding tool.
  • By refining every detail of the injection molding tool before mass production in an injection mold manufacturing plant.

For example, the part has an almost uniform wall thickness (which is important to avoid defects) and the part is made of a thermoplastic material (allowing the solid plastic material to melt repeatedly for the procedure). If you were designing a part with thermoset material, injection molding would have more nuances. You can inject mold thermoset material, but you can only do it once. If you try to melt thermoset plastic a second time, the material will burn. Likewise, apart with varying wall thickness would require more attention to the design of the mold tool to ensure uniform cooling and avoid defects during production.

RJ Frometa
Author: RJ Frometa

Head Honcho, Editor in Chief and writer here on VENTS. I don't like walking on the beach, but I love playing the guitar and geeking out about music. I am also a movie maniac and 6 hours sleeper.

About RJ Frometa

Head Honcho, Editor in Chief and writer here on VENTS. I don't like walking on the beach, but I love playing the guitar and geeking out about music. I am also a movie maniac and 6 hours sleeper.

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