In comparison to traditional manufacturing processes such as CNC machining, which remove substantial portions of a plastic block or sheet during the manufacturing process, injection Injection Molding produces a low rate of scrap.  This, on the other hand, can be detrimental when compared to additive manufacturing processes such as 3D printing, which have even lower scrap rates.

Injection Injection Molding has a low scrap rate because of its design.

An epoxy resin that cures when exposed to air is an example of a thermoset material.  If an attempt is made to melt the material after it has cured, the material will burn.  When compared to other plastic materials, thermoplastic material is one that can be melted, allowed to cool and solidify before being melted again without burning.

Thermoplastic materials can be recycled and repurposed multiple times over their lifetime.  This can happen right on the factory floor, in some cases.  They grind up the sprues/runners and any reject parts that come out of the machine.  Afterwards, they incorporate that material back into the raw material that will be used in the injection  press.  Re-grind is the term used to describe this type of material.

Most quality control departments will restrict the amount of regrind that can be reintroduced into the press after it has been processed. (Some of the performance properties of the plastic can deteriorate as the material is molded repeatedly. )

Alternatively, if a factory has a large quantity of re-grind, it can sell it to another factory that will benefit from it.  Regen grind is typically used for low-quality parts that do not require high performance properties, such as abrasive wheels.

Injection  makes use of repetition and consistency to its advantage.

Injection  is a highly repeatable process.  That is, the second part you produce will be virtually identical to the first part you produced, and so on.  This is an excellent characteristic to have when trying to achieve brand consistency and part reliability in a high volume manufacturing environment.

So, let's see. . . How Does Injection Molding Have a Negative Impact?

Because of the massive manufacturing scale that is typically involved in injection Injection Molding, even minor mistakes can have significant ramifications, both financially and logistically.  Despite the fact that the margin of error is small, the ramifications are significant.

When it comes to injection , even minor design errors can result in significant costs.

Because of the requirements for design, testing, and tooling, up-front costs are typically very high.  If you are going to manufacture parts in large quantities, you want to make certain that the design is correct from the beginning.  That is more difficult to accomplish than you might imagine.