Injection molding is a process used in the manufacture of multiple parts. It is very convenient, especially where identical parts are produced in thousands or even millions in succession.

Why injection molding?

Injection Molding

Injection molding is very practical and cost-effective since once the initial cost has been paid, the cost of production and running becomes extremely low. Other advantages of injection molding include the following:

  • It requires lower scrap rates as compared to other traditional methods.
  • It can be easily repeated

What are the disadvantages of injection molding?

The necessity of design, testing, and tooling drives the initial costs to be very high.  Look at it from this viewpoint; if you are planning the mass production of parts, you have to do everything you can to ensure that you get it right the first time. ‘Getting it right’ can be more complicated than you think. This is what it actually means:

  1. The initial design and prototype of the part. Often made of a different material from the final part, the prototype is often completed using a 3D printer and most times in a material such as ABS plastic
  2. The complete design of an injection mold tool for the initial production round. The massive production of injected molded prototypes will require you to develop an injection mold tool which can be very costly and time-consuming.
  3. Refinement of all the details of the injection mold tool before the mass production in an injection mold manufacturing plant.

Potential downside of injection molding

The top two downsides of injection molding are the large required lead times and the expensive tooling costs. Tooling can be viewed as an independent project on its own. It requires time, commitment and dedication. It also requires high precision and expertise. Keeping in mind that it is only one phase of the entire injection molding process, it can be quite demanding.

You will have to design the prototype part, and then design a metal tool that will produce the prototype in replicas. Keep in mind that you have to keep testing these parts to see if they work.

Also, this process requires a lot of your time and money.

It is very difficult to make any changes to the tools because they are made of steel which is a very hard and stiff material. This means that even a small change can mean that you have to entirely scrap of part of (or even the whole) material and re-build it again! In some cases, you might still get the undesired results after all that effort.

Uniform wall thickness is necessary

The recommended wall thickness is about 4mm thick. Using a wall that is too thick will mean a longer cycle and many inconsistencies, among other disadvantages. On the other hand, using a thin wall (less than 1mm thick) will give you too much trouble when filling the molding tool.

However, some manufacturing designs such as CNC do not really require uniform wall thickness.

Most times, injection molding cannot produce large parts as a single piece. This is because the process of injection molding has limitations regarding the machines and mold tools. However, alternative machines like CNC also have the same limitation. 3D printing machines have even more limitations as compared to the other methods.

Conclusion

Injection molding is an excellent advancement in the technological development of mass production of products. However, for cost-effectiveness, it is advisable to make use of 3D printing in the initial stages of the project then come back to injection molding in the final stages.To keep abreast of labor costs, putting time tracking software in place can be useful .