Reducing machining costs using on-demand injection molding

Most items made of plastic are manufactured using Injection molding since very high volumes of identical parts can be produced at a very low cost per part - image courtesy of APS

What is injection molding?

Injection molding is the technology used to create parts by melting plastic, then injecting it into the mold to cool and solidify taking the form of the mold. After it’s done the cooling, the part can be ejected and the process repeated. During injection, the solidification of the material impacts the key design restrictions.

This is a different way to manufacture parts other than subtractive CNC machining or additive 3D printing technologies. Injection molding services also beat sheet metal fabrication services as it produces better products that are more durable, attractive, and costs less.

Injection molding services are widely used around the world today for both engineering applications and consumer products. In fact, most items made of plastic are manufactured using Injection molding since very high volumes of identical parts can be produced at a very low cost per part. However, Injection molding startup costs are higher compared to other technologies since the process requires custom tooling.

All thermoplastic materials, various types of thermoset resins, and some types of silicone can be Injection molded.

Prototyping with low-run injection moldingProtoyping with low-run injection molding

Min. quantity: 10-100 parts
Typical cost: $1,000-$4,000 total
Lead time: 5-10 days

Learn more about this process >

Advantages and disadvantages of on-demand injection molding

With the advent of cloud technologies and artificial intelligence, the injection machining industry is moving from local production towards cloud platforms like 3D Hubs.

While using on-demand injection molding has many advantages it also has some disadvantages as well.


Advantages of on-demand injection molding

  • High efficiency

Compared to other methods of plastic manufacturing, the process of Injection molding is simulated, very fast and fully automated permitting extremely high production rates.

  • Realistic prototypes with accurate material properties, good dimensional control, and consistency

Injection-molded parts have good dimensional consistency, control, and can produce the most realistic prototypes with accurate material properties.

  • Complex and flexible part design

Injection molding makes it possible to manufacture complex parts with consistency as you can use many different materials, including opaque, clear, and flexible to manufacture intricate and highly detailed parts.

  • Allows you to use multiple plastic materials simultaneously

You can also use multiple plastic materials simultaneously like metal or TPU inserts, which can be molded with plastic parts.

  • Selection of colors

Using plastic over-molding allows you to use multi-color parts in manufacturing.

  • Ability to insert molding

During the injection molding process of plastic parts, plastic or metal part inserts can be over-molded.

  • Reduced waste

After injection molding, the excess plastic can be reused; however, degradation of material properties should be considered.


Disadvantages of on-demand injection molding

  • This prototype solution has high initial tooling cost

The tooling cost is very high and is required with initial injection molding. Therefore, injection molding is not recommended for small volumes. However, plastic prototyping techniques can be considered for low production volumes.

  • Not economical for low volumes

Injection molding for small quantities is not recommended due to the high cost and time required for tool development. Therefore, you should consider using other methods for small quantities of plastic part prototyping.

  • Smaller availability than CNC or 3D printing

Compared to 3D printing and other plastic fabrication, injection molding is very limited and unable to achieve smooth surfaces like the other technologies.

  • Part design restrictions

During production, guidelines for plastic part design need to be followed in order to achieve consistency and good quality.


How to start and get into production?

By simply uploading designs, engineers get an instant injection molding quote and the automated Design for Manufacturing (DfM) analysis will detect any potential issues even before production begins.


How to save money using injection molding

  • Increase Quantity

You can use injection molding to save money on manufactured parts by simply increasing the parts quantity. True the initial upfront cost required to design the mold is high due to the high cost of tooling; however, in the long run, you will save money by manufacturing parts in high quantities since one tool is capable of manufacturing many parts.

  • Eliminate undercuts and unnecessary features

Eliminating undercuts and unnecessary features can also save you some bucks as they can complicate the process and in some cases, undercuts can prevent part ejection. In addition, reducing cosmetic appearances can also make the process easier and cut costs.

  • Consider using a material that’s easier to mold

Many plastics overlap in functionality and strength, but there are some that are very easy to mold, which will also reduce part costs.

  • Reuse old molds

Rather than pay high dollar to manufacture a whole new mold for another project, consider modifying old molds to reuse them.