Cutting Costs With Traditional Injection Molding

Factory

Plastic injection molding is one of the most widely used manufacturing processes in the world today. Look around you and you’ll probably see dozens of injection molded parts in your wallet, kitchen, car and office. Here is a quick explanation on plastic injection molding process by MATRADE:

Injection molding is a process of injecting molten plastic into the mode made by custom moldmaker or toolmaker to produce the shape in the way it needs to be designed. This process is known as injection molding process or plastic manufacturing process.

The finished products are normally electrical & electronics parts or components, automotive parts, engineering parts and household products.

If you’re a custom moldmaker or toolmaker that owns your own molding machine, you’ll understand how plastic injection molding can be crucial yet deadly to your business. So in this post, we’ll be discussing on the advantages and disadvantages of injection molding, and how can we further mitigate the disadvantages.

Advantages of Injection Molding

With injection molding, moldmakers can typically enjoy:

  • Faster Production
  • Flexibility in Material & Colour
  • Low Labour Cost
  • Design Flexibility
  • Low Waste

Injection molding is capable of producing an incredible amount of parts per hour. Depending on how many impressions (or known as part molds) are in your tool, you can be expecting 15-30 seconds for each cycle time. Once you have your tool made ready, you can simply inject the material and color of the part that you’re producing at ease.

Most importantly, these are self-gating, automated tools that run on it’s own with little to no labour.

Disadvantages of Injection Molding

There are also some huge restrictions on injection molding:

  • High Initial Tooling Cost
  • Part Design Restrictions

Not only you need to own an injecting molding machine, you will need to be equipped with the technical know-how on designing the mold which can be very expensive. You will need to have some capital to start the project and here is why it is a make or break deal: sales must be guaranteed or at least assured before you start this.

It is also crucial to understand that mold tool is made from two halves that need to pull apart, and the injected part needs to be able to be released from the tool. The process of designing plastic injection mold will require a few key elements such as:

  • Good flow design
  • Good in cooling distributions (or conformal cooling application)
  • Good in air venting

You can also view this infographic guide for better understanding.

So How Do We Achieve Cost Savings With Injection Molding?

While there has always been a debate over whether mold design or molding machine is much more important.

Mold Design in Cooling Channel

If you look at it from the perspective of time spent to correct a problem, typically if there is a faulty molding machine you can simply move the plastic mold to a more capable machine or fix it within a day or two.

However, if the problem exists within the tool it may require a significant tool redesign that could take weeks or even months depending on the complexity of the tool. Tool design inclusive to steel type and construction details is critical for getting the mold initially qualified and also vital for long term quality parts coming from the tool.

If you’re a practitioner of lean manufacturing, it is always about getting it done the right way the first time. In this case, if you’ve gotten a good functional mold design at early stage, you’re gaining a significant amount of cost savings already, due to:

  • Manufacturers normally proceed with injection molding as the deal is confirmed. This manufacturing process allows you to reap the most productivity and savings.
  • If you cut down on time spent on design iterations and prototype productions, you’re earning on machine occupancy & productivity. That means more efficient process to get more business in.

Key-takeaway: It is extremely crucial to have a good functional mold designs. Don’t ever compromise on mold design. Period.

So How Do We Validate The Mold Design?

Here is a steps we used to validate mold design which greatly helped our clients:

  • Traditional Injection Molding Process
  • Part Design
  • Tool Design
  • Tool Machining
  • Molding Machine Setup
  • Sample (first article) run
  • 3D Printing & Injection Molding Process
  • Part Design
  • Tool Design
  • 3D Print Tool
  • Molding Machine Setup
  • Sample (first article) run

Yes, we merely swapped the tool making process by 3D printing it for production testing purposes. 3D printing an injection mold is best fit when:

  • Thermoplastics with reasonable molding temperatures (< 300 °C )
  • Good flowability
  • Candidates such as PE, PP, PS, ABS, TPE, PA, POM, PC-ABS or glass filled resins.

Number of Molded Parts by Resin class

The major savings that you can get from this refined process is:

  • A 50% – 90% on both time and cost savings.
  • The specification of output, spec resins or even production process can be simulated. You can do true functional evaluation.
  • Multiple design iterations won’t hurt your bottomline. You can now detect flaws in part & tool design much more earlier prior commit in mass producing.

Does this mean that I don’t need an aluminium mold anymore?

Injection Molding Sample

Not true. 3D printing injection molds are not meant to replace conventional mass manufacturing process. Alternatively, if you’re looking to do short runs without custom making tool template, 3D printed molds are best fit if:

  • Low quantities (5 – 100)
  • Mid-sized parts (<165cc[10 cu. in.])
    • 5 – 200 ton press.
  • Tolerances>0.1mm(0.004in) *tighter tolerances can be attained depending on post processing.

Conclusion

What we realize is that, if you’re a custom molders, OEMs or even tool and die services shops that requires:

  • Early, rapid product confirmation (design, function, standards (e.g. UL, CE)
  • Early rapid assessment of design for manufacturability.
  • And you’re in the following industries:
    • Consumer Electronics
    • Consumer Products
    • Medical Device

You’ll be able to benefit greatly simply by tweaking this process. Feel free to share with us on your thoughts and how you do cost savings for injection molding.

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