Even though injection molding is a cost-effective mass production method, it does involve expenses that can add up over time. At some point, you might realize that your per-unit cost is higher than you’re comfortable with.
This can happen for several reasons, most notably the time necessary for tooling production. The more complex the part, the longer it takes to produce, driving up the costs. Materials also play a big role as some are easier to mold than others.
Fortunately, there are many things you can do to lower injection molding costs. Let’s look at some of the most effective methods.
1.Think a Few Steps Ahead (subtractive nature of the mold machining)
Once a part goes into production, tool modifications aren’t possible – you can’t add material back to the mold. This is why you need to plan the process in advance.
Let’s say the wall is too thick due to an error at the design stage. You can’t make the wall thinner, so you’d need an entirely new mold. To prevent this, you could start with a thinner wall, as you can always make it thicker if necessary.
2. Analyze the Plastic Part's Structure
Before you start the production process, you should closely analyze the part’s structure to identify the areas that impact its quality and function the most. For instance, you may notice areas where a gusset is better than a solid area. Don’t hesitate to make design modifications before production, as they can save you money in the long run.
3. Choose Materials Wisely
While you should always strive toward high product quality, ask yourself if you can achieve the same standard with more cost-effective materials.
You might not need a high-end plastic resin to ensure quality and durability. Lower-end options paired with the right additives might meet all the requirements without the same outlay.
4. Reconsider Your Molds
Investing in steel molds might not always be a good idea. Even though their performance is unquestionable, you might be overspending if you can produce the part with different molds.
See if aluminum molds can give you the results you’re looking for. In some cases, you can also go with 3D printed options if not contrary to the product specifications. Finally, if the part isn’t larger than 20cc in volume, you can go with micro molds.
5. Eliminate Unnecessary Features
From a budget perspective, a good product isn’t the one jam-packed with features, but the one that ensures quality and functionality without unnecessary extras. Certain features involve processes like bead blasting or EDM, which can come at a high cost. For that reason, think about your product’s features and how many of them you really need.
6. Decrease Cycle Time
Cooling the plastic to achieve a solid state takes up around 85% of the injection molding cycle time. Naturally, reducing the cooling time is the best opportunity to drive down the whole cycle length. Check if you can reduce the melt temperature without disrupting the process. Any decrease, no matter how small it may seem, can save you a lot of resources with time.
7. Don’t Use Automatic Sliders
If you’re producing high quantities of complex parts, automatic sliders make perfect sense. But they’re only worth the investment in high-volume production. With low-volume production, it might be better to opt for manual work. Doing so will help you avoid overspending on a process you don’t necessarily need.
8. Optimize the Product’s Design
As mentioned, cost reduction should start at the design phase. Rather than putting the product into production as soon as the design is complete, review it to see if you can make any changes that will simplify the molding process and avoid unnecessary costs.
For instance, just by eliminating undercuts, you can remove the need for complex tooling and drastically reduce molding time and cost. You should also be mindful of finishes. While they undoubtedly add to the product’s look and function, you shouldn’t pay too much for cosmetic features.
9. Conduct a DFM analysis
Building on the above, it’s always a good idea to conduct a Design for Manufacturability (DFM) analysis. Aside from design concerns, the analysis gives you a close look at your entire system to see if improvements can be made. Cost reduction is among the main goals of a DFM analysis, so you can rest assured that the assessment will provide detailed input on everything you can do to drive the costs down.
10. Review Part Tolerances
Tight tolerances aren’t always necessary. They’re only justifiable if the return on the investment is large enough to cover the costs involved. For instance, Lego® building blocks have extremely tight tolerances (10 micrometers), but this is necessary to ensure consistency and is more than justified by the revenue.
Not all products call for this, so specify the tolerances that are actually necessary for the product’s function. This way, you’ll reduce molding and production costs, along with residual maintenance costs.
11. Automate Your Processes
Your mold injection process should be consistent and efficient. In many cases, manual labor can’t ensure this. Of course, some steps of the process must be manual, but you should look for opportunities to automate as many of them as possible.
You might be able to automate part picking, stacking, and palletizing. You can even automate sorting and set up tolerance alarms. Depending on your exact process, there should be at least some steps you can automate, so don’t hesitate to do so. Even the seemingly insignificant changes can add up to substantially decrease costs.
Improve Your Bottom Line
Hopefully, the tips provided here have given you an idea of how you can lower your injection molding costs. Granted, not all of them are universally applicable to every project, but there’s bound to be something that can improve your efficiency and save you more money.
Striking a balance between cost reduction and quality is anything but simple. It requires many considerations and meticulous planning. Start thinking about your budget from the design stage, and you’ll remove unnecessary costs. Modify your process as you go, and you’ll reach a standard that maximizes your profits without sacrificing the product’s functionality.
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