Cost to manufacture with injection molding

August 2, 2017

Product development teams have been relying on the injection molding process to manufacture polymer parts for decades. This time-tested process is robust, highly repeatable, and ideal for high-volume production. However, when product development teams think about the cost of manufacturing using injection molding, they typically think of the costs only in terms of direct materials, machine time, and direct labor costs¹ (Figure 1). This conventional cost model, although intuitive, does not capture the true total costs associated with manufacturing a part using injection molding.

Figure 1: Conventional cost model for injection molding

 

In reality, mechanical engineers, tooling technicians, and product development teams typically find that the actual costs to manufacture using injection molding are significantly higher than what the conventional model captures. More specifically, this approach misses five additional cost elements associated with injection molding: (1) tooling amortization, (2) prototyping/tooling change, (3) design for injection molding, (4) setup fees, and (5) minimum order quantity (MOQ) inventory waste (Figure 2).

Figure 2: Revised cost model considerations for injection molding versus conventional cost model

 

After decades of production experience, the injection molding process is well-characterized. However, the true costs associated with producing a part using injection molding are not as well-understood. Typically, the costs associated with tooling amortization and tooling changes during the prototyping stage are not considered in initial production estimates. These tooling-related costs add up quickly, driving up the total cost as each retooling change can add $5,000 to $50,000 (depending on the application).

The time and labor associated with design for injection molding represent important costs that are generally not factored into the total cost. In order to be manufacturable, mold design requires the correct application of critical design elements such as parting line location, shutoffs, drafts, fillets, gates, and ejector pins. Additionally, the complexity of intricate geometries, textures, and variable wall thickness requirements for a given part can become a considerable cost and time multiple. Setup fees reflect the time and labor it takes to mount the mold into a molding machine, pre-cycle, and calibrate the molding operation. This becomes a sizeable cost addition for most short-run injection molding operations.

Lastly, a natural outcome of the high tooling costs associated with injection molding is the tendency for the process to be chosen for high volume production applications to amortize the upfront tooling cost. However, this volume amortization does not work for many product development teams, since contract manufacturers often hide steep tooling costs under a minimum order quantity (MOQ) requirement. This requirement means that product development teams must often order parts in the thousands, even though they might only need a few hundred units. The MOQ also puts pressure on organizational operations and supply chain teams as it can introduce inventory holding costs and associated wastage of parts. National Institute of Standards and Technology² reported the existence of $537 billion locked in inventory by the manufacturing industry in 2011. This number has likely grown over the years. With additive manufacturing and the ability to produce on-demand, the perfect solution to reduce inventory holding costs and associated wastage is now within reach.

 

COST OF TIME TO MARKET

Many of Carbon’s manufacturing partners are challenged to launch products on time due to frequent delays throughout the end-to-end injection molding process. Staying on schedule is important for any industry vertical, but it is often more pronounced in highly competitive industries, such as consumer products or industrial electronics. In these markets, delays in meeting time-to-market expectations can result in lost revenue and lost market share against key competitors. In the case of industrial electronics, delays often translate into a part being designed out of the final product altogether, with implications of multiple years of revenue loss.

As highlighted in Figure 3, injection molding development timelines are lengthy with a significant variability that ranges from 6 to 23 weeks. The addition of design for injection molding and tool refinement can add anywhere between 2 to 7 weeks to the end-to-end process. Also, the tool-building step represents the highest variability; 2 to 12 weeks is typical for completion, depending on where the tool is being made (outsourced vs. in-house). To develop an accurate estimate, product development teams must consider time and variability associated with injection molding when they are evaluating manufacturing process options.

Figure 3: Representative view of injection molding development timelines

 

CONCLUSIONS

For customers new to the world of additive manufacturing, Carbon’s technology offers the following benefits that are inherent to true additive manufacturing: (a) lower upfront costs compared to injection molding, (b) agile part production, (c) the ability to iterate rapidly on design changes, and (d) lower non-recurring engineering expenses. Additionally, there are business scenarios where injection molding is not the most efficient method to make final parts. This is where Carbon’s Digital Light Synthesis™ technology is truly differentiated. Some of these scenarios are:

  • Impossible-to-mold geometries (i.e. complex parts with intricate channels, holes, and recesses)
  • Differentiated functional performance unique to Carbon (i.e. tunable lattices, textures, foam replacement)
  • Part consolidation (i.e. 3D printed single part instead of multiple part assemblies, simpler assembly lines)
  • Leaner supply chain (i.e. parts-on-demand, reduced supplier dependencies)

We already see numerous industrial and consumer product companies using Carbon’s technology to serve parts on-demand instead of sourcing or maintaining injection molding parts, especially for low-volume parts. Compared to the 6 to 23 weeks typical with injection molding development time, with Carbon, it is possible to collapse the production process to 2 to 3 weeks with much lower variability.

Additionally, Carbon’s technology offers engineers and product development teams new design freedom to rethink their product designs. Overall, our capabilities are complementary to injection molding, and customers should decide which approach serves them best for their end application or use-case. Most importantly, they should use the presented approach to calculate the true cost of injection molding before making a decision.

If you would like to learn how Carbon’s technology can help your product development teams to bring innovative products to market with leaner more agile supply chains, please contact us at sales@carbon3d.com.


¹Manufacturing overhead costs are always present and not shown for the sake of simplicity

²Costs and Cost Effectiveness of Additive Manufacturing, NIST Special Publications 1176, Dec. 2014