The Cost Impact of Additive Manufacturing

Additive manufacturing, also known as 3D printing, has been making headway in the world of manufacturing. What initially started as a useful rapid prototyping tool has developed into a promising technology with quick turn around times and low material costs. Oftentimes, additive manufacturing is used as a prototyping tool to quickly fabricate products in their early stages of design and development. A lot of times, this part in question will graduate and go on to be designed for injection molding or subtractive manufacturing for production. However, in recent years additive manufacturing has shown to achieve tight tolerances, exceptional surface finish, and excellent mechanical properties. As a result, using additive manufacturing as a means of production has become a reality, emphasizing on the importance of designing for additive.

Comparing additive manufacturing to its manufacturing counterparts, processes such as injection molding and subtractive manufacturing have high setup times, expensive tooling, and wasteful material costs. Additive manufacturing has found a way around these obstacles as it does not require intensive setups, tooling, or excessive bulk material to produce parts. One must wonder, what is additive manufacturing’s potential in production and how will the cost of manufacturing, via designing for additive, change?

Let us look at the life of a product going through manufacturing. Early in the manufacturing process, setting up tooling, machinery, and material is generally required of many means of production. Take injection molding, for example, this process will fall heavy on the setup of the tooling and machinery side of costs. A complicated mold, made for producing a complicated part geometry, can cost hundreds of thousands of dollars just to produce. As a result, it is incredibly important that a design is entirely correct, otherwise, an incorrect tool could cost a company dearly. Designing for injection molding can be limiting in many ways as features such as wall thickness and part complexity have various restraints. In addition to the high tooling costs, these molds must be set up and prepared for production, just tacking on costs in labor and time. When all is said and done, production can finally begin which then reflects the cost efficacy of injection molding.

Subtractive manufacturing has the advantage of lower setup costs and the capability of producing parts that require little to no post-processing. This is part of what makes subtractive manufacturing, especially CNC, a useful rapid prototyping tool. The most significant costs of subtractive manufacturing fall under materials and part complexity. A bulk of the material is required to produce a part with subtractive manufacturing which poses the potential of high material waste. In addition, a part that has complicated geometry will require various operations to accomplish the desired shape of the part. The more operations required to produce the part, the more time and money the process is costing. When designing for subtractive manufacturing, it is important to make good use of material being used and to limit part complexity as to cut down on the number of required processes.

Additive manufacturing has the advantage of low material costs, no tooling costs, and quick turnaround times as little setup is required. The only setup that additive manufacturing requires is uploading a 3D model into the machine’s software and press go. Machinery setup time is incredibly low and material setup is fast. Therefore, additive manufacturing saves time and money in the setup stage of manufacturing, especially in the case of part revisions with no variation in setup costs. Additionally, there are little design constraints on what additive manufacturing can achieve. The question becomes, which factors will most likely influence the cost of additive manufacturing in the context of design?

The next step in manufacturing is the processing of the part. When compared to injection molding, additive manufacturing has a disadvantage in processing time. Injection molding has incredibly quick processing times. Producing a part with injection molding can take mere seconds whereas producing a part with additive or subtractive manufacturing could potentially take hours. Subtractive manufacturing and additive manufacturing both have moderate processing times, but often additive manufacturing gains its advantage over subtractive manufacturing when geometry complexity is in question. Understanding this distinction is important because it highlights the fundamental differences between additive and subtractive manufacturing.

With additive technologies, like SLA or DLP, a part is printed in layers defined by its cross-section (check out the blog on Additive vs. Subtractive manufacturing for more information). There is a singular operation performed to produce the part. Depending on the complexity of subtractive manufacturing machinery, a complicated part geometry could take multiple operations, all requiring additional setup, to produce. A part can go from having a relatively short processing time to an incredibly long processing time depending on the part geometry with subtractive manufacturing. In many cases, this is not true for additive manufacturing as processing time will depend heavily on the height of the part, not geometry complexity. A simple way of thinking of this distinction is the more surface area required of a part, the longer subtractive manufacturing will take whereas additive manufacturing will largely remain unaffected. When designing for additive manufacturing, it is important to keep the height normal to the printing platform surface as little as possible. However, it is important to note that this is not completely true for FDM additive technology as this process operates on a coordinate system and singular tool, much like subtractive technologies. Yes, FDM can achieve complex part geometry but the tool used to create the part will follow similar movements to that of CNC.

The last manufacturing process that a part will go through is post-processing. This process can vary from technology to technology, so it is important to understand the differences between each manufacturing method. For injection molding, post-processing could include processes such as flash trimming. For subtractive manufacturing, post-processing could include processes such as grinding and polishing. For additive manufacturing, post-processing can vary widely depending on the type of additive manufacturing used. For additive technologies such as DLP, parts must be washed to remove residual uncured resin from their surface. In addition, materials must be cured, either thermally or via UV radiation, to set their final mechanical properties. Variance in these post-processes can prove to be significant. In fact, post-processing time is often the second most time-consuming process after processing. As a result, labor and time costs increase as a function of the number of parts produced. When designing for additive manufacturing, it is important to design a part to be easily cleanable. This could include features such as vents and smooth contours.

The process of injection molding gained popularity because of its ability to produce large quantities of parts with short processing times with the downside of expensive tooling. Designing for injection molding can often be restrictive and resistant to change. Subtractive manufacturing gained popularity because of its ability to produce quality parts with complex geometry but with the downside of extensive material waste. Designing for subtractive manufacturing emphasizes the importance of minimizing material waste. Additive manufacturing has made its headway in the manufacturing world because of its little setup time and flexibility in design iterations with little waste of material. Costs are racked up with additive manufacturing by long processing times, printing times, and variant post-processing times. Designing for additive manufacturing will emphasize the most cost savings when keeping processing time, related to part height, low and designing part geometry to be in favor of post-processing. Time is money and choosing the appropriate manufacturing process is very much a give-and-take relationship between preprocessing, processing, and post-processing.

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