Cost Analysis: Additive Manufacturing vs Conventional Methods

Brief about NIST report:

There have been extensive studies on cost analysis and costing models for AM based on Powder Based Fusion processes. Comprehensive summary of this work can be found in NIST report, which we are going to discuss. As any manufacturing process, cost of AM depends on factors such as machine cost, material cost. Also on build time, energy consumption, labor, and overhead costs including facilities and other costs. While most of these cost analysis are easily understandable, part size with respect to machine build envelop plays major role in determining per piece build time and cost.

This is because PBF processes require filling out entire build area with powder for each layer. And more efficiently build area gets fills with parts, per piece build time gets reduces as well as powder usage.

Two Models:

i) Francis Hopkinson and Dickens’ model calculates {average value monetary value price cost per half by dividing total cost by total variety of elements factory-made in year. Total cost is sum of machine costs (depreciated over 8 years), labor costs, and material costs. Three additional assumptions are. (1) system produces single type of part for 1 year. (2) it utilizes maximum volumes, and (3) machine operates for 90% of time.


ii) Ruffo, Tuck and Hague’s model based on particular activities with machine. They calculate total cost of build as sum of raw material cost and indirect costs. Like hourly rates for machine cost, labor cost, administrative cost, and facility cost multiplied with particular build time. Cost per part is calculated as total cost of build divided by number of parts in build. If build consists of parts with different sizes and shapes, per part cost is calculated as volume fraction of specific part with total build volume, multiplied with total build cost.

Discussion:

While Hopkinson model generates flat cost for machine, Ruffo’s model takes into account build envelop usage for a single part. Also volume of parts and volume of various different parts. And likely yields more accurate costing for part production using PBF systems. Refer figure given below. Both models are targeted towards production costs. And do not consider engineering cost involved in reengineering part for process, programming, as well as any postprocessing, etc.

Two totally different value models for an optical maser sintering system (PBF process).

Below figure shows typical cost breakdown of various steps involved in AM of titanium components using DED technologies. This model is based on following assumptions: (1) small batch size. (2) medium sized part, 600-900 mm in size and relatively simple geometry. Any and all of these factors can significantly influence cost. Batch size plays major role in costing for small batch sizes. While part size plays more significant role in costing for larger batch sizes.

Typical value breakdown of varied steps concerned in AM of atomic number 22.

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