The Real Cost of 3D Printing
After reading the now famous article about a ventilator valve that can be 3D printed for $1, compared to the traditionally-manufactured valve costing $11,000, I realized that the way 3D printing costs are calculated is still vastly oversimplified, which leads to reliance on two incomplete cost models. The most common says that unlike traditional manufacturing there are never economies of scale and that the cost per part stays constant, whether a single part or 100s of parts are printed. Another model is that 3D printing costs slightly decrease with the number of units as more parts are added to the build bed, and the average build time per part decreases.
Figure 1: Common models of 3D printing costs
Both of the above models provide a cost approximation and are often used by service bureaus, but they both have the same flaw: They don’t take the machine utilization into account.
For 3D printing, there are five main cost contributors:
Material cost: Material usage for the part, support material, and other material waste
Machine depreciation: Portion of the machine price attributed to a part due to the time the machine is being used to build the part
Consumable costs: The cost of consumables used for the build (build trays, argon gas, filters, printhead, etc.)
Labor costs: Personnel cost involved in the build (build file preparation, machine preparation, build monitoring, machine clean-up, and support removal)
Risk: Risk of failure involved in building this part. Usually comes in two different types, time risk – the longer the print, the higher the risk of failure, and geometry risk – certain geometries might have higher risk of failure for certain technology.
In this article we will take a deeper look at the machine depreciation cost and how machine utilization influences it.
Let’s start with a basic equation that is often forgotten or ignored but is essential to understanding the cost of 3D printed parts.
Figure 2: Machine Depreciation Calculations
The machine utilization is the percentage of the time during the year where the machine is producing parts. Because the utilization is in the denominator of the equation above, there is an inverse relationship between part cost and machine utilization. In other words, the part cost goes down as the machine utilization goes up.
Real machine utilization is very difficult to guess without having robust data available, so a lot of companies will use a fixed number for utilization. They often choose a number between 60% and 70%… a number that is often overly-optimistic.
Other companies with access to historical data will estimate machine utilization based on past figures. Many factors can influence the utilization figure, such as maintenance, down time, and build cleaning, but based on our experience the main contributors are staff availability to change...
