What Process Should Make This Part? New Tool for Comparing Production Methods

“If you want to buy car insurance today, you can go to a number of websites and get half a dozen quotes in a few minutes,” says Stephan Abt of Plus Manufacturing. But no such equivalent exists for the manufacturer trying to choose between half a dozen or more solutions. “Where does an engineer or designer go to compare different manufacturing processes and materials when developing a part?” Abt asks.

Of course, comparing manufacturing methods is slightly more complicated than comparing insurance coverage from different providers. When the potential options might include everything from aluminum sheet metal bending to steel CNC machining to, yes, additive manufacturing, maybe in exotic materials, it’s much more difficult to reach a true apples-to-apples comparison and there is more inertia to fight with any given change. But this Erlanger, Kentucky, company has developed a tool that distills information about a given part to help engineers and companies make better-informed decisions about how to manufacture it. 

The Tool: COSMO

The free decision-making tool is called COSMO, which stands for Cost Over Specific Modulus. Available for free download and use through a Creative Commons license on Plus Manufacturing’s website, COSMO is a spreadsheet with automated formulas that enables users to compare the cost, lead time and other variables for different materials and manufacturing methods, including a metal deposition AM process Plus Manufacturing has developed. (For now, the tool primarily considers metal manufacturing processes, but the company has reached out to other firms including plastic 3D printing companies and will continue to expand its scope through collaborations.)

How to Use COSMO

To use the tool, users plug in details about the part they wish to make and select the processes under consideration. Using the specific modulus (stiffness-to-weight ratio) as a stand-in for the part’s end-use performance requirements, COSMO provides the user with information about the typical costs associated with manufacturing it, including material, labor, finishing, corrosion protection, capital equipment and even floor space. Based on the part, process and materials selected, the tool outputs tables of information that make it easy to compare the different options and select the best one for the intended use case.

Example Analysis of an Electric Vehicle A-arm

For instance, for the electric vehicle A-arm pictured here, the automotive manufacturer might input the approximate part dimensions and manufacturing options being considered.

COSMO could then deliver the results shown below, which compare steel sheet metal, aluminum casting, aluminum milling, aluminum powder bed fusion, steel tubing weldment, full production via Plus Manufacturing’s own Advanced Material Deposition (AMD) 3D printing method in stainless steel, and a combination of AMD stainless steel joints and composite tubes.

As shown above, milled aluminum and AMD stainless steel result in the fewest number of operations; conventional sheet metal and aluminum casting (which both require long-lead-time tooling) have the most.

The cost-per-part comparison of the processes reveals that aluminum laser sintering AM is the costliest process. (Note that for processes that rely on up-front tooling such as stamping and casting, the cost of the tool is factored into the cost per part, divided across the expected batch size. These processes can achieve economies of scale at higher volumes, whereas the cost per part for additive manufacturing tends to remain stable.)

The three additive processes considered offer the lightest weight components; conventional aluminum casting and milling are the heaviest options. 

The cost and weight comparisons are valuable on their own, but engineers and designers are often striving for the strongest and lightest part at the lowest cost. According to Abt, the COSMO parameter (shown above) provides a single, objective number to allow comparison between materials and processes.

In the current A-arm example, the calculated COSMO parameter illustrates that the AMD process produces a strong yet lightweight part out of stainless steel, while the cost comparison shows it is competitive with steel sheet metal or an aluminum casting. 

Testing Assumptions

Plus Manufacturing acknowledges that specific modulus might not always be top concern, so part weight and cost comparison results are provided for cases where these factors, regardless of performance, might be highest priority. And although Plus Manufacturing is an AM technology supplier, the final conclusions derived through COSMO are not any more likely to turn up additive manufacturing as a solution — instead the goal is to get to the most efficient production method for the part. COSMO is meant to help business leaders and engineers question and test their assumptions, with confidence in the result.

The advantage of a tool like this, Abt says, is that it can actually help those involved in manufacturing change their thinking. A decision-making process based on data like this helps shift an engineer from defaulting to their typical production process. Instead of saying, “Let’s make this new part out of sheet metal — I know how to do that,” that engineer might instead decide to pursue composite or additive manufacturing, because the advantages over sheet metal can now be quantified. COSMO has the potential to get engineers out of their own heads and help them consider other production methods, including additive, with confidence.

“It allows engineers to go down a path knowing that it leads to a reasonable result,” Abt says.