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Manufacturing cost is a crucial aspect of product design. Delighting the user is not enough; the bottom line must work too.
Mechanical engineers must rely on our knowledge of different manufacturing processes such as machining, casting, molding, forming, joining, and additive manufacturing to make sound design decisions. Having a good instinct for manufacturing costs helps us balance the various trade-offs when determining the most appropriate manufacturing method for a given part.
At 219 Design, we’ve made a game to accelerate developing this cost knowledge and to hone our intuition. We call it the “Estimation Game,” and now you can play it too!
When someone on the team quotes a custom part, they add the part description to the Estimation Game spreadsheet with the final cost hidden. Then, in our weekly team discussion, each person writes down their guess and, finally, there is a big reveal of the actual cost. Easy!
Want to try it? We’ll give you the manufacturing cost of the ribless part (left): it is $8.28. How much would the ribbed one cost (right)?
Here are more details about the parts:
Go ahead, make a guess. We will let you know the answer a bit lower in the blog, in the Example Part Cost, Revealed section.
At 219 Design, we constantly balance the tradeoffs of price vs. function as we design custom parts. In this case, I expected the added ribs would add cost in two ways 1) time for machining the mold and 2) extra plastic for the ribs. But are those increases 1%, 10%, or 100%? Will the added stiffness from the ribs be worth the money?
The Estimation Game tool seems like a simple spreadsheet, and it is. However, this simple setup has surprising benefits.
In addition to sharpening individual skills, the Estimation Game disseminates some team-wide learnings. For example, our favorite vendor for out-of-house 3D prints has transitioned from Shapeways to CraftCloud as the latter has consistently surprised us with lowest costs.
Also, we have built up rules for which variables are the most important. For instance, the thickness of a sheet metal part has a large impact on its cost, where the thickness of a machined part contributes much less. I was also surprised about the added ribs from our initial injection molded part…
As a reminder, the manufacturing cost of the ribless part on the left is $8.28. Adding ribs raised the price by…
+ $0.19 → $8.47!
A mere 2% increase, less than I guessed! What surprised me the most is that Xometry’s quote for the molding tool ($52731) did not change at all, even though I expected the ribs to add machining cost. The increase came completely on the ‘per part marginal cost,’ which I suspect is mostly from the additional plastic. The Estimation Game highlights exactly these sorts of learnings.
The Estimation Game originated with our mechanical team, but applications of the game extend beyond just mechanical engineering. At 219 Design, we have also used the game with electrical engineers to guess the costs of custom boards, with officemates to guess the price of an office construction project, or even with project leads to predict the overall cost to develop a product. Anytime a group needs to build an intuition around cost, the Estimation Game is a tool at your service.
We hope that you are able to use the Estimation Game in your organization (link to Estimation Game Template). If you would like to pull in additional resources, we can happily focus our trained intuition on your organization’s design. Reach out to us a [email protected].
1This price is nearly the number of feet in a mile. This is a coincidence.
Date published: 11/17/2022