Case Study: Automotive Console—From Prototype to a Production Run of 500 Units

The customer came to us with a finished STEP file for a bracket designed to hold a cable harness in an electric vehicle. The model was functionally correct but not optimized for manufacturing—and as it turned out, a whole range of costs could be eliminated even before the first chip was cut. Here’s the whole story, from the first model to 500 parts on a pallet.

This case study shows what can be gained when DFM and technology selection are addressed at the outset, rather than after the first expensive production run. The part is simple—a cable harness holder—but it is precisely with simple parts that the difference between “it can be manufactured” and “it can be manufactured well and cheaply” is most evident. The project took six weeks from the first prototype to series delivery.

The bracket holds the cable harness in the electric vehicle’s chassis—it carries a light load but must fit precisely into two mounting points and withstand vibrations and temperature cycles. The customer supplied a finished STEP file: a CNC-milled aluminum block (6082-T6) with a tolerance of ±0.05 mm across all dimensions, with a planned production run of 500 units. Functionally, the model fit, but it was designed “from solid,” without regard for how it would actually be manufactured.

A DFM check and a subsequent manual review revealed three specific issues—each of which could be resolved individually, but together they turned an inexpensive part into an expensive one:

• Inner corner with a zero radius — impossible to machine with a milling cutter; it would require EDM or a compromise; the classic sharp-corner trap
• Two mounting holes that are too close to the planned edge and in a location where, in the sheet metal version, they would be within the bend zone
• A flat tolerance of ±0.05 mm on all surfaces, even though only two mating surfaces and the mounting hole spacing were functionally critical

Conclusion: The part would have to be machined on a more precise (and more expensive) machine, with finishing passes on surfaces where the function does not require them at all, and with a risk at the sharp corner. The original DFM score was 62/100.

The fundamental question was not “how to machine it more cheaply,” but “is CNC even the right technology?” The shape of the bracket—essentially a bent profile with mounting tabs—is a textbook example of sheet metal work. After consulting with a production engineer, the part was redesigned as a 2-mm-thick bent steel sheet: two bent arms with mounting tabs, an inner radius equal to the thickness, and rigidity provided by the hem rather than the material itself. The function remained unchanged, but the economics shifted—with sheet metal, you pay for cutting and bending, not for hours on the lathe.

The transition to sheet metal wasn't a one-click remodel—it took place over three rapid iterations, each with a specific correction verified on the development model and a new cost estimate:

• Iteration 1 — first bent version: the shape and mounting spacing were correct, but one hole fell within the bending zone and would have stretched into an oval in the flat pattern
• Iteration 2 — holes offset by ≥ 3× the thickness from the bend; a perimeter flange was added for stiffness (so that the thinner sheet metal would not compensate for the weight of the milled block by sacrificing strength)
• Iteration 3 — tolerances limited only to the mounting hole spacing and the seating surface; the rest set to general tolerances; alignment of bend radii to a single press tool

After the third iteration, the DFM score was 91/100, and the part could be manufactured "in a single operation"—laser-cut and bent without having to readjust the press.

Before series production began, the first-article part was manufactured and measured against critical dimensions—the hole spacing and contact surface were within tolerance, and the springback from bending was fine-tuned by adjusting the press. A production run of 500 units with a powder-coated finish was then completed; the part was manufactured and shipped in two weeks instead of the four weeks originally estimated for the CNC version. The lower weight also resulted in savings in logistics and in the end vehicle.

The cheapest and fastest savings weren't achieved in production, but in the first two days—through the right choice of technology and three targeted design adjustments.

Three lessons apply even beyond this specific part: (1) decide on the technology before the details—the switch from CNC to sheet metal yielded the majority of the savings, not micro-optimization of machining; (2) set tolerances based on function, not across the board; (3) Iterate based on actual costing and DFM, not just on gut feeling. If the part had gone into production in its original form, the customer would have paid 41% more per unit and waited twice as long—and none of that would have added any functionality.