Case Study: Justifying the Prototype Die

The term "prototype die" is almost an oxymoron. Usually, it isn't quite cost-effective to CNC mill a 400 lb block of tool steel to produce less parts than most people have fingers.


Recently, a customer presented KLH Industries, Inc. with an opportunity to satisfy that very same condition: create a precision-tooled form die for prototyping (seen in-process above) that is less than the cost of hand fabrication.

In order to meet an aggressive delivery schedule, the customer wanted to utilize the dimensional accuracy and repeatability of formed parts. By choosing to build a forming die, the customer could produce sheet metal prototypes that require significantly less tweaking (or time) than the hand fabricated counterparts.

Of course, forming dies are not exactly innovations to the manufacturing industry. Forming dies for a total of eight pieces, however, are a bit uncommon. This unique criterion pushed KLH to take a "low" approach: low cost, low hours, and low risk.


A chief principal in KLH's strategy would be choosing an appropriate Rockwell, or hardness, for the die. Although hard and soft are polar opposites, this die truly needed to be both hard and soft.

Hard, to ensure durability and toughness while forming, yet soft, to be efficiently machined. Steel too soft will not hold up to the extreme pressures during forming, wasting materials and time. Steel too hard slows cutting time, consuming expensive tooling, and increasing overall machine time/cost.


Fortunately, the customer had already engineered a solid model of the finished part, which reduced engineering time for KLH's Project Engineer, who instead only had to design tooling around the preexisting model.

From there, the Project Engineer worked closely with both the CNC technician and the certified heat-treating vendor. By utilizing multiple avenues of experience, the group settled upon a hardness of 40-42 RC. Not long into machining, the operator knew the die was a suitable hardness.

The true test for a forming die, however, is not how it is machined, but how it performs once the press has cycled.


The die created within-tolerance stampings from the start, without any significant adjustments or alterations. In the end, the customer received exactly what they had requested: a low-cost forming die for low-volume production.

Employees who would have spent days or even weeks hand-fabricating these parts, were now free to work on other projects. Which, according to the customer, is "difficult to put a price on."

Using a form die not only freed scheduling time for the customer, but also virtually eliminated any lead time or labor cost associated with follow up pieces.

By seeking CNC milling services over hand fabrication, the customer was able to produce near-identical prototype parts for less than the cost of hand fabrication.