© Foto: D. Schumacher

Caps that do more than just cap costs

The thing looks unspectacular to the maximum: A sheet metal strip, 220 mm long by 160 mm wide, provided with two elevations and three tabs. Until you learn that this will one day become the dust- and waterproof cover of an electronic control unit for the rear-axle steering of a premium SUV. Produced at EK from a material specification of high-quality aluminum – in a specially designed progressive die with around 800 components.

The production request from a major customer in the automotive sector. The search is on for a ‘lid’ for the control unit for the rear-axle steering of SUVs. This becomes necessary in order to comfortably park and unpark ever wider car bodies in seemingly ever narrower parking garages. A typical case for EK design, which of course knows that the customer also demands the highest quality for this component and at the same time wants to produce it as cheaply as possible. Joachim Fohr takes over the technical elaboration of the customer’s inquiry as well as, with the creation of the so-called strip layout, the preliminary design of the tool production. Right at that, we take a look over his shoulder.

Cost saving the first

EK expert Joachim Fohr’s first recommendation to the customer: It is better to use a different aluminum specification than the one provided in the inquiry drawing. For two cost-saving reasons at once: Firstly, the proposed material would require a much more complex mold to carry out the forming process. And secondly, the alternative material saves valuable base material because it can be stretched much further. In figures, the cost savings amount to a whopping 30 percent in the manufacture of the mold and 20 percent less expensive production. The response of the customer – any customer – to this recommendation is abundantly clear.

Cost saving the second

As an outspoken tinkerer, Joachim Fohr next tackles the distribution of the material strip in the composite mold. He knows how to ‘nest’ the workpiece so cleverly that as little material loss as possible occurs. This saves the customer up to 13 percent material usage. A pleasant side effect is that this also reduces the feed per piece by 20 millimeters – and makes the workpiece even more cost-effective overall. This EK proposal also meets with the customer’s approval.

Where there’s milling, there’s cutting. Not so with EK.

Under the cover will be subsequently mounted a printed circuit board with components of the electronic control system. In order to prevent chips from settling on it, which could possibly trigger a short circuit and thus cause the failure of the control system, the EK expert excludes the possibility of this happening on the rear-axle steering system through the design of the composite tool. Instead, the machining stages are cleverly arranged so that the ‘overcuts’ meet exactly – and thus no chips are produced in the first place.

From conception and construction to production

After one week, the preliminary design is ready: The material strip is to be cut, bent, perforated, punched and finally pushed out in the 300t series press over 10 stations – according to Joachim Fohr’s plan, a perfect lid tailored to the customer’s wishes. And because EK always delivers added value, product cleaning and the application of a circumferential sealing cord are to follow. And so that the automotive customer can safely remove the ready-to-install lids later in assembly, the finished parts are individually magazined in trays. But before that, the second phase of the project begins – the manufacture of the 1.80-meter-long and 75-centimeter-wide tool at the supplying toolmaker. A huge hunk – for an itty-bitty part. This takes another 20 weeks or so, including an optimization phase. It should be noted that almost three quarters of the tool, which consists of around 800 components, are specially manufactured one-offs. Now the 300t series press has been started up at EK – and is producing lids, lids, lids, lids, lids … every second.

Self-steering rear axle from ZF © Photo: ZF

For the cost-effective production of large quantities of sheet metal components, complex progressive dies are used at EK which have to meet the highest requirements in terms of precision and durability. In such a tool, sheet metal strips are transported from station to station, where they are punched, milled, shaped and perforated with the utmost precision – until they finally leave the series tool in the desired shape as finished components.