ZF Lemförder GmbH, a member of the ZF Friedrichshafen AG group of companies, makes products such as tie rods, steering rods, suspension components and suspension modules. As a value-chain partner to the commercial vehicle sector, it places special emphasis on customer orientation. This has led to an enormous number of variants in its range in recent years, which is making it more and more difficult for ZF Lemförder to live up to its goal of reacting quickly to customer needs. The Management-Innovation-Technology (MIT) Steinbeis Transfer Center helped ZF Lemförder streamline its portfolio of variants and introduce a sustainable process for continuously managing variants.
In recent years, the number of different steering tie rods, axle rods and ball joints has risen sharply. “We guarantee our customers exact adherence to specification, under tight development deadlines – but it was increasingly becoming impossible to do so, given the variety of products we were dealing with and the resources available,” explains Holger Bublies, head of D&D. The aim was therefore threefold: to slash the time needed for D&D to issue a detailed offer; to reduce prototype delivery times once quote were given the go-ahead; and to shorten delivery lead times for serial products. All of this should be achieved by standardizing products and processes, as part of on-going plant development projects.
Even as the project got underway, ZF Lemförder knew it would be necessary to address many issues. “We didn’t want to leave the task of overhauling our variants just to development,” says Hubert Gross, who heads up the commercial vehicle chassis module department. “Our processes are integrated, so sales is involved through actively selling product standards, production is involved with standardized manufacturing processes, and financial accounts are involved with fixed calculation models for standardized products.” The scope of the project was therefore clear: a new end-to-end variant management system was needed, involving standard processes that make it possible to shorten lead-times by more than 50% – from the first point of contact with the customer to final delivery – without reducing the deliverable scope of products or raising prices. The aim was to map customer solutions by using components and assemblies made from defined (standard) “building blocks.” Working with the experts from the Steinbeis Transfer Center, the ZF Lemförder project team used a 3-step model (see box, next page).
To define standard products, consensus was needed with all departments as to which standards should be used. An important tool in this respect was the use of a software program for product configuration. This made it possible to significantly reduce the time taken to submit offers, draft designs and prepare work processes.
Equally important was the task of dividing the entire job handling process into standard product processes and special product processes. A major help in this respect turned out to be a lean production system (LPS) which had already been in place at ZF Lemförder for a number of years. Because of the underlying principles it is based on, an LPS makes it possible to make variants quite late in the production process. This makes it easier to reconcile the goals of maximizing capacity use while keeping batch sizes and variants flexible. Extending LPS principles to the entire job handling process – based on similar methods – made a significant contribution to achieving overall goals. However, the project team at ZF Lemförder were not content to leave it as a “specialist” departmental project. “We could tell that introducing variant management in the long term would require a new mindset,” explains Hubert Gross. “People need to see discernible benefits through standardization and not feel like their creativity’s being straitjacketed.” As a result, the project was underpinned by training provided by the Steinbeis Transfer Center to three interdisciplinary product teams. Instruction covered the theory underlying the new system as well as knowledge-sharing by learning “on the job” as part of live project work.
In the three areas looked at – ball joints, axle rods and steering/tie rods – laying down standards based on pre-defined building blocks resulted in different levels of standardization. In some areas, this was as high as 65%. In combination with process optimizations, the resulting throughput times were more than halved, which was even better than planned. But for Hubert Gross, the change in attitude among co-workers was more important than bare numbers: “We want to stay number one for our customers for top-of-the-range solutions, solutions that don’t come off the shelf. But at the same time, we want to keep earning money!”
Dr.-Ing. Günther Würtz, Director at the MIT Steinbeis Transfer Center, compares the new solution to the “kebab principle”: “The purchase of a doner kebab provides a simple yet striking analogy with the underlying principles of variant management. Kebabs are a standard product, based on building blocks (lettuce and tomatoes) with the customer deciding just at the last moment what goes in it – i.e., just before paying. What could be better?”