Application Otto Bihler, Halblech

A premium automotive supplier in southern Germany produces many variants of an important connection part in e-mobility. Linear machines from Otto Bihler Maschinenfabrik ensure for an economical production. The vertical machine tables are equipped with AMF zero-point clamping modules so that the frequent tool changes of the multi-variant series can be carried out quickly and reliably. In this way, the numerous modular linear tools can be set up in a time-saving and economical manner using the "Plug & Produce" principle. This gives premium electric vehicles from Stuttgart a further boost.

"Without our "Plug & Produce" principle with AMF zero-point clamping systems and modular linear tools integrated in the machine, we would never have got the order," emphasises Marc Walter, head of design and development at Otto Bihler Maschinenfabrik in Allgäu, Germany. However, a current-generation linear machine from Bihler has recently been producing the busbars for premium electric cars from Stuttgart. These highly important busbars, which connect the battery to the drive unit, are virtually the lifelines of electric cars. And anyone who thinks that parts for electric vehicles can be produced just like that are very much mistaken: the requirements for precision and tolerances are often higher than for combustion technology.

Short tool change times make small series profitable

"For annual quantities of 10,000-50,000 parts, as requested by the customer, our powerful new linear machines are ready in one to three hours", Marc Walter reports. With the tool change times of several hours to a whole shift that are common in the industry, such orders could not be carried out economically. With the new linear machines from Bihler, the whole process only takes about one hour. This is due to the modular design of the machines and, in particular, the tools. According to the clever "Plug & Produce" principle with standardised interfaces, the linear punching and bending tools are simply plugged into the vertical machine table and the next job can start. In this way, smaller batch sizes can also be produced cost-efficiently between the usual series of millions.

The tools which are compatible between each other are picked up by the built-in AMF zero-point clamping modules. Five mounting stations in the machine table - traditionally arranged vertically at Bihler - define the interface for the tools. Each receptacle is equipped with four KP5.3 zero-point clamping modules. They are pneumatically controlled with a pressure of five to a maximum of twelve bar. The base plates of the tool modules are equipped with four matching clamping pins. When the operator inserts the tool, these clamping pins are each retracted with 1.5 kN and held in place with 13 kN. Control functions for interlocking, opening and support ensure the correct seating of the tool. "These processes run reliably and safely with a repetition accuracy of less than 0.005 millimetres," assures Manuel Nau, Sales Manager at AMF. Optionally, four more clamping modules of the SP150 models are installed. These can be used to fix centre punches for ejecting the parts.

Best machines, even in the 70th anniversary year

When the high-performance linear machines of the new product line comprising four highly standardised machine types of the latest generation get started after a tool change, the series quickly run into the millions of items. Punching, bending and forming is carried out as fast as the eye can see. This was already the case in the 1950s when Otto Bihler founded his company and presented the first punching and bending machine of this type at the Hanover Trade Fair in 1957. The basic concept of the machines with the vertical machine table has not changed to this day in the 70th year of the company's existence. When the MACH 1 machine broke the sound barrier of 1000 strokes per minute at the time, it represented a major milestone not only in the company but in the industry in general.

"In the early years, a tool change could take up to two days", Marc Walter reports. And even later, the technicians had to unscrew the special tools in long-winded processes, attach new ones and set them up. Even with modern machines, several hours or even a whole shift of production time were lost. It was only with the modular tools and the equipment of the machines with AMF zero-point clamping technology about ten years ago that productivity was given a huge boost. "Since the new linear machines that are also modular, tool changes are now usually completed within one to two hours," says the experienced design manager.

The clamping modules are small, robust and technically clever

The reliable AMF built-in clamping modules play their part. The cover and piston are hardened and thus particularly robust. "Practically nothing ever breaks," assures Rainer Guggenmoos, sales engineer at AMF, who has been supporting Bihler for years. Because the modules are very compact, they can also be easily screwed flush into the machine table. "The fact that the technology inside the small power packs is not entirely trivial has been experienced by some users who wanted to replicate our modules themselves", says Manuel Nau. The users and machine operators of the Swabian automotive supplier are also thrilled that they can manufacture the 18 different variants of the busbars with the highly productive linear machines from Bihler, quickly and automatically as well as with process reliability and repetition accuracy.

Without the fast tool changes, such orders could never be produced as cost-effectively that the purchasers of the premium OEMs would be satisfied with them. Naturally the busbars for the premium electric vehicles are the highlight of the products manufactured on the highly productive linear machines. But these are by no means the only smaller series for electric mobility products. For example, hairpins, HV connectors, cell connectors or the ZSB circuits of the current distributors for power distributors are also produced on them.

Partnership equally enables small and mass production

Bihler addressed this growth market at an early stage. Thanks to the long-standing and pleasant partnership with AMF and their zero-point clamping modules, the machines are also lucrative for smaller batches. And if production in e-mobility goes in the politically desired direction with quantities in the millions, then the linear machines will no longer have to prove their performance anyway.