Applications

WAGO I/O SYSTEM Helps BMW Run on All Cylinders

Because of its location limitations, expanding the Munich site is impossible. Therefore, all available rooms need to be used to their fullest capacity. This applies as well to the raw material and the production facilities that press each individual part of an automobile using over 400 robots.

Historically, each change in production required a completely new I/O configuration. In these instances a standard fieldbus node was not used to its fullest potential and therefore was too expensive for many applications. Engineers at BMW reacted quickly to allay this inefficiency by using the WAGO-I/O-SYSTEM as a standard installation for the past two years, (mainly as point control in the distribution of raw material.)   

Network

The various production models at times run through one station and at others they run through multiple, different production stations. In addition to these production statins, there are also stations for random quality controls and for re-working. The conveyor used by BMW resembles more of a network than the classical separate lines. This network is adjusted for the production of new models and any variations. BMW uses an electronic hanging conveyor system from AFT GmbH (Schopfheim, Germany) for moving crude car assemblies throughout the plant. This conveyor utilizes both signal and hoist joints. A ceiling rail carries the electronic transport device attached with different items such as parts or partial assemblies. Each moving device is equipped with its own electronic drive. Even fifteen kilometers of rail at different levels connected by a hoist joint can work well. The work stations are at ground level and the above tracks distribute and shunt the units.

The Problem

Each line contains a write/read system that uses an antenna to communicate to the SPS. Switches and disconnectable channels make it possible to control each individual carrier. During a large remodeling project in 1996, the communication between the carriers and SPS was changed to fieldbus technology. Parts for production were already being delivered using the Interbus protocol. Introducing fieldbus technology into the advanced technology of the, gave the planner yet more specialized problems:

Though only binary signals are being processed, input and outputs are distributed extent routes. The pneumatic operated devices with one straight and one branched rail have more than 200 switches and need 8 inputs and 2 outputs with 24 V control voltage. Depending on the routing track, switched paths, empty carriers, detection, etc are needed. An input and output of 24 V to 230 V is needed. Standard fieldbus nodes with exact quantity of inputs and outputs and only one switching voltage, usually had unused modules or complex wiring.

 

Changes to these routes need be made efficiently. Engineer Michael Philipp is responsible for the planning of advanced technology of BMWs raw material.  He states. "The limited space in the building needs be used optimally. Any remodelling cannot stop production." The remodelling of the routes must therefore be done in small steps and during breaks. This creates a need for the fieldbus node to communicate with the switches. If a route change was imminent, the switch including the controller would need to be changed. The fieldbus and power supply could then be reconnected. This requires that any additional inputs and outputs needed for more switching positions should be easily installed. The search for an ideal solution brought Mr. Philipp to the WAGO I/O SYSTEM. BMW had already been using WAGO rail-mounted terminal blocks with CAGE CLAMP in its applications so it was a natural extension of this success.

The Solution

Due to these successes, the new system was accepted with an open mind. Michael Philipp commented on the selection process. "We already had determined to go with the CAGE CLAMP connections when WAGO made its offer." Within a short time frame, a test program was initiated.

Test Phase

During the test phase, compatibility with the existing controls was proven quickly. A test length of 4 weeks verified that the WAGO I/O SYSTEM would have no problems. Nothing stood in the way of installing a prototype into the extisting device field. Only 3 months after the start of th test, BMW was convinced of the benefits of the WAGO IO SYSTEM.

The implemention occurred from 1996 to 1998 and went smoothly. Since then the system has proven itself as absolutely realiable. The switch boxes are built perfectly around the nodes. The limited space left still allows further expansion if necessary. BMW's Michael Philipp states "If a production change requires additional input or outputs, we just fit the new bus modules to the node." Even permanent sub-distribution is more compact thanks to WAGO's front entry technology.  

The Finish

Besides switch controls, BMW uses the WAGO I/O SYSTEM in the finishing of the front-end assembly, hood and trunk. Space is a concern even here and can become an issue for the designer. No space is available for stocking parts next to the production lines. Parallel to the lines, therefore, is an endless chain of parts for each work station. The speed of the chain allows for assembly and removal without any stoppage. The minimal distance and an ergonomical height eases the workflow. Furthermore, compact and user-friendly tools and assembly devices are integrated into each workstation. Parts are taken from a rail that runs over the production line and then attached to the automobile. As the line moves, the tool moves along on the rail.