Two things make BMW Munich plant stand out. Firstly it’s the only one of the manufacturer’s plants to produce both vehicles and engines. Secondly, and perhaps more significantly, is its location. The plant, established in 1922 to produce aero engines, is now situated in the middle of a densely populated and built up urban environment; not ideal for a carmaker that needs to develop and expand its production capacity. Obviously this was not the case when the facility was established, but now the city has grown rapidly around the plant.
With no room to expand outwards, the plant has built upwards, and now incorporates fives levels of production. Although this may be the company’s oldest plant it utilises the latest production technology to optimise the space available. First stop was the press shop. You might expect to hear or feel the presses in operation before you enter but BMW has gone to great lengths to minimise the impact of production activities on the surrounding area. As such, the presses are housed on the first floor, rather than at ground level. This reduces the transmission of vibrations and noise; and it works, the hall is eerily quiet.
This area has two press lines. One is a newly installed (2011) Schuler servo driven press, delivering 9,000 tonnes of force, to produce whole vehicle outer side-panels. The process is fully automated from handling robots placing blanks on the line, through the several pressing operations to the finished piece. At this point workers manually inspect and remove the panels ready for delivery to the bodyshop. Detailed quality control requires a sample batch of panels to be removed periodically. The second press line is older and produces smaller parts for the body construction. A key factor in the installation of the new servo press line is the speed of tool changing. The dies can be replaced within three minutes through a simple operation – sliding out one die and sliding in the replacement. Previous press equipment would need 15-25 minutes to complete the change over.
Close technical support
Whatever the challenges presented by the plant’s location there are also some advantages. The tooling for the dies is developed and produced at the nearby FIZ research and development centre, allowing for fast delivery of tools and close technical support. The press shop handles up to 20 different types of steel, including UHSS elements. The latter parts are ‘warm’ formed with the hardening process carried out in stages, the final one being in the paintshop ovens. To ensure consistent pressing quality, the dies are regularly inspected and cleaned. As such, BMW says it will deliver a service life of up to 17 years. With the vehicle production lifespan being around seven years the tooling is sold on to other companies to produce spare parts.
Automation and repair
Automation is at a high level at this stage of the production process with the press shop at almost 100% and the bodyshop at over 90%. There are 650 robots in use at the plant, supplied by Kuka and ABB. Operating between 6-7 axes, these perform a mix of handling, welding and painting operations. The robots operate in densely packed cells, with operations closely overlapping. This has enabled BMW to maximise the production space at Munich. The facility houses a robot ‘hospital’ for repair, reprogramming and training. Spare robots are located in a separate cell, performing basic routines in readiness to rapidly replace any units in need of maintenance or repair.
A new addition to the bodyshop was added in 2011 – expanding upwards. Here the robots join the front and rear sections to the to the floor pan. Further along the line a turntable system holds the bodyshell (alternating between sedan and touring models) allowing workers to place smaller structural sections into position. This then rotates to a robot welding station where the parts are fixed in place. This again saves space and improves productivity. Another example of the unique production structure at Munich is the robot cell dedicated to applying and checking the ‘crash glue’ bonding agent and spot welding the inner side-panels to the body. Instead of operating in a traditional line the process is split over two levels. The cell features 12 robots carrying out handling, bonding and welding operations. After the glue has been applied to the panel is it presented to a machine vision system to establish the accuracy of the application. The panel is then positioned on the body and welded into place. This operation sees the robots perform 100 spot welds in 60 seconds. As this is a mixed line (sedan and touring bodies) the framing units swap automatically according the body type coming through.
Each body shell consists of 600 separate parts and requires 6,000 spot welds to complete. There are two ‘in-between’ levels that provide storage for the bodyshells and transport to the paint areas. Reducing energy consumption and minimising harmful emissions are key priorities for the running of the plant. In the paintshop, great efforts have been made to reduce the amount of VOCs produced per car and this now stands at 1.81kg per vehicle; reduced by 30% over the last six years. Water is used to remove the overspray from the paint booths but again the plant achieves a recycling rate of 99%. Each painted car accounts for 240 litres of waste water, down from 460 litres per car in 2006. The resulting waste to be disposed of is down to just 50 grams per car from over 2kg in 2006. As mentioned earlier, plant Munich also assembles engines. Here the production covers a variety of units, from hand built V12s for Rolls-Royce and 7-Series models, to V8s for the M3 and M5, 6-cylinder diesel and the new 4-cylinder engines. All finished units are subject to cold testing, again as part of the drive to reduce emissions produced by the plant. BMW’s oldest plant uses the latest technology to optimise production space and reduce waste and emissions, but it also leads the way in developing the production processes for new models – quite an achievement in the middle of a major city.