When Rover took the decision to invest in a new paint plant, the brief was to provide a facility using the latest technology and to minimise installation costs. The turnkey contract was for a flexible facility capable of painting a wide range of vehicle models.
Durr specified Rockwell Automation as project partners. George Laing, software systems manager for Durr explained: “The selection of Rockwell as the supplier of control and automation equipment was critical.” They were specified to supply Allen-Bradley PLCs, industrial computers, overhead displays and network. The project also included a dedicated applications engineer.
THE OPEN NETWORK
Durr had installed many systems over the years using traditional point to point I/O connections. This time, however, a decision was taken to install a ControlNet network throughout the plant. ControlNet offers a high speed, open network, for transmission of time critical application information. Benefits include a modular design that is easy to install and commission.
The cabling infrastructure is dramatically reduced, providing sizeable savings in installation hardware – typically a 60% saving in control panel suites. These savings are compounded with reductions in both installation man-hours and commissioning time. At Rover’s Oxford facility, these savings are in the order of 50%. A further benefit of the reduced cabling, is a far neater installation that is much easier to manage and trouble shoot.
John Painter is Rover’s engineer responsible for the control systems in the new plant. “The decision to use ControlNet has been fully justified, with the system proving reliable and easy to use. Detailed information can be obtained about the process in any part of the building, down to the status of individual motors, drives and control components,” he explained.
Access to the data can be from the central control room or anywhere on site using PanelView graphic displays. With any new system there are issues related to training. Painter added: “We were initially concerned about training for process operators.”
Rockwell Automation provided training where operators could familiarise themselves with the technology in a safe, simulated environment.
PAINT SHOP TECHNOLOGY
The paint shop at Rover, Oxford was both slow – taking about 14 hours for a car body to pass through – and would not meet environmental goals to reduce solvent emissions. The plant was to be the first in the UK to use waterborne paint shop technology, developed with the support of paint manufacturers PPG, and results in an efficient process with minimal emissions.
The paint process includes body preparation and seam seal, primer coat, base coat and a two component clear topcoat. Each coat is oven cured with air jets and a feather duster process ensures that all particles are removed prior to the next painting station.
The consistent high performance of the plant has significantly improved productivity with over 94% of bodies being right first time. The throughput of the plant is currently 35 bodies/h, with a potential capacity of 60 bodies.