This summer, in a record change-over time, Chrysler stopped production of its old Grand Cherokee and started building a new model. Contractors were allocated just three weeks to install the new production line, and 3,000 people worked day and night to complete the task. For the conveying systems suppliers, it was one of the most challenging experiences they’d had.
Over the past 20 years, the length of plant shutdowns for model changeovers has shortened dramatically, says Dave Standen, operations manager at the Detroit Jefferson North plant, where the Chrysler Grand Cherokee is built.
‘Downtime is very expensive,’ he says. ‘There is the cost of the building standing idle and people lose their skills when laid off for a long time.’
Standen reckons most of his colleagues in the car industry have achieved 10 12 week shutdowns, compared to the average of 16 weeks 20 years ago. But the Grand Cherokee plant’s three-week shutdown really made history.
Chrysler’s task was easier because it had spare land next to its plant where, in the two years before the shutdown, extensions to the body, paint and assembly shops were built, adding 800,000sq ft to the existing 1.8 million sq ft plant.
‘The approach was similar to the rolling launch method used by Japanese car companies,’ says Standen. ‘They use two body shops to make the two models and then send them down the same assembly line.’
Chrysler built a duplicate body shop in the run-up to changeover. An additional spray booth and oven was installed and extra assembly capacity provided. During the three-week changeover period, all that had to be done was to link up the old and the new parts of the plant.
It sounds simpler than it was. Every conveyor and sub-system had to be replaced. For Dearborn Mid-West Conveyors, supplier of $100m worth of conveyors to the body and trim shops, it was the largest project the company had completed in such a short time.
Such a short timescale has an enormous impact a project’s management, says Wes Paisley, president of Dearborn Mid-West Conveyors. ‘You have to be sure-footed and quick on your feet. You need to plan in advance and prepare the systems well. As soon as the window opens, you have to go in with a massive workforce and get the equipment fully tested and running.’
On the Grand Cherokee project, the change-over period was planned out day-by-day, hour-by-hour, in terms of crews and material logistics. ‘We used 1,500 field personnel, mostly union and trades people from all over the country who we had never used before,’ Paisley says. ‘Our 50 100 supervisors coordinated them. It was very crowded and very hectic.’
Jervis B Webb, responsible for a $40 50m contract to equip the paint shop, started work in the plant the previous Christmas. ‘We’d go in at weekends and holidays and do whatever we could without disrupting existing systems,’ says Bob Pierson, Jervis B Webb’s vice president for sales and marketing. ‘In some cases, we installed a new conveyor parallel to the existing one, so that it could be quickly linked up during the shutdown. In others, we modified existing conveyors in a way that had no impact on production.’
Chrysler’s Standen is very proud of the fact that in the run-up to the changeover, no disruption of production occurred. ‘We were running a three-shift, six-day week, at the highest output the plant had ever achieved.’
In conveyor technology, little has changed over the decades. However, shorter installation periods have led to modular construction. ‘Conveyor systems made in modules, which can be hooked up and plugged together in the field, save time on-site,’ says Pierson. ‘They also reduce your reliance on a lot of highly skilled installation people.’
A module, he adds, could take the form of a 40 60ft section with as much of the control and pneumatic ancillary items as possible mounted on it. It would be pre-wired and pre-tested. ‘When you go into the customer’s shop, you have to mount five pieces of equipment instead of 100,’ he says.
The need to pre-wire conveyor modules off-site has driven the industry to replace conduit wire with communication cable. This evolution has been resisted for many years in the US, says Paisley.
‘There were worries about safety,’ he says. ‘The industry likes everything to be in conduits to make it impervious to damage. But without cables, it would be impossible to meet the deadlines.’
The Grand Cherokee project was the first time Dearborn Mid-West Conveyors had installed a cabled system, but it is a trend that will grow, Paisley forecasts.
He says the experience at the Detroit plant was a great success. ‘However, we would not want downtimes to shrink any further. It really tested our company on its ability to coordinate the efforts of a lot of people and get the job done quickly.’
Standen also doubts whether an even shorter changeover period would be feasible. ‘For one thing, there is not enough space to have more than 3,000 people working in the plant at the same time,’ he says. He adds that the modified plant has been tooled up in a way that should accommodate the next model without big changes.