Designing and building a compact—600-m² (6500-ft²)—all-new assembly facility to produce the high-performance power units of the McLaren MP4-12C would be a real challenge for any engine manufacturer.
But engine production is a first for automotive engineering and strategic consultants Ricardo. Closely involved in the design and development of the McLaren’s M838T V8 (as it has been for many gasoline end diesel engines for decades), Ricardo also took on the role of engine builder in a tightly planned area with equally tight timing of 18 months from inception to pilot production.
The facility is built around a 10-station line with incoming materials inspection and line-side component delivery. MacDonald Humfrey Automation (MHA) and and its sister company, Exmac Automation, played key roles in making it all happen in near-cleanroom conditions at Ricardo’s Shoreham Technical Center in southern England.
Each of the stations has a human machine interface (HMI) system supplied by MacDonald Humfrey. It provides guidance to the operator on the precise sequence of operations required at each stage of assembly. The tools and assembly equipment used at every station are instrumented and provide data directly into a central warranty database for each engine built, to give complete finished product traceability.
The individual line stations are interlocked via their HMI to ensure that all operations and checks have been successfully completed and recorded before the line can be indexed and the engine advanced to the next station.
As well as the main production line, the Ricardo facility includes a cylinder-head subassembly line, dress area, and an end-of-line hot-test cell that enables the performance of every engine to be fully tested and validated.
Because of the small size of the facility, "designing the conveying system proved particularly challenging, as did the 50-minute TACT [total average cycle time], which was relatively slow due to the low production volume of eight engines per shift,” explained Ricardo technical specialist Dave Thompson.
The Exmac handling system allows workers to load engine blocks on the line and rotate them at any of the assembly stations. The system is also indexed manually to allow greater control over the assembly process, provide the flexibility to accommodate long cycle times, and enable Ricardo to achieve batch production of single engines or different engines as required.
Exmac designed the 10-station line to take up very little floor space. Engine blocks are fixed to lightweight trolleys using a vertically mounted slew ring and quick-release plate, which mates with a bracket located on the engine bell housing.
With the engine block locked in place, it can be rotated through 360°, allowing complete access for operators. At station 1, when all assembly functions are completed, the Exmac control system allows a stop to retract, enabling the operator to push the trolley to a holding position until station 2 is clear. The system then allows the trolley to be pushed to station 2, where the same stop and lock procedure holds it in place for that station’s assembly functions. This continues to the end of the line.
If there is a problem at any station, the trolley continues to the end of the line where it is removed to a holding position for the engine to be reworked as required. Trolley and engine are then returned to station 1 and moved to the appropriate station to allow the engine to continue its build program.
Exmac-designed mechanical locking systems locate and secure trolleys in position at each station while ensuring that they cannot be released until the HMI system confirms that operators have completed all required tasks at each station.
Manufacturing innovations include a novel, low-cost method of rotating the engine using a battery-operated electric drill fitted with a special socket that is attached to the gearbox.
Thompson noted that Ricardo also required “an aesthetic approach” to the design of the line, ensuring that it complements the new engine-build facility and presents an attractive and technically advanced visitor environment.
Commenting on the HMI system, MacDonald Humfrey Project Manager Paul Crosbie explained that Ricardo envisaged a bespoke tracking system that would provide its production engineers with a list of operations that they could vary and configure themselves. For example, not only did they want to be able to set task-by-task instructions showing assembly operators how to build the engine, but they also wanted to include time allocated to each task, such as air tests and gasket glue plotting.
The HMI also needed to integrate all the operations and provide confirmation—with a time and date stamp—that all tasks had been completed. Effectively this meant that every operation needed its own program. Such complex HMI systems must be developed as bespoke schemes, something MacDonald Humfrey had previously achieved for Aston Martin, BMW, and Jaguar Land Rover.
The HMI system developed for Ricardo’s engine line takes operators step-by-step through the process of building an engine, providing detailed on-screen information and visual aids at every station, even including instructions for each bolt to be tightened and the torque setting required. The screen for this operation highlights the specific bolt to be tightened. A green light is used to confirm that the bolt has been tightened properly, and then the next bolt is highlighted.
Use of dc tooling allows for the measurement of torque and angle to provide full traceability. Scanners record the 2-D bar codes of every component at each station so any operation can be reviewed, if required.
A Siemens programmable logic controller drives the mechanical operation of the line such as the stops, the push buttons, and the interlocks for the tools. It is backed up by a server-based PC system that drives the build instructions and logs all the information. The build number of each power unit is scanned at the start of the line, ensuring that all subsequent operations are logged to that particular engine as it moves through the build process.
Data is fed to a MacDonald Humfrey MachPick pick-to-light system to ensure efficient error-proof component picking. The system is user-configurable to allow sequential or simultaneous picking, with real-time event reporting and control. It also provides zone indication alerts and profile checks, plus stock monitoring for replenishment.
The system uses algorithms to examine the different tolerances of matched components such as crankshafts, pistons, shells, and clamps and, in this case, automatically identifies shims to match the tolerances of the different parts.