CAD Integration and Dimensional Management
Radical new technologies play an important role in the development of the Rover Group's new executive saloon car, the Rover 75. The vehicle design has been engineered using a revolutionary electronic build, or "E-Build," process a virtual prototype of the car is assembled, component-by-component, three months in advance of the actual hardware.
"The new processes and technology provide the catalyst for introducing engineering excellence into a time-compressed vehicle program," said Paul Towers, IT Manager, Rover Large Car Products.
Rover's E-Build uses Tecnomatix Technologies' DYNAMO as the visualization tool to package component parts into assemblies, define insertion and extraction paths for parts and services, and check service and maintenance procedures before the first prototype is built. Each stage is viewed as a 3-D large screen projection, allowing a multi-disciplined team of engineers to work together in a virtual environment. Engineers can deal with problems, review design issues and initiate auditable change control documentation in this environment where the virtual world mimics the physical world.
The process has highlighted a large number of potential problems at a preliminary stage when revisions can be made at a minimal cost and without jeopardizing the timing of the project.
"The exploitation of Information Technology has resulted in a step change in quality, and significant lead time benefits," said Peter Morgan, Project Director, Rover 75. "We have enhanced our simultaneous engineering approach, particularly in strengthening our links with manufacturing."
In addition to checking the detail design of the car, Tecnomatix' software is used to optimize manufacturing operations and ensure product quality. VALISYS tolerance analysis software is used to study the assembly process and assess critical areas such as the gaps between panels. ROBCAD enables critical manufacturing processes to be modeled as a 3-D computer simulationthe digital factory. ROBCAD/Man, a computer mannequin, is used for driver studies, such as the operation of the sun visor, ergonomic studies and assessing repetitive manual operations on the assembly lines.
The Rover Group has completely re-engineered its business processes for the development of Rover 75the first major saloon car project following the acquisition of BMW. A key element of the investment was the introduction of the E-Build process, using Tecnomatix' DYNAMO as a means of integrating CAD data from multiple sources.
Complex structures such as the suspension exhaust system or the packaging of the engine bay can be assembled and viewed as 3-D images. The entire car design involving over 2,000 components is modeled in CAD. Different build stages, of more than 1,000 components or the equivalent for the total engine bay, can also be assembled. As confidence in the E-Build process grew, Rover received immediate savings by canceling all the under-bonnet hardware bucks. It became rather apparent that these would never keep up with modifications and would be costly.
Rover manages design changes through a Concurrent Engineering EPD (electronic product definition) infrastructure which links across to 90 suppliers for the Rover 75. This ensures that the master database is updated within 24 hours if any component is modified.
"The main purpose of the E-Build process was to address the quality issues," said Towers."By building the prototypes virtually, in advance of the actual hardware, we had the opportunity to focus on the engineering performance as opposed to the fit or assemble-ability of individual components.
"The use of visualization and multi-functional design reviews are now standard procedures at Rover. The stereo 3-D capability is very valuable, especially in the early stages when people are not familiar with the car. It really gives the depth of perception not possible by viewing computer screens. It has been used effectively on a range of issues such as routing pipes and hoses, which are now all being done in the virtual world rather than on actual hardware," he continued.
Over 500 E-Build design reviews have been undertaken during the Rover 75 development and over 750 problems were highlighted and rectified by the process. If these problems had not been highlighted early in the design process, considerable re-tooling costs would have resulted which is aside from the impact on the program time-scales.
Notable successes resulted where the assembly process was amended to make it easier for a part to be installed. For example, an apparent tooling problem in a rear suspension upper arm was resolved simply by changing the order in which the components were assembled.
CAD Integration and Dimensional Management
An important feature of DYNAMO is its ability to support a large amount of data to cover major areas of the car and provide a totally integrated solution with multiple CAD systems.
"We didn't want to go through data conversion and needed a system that could handle large amounts of data. In addition to the dynamics of how the car is assembled, the system had to support the virtual package reviews which were being conducted at regular two-week intervals during the development program," Towers said.
"Since we have to perform electronic builds in a very reactive way, both the architecture and the direct integration that gives up the rapid concurrent updates across sites and suppliers is fundamental," he added.
A typical E-Build review will start at 9:00 am, allowing an hour to pull together all relevant data to build the virtual car. Data will also include permutations of different body styles, engines and transmissions. The Rover 75 will have over 20 vehicle options, typically front fog lights, drive intelligence packs and navigation systems which all need engineering into the vehicle.
The review deals with all aspects in the packaging and engineering and whether the components can be assembled. Potential quality problems and typical what-if situations are also assessed. These may range from the implications of the harness sag or the incorrect routing of a hose. Could it fowl or touch a hot part of the engine? What are the implications of a clip failing?
Engineers will also be looking for areas of the vehicle that are subject to a high tolerance stack through the interaction of a number of components. These components might reveal a high level of variation in a particular gap. Any deviations or potential clashes are then followed up by a rigorous analysis to establish the critical tolerances. These can be then traced back to the component supplier either to improve the manufacturing capability or modify the jiggling process for the assembly.
Tecnomatix' ROBCAD is used for engineering two main areas of the production process; the body-in-white assembly line and the trim and final line. ABB Preciflex supplied the main body framing stations and body assembly lines. The layout for the complex facility, which incorporates 159 ABB robots for spot welding and material handling, was designed and optimized on ROBCAD workstations. Commissioning is simplified since over 90% of the programming work is generated in advance by using ROBCAD's off-line capability.
Rover used ROBCAD/Man for a number of ergonomic studies to establish safe and acceptable working procedures. A detailed study was undertaken to develop a procedure for installing the airbag assembly from outside the vehicle. As a general rule, the vehicle fitters work from outside the vehicle; an exception was made for the installation of the grab handles so they could be put in after the seats were installed.
Rather than trying to simulate every detail of the assembly process, Rover decided to focus on critical operations involving kinematics assistersspecially designed handling devices for supporting heavy components while they are maneuvered into position.
Examples of this process include installation of the heater, installation of the carpet and the door on/off process. Rover has modeled all the most relevant tooling using ROBCAD to provide the kinematics and explore the most efficient methods for completing these tasks.
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