Flexibility, affordability, and efficiency are key ingredients of today’s successful automotive assembly lines. In the past, traditional auto plants produced only a few models of a car or truck, relying upon fixed tooling. But, one of the biggest issues in today’s production environment is the incorporation of multiple vehicles at the same plant in much higher densities than would ever have been considered in the past. As reported in a recent 2006 Harbour Report, assembly plants that are flexible generally have higher capacity utilization, which is a critical element in generating higher earnings and reducing capital costs.
3D, Not 2D
For the HMS Co., Troy, Mich., a design engineering firm that specializes in providing automation systems and vehicle assembly line tooling to the automotive industry, the level of complexity in today’s assembly lines cannot be accomplished in a 2D environment during processing, but must be simulated in a virtual 3D world.
According to HMS Information Technology Manager, John Haning, “With dedicated lines, we felt relatively confident that our lines would perform as intended once they were built on the plant floor. But today’s flexible plants incorporate such a high level of automation including robots, conveyors, fixtures, and other equipment that we need to verify that all of this can be reprogrammed or reconfigured to build vehicles with vastly different designs -- such as a four-door sedan vs. a pickup truck.”
Simulating the Assembly Process
To provide the simulation techniques they need, HMS relies upon DELMIA IGRIP software with the UltraSpot add-on. IGRIP is a physics-based, scalable robotic simulation solution for quick and graphical modeling and off-line programming (OLP) of complex, multi-device robotic workcells for various applications.
The UltraSpot add-on provides both traditional and fixed TCP spot welding applications with a fully functional tooling interface for the design and simulation of complex tooling and fixture device clamps. Collision-free robot trajectories can be automatically verified and numerous optimization features can be used to reduce process cycle times. HMS relies upon UltraSpot for robot positioning, tool and peripheral equipment placement, reachability, cycle time, validation of the process, and off-line programming.
Planning Robot Time
When working on a project, HMS will usually receive from their customer a rough design of the assembly process consisting of set robot speeds, predicated welds, cycle times, etc. HMS evaluates the supplied process, optimizes it, and finalizes it after simulation.
“The whole point is that we find the issues during simulation, correct them, utilize the available time for the robots, and make the line function to its best ability,” says Mark Kuzniarski, HMS simulation manager.
Kuzniarski states a particular example where a material handling robot was sitting idle for a period of time. Simulation helped HMS to determine that the robot could be welding while it was waiting, so a weld gun was moved off of one robot in the original design and mounted to the material handling robot, which could now handle multiple functions. This eliminated the cost of an entire robot.
The OLP function of DELMIA IGRIP is also very important to HMS, allowing them to accurately program its robotic systems without tying up physical resources on their customer’s factory floor, thereby reducing man-hours and process engineering lead-time while improving accuracy.
No Loss of Production Time
In addition to the difficulty of planning for multiple vehicles to be assembled on one line, most of HMS’ work occurs at plants that are already running production vehicles. HMS is often retrofitting an existing single model plant to become multi-vehicle ready.
In one situation, HMS was able to retrofit 150 robots with 40 stations comprised of an average of 50 tools at each station across two plants within six months. The project involved a six-year-old line reconfigured to accommodate both increased production of the existing model and a brand new style, all without losing any production time.
“This is probably today’s biggest task,” says Glen Porter, HMS general manager. “You go into a plant that’s already running and say ‘I’m going to go in and rip that plant in two, mess with it for about six months, and then guarantee that we’ll run both old and new product with no loss in production during this conversion.’”
Sounds impossible, but HMS has found that with simulation it can actually meet or beat that expectation. And, assembly lines are being planned and produced in half the time it used to take. “Today, despite a two to three times heavier workload, we’re producing faster because of simulation,” adds Haning.
Porter concludes, “Our use of the IGRIP UltraSpot tool provides us an edge in that we know how to leverage the simulation to its fullest, allowing us and our customer to be winners at the end of the day.”
