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Kick Starting CAM at Chrysler: Making Control Programming Viper-Fast

To simulate manufacturing processes is fine. It gets you closer to the real thing a whole lot faster. But with a new technology development, Chrysler is not only able to simulate workcells, but to actually generate the actual programs needed to run the real equipment at the same time.

We've all seen the Chrysler commercials touting the company's implementation of digital technology for the development of its vehicles. This work, which is being performed with CAD/CAE/CAM software developed by and with Dassault Systemes (U.S. operations: Burbank, CA), isn't particularly unique as compared with what is being done by other automakers. But let us hasten to say that there is a difference, perhaps, in the degree or the extent to which Chrysler utilizes the software (and we just don't mean in making clever commercials, either).

CATIA software was first used by Chrysler in 1984 (the influence of its absorption of American Motors, which had gotten together with French automaker Renault, had a big effect on Chrysler's implementation).

When it comes to the software, one thing that Chrysler has done, relentlessly and consistently, is to say, in effect and in practice, "This is what we use, no ifs, ands, or buts." Fully recognizing the importance of the system to their vehicle design, engineering and manufacturing, Chrysler engineers and programmers have worked with their counterparts at Dassault to further enhance and optimize the software. One interesting aspect of this is that although Chrysler is well known for permitting its suppliers to do what the suppliers do best and leaving them alone to do it, CAD/CAE/CAM is something that is seen as having a pivotal effect on the overall capabilities of the company, so they are actively participating in what's occurring at Dassault.

Importantly, the Chrysler engineers are not only interested in the ways and means to achieve better, faster, and more descriptive design capabilities, but also in improving the manufacturing necessary to take those CAD models and to turn them into actual products. This latter work led, in 1995, to the introduction of the Digital Manufacturing Process System, (DMAPS), a joint development of Chrysler and Dassault.

DMAPS Described

DMAPS is to the process what CAD is to a product. That is, when product engineers are working with their CATIA software, they are not just designing parts individually, but in the context of other assemblies. After all, things must fit together. If Part A is to be inserted in Part B, then the mating interfaces must be sized appropriately. This is one of the fundamentals of why it is important to use a common database.

Beyond (but including) architectural considerations, there is the issue of taking those various and sundry components that must be made—whether it is an intake manifold or a body-in-white—and determining the processes that must be employed. This is the issue of looking at the tooling, the material handling, the process layout, and all of the other manufacturing-related issues.

What DMAPS permits Chrysler's advanced manufacturing people to do is to take the CAD data and use it to simulate the processes. If a robot is expected to make spot welds at various points along a flange, for example, then it is a good thing to know that the robot will actually be able to reach those points before the cell is constructed. While this is generally done as a matter of course whether manufacturing engineers are using paper and pencil or workstations, DMAPS provides the additional benefit of working with the CAD data, including part tolerances, so the digital mockup of the processes are closer to what will actually be the case on the factory floor. This simulation step helps validate the processes.

Beyond DMAPS

Chrysler and Dassault, which were ably assisted by supplier partners Rockwell Automation, Deneb Robotics (a Dassault company), and Progressive Tool & Industries (PICO), have taken DMAPS to a new level, one that provides much more breadth to the capabilities. They have developed what is designated CPGA, for Control Program Generation and Analysis.

Before examining this, let's simply cut to the chase.

"This CPGA technology will reduce the time it takes to program a typical workcell by thousands of hours, shave two to four months of the development time of passenger vehicles and save upwards of $20 million per assembly plant," according to Frank Ewasyshyn, Chrysler's vice president, Advance Manufacturing Engineering.

That's right: thousands of hours and millions of dollars.

And what is startling about all of this is that fundamentally, no one is really having to do anything they're not already doing. (Note: According to Ewasyshyn, this technology is proprietary to Chrysler for the next several months, which just goes to show you how good it is to work with suppliers on technology development. Of course, they spent 2.5 years working on development, so some advantage is to be expected.)

Hours to Minutes

 

Ewasyshyn provides a real-life example of how these savings are achieved through CPGA: Say there are two robots and six clamps involved in a process. In order to do the programming for that setup, it ordinarily takes eight to 10 hours. With CPGA, it can be done in six minutes. Multiply that by the hundreds of robots and thousands of clamps in any given assembly plant, and you can quickly gage the time advantage realized with CPGA.

Rockwell Automation is a controls company, such as its line of Allen-Bradley programmable controllers (PLCs). Deneb Robotics is not a robot company, but provides simulation software. PICO is a leading Detroit systems house.

The key functionality of CPGA is that it actually generates and validates the control code used by PLCs to run the factory equipment, such as clamps and robots.

What this means is that there is the product definition that comes through CATIA, which then goes to the process definition created by DMAPS, then the result is the code generation and verification with CPGA—and it is fully associative.

When performing DMAPS, there is a computer simulation of the process. This simulation is also performed in the CPGA arrangement, using Deneb's IGRIP 3D graphics-based simulation package. But it is being used in an atypical manner.

Typically, explains Bernard Charles, president of Dassault, when process simulations are performed, the whole thing is "theoretical." It is truly a simulation.

The Real Stuff

But in the case of CPGA, the engineers simulate the workcell performance with the IGRIP program with actual part data from the CATIA package, as well as fully described equipment models within the simulation software itself. Once that checks out, program code is generated. In order to validate the code, IGRIP interfaces through Rockwell Automation's RSLinx to Rockwell's PLC emulator, RSLogix (all of which operate under Microsoft Windows NT). The PLC emulator then drives the simulation with the program code just as an actual PLC would. This then allows the determination if, indeed, the program is correct, not only in terms of spatial considerations (e.g., no collisions) but also in terms of sequencing (e.g., parts are clamped before they are welded). Should there be issues, they can be quickly resolved within the digital space, well before the factory floor.

"We can go from the model to the control code," observes Ewasyshyn. That's a major advantage of CPGA. What this means is that the workcells can be produced (by an outfit like PICO) that will not only be configured correctly from the standpoint of necessary equipment and relationships, but will also come up faster because the program will have been generated and validated.

According to Ewasyshyn, this technology is not only applicable to body shops, but to any part of the process that uses control.

Charles cites an additional benefit of the CPGA. It's "memory." As he puts it, often times, when equipment is put on the floor of a plant, it is "tweaked" in order to get things operating just right. What can happen is that the person who did the adjustment is either gone or has forgotten precisely what was done. It is consequently impossible to replicate that workcell. Given that there are efforts throughout the automotive manufacturing community to find the best way to do something and then repeat it over and over again, a lack of memory can be troublesome. But through the use of CPGA, there is the ability to reuse the process as the tweaking is performed digitally.

 

control programming

Before all of the tooling and equipment and parts shown here—in this simulation generated with software from Deneb Robotics—are in place, it is useful to make sure that everything fits and that the sequences are correct. That's a standard reason for using simulation software. But Chrysler, through a development that was performed by its people as well as with engineers, programmers, scientists, and other personnel from Dassault Systemes, Rockwell Automation, Deneb, and Progressive Tool & Industries, now has the ability to not only simulate the process, but also generate and validate the actual program code that will be used to operate the PLCs that will run all of this when it goes from the digital world to the physical one. The time and money savings are enormous.