Chrysler Corporation, Belvidere (Belvidere, Illinois), the assembly plant for the Dodge, Chrysler and Plymouth Neon, has initiated a program of verifying the integrity of tooling on the production line. A  portable articulating arm measurement system is being used on the assembly line to periodically check pin diameters, dimensional location of pins and location of part resting pads. As a result, it is now possible to research previously undetectable problems in tooling to see if adjustments need to be made.

According to Don Pollock, Contact Engineering Supervisor, BIW, build problems are the result of any of the following: parts that are out-of-tolerance; manufacturing process problems; tooling that is worn, damaged, out-of-specification; or a combination of any of these.

Identifying tooling as a root cause had to be done by inference because the only practical way of getting data would be removing the fixtures from their stations and bringing them off-line to a coordinate measuring machine. Of course, this is not feasible and does not address the problem of whether or not the tooling station itself is set up properly.

On occasion, theodolites had been employed for tooling verification. The downfall of the theodolite system is that they are limited to line of sight only and are not user friendly. The measuring would typically be done on a weekend when the line shut down because the theodolite system does not lend itself to “fast checks” and routine data collection for preventive maintenance.

Pollock said, “Realizing there was a real need to fill on the production line, the dimensional control team here in the body shop focused on finding a product that could quantify stations and tooling without disrupting our process. Our inquiries led to a manufacturer ofarticulating arm-type measuring machines . The Chrysler Tech Center helped us by finding another measuring arm manufacturer and an alternative technology that uses cameras and LEDs.” (The latter was ruled out on the basis of cost and performance.) After watching in-plant demonstrations of the three systems, Belvidere Assembly selected the CimCore measuring arm system.

Key considerations in selecting this particular product included:

• Experience
• Product was already used successfully in similar applications.
• Consistent volumetric accuracy no matter where the arm was mounted.
• It could even be suspended upside down over the line to measure in congested tooling stations.
• Wrist mouse. There is button on the measuring arm’s wrist that allows it to be used remotely as a mouse, so the operator can interact with a computer up to 12 feet away, on the other side of a safety fence. This feature saves time and protects the computer from oil and grease.
• Easy-to-use software. The arm at the Neon plant is utilized by the tooling department, people not accustomed to using coordinate measuring machines. The software had to be user-friendly. Toolmakers at the Neon plant went through two weeks of training with the software and arm. After practicing with some test fixtures and doing some field tests on the assembly line, they were proficient enough to begin collecting their own data using this system.

Quick & easy troubleshooting

The basic requirement is to establish the location of steel rest pads and locating pins at a station. The arm and software allows for fast setup, alignment and collection of this essential data. As data is collected for each station, the X, Y, Z coordinate value of the pins and rest pads are recorded and kept in a "library". Then, if something goes wrong in the future, the amount of change in the location of the points will indicate how much of the problem is attributable to tooling.

Pollock said that the tool makers are pleased to have the measuring arm at their disposal because they can capture the kinds of data useful in problem solving. “We are opening a window of knowledge for how a station is configured. We can see if the tooling is still as precise as it should be, or if tooling components have become worn, damaged or changed location.”

Versatility

Engineers at Chrysler Belvidere are looking for other ways to use the arm on the assembly line. One possibility is measuring critical points on the underside of the vehicle while it is on the conveyor in assembly, rather than bringing it back to the CMM room. The arm may also be set up inside of a car to check trim garnish and seat track mounting. Layout people may also start using it when there is a critical part to check and their surface plate is occupied in the process of checking a car.

The changeover for the new Neon will not be a complete removal of current body shop machinery. New model fixtures will be inserted in “protected” areas throughout the body shop and carryover fixtures will be “kitted” with new tooling. Each new fixture will have small locating holes to be used as benchmarks for fixture alignment. This will allow for a rapid alignment of the arm, cutting down on the time the toolmakers need to spend at a station.

The portable CMM will be used to document current location of the tooling when pilots are built and to certify the proper location when the kits are installed. Being able to insure that tooling is on the correct location to start with will make for smoother transition to the new model and allow us to build a better car.