Planning Your Tooling PdM Program

Since 1992, the Warren Stamping Plant of Chrysler Corporation has been travelling a road toward total control of their dies, jigs, welders, fixtures and other assorted tooling which are part of The Process. The Process is just that. Every tool, machine, procedure and person involved with the process of manufacturing automotive sheet metal body panels is being fine-tuned, so to speak, and prepared for error free performance.

The people are trained and then they contribute to the development of sound, practical procedures which expedite manufacturing. Presses and machines are subject to a regular preventive maintenance (PM) program. Tooling has been brought under control through a strict regimen of PM which utilizes customized checklists and a cycle-based frequency of 100k hits (some are on a 50k schedule). We are, however, some distance from total control or, more commonly, total productive maintenance (TPM).

"Run tooling to failure" is the mindset that we have been fighting since we began our efforts in 1992. It is an idea that industry-at-large believes - notice the dearth of tooling PM seminars being offered. It is an idea we de-bunked with $$$. Cost-avoidance $$$. Compared to 1992, we are now avoiding $1.2 MM in downtime costs every month. The reliability that has resulted from PM has allowed other profit centers to be developed by reducing just in time (JIT) parts storage and, by converting that floor space to sub-assembly production, Warren Stamping is able to ship assemblies - instead of parts -which are less prone to damage due to handling.

The opportunity for cost savings is substantial at Warren Stamping. The facility boasts 43 acres under roof (1.8mm sq. ft. of floor space); 20 major press lines; 18 major assembly lines (6 more planned); 1,700 tons of steel disbursed daily; 23,000 major assemblies produced daily; and annual sales in excess of $600MM. When we "prove" a pilot project on a press line, it will be rolled out to 20 lines and the cost savings pour in 20-fold. Ditto with the assembly process where John Hillegonds is perfecting that PM program.

Achieving the success of a competent PM program brought almost universal acceptence by the workforce. In fact, both management and labor have embraced the basic principal of tooling maintenance. It is this fact that encourages us to proceed to the next step - predictive maintenance (PdM). Let me warn you, this will not be a typical PdM program, per se, but one that has been designed to achieve the same results as equipment PdM.

A basic component of PdM is the ability to measure wear and interpret the resultant manifestations, be they thermal, acoustic, vibratory, etc., to pinpoint a potential problem before it degenerates enough to cause failure. Because most facilities use multiple installations of the same equipment, wear data from one will help to predict the longevity of its replacement. This feature is not one that is shared with tooling. Most tooling is unique to the installation and, therefore, prediction based on "similar" tools is a useless commodity - fine for PM but not for PdM. To get "in process" wear data, we have to monitor the condition of the sheet metal panel we produce. Obviously, SPC data would best serve our needs. The question is how.

Back in 1992, we enjoyed the participation of the University of Michigan School of Mechanical Engineering. Specifically, Dr LinnChu Mu and Dr. Bia Zhang. Together they suggested that panels could be monitored through the use of a simple fixture and a series of electronic gauges connected to a computer.

With simple software, up to 20 critical points could be monitored for wear and the resultant SPC data could point the finger at potential failures. We were not in a position to utilize this method in 1992. Sort of like pushing gravel when there were boulders to deal with. Now, in 1997 the boulders are gone and only gravel remains. The proposed method is being spruced up by adding more advanced technology to gather the data necessary for PdM.

In the meantime, certain basic steps are being taken to expedite the die maintenance process. Primarily, we do not want to create a special class of people who "read" the problems and, then, try to communicate the problem to those who will repair the tool. In our facility, communication is problem #1. To alleviate the inherent problems associated with communication, the "reader" will be the die repair person. Before I get ahead of myself, let me relate to you each part of the process by which we arrived at a tooling PdM program.

To distribute work in an equitible manner, six person teams are formed - 2 from each of 3 shifts; die maintenance hours were compiled for every die in house, including die repair and die PM; every die was rated to a complexity scale of 1 thru 5; using simple arithmetic we divided total maintenance hours by total complexity points to arrive at 184.5 annual total maintenance hours per complexity point; each trades person is assigned 10 complexity points. A team of six, therefore, is responsible for enough dies to add up to 60 points. The theory behind die assignment to specific tradespeople is simply an extension of past practice. Whenever we had a problem die with recurring failures that were hard to rectify, a team of die makers was assigned exclusively to that die. The experience gained with the tool by this focused team eventually led to a lasting "fix" that eliminated or greatly reduced the extraordinary downtime. This program for PdM builds on that concept to the point that every die will be treated to that same scrutiny by "experienced" caretakers.

Communication between the 3 shifts is accomplished through the corporate Total Maintenance System (TMS). One shift lines up the other via specific notes left on a TMS module. The PM Facilitators have a ready resource from which to compile data relative to die repair/maintenance. This data is what drives the system and allows for planning and (so far) pretty accurate projections concerning cost savings, cost avoidance and budgetting for die maintenance. The supervisor is left to expedite repairs by acting as liason between Die Maintenance and the rest of the world and to planning for extraordinary repairs and metal treatments.

In keeping with their new found authority and commensurate responsibility, die makers are trained to use the TMS software, root cause analysis for tradespeople and (soon) the principles of SPC data collection and analysis. As stated, TMS is used for communication and data storage and analysis. Root cause analysis for tradespeople gives them the tools they need to analyse recurring problems and assess the validity of current processes. The ability to read SPC data will be the final step into PdM. Reading distortion, surface wear and imperfections, inboard/outboard datum, etc. will enable the die maker to know that they must make the necessary adjustments to the tools before parts go out of specification. Although this last step is being piloted right now, there is every expectation that it will succeed. The technology is available at nominal cost. Management is determined to expend the necessary resources to bring the stamping process under complete control. And, the trades people are aware of the benefits that accrue to a world class stamping operation in areas such as work enviroment, remuneration and load. In our experience, this combination is like a stacked deck. Guaranteed to succeed.

This, then, is PdM for tooling. Expending resources, only as needed, to ensure a world-class manufacturing process and product. This is the goal of Chrysler’s Warren Stamping Plant employees and management. If anyone can figure out a better way to bring tooling under the PdM umbrella, we are all ears.