Simulation: Tools of the Trade.
In a panel on applying principles of lean manufacturing to current foundry processes, F.E. Peters, Iowa State Univ., focused on material handling, D. Bordner, Dalton Corp., spoke on optimum manning and T. Grohman, General Motors Corp., described what is needed to make a change to lean manufacturing.
Since more distance equals more cost, Peters suggested drawing a flow path detailing the process in which a casting travels through a foundry. The next step is to take a systematic look at the problem to determine where the bottleneck(s) may be. When a course of action is decided, a person should be assigned to the specific task of system improvement and compliance. Implementing lean manufacturing in one foundry required the task of parts inspection being performed immediately, the cross-training of a welder and a staggered work force. All of which reduced costs, Peters said. Another recommendation is to have a manufacturing engineer determine the most efficient location for a new piece of equipment. It should not be placed in the same location as the old piece unless it makes the process flow smooth, he added.
Bordner said the most cost-effective method may be better than the most productive method. Using charts and graphs, he showed how the number of pieces produced vs. manhours required could be more cost effective with a lowered production rate. It would result in cost savings in manpower, time and storage, he said. "If you increase or decrease beyond the optimum, you begin to increase material handling," he added. A foundry must weigh its options, however, by taking into account factors like its current limitations, customer requirements, required shipment dates, lot sizes, setups and bottlenecks. He emphasized that the most important requirement in making lean manufacturing succeed is cooperation among all foundry personnel.
Grohman listed the prerequisites to implement lean manufacturing as a desire for change, a paradigm shift, an attack of non-value-added operations, customer requirements, and cost and impact analysis.
Another panel focused on saving money through casting process simulation. In his talk on gating/risering simulation, X. Guo, Crane Valves, explained how computer simulation technology can help foundries reach the goal of "making parts right the first time." Computer modeling can reduce the lead time by doing it right the first time, reduce the cost by eliminating trial-and-error sampling and solve a shrinkage problem. Simulations reduce riser size and/or eliminate unneccessary risers.
In one situation, he said the simulation not only solved a shrinkage problem but also increased yield by 8%. In another case, Guo used computer simulation to review the gating setup that had been in use for more than 30 years. As a result, he suggested changes, which generated significant savings. In fact, Crane Valves has saved $40,000 a year since 1998 due to simulation changes. Money also can be saved on staffing because a full-time workforce is not required for simulations. The program can run overnight and the results reviewed in the morning, he added.
Meanwhile, panelist J.V. Shah, K+P Agile, Inc., examined process simulation of SSM (semi-solid molding) and lost foam processes. Shah said savings from process simulations can be seen in the form of improved die life, reduced scrap and retooling costs, and an improved product development cycle time with a "first-time right prototype." Additional incidental savings included time compression, lower energy costs and consistent quality, he added.
In his paper, which detailed a means to evaluate castability from CAD solid models through computations (01-073), D.H. Jensen, Oregon State Univ., provide an objective function that selects the optimum draw direction for a particular part in an automated molding design system. If the part/mold orientations have already been optimized, the computerized method can be used to evaluate the castability of competing part designs.
H. Makino, Shintokogio, Ltd., along with Y. Maeda and H. Nomura, Nagoya Univ., demonstrated in their paper, "Computer Simulation of Squeeze Molding Using the Distinct Element Method (01-135)" that it is necessary to define a molding method that will best use the green sand molding process. Using a mathematical model, they analyzed various molding processes to determine which was best to meet demands of near-net shape iron castings. Through simulations, the segmented squeeze molding was proven to be most effective for complex patterns.
Other papers described a design to simulate metal solidification and fluid flow in zero-gravity; a method to calculate the solidification parameters of titanium alloys; data to improve fill times through cellular and foam iron filters; and a virtual casting process design strategy to reduce microporosity in machine face wheels.
A report (0 1-148) was developed to improve the general quality in foundries.
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|Title Annotation:||lean manufacturing, optimum manning|
|Comment:||Simulation: Tools of the Trade.(lean manufacturing, optimum manning)|
|Article Type:||Brief Article|
|Date:||Jun 1, 2001|
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