Original Date: 05/12/1997
Revision Date: 01/18/2007
Information : Precision Engineering
Cincinnati Milacron’s Machine Tool Group (MTG) produces precision metalworking machines and products. The company recognizes that customers want to purchase accurately-constructed machines and products as well as equipment that produces accurate products. Consequently, Cincinnati Milacron has invested considerable engineering effort in identifying and measuring those elements which contribute to inaccuracies in workpieces produced on machining centers. These measurements were then incorporated back into the product design and development processes to improve resultant accuracies.
Approximately 50% of the resultant inaccuracies are machine related with the remainder due to measurement uncertainty and process issues. Machine-related inaccuracies were further analyzed into thermal sources (slight majority) and geometry elements. Thermal sources were defined down to the level of coolant and environmental elements. Geometry elements were analyzed with allocations to the various linear, rotary, and spindle axes. Similarly, measurement uncertainty and process issues were analyzed into their constituent components. Measurement uncertainty was primarily thermal, while process issues (in descending order or significance) included choice of tooling; choice and sequence of operations; choice of fixturing and locating surfaces; and thermal contributors.
In addition to facilitating trade-offs during product development, Cincinnati Milacron’s analyses have recently led to an efficient, condition-based maintenance process known as the Fast Accuracy Condition Test™. This process can quickly gather data on the machine, perform basic diagnostics from minimal measurements, and provide trend information indicating maintenance needs before costly scrap product is produced. The artifact and probe process for monitoring geometric alignments of machine tools by the operator is accomplished without any equipment shutdown. The use of a dedicated pallet for bringing the artifact into the machine complements the current use of a master pallet for registration. The artifact, probe, and supporting software provide the means to quickly assess a potential or apparent problem, and to gauge the process variability of a machine.
The process enables continued product output by eliminating sophisticated equipment requirements, equipment shutdown, and outside personnel. Requiring less than ten minutes, the process also offers minimal interruption for product output. Further advances are underway to improve the implementation of the automatic test system capabilities, so they will support the full range of production, field service, and customer personnel.
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