One of the main questions for appliance manufacturers is, “Why consider RAST?” The main reason RAST has taken hold in Europe is the reduction in harness production time. This reduction has allowed many European appliance manufacturers to enjoy lower installed (or applied) costs for their harnesses. Furthermore, since the RAST interface is standardized, engineers can design for a known interface, which eases designing how a component or device will connect to the harness. Another benefit of RAST implementation is a reduction in wiring or plugging errors. Since RAST connections can be keyed to each connection point, errors and rework are minimized, thereby enhancing the quality and cost effectiveness of each appliance coming off the production line.
Once the concept of RAST is embraced, it is important that RAST be ubiquitous in the concept, design and manufacturing processes. Changeover from point-to-point connections to RAST must involve the design process. If a harness design, for example, merely changes out non-RAST product for RAST product, the cost savings and reliability benefits will not be fully realized.
The initial harness design essentially dictates installed cost savings and, often, RAST implementation will simplify harness design mainly due to the parallel jumpers that are part of RAST harnesses. While in the design process, it is also important to consider how the harness can be optimized so the termination machinery is used to its potential. In other words, design the harness so the machine makes as many terminations as possible in one cycle. In addition, by fully integrating RAST components throughout the appliance, machine changeover for non-RAST connections can be minimized or eliminated, thereby keeping harness cycle rates high.
The harnessing machinery used with RAST interconnections is critical. It is different than traditional crimp processing equipment, but allows for greater flexibility and efficiency when factored early in the process. RAST termination machinery yields the most benefit from a fully optimized harness, where harness design and production work hand-in-hand. With an optimized harness design, machinery cycle times are faster and production costs are reduced. In addition to the machine’s speed and wire handling capacity, it is also important to examine its capacity to mass terminate and its ability to multitask.
Avoiding the temptation of “piecemeal” RAST implementation is crucial. Since RAST is a system approach to harnessing, skipping steps to secure “one-time” cost advantages may negate some of the installed cost benefits of a fully integrated RAST design and production program. For example, replacing point-to-point connections with mass-terminated, ganged RAST connections reduces labor and production time. Indeed, for each point-to-point connection without a RAST interface, installed costs increase. Also, RAST harnesses have been designed for easy installation. RAST harnesses have features to minimize connection errors and, by bundling jumpers together, wire handling is more organized and clean. Further, issues with harness pull-through are generally fewer with RAST harnesses. Finally, in harness production, RAST terminations typically are made on one machine, while point-to-point termination may require several machines.
The gradual acceptance of RAST harnessing is affecting how appliances are designed and produced. Since the appliance industry is global, components are sourced globally, calling for some degree of connection standardization. With this, globally available components increasingly have RAST interfaces. When designers deliberate over harness design (i.e., RAST or point-to-point), the entire process must be thought out. By considering the labor and production implications of a RAST harness, appliance OEMs should note that full implementation of RAST typically yields labor, cycle time and quality benefits compared to other connection methods, including partial RAST and point-to-point.
This information is provided by Jeff Hummel, RAST product manager, Tyco Electronics Corporation, Harrisburg, Pennsylvania, U.S.