When planning and implementing machining processes, manufacturers generally focus on manipulating elements of their internal operations and may lose sight of the end purpose of their work: assuring customer satisfaction. To a great extent, customer satisfaction is based on minimizing the time between the placement of the customer’s order and delivery of the finished product. In the past, manufacturers minimized lead times by machining thousands of identical parts and creating large inventories from which they could ship products immediately. This low-mix, high volume production (LMHV) scenario enabled manufacturers to meet customer needs in a timely way throughout gradual development of the machining process and unanticipated production errors and interruptions.
Today’s market requirements, however, are radically different. Customers increasingly order small batches of products tailored to specific needs. As a result, manufacturers rarely make long production runs. Groups of duplicate components are not produced in the thousands, but rather in hundreds, tens or even single units. These high-mix, low-volume (HMLV) scenarios leave no room for ongoing process development or unanticipated interruptions. Manufacturers are under pressure to develop machining processes that are totally reliable beginning with the first part. Immediate speed, consistency and predictability are paramount. Nevertheless, many manufacturers continue to focus on what they call “efficiency,” developing manufacturing processes aimed nearly exclusively at maximum output and minimal cost. They unintentionally ignore “the elephant in the room” – the crucial priority of satisfying their customers, especially customer demands for timely delivery.
Conceived in the early days of the HMLV era, a concept called Quick Response Manufacturing (QRM) underscores the critical role of time in the manufacturing process. QRM strategies, along with zero-waste and process optimization efforts, provide a roadmap that can put manufacturers on a path to minimize lead time and thereby maximize customer satisfaction.
Rajan Suri, a professor of industrial engineering at the University of Wisconsin-Madison in the 1990s, recognized looming changes in manufacturing markets, particularly the trend towards HMLV production. In 1993 he founded the Center for Quick Response Manufacturing. The Center’s purpose is to create partnerships between the University and manufacturing companies to develop and implement ways to reduce lead times. QRM strategies are often applied in addition to lean, Six Sigma and similar process improvement initiatives.
The Traditional Approach
Production managers in traditional machining environments seek maximum machine utilization above all. If a machine is standing still, it is not efficient and is costing money, not earning it. The goal is to produce large batches for inventory. Parts in stock buffer fluctuating customer demand. In HMLV manufacturing, however, a job is put into production not for stock, but to fulfill a customer order for a limited number of specific components.
There is no buffering inventory. Further complicating the situation are factors such as so-called “hot jobs” that arrive unexpectedly in response to emergency circumstances or special requests by important customers. If all of a facility’s machines are running, other jobs will be delayed to deal with the hot jobs. Then the delayed jobs themselves become hot jobs, lead times increase, and chaos begins to creep into the production process. Another issue is the tendency of manufacturing staff to concentrate on finding ways to meet internal goals, such as achieving 100 percent on-time delivery. Planning often is carried out with those internal goals in mind
Roadmap for HMLV Production
In a HMLV production environment, first time part yield and consistent quality in production of non-identical workpieces is key. The objective is to provide customized products where the part in a one piece batch costs the same as a part in a million piece batch and immediate delivery is assured.
Producing good parts from the start depends on establishing a trouble-free and reliable machining process. It currently is fashionable to point to the newest production techniques and digitization technologies as solutions to machining problems. However, speed, consistency and flexibility always have been, and still are, based on a foundation of operational excellence as well an educated manufacturing staff with a positive mindset and motivation.
A Zero-Waste Workshop
Reducing lead times requires elimination of waste in the manufacturing process. A zero-waste workshop does not over-produce parts, fully utilizes work piece material, and does away with extra movement for semi- finished parts. Wasteful and time-consuming activities in the machining process itself include production of burrs, bad surface finishes, long chips, vibration, and machining errors that create unacceptable parts. Bad parts must be reworked or rejected and remade, either of which adds waiting time to the production process.
Even producing part quality that exceeds customer requirements represents wasted time and money. Shops must realize that it is necessary to achieve only the lowest possible work piece quality that meets customer specifications and functional requirements. If a part tolerance is five microns, achieving three microns is wasteful. Higher quality tooling and more precise operating processes will be required to meet the tighter tolerance, but a customer will not pay for the unrequested higher quality. The job will be a money-losing proposition for the shop.
While high-performance, specialized tools can boost output speed, recognizing process constraints may prompt the choice of tools developed for versatility. When tools are selected for maximum productivity and cost efficiency in machining a specific part, a change from one work piece configuration to another may require emptying the machine turret completely and replacing all the tools. In HMLV situations where smaller runs of different parts change frequently, that changeover time can consume all of the productivity gains resulting from use of maximum-productivity tooling.
In cases where tool performance is stretched to the maximum, some operators will reduce cutting parameters in fear of tool failure and disruption. Versatile tooling, on the other hand, is applicable across a wider range of cutting conditions than productivity focused tooling, although at less-aggressive parameters. When versatile tooling is applied to process a variety of different workpieces, actual machining may be somewhat slower or more expensive, but the reductions in setup time, scrap, and lead time make up the difference and then some.
Customer satisfaction is the goal of any business relationship, and a key element of customer satisfaction in manufacturing is timely delivery of machined components. HMLV production scenarios put pressure on manufacturers to optimize their operations to reduce lead times and speed delivery. Applying the concepts of Quick Response Manufacturing and zero-waste and optimization initiatives enables manufacturers to achieve the speed and reliability needed to fulfill customer demands for timely delivery while also assuring manufacturing profitability.
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