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.
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.
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.
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.
Planners add a time cushion to avoid incidents of “acoustic management” – being reprimanded by management. However, if similar behaviour is common throughout a shop, two weeks of lead time can grow to perhaps seven weeks. On-time delivery performance as measured internally may be 98 percent, production personnel are happy to meet internal goals, but the customer who needed the product in two weeks is not happy at all.
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.
Before discussing digitization and optimization, it is necessary to look at the workshop operations overall, determine where waste of time and resources occurs, and develop methods to minimize it. After that, the emphasis shifts to process quality or reliability.
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 workpiece 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 workpiece 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.
The first phase in establishing a balanced machining process is choosing tools with load capacity that meets or exceeds the mechanical, thermal, chemical, and tribological loads present in the metal cutting operation.
Applying cutting conditions outside the constraints of the specific situation will have negative consequences, including higher costs and lower productivity. The majority of the problems experienced during machining result from a lack of respect for the constraints that physical realities place on the cutting process. When cutting conditions do not exceed real-world constraints, the operation is safe from a technical perspective.
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 workpiece 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.
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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