A machining workshop seeks to produce a certain number of parts, at a required level of quality, in the most efficient way, delivered on time. Traditionally, manufacturing businesses defined efficiency by return on investment. Success was measured in terms of continuous runs of thousands or hundreds of thousands of pieces and maintaining steady output from one or many machines was the goal. From that point of view, a machine that was running and making parts was considered efficient.
In the current manufacturing environment, true manufacturing efficiency involves striking a flexible balance between maximum output and timely fulfillment of a wide variety of individual customer orders. The focus is on the end result: on-time product delivery and satisfied customers.
While balancing output and demand, manufacturers must be careful to maintain product quality. Dealing with parts of unacceptable quality will force unplanned changes in production schedules, consume time and money and delay deliveries. Haphazard planning will cause production stoppages and leave machines sitting idle while shop floor labor costs multiply to handle the unforeseen problems the stoppages create.
Workpiece quality in manufacturing generally is described in terms of meeting part dimension and surface finish requirements. An additional measurement of quality, namely on-time delivery performance, can be called process quality. The manufacturer must control processes to the degree that the planned production time is sufficient to complete the work and deliver it to the customer at the promised time.
Pleasing Customers Versus Posting Profits
A shop’s machines can run 100 percent of the time, but if poor delivery performance disappoints customers and they stop buying the shop’s products, the shop will fail. Keeping customers happy is a primary goal but concentrating on customer satisfaction alone can threaten profitability. Focus on the customer is critical, but a manufacturer must maximize utilization of its equipment while also meeting customer part volumes, quality requirements and delivery requirements.
Promises and planning
Successful manufacturing involves coordinated interaction of multiple groups within the manufacturing organization. One group promises customers certain outcomes regarding the cost, quality and time of delivery for the parts they order. The other groups in the organization, including engineering, purchasing, workshop personnel and administrators, make sure that those promises are kept.
The various groups define efficiency differently. Machining staff want to optimize individual machining processes for maximum output. Groups outside the technical machining process concentrate on improving the performance of the system overall. Their analysis covers issues such as overall equipment effectiveness (OEE) and labor productivity.
The Heart Of Efficiency
To describe manufacturing efficiency in basic biological terms, the heart of any production operation is the machining process. Although the body’s heart is indispensable, it does not work on its own. It is part of a system that includes the rest of the body and the brain.
In manufacturing, if the heart is machining technology, the body is the overall manufacturing organization including engineering, business planning and administration. The brain of the organization is the group of personnel who coordinate all elements of the system. However, the brain cannot simply decide that the heart should pump faster, just as a person cannot control his or her heartbeat just by thinking it will be so. In the same way, a machining process is not always controllable from a rational perspective.
In today’s world of digital technology and the Industrial Internet of Things (IIoT), people, especially young people, want answers and clear rules for controlling the machining process. Unfortunately, in many cases there are no rational rules, and it is necessary to accept, react to and solve the unexpected problems of machining.
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Unexpected Problems And Unskilled Workers
In a perfect world, shop personnel have the knowledge, skills and experience needed to handle unexpected problems in the machining process. However, many shop owners complain that it is difficult to maintain a sufficiently capable workforce. While training would appear to be a way to overcome the shortage of skilled workers, surprisingly, though, some shop owners say their training efforts often are wasted because employees lack a positive mindset towards learning new skills. Owners report that in many cases where they offer technical training, employees believe that they already know enough to do their assigned work and require no additional training. (see sidebar)
Total Manufacturing Time
Analyzing a shop’s efficiency and eliminating waste can provide additional time for machining and thereby greater flexibility and responsiveness to customer needs. The total time required to manufacture a part is the sum of many separate activities. They include actual machining time, tool handling, workpiece manipulation, quality checking, unplanned problems, waiting, administration tasks and others.
Some of the activities are essential and cannot be eliminated, such as tool changes and workpiece manipulation. Beyond required activities, shops also spend time handling unforeseen circumstances such changes in planning, quality problems and waiting for missing tooling or workpiece materials.
In one case, a shop reviewed a number of different activities involved in machining a part to find the amount of time each consumed (Figure 3). Actual machining time was 15 percent of the overall production total, while setup and waiting consumed a quarter of the time and unplanned problems, such as missing or delayed tooling or stoppages to clear excessively long chips, represented another 25 percent. By reducing the time taken for unplanned problems, setup time, tool handling, waiting and administration, actual machining time grew to 50 percent of the total (Figure 4). The expanded time gave the shop greater flexibility to match machining operations to specific customer job requirements.
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Unforeseen Effects Of Time-Saving Efforts
As a result of a time-saving investigation like the one noted above, another shop was able to triple the hours that spindles were actively cutting parts. However, the shop found that part output did not triple in return.
Further study revealed a number of issues that contributed to the phenomenon. A major issue was that the original process time included off-machine deburring. The time saving initiatives indicated that deburring could be performed more efficiently on the machine itself. However, when the off-machine deburring was moved to the machine tool, overall spindle time increased to account for the deburring operation. The situation shows that time savings in one area can result in increased consumption of time, or apparent decrease in efficiency, in another area.
The lesson is that operational changes must be considered in relation to the manufacturing process overall. It is a difficult balance, and there are no general rules except to look for ways to use the available time as effectively as possible.
Achieving efficiency and flexibility require continual adaptation to changing production demands. Changes often originate externally when a customer modifies a product design or changes the number of parts required. The manufacturing shop must alter its plans in response, but that can disrupt the shop’s plan overall and lead to a disorganized response that causes further disruption.
When planning is disorganized, some shops push workpieces through the workshop in random ways, putting the work on any machine available and causing more problems. The situation can become a vicious circle. When planning issues begin, they can multiply like a virus. A small disruption soon can become large. And like a human virus, the disruption can be very difficult to overcome.
The Spare Capacity Option
One way to effectively raise shop efficiency and flexibility is to add spare machining capacity. The concept of spare capacity is foreign to the majority of shops, and a shop’s finance department may endorse investing in new machining capacity but demand that the new equipment does not sit idle. They see a machine as a one or two million Euro (or dollar) investment, and can’t understand that when it is purchased as spare capacity it may stand unused and not regularly do anything. But in reality, it does do something significant: it ensures happy customers. It is a useful backup that supports flexibility and facilitates handling of unforeseen problems.
In some situations, instead of purchasing a backup machine a shop will work with its own equipment until overload occurs then enlist a subcontractor. But if that subcontractor is struggling with the same problems of too much work and insufficient staff, the responsibility simply shifts to a different party. It is extremely difficult to convince shops to build spare capacity with the possibility it will be used rarely at best.
Long Delivery Times Versus On-Time Delivery
The pressure to deliver on time may extend the actual production time. If manufacturing a job under normal conditions takes a week, but the customer wants an absolute guarantee that delivery will be on time, a shop may state a lead time of two weeks to provide a time cushion/buffer. In another instance, if a customer needs one completed workpiece by a certain date, a shop may start two workpieces to have a backup in process in case something unforeseen happens to the first part. These makeshift practices needlessly consume production time and expense and actually extend delivery times beyond what they would normally be.
Another way to increase shop efficiency and flexibility, although expensive, can be to employ automation in the form of a multi-tasking machine and a pallet pool. A shop can quickly change an automated cell from one job to another and use the pallets to build and store future setups. Such a system can be built around a multi-tasking machine surrounded by workpiece pallets and accompanied by a tool magazine with multiple tools, all serviced by a robot. In this arrangement, day shift personnel can set up the machine and pallets to process a variety of parts, and the night shift can produce the parts. This solution, however, is relatively expensive and is not the level of investment that every company can afford.
Impediments to Multi-Tasking
An organizational impediment to the multi-tasking approach is the typical factory practice of arranging machines based on function alone, as in maintaining a separate milling department, turning department, etc. In many cases, it is better to have machines organized into cells where each group of machines has certain process capabilities suited to specific groups or families of workpieces. Grouping of machines simply by function also encourages shop personnel to describe themselves in a limited way, such as lathe operator or milling machine operator. Training operators to be multifunctional and able to operate different types of machines gives a shop the flexibility to balance its own internal capacity issues.
Present-day efficiency in manufacturing includes a strong emphasis on customer satisfaction in addition to finding the best ways to machine parts. Manufacturers must balance efforts to consistently provide on time delivery with the need to be profitable. In addition to optimizing the machining operations, careful attention to issues including part and process quality, planning organized from the perspective of the manufacturing organization as a whole and continuing analysis of the elements of machining time consumption can significantly expand the time available to machine parts and result in increased flexibility and efficiency.
Supporting an Efficient Manufacturing Mindset
Evolution of manufacturing strategies presents machinists with a range of new challenges. Highly automated machine tools, intuitive software and advanced cutting tools have reduced a machinist’s hands-on responsibilities. Unfortunately, one side effect of this sophisticated manufacturing technology is a tendency of some manufacturing personnel to settle into a “good enough” frame of mind regarding their job skills.
Many shop owners have found that when some employees are offered job training, they are unenthusiastic and feel that they have sufficient skills to handle what they are required to do. Those employees do not have the mindset necessary to grow and advance in the new manufacturing environment.
In Flanders, this frame of mind is described with the saying: “It is useless to give a candle and reading glasses to an owl, if he is not able to or not willing to read.’’ The U.S. phrase equivalent is “You can lead a horse to water, but you can’t make him drink.” Basically, no matter where in the world, people may be given all of the means they need to accomplish a goal, but if they don’t want to participate, the effort is in vain.
In most machine shops today, the hardware, tooling and machining programs are present and powerful. Accordingly, people have become the crucial element of manufacturing efficiency. Along with a forward-thinking mindset, the special skill required today is an ability to read the machining process – not by working with a computer but by standing at the machine and listening and observing the process.
Generally, the process will indicate its status, in the same way that one can listen to his or her own heart and feel if it is going well or not. That awareness is not calculated with a formula. It is essential to know what to watch for and what the favorable factors are in the process environment. Seco provides many forms of technical training, machining knowledge and support. When shop employees have the right mindset, Seco is there to help them learn and apply what they need to be successful.
Patrick de Vos, Business Development Manager & Technical Education Manager Seco Consultancy