Voice of Process
Quality is a must in the present market place for survival. In the long run, the most important single factor affecting business performance is Quality. Although, market share and proﬁtability measure the business performance, better Quality help earn higher returns and market share. In other words, Quality and market share drive proﬁtability and growth. To become superior in Quality, we must achieve zero defects in our supplies. To achieve zero defects, we must have good control on process.
Process Deﬁnition:A process is a step or sequence of steps that uses inputs and produces products or services as an output. Every process has inputs that are traditionally categorized as material, man, machine, methods etc. We may also include measurement system as an input since it has an impact on the perceived output. Process is often made up of smaller sub processes. For example, a part may be produced using a process that has a molding step. This molding step may be thought of as a process whose steps might include R Sai Krishna Rayalu Dy GM Quality, Indo MIM mold closing, injection, metering, molding opening and ejection of the part. In addition, the injection step is a process in itself.
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such as methods, equipment, people, materials, and policies those inﬂuence variability. Environmental factors also contribute to process variability. Process variations are traceable to two kinds of causes : 1. Common or random or chance causes. 2. Special or assignable causes. Control of a process is achieved through the elimination of special causes. Improvement of a process is accomplished through the reduction of common causes. These causes can be tracked by using
Variability is a part of any process, no matter how sophisticated it is. Several factors over which we have some control,
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data, variations in customer load, and variation in computer operations. Some authors refer to common cause variation as natural variation. Management alone is responsible for common causes. It is believed that about 85% of all control charts. The principal purpose of control charts is to help the process operator recognize the presence of special causes so that appropriate action can be taken in a timely manner. problems are due to common causes and hence can be solved only by action on the part of management. In a control chart if quality characteristic values are within the control limits and no random pattern is visible, it is assumed that a system of common causes exists and that the process is in a state of statistical control. A principal problem in process management is the separation of special and common causes. If the process operator tries to adjust a process in response to common cause variation, the result is usually more variation rather than less. This is sometimes called over adjustment or over control. Most of the defects caused due to common causes are documented during development stage, before SOP(start of production) are readily available for reference Common causes:Process variability due to common causes is something inherent to a process. Generally these are not controllable by process operators. It exists as long as the process is not changed and is referred to as the natural variation in a process. It is an inherent part of the process design and affects all items. This variation is the effect of many small causes and cannot be totally eliminated. When this variation is constant, we have what is known as a stable system of common causes. A process operating under a stable system of common causes is said to be in statistical control. Examples include inherent variation in incoming raw material from a qualiﬁed vendor, a lack of adequate supervision skills, the vibration of machines, variation in ambient temperature & humidity, variation in electrical or pneumatic sources, variation within equipment such as worn bearings and ﬂuctuations in working conditions. In the case of service processes, common causes typically include variation in the input Special causes:Process variability caused by special causes is something that is not inherent in the process. That is, it is not part of the process as designed and does not affect all items. Special causes can be the use of a wrong tool, an improper raw material, or an operator error. If an observation falls outside the control limits or a non-random pattern is exhibited, special causes are assumed to exist, and the process is said to be out of control. One objective of a control chart is to detect the presence of special causes and ensure that they are eliminated through remedial actions; so that the process is again brought to a state of statistical control. It is believed that 15% of all problems are due to special causes. Actions on the part of both management and operators will reduce the occurrence of such causes. with reaction plan. If a process operator fails to respond to the presence of a special cause of variation, this cause is likely to produce additional process variation. This results in producing defects that are not documented. Many Quality tools and techniques are readily available for preventing defects and minimizing variability in process. We know that it takes time to ﬁnd root causes and to implement respective corrective actions. We can’t stop supplies to customers during this time as it may cause line down situation at customer end. So, we need to keep supplying the parts with good Quality if the percent defective is low. There is no point in producing the parts if the percent defective is high. At this scenario, we have to perform 100% inspection to prevent the defects passing to next processes steps. As we know, 100% inspection is not fool proof
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to detect 100% defects. So, to prevent defects passing to external customer we at Indo-MIM came up with a new practice called “Voice of Process” Concept of “Voice of Process” 1. Alert the next process owners about the non-documented defects that occurred in present process due to special causes, so that they keep track of these defects during their process steps if they missed to detect at previous process step. 2. Highlight the impact of this defect on the next process, if any. 3. Indicate checking method if required.
6. Eliminates adding further value on defective parts.
was used for molding the parts even after completing its designed life cycle. The next new tool was manufactured and is in PPAP approval stage, hence the production team molded the parts using old mold to meet customer urgent schedule. Additional special instruction were prepared and given to the molding operators. Relevant parameters were ﬁne tuned to reduce the defect rate.100% inspection was in place at the molding stage by molding operator. As we know, 100% inspection is not error proof to prevent defects reaching to next process or even to customer. The same thing happened in this case, as three defective parts escaped from all process stages and made it all the way through to the customer. Subsequent process could also not track this defect it being a rare defect and unusual (not documented). Then, we came up with a concept named as “Voice of the Process” that carries and passes the details and information about the previous process rare defects like the one explained above, to the next process along with the route card. This helped the next process operators be aware of the previous process’ defects and enabled the tracking of the same so as to prevent the defects reaching to the next process and to the ﬁnal customer.
Customer: Indian Automotive vehicle manufacturer. Problem: We supply a part which is an import substitute to this customer. Customer reported a functional problem of the part in the assembly line. We were shocked to hear about this quality issue as these parts are in green channel at customer receiving inspection from day one and achieved Zero defects PPM level as well. Sorting team reported only 3 parts with this defect. Actions: Containment actions drawn on the parts at various stages and submitted to the customer as part of 3D process. Root Cause:
Mainly above concept is designed for molding process or similar processes with following observations: 1. Short ﬁll, 2. Sink, 3. Crack, 4. Excessive ﬂash on parting line, 5. Parting line offset, 6. Gate protrusion or depression, 7. Ejector pin protrusion or depression, 8. Edge Damage Beneﬁts: 1. Prevention of defects passing to customers. 2. Reduces cost of poor quality. 3. Reduces customer complaints. 4. Improves operator’s awareness towards quality. 5. Avoids heavy penalties due to customer end assembly line down.
Root cause analysis nailed down to mold. One of the functional geometry of the part got damaged during ejection of the part from the mold. The percent defective is very less i.e. less than 0.02%. This was a rare defect caused due to a special cause. The special cause is that the mold
Below is the graphical example for the “Voice of the Process”: