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Quality control (QC) 质量控制


Quality control (QC) 质量控制

The ISO 9000 definition states that quality control (commonly abbreviated to QC) is part of quality management focused on fulfilling requirements. What the definition fails to tell us is that controls regulate performance. Control is sometimes perceived as undesirable as it removes freedom, but if everyone were free to do just as they liked there would be chaos. Controls prevent change and when applied to quality they regulate performance and prevent undesirable changes being present in the quality of the product or service being supplied. When operations are under control they are predictable and predictability is a factor that is vital for any organization to be successful. If you cannot predict what might happen when a process is initiated, you are relying on chance. The quality of products and services cannot be left to chance.
ISO 9000定义:质量控制是质量管理的一部分,致力于满足要求。该定义没有告诉我们的是控制操控绩效。有时候控制被视为是不情愿地剥夺自由,但是如果每个人都按照自己的想法任意干,那就会是一团糟。控制预防改变,在应用于质量时,控制操控绩效并预防不期望的产品和服务提供中质量的改变。在运行受控时,运行是可预测的,而且这种可预测性是任何成功组织的关键要素。如果在一个过程启动时,你不能预见可能要发生什么,你就只能靠运气了。产品和服务的质量不能依赖于运气。
The simplest form of quality control is illustrated in Figure 1.6. Quality control can be applied to particular products, to processes that produce the products or to the output of the whole organization by measuring the overall performance of the organization.
图1是最简单的质量控制形式。质量控制可应用于特定产品,生产产品的各种过程,或测量组织整体绩效的整个组织的输出。


图1.6 初始控制模型
Quality control is often regarded as a post-event activity: i.e. a means of detecting whether quality has been achieved and taking action to correct any deficiencies. However, one can control results by installing sensors before, during or after the results are created. It all depends on where you install the sensor, what you measure and the consequences of failure.
质量控制通常被视为是事后活动:即检查是否达到质量(要求)和采取措施纠正任何缺陷的工具。但是,我们可以通过在结果产生之前、之中或之后安装监视器来控制结果。这取决于你在何处安装监视器,测量什么,以及失效的后果。
The progressive development of controls from having no control of quality to installing controls at all key stages from the beginning to the end of the product cycle is illustrated in Figure 1.7. As can be seen, if you have no controls, quality products are produced by chance and not by design. The more controls you install the more certain you are of producing products of consistent quality but more control does not mean more inspection neither does it mean that the checking of work has to be performed by personnel different from those who carried out the work. In Figure 1.7, the work, checks, remedial action and corrective action could well be performed by the same individual. In some cases each task may be performed by different organizations. It rather depends on what the most effective and efficient solution might be.
图1.7给出了从没有质量控制到在产品实现全过程的关键阶段设置控制的控制发展演变进程。如图,你可以看到,如果没有控制,好产品是靠运气而不是靠设计生产出来的。设置的控制点越多,你就对生产一致质量的产品越有把握,但控制点越多不意味着检查点越多,而不意味着检查是由非执行工作的人进行的。图1.7中,产品实现、检查、补救措施和纠正措施可以由同一个人完成。在某些情况下,每项工作是由不同的组织来完成的。这取决于最有效和最有效果的解决方案是什么。

Control before the event 事前控制
Some failures cannot be allowed to occur and so must be prevented from happening through rigorous planning and design. One example is the use of reliability prediction performed before the design is complete to predict whether product reliability will meet the specification. Another is the use of competence based assessment techniques where personnel are under close supervision until they demonstrate competences following which supervisory controls are removed. This allows you to remove output checks because you know that if you were to inspect the work you would find it to be correct. Instead of checking every product produced, you check competency periodically and assign responsibility to personnel for checking their own work. Another method is the use of prevention-based error-proofing mechanisms that sense an abnormality that is about to happen, and then signal the occurrence or halt processing, depending on the severity, frequency or downstream consequences. (This has been referred to as “autonomation”, see Appendix A.)
某些失效是不能容许发生的,所以必须通过严格的策划和设计来预防其发生。一个例子是在设计完成前利用可靠性预测来预知产品的可靠性是否满足规范要求。另一个例子是基于评价技术的能力的利用,该技术对人员进行严密监视,直至证明了去除监视控制后的能力。这就容许你去掉输出检查,因为你知道如果检查的话,你也会发现结果无误。你定期检查能力并分配人员检查自己工作的职责,而不是对每个生产出来的产品进行检查。另一个方法是利用预防为基础的防错机制,即感知即将发生的异常,发出信号或停止操作,这取决于异常的严重程度,出现的频次或后续后果。

Control during the event 事中控制
Some failures must be corrected immediately using automatic controls or error proofing. By continuous monitoring of parameters in a processing plant the temperature, pressure, quantities etc., are adjusted to maintain output within specified limits. Electronic components are designed so that they can only be inserted in the correct orientation. Computer programs are designed so that routines will not run unless the correct type of data is entered in every field.
有些失效必须马上通过自动控制或防错方法予以纠正。通过连续监视加工工厂的参数,调整温度、压力、数量等,以确保输出在规定的范围内。这样设计电子元器件:按照确定方向插入。这样设计计算机程序:只有在每个域都输入正确类型数据时才开始启动工作。【即防错的概念——jelly】
Control after the event 事后控制
Where the consequences of failure are less severe or where other types of sensors are not practical or possible, output verification can be used as a means of detecting failure early in the process and preventing the subject product passing through subsequent stages and increasing the cost of rectification. Although errors have occurred, measures taken to contain them or remove the defective products from the production stream automatically are another form of errorproofing method. Product inspection and test is control after the event because it occurs after the product is produced but before the product is released out of the organization’s control.
当失效后果不十分严重,或无法使用或不能使用其它类型的感应器时,可用过程结果输出作为工具来检测过程早期失效和预防产品通过后续阶段增加纠正成本。尽管差错已经发生了,但抑制差错产品或从生产线上自动移除所采取的措施是防错方法的另一种方式。产品检查和试验是事后控制,因为是在产品生产完成后,但却是在产品发行脱离组织控制之前进行的。
Where failure cannot be measured without observing trends over longer periods, you can use information controls. Many managers receive reports weeks or months after the week in which the deeds were done. Reports produced on long-range frequencies are often only of use to long-range decisions such as setting objectives, policy making etc. They do not stop immediate operations but may well be used to stop further operations when limits are exceeded. The danger in control after the fact is not only the slowness of reporting but also the oscillating effect of any action that is taken. If data on utilization does not reach the manager until weeks after the effort was spent, it is highly likely that when he or she takes action, the demand will have changed and staff will be working overtime to catch up. Observing the overtime the manager recruits more staff but by the time they are operational the demand has reduced once again. It is often deemed that quality assurance serves prevention and quality control detection, but a control installed to detect failure before it occurs serves prevention, such as reducing the tolerance band to well within the specification limits. So quality control can prevent failure. Assurance is the result of an examination whereas control produces a result. Quality assurance does not change the product, but quality control does. Quality control as a label “Quality control” is also the term used as the name of a department. In most cases Quality Control Departments perform inspection and test activities and the name derives from the authority that such departments have been given. They sort good products from bad products and authorize the release of the good products.
在需要通过长时间观察其趋势才能测量到失效时,需要使用信息控制。许多管理者是在事情完成后数周或数月后才收到报告。时间频次较长的报告通常只用于做长期决定,如制定目标、方针等等。这样做不能立刻制止运行活动,但在超出界限时,可能被用来制止下一步的运行活动。事后控制的危险不仅仅是报告的不及时,还包括采取任何措施结果的摇摆不定。当数据是在产生效果后的数周才送到管理者手中,管理者要采取行动的情况下,很有可能要需求发生变化,员工就要加班工作以赶上进度。看到超时工作,管理者会招聘更多的员工,但当员工上岗可以工作时,需求又下降了。人们常常认为质量保证是预防,质量控制是检查,但在失效发生前进行的检查则是预防,如降低公差带至规范之内。所以质量控制可以预防失效。保证是检查的结果,而控制产生结果。质量保证不改变产品,但质量控制却可以改变产品。作为质量控制的标记QC也用于部门名称。在大多数情况下,该部门进行检查和试验活动,而且名副其实地进行质量控制。该部门从质量差的产品中挑出好产品,并批准放行质量好的产品。
It is also common to find that Quality Control Departments perform supplier control activities, which are called Supplier Quality Assurance or Vendor Control. In this respect they are authorized to release products from suppliers into the organization either from the supplier’s premises or on receipt in the organization. To control anything requires the ability to effect change, therefore the title Quality Control Department is a misuse of the term, because such departments do not in fact change the quality of the product they inspect. They do act as a regulator if given the authority to stop release of product, but this is control of supply and not of control of quality. Authority to change product usually remains in the hands of the producing departments. It is interesting to note that similar activities within a Design Department are not called “quality control” but “design assurance” or some similar term. “Quality control” has for decades been a term applied primarily in the manufacturing areas of an organization and it is therefore difficult to change people’s perceptions after so many years of the term’s incorrect use. In manufacturing, inspection and test activities have been transferred into the production departments of organizations, sometimes retaining the labels and sometimes reverting to the inspection and test labels. However, the term quality control is used less frequently in the west probably because of the decline of manufacturing. It has not been widely used in the service sector.
通常还可以发现质量控制部门对供应商进行控制活动,这被称之为供方质量保证或供方控制。在这方面,该部门被授权,或在供方场地或在组织内,放行来自供方的产品运入组织。控制需要具有改变结果的能力,因此,质量控制部门的名称是种误用,因为该部门事实上不能改变检查产品的质量。如果授权是制止放行产品,该部门只是作为调节员,但这是控制供应,而不是控制质量。改变产品的权力通常是在生产部门手里。需要指出的是设计部门类似的活动不被称作“质量控制”而是“设计保证”,或类似的名称。“质量控制:”被应用于组织生产领域已经几十年了,因此很难改变人们的观念,即使被误用了这么多年。在制造领域,检查和试验活动已经被转移到组织的生产部门,有时候还保留着名称,有时候则转换为检查和试验的名称。但是,质量控制一词在西方可能很少使用了,因为制造产业的下滑。在服务领域很少使用质量控制这一名词。
A reason for this could be that it is considered more of a concept than a function.
其原因可能是从概念而不是功能来考虑的。

Universal sequence of steps 通用步骤
The following steps can accomplish control of quality, or anything else for that matter (Juran 1995):
以下步骤可以用来建立质量的控制,或类似的活动(朱兰 1995)
  1. Determine the subject of control, i.e. what is to be regulated 确定控制主题,即要控制什么
  2. Define a unit of measure – express the control subject in measurable terms such as quantities, ratios, indices, rating etc 确定测量单位——以测量的术语来表达控制对象,如数量、比率、指数、权数等等。
  3. Establish a standard level of performance – a target to aim for 建立绩效标准水平——要达成的目标
  4. Select a sensor to sense variance from specification 选择感受差异的感应器
  5. Install the sensor at the stage in the process appropriate whether you need to control before, during or after results are produced 在过程的适宜阶(结果产生之前,之中或之后)段置入感应器。
  6. Collect and transmit data to a place for analysis 收集和传输数据至分析位置
  7. Verify the results and establish whether the variance is within the range expected for a stable process (the status quo) 确认结果并确定差异是否是在稳定过程(情形)期望的范围内
  8. Diagnose the cause of any variance beyond the expected range 分析差异超出期望范围的原因
  9. Propose remedies and decide on the action needed to restore the status quo. 提出补救措施,确定恢复原状所需的措施
  10. Take the agreed action and check that process stability has been restored 采取同意的措施,并检查过程的稳定性是否得到了恢复。

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  • 发布时间: 2009-10-11 08:17
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