Difference Between Process Capability and Machine Capability (With Table)

Process capability and machine capability are two of the capabilities which work in completely different areas. Process capability refers to the overall process capability specifically in terms of all chucks, fixtures, etc.  The machine capability takes into account the capability of only one chunk, fixtures, etc.

Process capability is determined by utilizing specialized software, whereas machine capability is determined by a third-party evaluator or its manufacturer. The difference between process and machine capability does not end here. There are many other differences which are discussed below. 

Process Capability vs Machine Capability 

The main difference between process capability and machine capability is that process capability is heavily dependent on data, whereas machine capability is reliant on performance. All six factors influence the process capability result. On the other hand, machines and measurements highly influence the result of machine capability. Process capability is a long-term study, while machine capability is a short-term study.  

Process capability is referred to as a statistical measure of a given characteristic’s inherent process variability. It can be used to access the process’s ability to meet specifications. During an initiative of quality improvement, a capability estimate is obtained in the study from start to end for the reflection of improvement that occurred.  

Machine capability is referred to as a measure of a machine’s actual quality concerning its specifications. This is a short-term capability derived from the observations of the uninterrupted production run. When measuring machine capability, altering machine tools and change settings are not preferred.   

Comparison Table Between Process Capability and Machine Capability 

Parameters of ComparisonProcess CapabilityMachine Capability
InterpretationIt is a statistical measure of a given characteristic’s inherent process variability.It is the measure of the machine’s actual quality with respect to its specifications.
TimeLongShort
FocusesOn production processesOn machines themselves
BiasedNot biasedBiased
FormulaCp = (USL-LSL)/6σCm = USL – LSL / 6s

What is Process Capability? 

The process capability is the process’s measurable property to the specification. It can be expressed as a process performance index and process capability index. The output is often illustrated with the help of a histogram and calculation of this measurement. They mainly predict how many parts can be produced out of specification (OOS).  

Process capability has mainly two parts as measure the variability of the process output, and compare that variability with a product tolerance and proposed specification. The process input generally has at least one or more measurable characteristics to specify outputs. The number of components included in process capability is 50- 250.

A process should be estimated with suitable process controls in place. To determine if the process is “statistical control”, the control chart analysis is used. The capability has no meaning in case the process is not in statistical control. Consequently, the process capability consists of only common cause variation but not special cause variation.  

The process output is expected to meet the requirement, engineering tolerances, or specifications of the customer. Engineers conduct the study of process capability, to determine the extent of the process to meet these expectations. It majorly centers on the whole process of product delivery from conception to delivery routes.

What is Machine Capability? 

Machine capability is the measure of actual quality with respect to the specifications of the machine. It mainly refers to the capacity parameters of a specific piece of machinery. The parameters consist of the number of raw materials or loads, length of time between services, and the machine’s speed of production.  

The production speed is the most important capacity of a machine. With the help of the extension, the machine tries in the least possible time to operate in doing all tasks. It centers on the machine capacity to deliver on the production process. The production line could be affected due to any lag in speed.  

Machines and measurements highly influence the result of machine capability. Manufacturers of machines generally list all of the particular capabilities of a machine in the user manual. But it is also important to check with a test for a third-party machine capability to acquire the better-quality machine for a certain job.  

The third-party inspection also has another benefit like revealing the real machine capabilities. As well as to detect mechanisms that can help to prevent future problems. Machine alternate parts and accessories can also enhance by machine capability.   

Main Differences Between Process Capability and Machine Capability 

  1. Process capability centers on the whole process of product delivery from conception to delivery routes, whereas machine capability center on the machine capacity to deliver on the production process.  
  2. Process capability is calculated on sample individual and subgroup both with average x bar, while calculation of machine capability is done on target value with the unchanged condition in individual sample standard deviation.  
  3. Process capability is determined by utilizing specialized software, whereas machine capability is determined by a third-party evaluator or its manufacturer.  
  4. Process capability is part of the development of the product. On the other hand, machine capability is in evaluator for purposes of buying.  
  5. Process capability is heavily dependent on data, especially graphical data. On the other hand, machine capability is reliant on performance. 

Conclusion 

It can be concluded that process capability and machine capability are two of the capabilities which work in completely different areas. Process capability is a statistical measure of given characteristics inherent process variability, whereas machine capability is a measure of a machine’s actual quality concerning its specifications.  

Process capability mainly focuses on the production process, while machine capability focuses on machines themselves. The number of components included in process capability is 50- 250, whereas machine capability included 20- 50 in succession. Process capability is determined by utilizing specialized software. On the other hand, machine capability is determined by a third-party evaluator or its manufacturers. 

References 

  1. https://www.tandfonline.com/doi/abs/10.1080/00224065.1986.11978984
  2. https://www.sciencedirect.com/science/article/pii/S0924013604001074
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