Process analysis
An operation consists of processes for added value by transforming the useful inputs and outputs. Entries can be material, labour, energy and capital goods. Outputs can be a physical product (maybe used as an input to another process) or a service. Processes can have a significant impact on a company's performance, and improving the process can improve the competitiveness of the company.
The first step for improving a process is to analyze it to understand the activities, relationships and values of relevant parameters. Analysis of the process generally involves the following tasks:
• Define the process boundaries that mark the points of entry process inputs and process outputs output points.
• Build a process flow diagram that illustrates the various activities of processes and their interrelationships.
• Determine the capacity of each step of the process. Calculate other measures of interest.
• Identify the bottleneck, i.e. the phase with the lowest capacity.
• Assess further limitations in order to quantify the impact of the neck.
Process flow diagram
Process boundaries are defined by the points of entry and exit of inputs and outputs of the process.
Once the limits are set, the diagram of process flow (or process flow diagram) is a valuable tool for understanding the process using graphics to represent tasks, flows, and storage. Here is a flowchart for a process that is simple, with three sequential activities:
Process flow diagram
The symbols in a process flow diagram are defined as follows:
• Rectangles: represent tasks
• Arrows: represent the flow. Flows include the flow of materials and the flow of information. The flow of information may include instructions and production orders. Traffic information may take the form of a piece of paper that follows the material, or it may be sent separately, perhaps before the equipment in order to prepare the equipment. Material flow is usually represented by a massive flow of line and information by a dotted line.
• Inverted triangles: represent storage (inventory). Storage bins are generally used to represent stocks of raw materials, work in process inventory, and finished goods inventory.
• Circles: represent the storage of information (not shown in the diagram above).
A process flow diagram, tasks one after the other in the series are executed sequentially. Designed in parallel tasks are performed simultaneously.
In the diagram above, raw material is held in a locker storage at the beginning of the process. After the last task, the output is also stored in a storage bin.
When building a workflow diagram, need to avoid pitfalls that could cause the flowchart, do not represent reality. For example, if the diagram is constructed using information obtained from the employees, the employees may be reluctant to disclose rework loops and other potentially embarrassing aspects of the process. Similarly, if illogical aspects of the flow process, employees may tend to present it as it should be and not as it is. Even if they describe the process as they perceive their perception may differ from the operation. For example, they can leave out important activities that they deem to be insignificant.
Process Performance measures
Operations managers are interested in certain aspects of the process such as cost, quality, flexibility and speed. Performance metrics of processes that communicate these aspects amongst:
• Ability to process - the process capability is its maximum rate of return, measured in units produced per unit of time. The ability of a series of tasks is determined by the task of lower capacity in the chain. The capacity of the parallel chains of tasks is the sum of the capacities of the two chains, except in cases where the two chains have different results that are combined. In this case, the ability of the two parallel chains of tasks is the parallel chain of lower capacity.
• Capacity utilization - percentage of the capacity of process that is actually used.
• Flow rate (also known as flow) - the average rate on which flow units beyond a specific point in the process. The maximum throughput is the ability of the process.
• Flow time (also known as the time flow or turnaround) - point of the average duration that requires a unit to move through the process of entry to the point of exit. The flow time is the length of the longest path through the process. Flow time includes both processing time and anytime the unit passes between steps.
• Cycle time - the time between successive units they are output of the process. Cycle for the process time is equal to the inverse of the speed. The cycle time can be considered as the time required for a task to an eternal repetition. Each series in a process task must have a cycle time of less than or equal to the duration of the programme for the process. In other words, the process cycle time is equal to the longest task duration of cycle. The process is said to be in equilibrium if the cycle times are equal for each activity in the process. This balance is rarely reached.
• Time - the average time that a unit is development. Execution time is less idle time flow time.
• Idle time - time when no activity is performed, for example, when an activity is waiting for work arrive from the previous activity. The term can be used to describe the inactivity of the machine and worker idle time.
• Work in progress - the amount of inventory in the process.
• Set up time - the time needed to prepare the equipment to perform an activity on a lot of units. Assembly time is generally not strongly dependent on lot size and can therefore be reduced on a per unit basis by increasing the size of the lot.
• The content of labor direct force - the amount of work (in units of time) actually contained
Little's law
Inventory in the process is related to the flow and time flow by the following equation:
Inventory W.I.P. = rate x time
This relationship is known as law of Little, named after John D.C. Little, which proved mathematically in 1961. Since the flow is equal to 1 / cycle time, Little law can be written as:
Flow time = stock W.I.P. x Cycle time
The bottleneck of the process
The process capability is determined by the task of slower series in the process; in other words, given the slower rate or longer duration of cycle. This slower task is known as the bottleneck. Identification of the bottleneck is an essential aspect of the process analysis, because not only it determines the ability of the process, but also offers the possibility of increasing this capacity.
Saving time in the activity of bottleneck saves time for the whole process. Saving time in a non-goulot activity does not help the process, since the flow is limited by the bottleneck. It is only when the bottleneck is eliminated that other activity will become the new bottleneck and present a new opportunity to improve the process.
If slower next task is much faster than the bottleneck, then the bottleneck is having a major impact on the ability of the process. If slower next task is only slightly faster that the bottleneck before increasing the flow rate of the neck will have a limited impact on the capacity of the process.
Famine and blocking
Famine occurs when a downstream activity is not used with no entry to address delays upstream. Blocking occurs when an activity become inactive, because the next activity downstream is not ready to take. Famine and blocking can be reduced by the addition of buffers that hold stocks between activities.
Process improvement
Improvement costs, quality, flexibility and speed is commonly sought. Here are some of the ways that the process can be improved.
• Reduce stocks of work in progress - reduces the execution time.
• Add additional resources to increase the capacity of the bottleneck. For example, an additional machine can be added in parallel to increase capacity.
• Improve the efficiency of the activity of bottleneck - deal with the increases in capacity.
• Move work off critical resources when possible - treat capacity increases.
• Increase the availability of critical resources, for example, by adding an additional offset - increases process capability.
• Minimize non-value adding activities - reduced costs, reduced the turnaround time. Non-value adding activities include transport, rework, waiting, testing and inspection and support activities.
• Redesign of the product for better manufacturability - can improve several or all the performance measures for the process.
• Flexibility can be improved by the outsourcing of certain activities. Flexibility can also be improved by Report, which moves the activities of customization at the end of the process.
In some cases, dramatic improvements is possible at minimal cost when the bottleneck is severely limiting the ability of the process. On the other hand, in well optimised processes, significant investment may need to reach a marginal operational improvement. Due to the large investment, operational gain cannot generate a sufficient return rate. A cost-benefit analysis should be conducted to determine if a process change is worth the investment. Ultimately, net present value will determine if an improvement 'process' is really an improvement.
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