Wasted Motion The Basics of Conducting a Motion Time Assessment at Your Facility
Wasted Motion: Identify production process waste through a motion/time study at your facility. This article covers the basics required to conduct a basis assessment.
By Henry Quesada, Paula Fallas and Nicolas Navarro
Date Posted: 3/1/2018
The most important goal in lean management is the elimination of waste in the production process and any related business activity. But how can you know for sure that your current process is as efficient as possible? The answer is to conduct a motion/time assessment of your work flow.
When attempting to improve the production process, the focus should be on documenting, analyzing and implementing changes to the activities in analysis so that the safety of the workers, the productivity, and the quality of the end-product will increase.
A work study includes two elements: a motion study and a time study. A motion study is conducted with the goal to eliminate or improve unnecessary elements that could be impacting critical productivity, safety and quality metrics. A motion study must be made before the time study, for it would be a waste of resources to determine time standards for poorly designed jobs.
In a motion study, the analyst is challenged to break down the process’s activities into tasks and the tasks into steps so all specific movements the worker performs are documented and properly classify as value-added and non-valued-added activities. In most cases the level of analysis goes down to each movement (of every hand) the worker needs to perform to complete a task, and usually these tasks are repetitive. A well-conducted motion study will allow the analyst to develop standard working procedures that can be easily followed by any the worker.
A time study requires the analysis to determine the time that it takes to complete a specific process, activity, task or step. A time study is a critical component in determining throughput, cycle times, cost allocation, lead times, idle times, line balancing, and in general any other performance metric based on time metrics. In conducting a time study some basic knowledge of statistics is required including the mean, standard deviation, and confidence intervals. In most cases, process times are considered to be normally distributed so the use and interpretation of the normal standard distribution is also required. This knowledge will help the analyst to get a better estimate of the number of samples required to conduct a statistically valid time study.
Figure 1 shows the required steps to perform a work study. Once the motion and time study are performed, the next step is to keep the performance of the operation or activity under control. While the motion study facilitates the elimination of wasted motion from the process, the time study will help to keep the cost under control. There are few recommendations that need to be followed in order to perform a successful work study. Figure 1 explains the proper process to conduct a proper study and analysis.
• In most cases, workers will be aware of your presence. This could make them nervous and thereby negatively impact the study. Before you start the work study, make sure the workers are aware and explain what you will be doing.
• Ask workers to perform their tasks on a normal pace.
• Prepare the proper forms required to capture data. In most cases, the analyst will only need a clipboard and a stop watch.
• Frequently cameras for pictures and video taking are very good tools for documenting the process for further analysis.
Figure 2 shows a visual form that can be used for a motion study. The symbols and classification of the operations need to be previously defined by the analyst.
Registering can use graphs that register the sequence of the facts or with a time scale or diagrams that indicate movement.
Example of Registering Using Bimanual Diagram
1. Define Symbols
2. Graph the activity
3. Do a visual representation
The form in Figure 2 is recommended for performing a bimanual motion study. In addition, operations can be easily separated into value-added and non-value-added activities (productive and unproductive). By observing the operation and using this form to document every step, the analyst should be able to identify excessive waste and potential areas to improve the operation.
As mentioned before, a time study covers a series of techniques aimed to determine a standard time for a specific activity or task. In essence, this is the time required to produce a product at a work station with three conditions: 1.) a qualified, well-trained operator, 2.) working at a normal pace and 3.) doing a specific task. A time standard is used to determine certain variables in the manufacturing process:
• Cycle times
• Lead times
• Manufacturing costs (labor and machine cost)
• Number of machines to buy
• Number of operators required
• Scheduling and coordination of machines, operations and people
There are some tips to consider when selecting an activity or job to analyze. If several people perform the same job, select at least three of them. Do not select the fastest or the slowest person, nor anyone with negative attitudes. It is important to get a full description of the job, its purpose and all materials and tools involved. Make sure the method is the standard and right method and verify quality is performing well.
How you divide up the job can be important for proper analysis. Elements should be as small as possible. Keep in mind that it is better to have too many elements than too few. To identify where the hang ups occur, separate machine-controlled elements from operator-controlled elements. Finally, beginning and ending points should be easily described.
How you actually conduct the calculations involves a few math formulas. Those are covered in a detailed White Paper on this topic that can be downloaded from www.palletenterprise.com/wastedmotionstudy.
Performing a work study has many advantages but the organization must commit resources to the project so the study is conducted and well-aligned with the organization’s strategic goals. A successful work study can help the organization increase raw material yields, increase productivity measurements and improve employee motivation. Get you stop watch ready because analyzing your process can be critical for making your operations perform to its peak potential.
Editor’s Note: If you would like assistance in conducting lean audits or motion/time studies, contact the experts at Virginia Tech. Email email@example.com or call 540-231-0978.
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