Method study: flow process charts, two-handed charts and principles of motion economy
In one sentence
Method study questions whether work is needed and how it is done before measuring it; motion economy aims to achieve the same result safely with less unnecessary motion.
By the end of this lesson
- Distinguish the five activity types in a flow process chart and verify the total step count.
- Align both hands' activities on a common time axis and identify holding and idle time.
- Calculate a method change's effects on steps and time separately.
- Reject an unsafe motion proposal and define the verification needed before measurement.
Why it matters
The first question in a time study is not how many seconds the work takes. First establish what work is done, by which method and under which acceptance criteria. Carefully measuring unnecessary transportation does not prove that it is needed. Including reaching caused by a poor layout in standard time does not solve the method problem either. Method study makes the work visible from start to finish, separating necessary work from unnecessary motion. Time is then measured for a defined method that can be applied safely. The standard thus stops being a number that makes an incidental practice permanent; it rests on a work definition whose conditions of validity can be explained.
A flow process chart records the sequence followed by a selected part or person as operation, transportation, inspection, delay and storage. Following a part on one row and a worker on the next confuses the scope. Write the entity being followed at the top of the chart. A two-handed (left-hand/right-hand) chart examines a narrower task: it shows what the right and left hands do in the same time interval, side by side. Prolonged holding by one hand while the other searches requires an investigation beyond simply asking for faster movement. The two charts answer different questions; one does not replace the other.
Motion economy does not mean that a person must move at every moment. Reducing unnecessary reaching, presenting the part in a suitable position and replacing holding with a safe fixture can help. However, simultaneous movement of both hands is not a success in itself. Simultaneous motion that blocks the view, puts fingers in a pinch point or makes control harder is unacceptable. Test a proposed method for safety, quality and feasibility together. If the fixture creates a new clamping task, record that task too. Account for new movements as well as those removed.
In this lesson, step count, time and risk are separate results. Fewer rows do not automatically prove a shorter time; grouping a long operation into one row only shortens the chart. Show why the proposal helps at the activity level and verify it in a trial. Predetermined time systems, covered in M8, also require defined motions and conditions; no ready-made time table is used here. The aim is to establish a measurable method. Work element boundaries, stopwatch measurement and statistics in later lessons will build on this method. This is also why old times cannot be transferred directly to new work when the method changes.
Formula
Total steps (steps) = Operations + Transportation + Inspections + Delays + Storage
New steps (steps) = Old steps − Removed steps
Step reduction (%) = Removed steps ÷ Old steps × 100
Time difference (s/cycle) = Old time − New time
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- Step-by-step instructions
- Worked example with real numbers
- Where the method misleads
- Common mistakes