By Jon Miller | Post Date: January 19, 2008 6:46 PM | Comments: 0
We're big fans of making significant organization-wide change by involving everyone in minor improvement activity every day. This is especially important for sustainability as you progress on your lean journey. As you progress in lean and succeed in taking out the waste, it can become harder and harder to find minor improvements. As the so-called low-hanging fruit is picked, people think that they need to attack major improvements higher up the tree. Major improvements are certainly important, but may involve time, money or other resources that are not available to everyone every day. What do you do when the low-hanging fruit is gone, an you have no ladder? Hint: Forget the tree, dandelions are edible, delicious, and growing all around your feet.
In order to help you see those metaphorical dandelions, we introduce the Minor Motion Analysis worksheet, a Gemba Research original and one of our 101 kaizen templates. The idea of motion analysis is not new or original to Gemba, but we put together this kaizen template as a simple way for people to observe movements of the arms and find wasted motions. The human arm is a marvelous and complex piece of anatomy, and we should pay more attention to how it moves so that we can design processes that are more fluid, safe and efficient.
You may notice that in the example given above the arm was a robot arm. The Minor Motion Analysis template can be used for robot arms as well as human arms. There is a LEFT ARM and RIGHT ARM section of this template (top and bottom half) but in the case of this robot, it was a lonely arm without body, legs or head so only the top half was used. When there robot or person has two arms, both sections must be completed.
This template is really very easy to use and I recommend every try this, whether in an assembly line, inspection work, a CNC machine turret, or in any repetitive process where you can observe several cycles of the same steps. All you need to get started is this template and a pencil. Although we do want to know total cycle time for the process, we don't need a stop watch. A wrist watch will do in this case since we just want to see "cycle start to cycle start" and not detailed task times. Here are a few key points to using the Minor Motion Analysis worksheet:
Select the process scope to observe
If you have good work instructions, job breakdown sheets or standard work then select a series of connected process steps that add up to between 15 and 50 seconds, as a rule. If the motions are much faster or slower, adjust times accordingly. The key point is to break down or combine the processes steps into sensible chunks rather than to attempt observation on a complete process in one go. The reverse holds true, in that there is no sense in observing a repetitive 5 second process that really needs to be combined with the upstream and downstream processes to make a more reasonable manual work cycle.
Draw the arm you are observing
The middle section of the template is used as a pictogram, which is another kaizen template we may return to later. Simply draw a reasonable resemblance of the arm you are observing, clearly showing shoulder, upper arm, elbow, lower arm, wrist, hand and fingers. The purpose of drawing the arm is to allow you to tick off the number of times that area of the arm has moved, as you see with the vertical and diagonal marks on the example above.
Start with the left arm
This is for no reason other than to make sure that you do observe the left arm. We have found that in many cases, the left arm is idle, used as a jig to hold the part, or people return from their assignment to observe minor motions saying "the left arm did the same thing as the right arm" which is unlikely. If the left arm is idle, acting as a jig, or moving much less than the right arm, this is OK and in fact it will give you a chance to practice and get used to looking for should, elbow, wrist and finger motions. If the left hand is idle, it is important to show this as a series of "0" values in the Current Motions, with the target being to use both hands by sharing some of the motions of the right hand. The reverse is also true if the right hand is idle. Again, the only reason the above example is blank is because it was a robot (one arm) and that's the only example within easy reach for me at the moment.
Number of cycles to observe
A good rule of thumb for time observation is to observe 30 cycles in order to get statistically valid data, and this is probably true for looking at the motion. Even in processes where the cycle times are fairly stable within 5%, we find that the number of minor motions can vary by 15%: just observing the task time does not tell you whether in fact there is variation and more motion is required to get the job done in the same amount of time. In the robot example above the movements of the robot arm had almost no variation so we concluded that we had enough information after observing 15 cycles.
Counting the number of motions
The first thing to do is to watch how many times the shoulder moves each cycle. Reaching up, down, stretching, reaching, rotating the arm, and any such motions that are driven by the shoulder should receive a mark on the pictogram. Proceed to elbow, wrist and fingers after you have observed 5-6 cycles each, leaving 5-6 cycles at the end to check your work, for a total of 30 cycles of observation. The finger and wrist motions are fairly obvious, but sometimes there are motions that appear to be shoulder-elbow or elbow-wrist, particularly for turns. A good way to check this is to try the motion yourself, or ask the person you are observing to make the motion while keeping either joint still. In some cases motions of two parts of the body can be combined for more fluid or safer motion, while in other cases one motion is superfluous and can be removed through better placement of parts, tools or through training.
Corrective action description
In this section you write down your observations specific to how a motion can be eliminated, combined with another, reduced or simplified. These are kaizen ideas that you will test.
Once you have completed your observations and identification of kaizen ideas, write down your estimate of the new total time. This is your hypothesis, if you will. Ask the worker or robot to try the new method, observe, time and kaizen further.
This is an area for general comments on the condition of the work area, conditions during observation, individual difference between sizes of operators' arms and other information for future reference.
The result of this minor motion analysis and kaizen activity should be reflected in the job breakdown sheets or standard work instruction sheets as key points, knacks etc. for that process. Lacking standard work, the minor motion analysis can still be used to make improvements in tooling, equipment, part presentation, work methods and overall safety.
If you have conducted similar minor motion analysis activities please share your experiences or things you have learned as a result.Comments are moderated to filter spam and inappropriate content. There may be a delay before your comment is published.