Friday, September 29, 2017

MOTION STUDY VARIABLES - Frank B. Gilbreth - Part 6

Frank Gilbreth - Motion Study

CHAPTER IV -VARIABLES OF THE MOTION - Continued

NECESSITY

The necessity of the motion is such an important variable that an investigator is tempted at first glance to divide all motions into necessary and unnecessary, and to eliminate with one stroke those that appear to him unnecessary. A more thorough investigation will be apt to prove that no such summary elimination is advisable.

A motion may be an unnecessary motion in a necessary sequence, or it may be a necessary motion in a certain sequence, but the whole sequence may be unnecessary or inadvisable.

Example. In opening a paper bag of cement the average untrained laborer usually cuts the bag in two and removes the paper in several pieces and with many motions. The correct way is to cut the bottom with a shovel and pull the bag upward in one piece by grasping the bag just above the string.

This example shows both how motions may be unnecessary in themselves and how they may belong to a sequence that is unnecessary.

The only final solution as to the necessity of a motion will come when the trades are completely standardized. It is impossible to determine whether or not a motion is absolutely necessary until the method of doing the work in which it is used is standard.

Examples. i. Motions which were relatively proved necessary in laying brick by the " pick-and-dip " method or " stringing-mortar " method, the brick being lifted from the stock platform, became absolutely unnecessary when the "packet-on-the-wall" method of handling brick was adopted.

2. The same thing is true of motions eliminated by handling mortar in a fountain trowel.

The final solution of the problem of necessity of motions will be discussed later, though the subject is so large that no amount of discussion could do more than touch it.

PATH

The determination of the path which will result in the greatest economy of motion and the greatest increase of output is a subject for the closest investigation and the most scientific determination. Not until data are accumulated by trained observers can standard paths be adopted. The laws underlying physics, physiology, and psychology must be considered and followed. In the meantime, merely applying the results of observation will reduce motions and costs and increase output to an
amazing degree.

The path most desirable is usually that which permits gravitation to assist in carrying the material to place.


Example. We have found that the most economical height for laying brick is twenty-four inches above where the bricklayer stands, while it is most economical to pick the brick from a height about three feet above where the bricklayer stands; that is, about one foot higher than the top of the wall where the brick is to be laid.

The path is affected by the direction that the material is to be shoved as it moves into its final resting place.

Examples. When the packet is placed on the wall it should be placed so that the brick can be picked up and moved in a comparatively straight line with the direction that the brick will be shoved for filling a joint.

In theory the ideal path would be in a line of quickest speed from the stock platform to the wall.

In practice it is seldom that the most economical path for carrying a brick or mortar from the stock platform to the wall is exactly a straight line from one to the other. It will generally be most economical to move the brick in the path that will bend the arms the least and that will
permit almost a swing from the shoulder.

PLAYING FOR POSITION

Each motion should be made so as to be most economically combined with the next motion, like the billiard player who plays for position.

The direction in which a motion is made may affect the time required for a subsequent motion.

Example. In laying brick the motion of placing the mortar for the end joint can be done quickest if it is done in the direction of the next motion, such, for example, as the next motion that puts the trowel in the position to cut off the hanging mortar.

The sequence of motions in bricklaying, that determines when the particular motion is to be made that puts the mortar in the end joint, depends upon whether the "pick-and-dip" or the " stringing-mortar " method is used.

When the motions are made in the correct sequence, many of them can be combined so that two, and in some cases three, motions can be made as one motion, in but little more time than is required for one motion.

Example. Cutting off mortar, buttering the end of the laid brick, and reaching for more mortar all as one motion, in the " pick-and-dip " method.

SPEED

Usually, the faster the motions, the more output. There are other advantages to speed of motions besides the fact that they require less time. Speed increases momentum, and this momentum may be utilized to do work.

Example. The momentum of the brick helps to shove the mortar better into the joint.

Again, high outputs are generally the result of the habit of speed in motions. Habits of speed are hard to form, and they are hard to break.

Next to fewest motions, speed of motions is the most important factor of high record of outputs.





The list of variables here given makes no claim to being complete. The field of study is so immense that it is impossible as yet to give a complete and detailed method of attack.

It will be noted in reading the discussion of the variables that it has been found extremely difficult to handle each one separately. It is needless to tell the student, the investigator, the cost-reducing manager, that, difficult as the task is, for the best results each variable must be studied alone. The effects of all variables but one must be eliminated, or, better perhaps, all variables but one must be maintained constant.

Quicker results may often be obtained by studying several variables simultaneously, and for short jobs this may be advisable. But for long jobs of repetitive work there is no way so accurate and satisfactory as studying one variable at a time.

Please Give Your Comments.


What is the relevance of Gilbreth's initial writing on Motion Study today?
What are new developments in this area?
What are new scientific discoveries related to human effort productivity?
What are new developments in human effort productivity engineering?
What are new development sin human effort productivity management?

Updated 30 September 2017, 19 August 2015

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