This section is from the "Modern Machine Shop Construction, Equipment, And Management" book, by Oscar E. Perrigo. Also see Amazon: Modern Machine Shop Construction, Equipment, And Management.
The question of efficiency. Classification of betterment work. Preparatory analysis. Classification of machine work. Planing. Shaping. Milling. Heavy turning. Medium class of turning. Gear and rack cutting. Drilling and boring. Grinding. Improving the design of machines. Increasing the efficiency of a vertical boring mill. Better tools. Arrangement of machines. A specific example of re-arrangement. Transportation facilities. Beneficial results. Systematic planning.
The question of efficiency is one of the most important with which the engineer has to deal. In the plans which he may devise for the arrangement and the erection of manufacturing buildings; in providing these buildings with power, heating, lighting, and transportation equipment; in inventing or purchasing the machinery best adapted for turning out the proposed product; and in employing the best workmen that can be found to operate these machines, - his plans will end in partial or complete failure if he shall not have kept in mind continually as his aim and objective the condition of realizing the highest efficiency of every piece of machinery and of every individual man of the plant.
It is a positive fact, often proved by such specialists as the mechanical engineer, the production engineer, the standardizing and the efficiency engineers, that in a large majority of manufacturing plants at the present time the actual efficiency of the entire plant will fall below 50 per cent. This being the case in a large number of plants, it is our duty to ascertain the reasons for these conditions and to work out such plans for the betterment of these as may promise to produce the greatest benefit in the most economical manner.
In considering the problem involved in this betterment work we may properly divide it into classes, which for logical consideration will be as follows:
The selection and adaptability of the machines used for the purposes for which they are intended.
The improving or re-building of existing machines so as to increase their range of work and efficiency.
The arrangement of machines with relation to each other for efficient operation.
The transportation facilities for bringing the material to the machines, and for removing that which has been operated upon.
An accurate record of the hours of running time, and the idle time, of the machines.
These several propositions will be taken up in order and the comments and explanations in relation to them will embody the results of the engineering experience, practice, and development of the present day.
Primarily we will consider the extent and the nature of the work to be done, before we can make any calculation on the classes or the numbers of machines that may be necessary. This will be the work of an expert mechanical engineer, who must analyze the product to be turned out as to the form and weight of the machine parts, the material of which they are to be made, and the machine operations necessary to prepare them for assembling them into the complete machines. This will be a long and arduous, as well as complex, task and one in which every new case will present differing conditions and circumstances which will call for much ability and good judgment of technical and manufacturing conditions. For these reasons it is manifestly impossible to lay down more than a few general observations upon this important question.
The following suggestions are given as representing the best machine shop practice in providing machines for the various classes of the work. The general class of work is given first, then the class of machines upon which the work is most efficiently and economically done.
Planers are used for long cuts on heavy work. The product may be a single piece of considerable size and weight, and proportionately long. Or, a number of like pieces which may be placed end to end on a long planer table and cuts run over them all.
The shaper is equally well adapted for work requiring shorter cuts, and work within its limits can usually be done more expeditiously than on a planer, particularly such work as is not adapted to be done with a single tool.
Of milling machines there are two general types, horizontal and vertical. The horizontal machines may be of the plain or universal forms. The vertical may have one or two spindles. There are also several kinds of special machines adapted to a certain range of special purposes. The milling machine in its various forms is adapted to a very large variety of work, particularly short cuts of irregular cross section. The vertical type is now used with a high degree of efficiency and accuracy on many kinds of work that was not formerly thought possible. The comparatively recent appreciation of the efficiency of the inserted tooth cutter has much to do with this fact as well as the added usefulness and adaptability of the milling machine for many new uses. A form of large machine of somewhat similar construction as a planer makes wide and heavy cuts, frequently exceeding a planer in efficiency and accuracy.