Material Handling Developments
The One Level Shuttle AS-RS (OLS) is a highly efficient Automated Storage and Retrieval System designed for expedited handling of cartons, totes, and trays in high transaction environments.
For more information on recent development in material handling visit
Material Handling Solutions and Equipment - Information Board
Comprehensive Lecture Notes on Material Handling Equipment - 2012 - Michael G. Kay, North Carolina State University
Material Handling System Design and Redesigm
Material Handling - Explanation by MaynardIn Operation Analysis Book
The handling of material costs money, and therefore it should be eliminated or reduced as much as possible.
The material must be transported to the work station, it must be handled by the operator before and after processing, and finally it must be taken away again. On a punch-press operation, for example, the processing time is the time required for the press to make a single stroke, is extremely small.. All the rest of the labor expended on the part is material handling.
Material handling adds nothing to the value of the part, although it does increase its cost. Therefore, a determined attempt should be made to reduce material handling to an absolute minimum.
The material-handling problem resolves itself into two natural subdivisions, the handling of material to and from the work station and handling at the work station.
Material Handling to and from Work Station. There are a number of different ways of transporting material to and from work stations, and the one which is the most effective and efficient will depend upon such individual conditions as the size of the material to be moved, the amount, the frequency of movement, and the distance transported.
The oldest, and probably even yet the most commonly employed method is movement through human agency. A move man or an operator carries or trucks material from place to place.
In certain instances, this is a proper and efficient method. For example, if a given material is so light and so small that a supply sufficient for 2 hours work can be carried in a container the size of an ordinary bread pan, a mechanical means of transportation would be uneconomical. The handling time during the process of manufacture between operations may be as little as 1 per cent of the total processing time, because of the large number of pieces that may be carried at one time. This could undoubtedly be reduced somewhat by relaying out the work space and arranging the operators so close together that they can pass material from one to the other without getting up. Even this Is not particularly desirable, however, for little if any real saving would be made. The operations performed on such parts are usually rapid and comparatively monotonous. Getting up and going for a fresh supply of material every 2 hours or so breaks the monotony and actually acts as a rest period by providing a change of occupation. If the, handling operation did not provide this interruption and rest, fatigue would cause the operators to seek it anyway by extra trips to the washroom or drinking fountain. Material handling on small parts that provides an occasional break during a monotonous operation is desirable, and no attempt should be made to eliminate it.
Hand Trucks. The larger the parts are, the more effort is required to handle them by hand. Added weight involves added muscular effort, and .added volume means more trips to transport
a given number of pieces. As weight and volume increase, trucks of some sort become increasingly desirable. . Human labor is required to push them from place to place, but they add to the effectiveness of that labor by making it possible to move a large number of parts easily and at one time.
Hand trucks are superior to no trucks at all, but they offer a number of disadvantages. They are bulky, and since they must be pushed through the aisles that are used by anyone who desires to go from one part of the plant to another, with or without material, they cause interference to easy movement and often
serious congestion. Where only one aisle is available, empty trucks commonly flow back against the stream of loaded trucks. In addition, the trucks occupy considerable valuable floor space at the various work stations. The replacing of hand trucks by conveyers will often result in worth-while economies.
Electric Trucks. Electric trucks are used for much the same purpose as hand trucks. They require the services of an operator, but usually more material may be handled per trip, and handled faster. Electric trucks are made in a number of different styles, and special trucks are made for special applications.
Tractor-trailer Systems. When miscellaneous material must be transported to a number of different places located over a large area, electric trucks may be replaced to advantage by a
tractor-trailer train. For example, a train replaced eight electric trucks. Before its instal-lation, the electric trucks were used to transport material, some of them being assigned to- specific departments and some operated from a central point. Wherever material had to be moved, the electric trucks were used. The departmental trucks took finished material to other departments and usually returned empty. The
other trucks were sent empty to whatever part of the plant they were needed. They did the required moving and then returned to the dispatch station empty. An earnest attempt was made by the dispatcher to route the trucks so that they were loaded as much as possible, but it was a difficult task. In addition, often when a rush call for service was received, all trucks were , and delays were frequent.
The installation of the tractor-trailer system reduced labor and greatly improved service throughout the plant. A route was laid out that took the train past every important material station in the plant. A regular schedule was set up, calling for several complete trips per day. The train moved along its route, drop-ping off trailers at the proper destinations and picking up others bound for different departments. Delays were reduced to a minimum, and each department knew, within a minute or two, the time it would receive incoming material or could ship outgoing material. A few of the old electric trucks were retained at first for emergency service, but the tractor-trailer system functioned so well and gave such rapid service that there was little call for
Conveyers are widely used throughout industry and, where they are properly installed to meet a definite need, will give worth-while economies. Considerable care must be taken to determine if a conveyer will really be an advantage before it is put in, for not all handling problems can be solved by this means. A shop superintendent was once heard to refer contemptuously to an elaborate overhead conveyer system as a "traveling storeroom/ 7 As a matter of fact, this is just what it amounted to. Because there was no real need for a conveyer in this department, it was used principally to keep unwanted material off the floor. Material would sometimes slowly circle the department for a week at a time before it was removed from the conveyer. This was wasteful, of course, and was the direct result of an improper installation.
There is a wide variety of kinds and types of conveyers offered by conveyer manufacturers for industrial use. Since conditions in every plant differ, all installations are in a sense special, but most conveyers designed to handle standard materials such as cartons, boxes, or tote pans are made up of standard sections or units. Gravity conveyers are in general cheaper than power-driven conveyers but, of course, require that the opposite ends of the conveyer be at different levels.
A conveyer does not have to be expensive or even purchased to be effective. Often a homemade arrangement of wooden boards will be as efficient as any conveyer that can be installed. On punch-press work, for example, where a product is made in several operations of approximately equal length, if the punch presses are set side by side, wooden chutes make excellent conveyers. At a given work station, the operator lays aside his finished part in the raised end of a chute. The part rolls or slides to the next operator and arrives in a position convenient for grasping.
Roller conveyers take advantage of the force of gravity to bring about material movement. The rollers run freely on ball bearings ; hence, a comparatively slight drop per foot of travel is necessary. If long distances must be covered, an occasional belt conveyer may be used to boost the material from the low end of one roller conveyer to the high end of the next. .
Other commonly used conveyers are the belt conveyer, , the spiral conveyer which may be either a roller conveyer or - a sheet-metal spiral with a steeper pitch, and the overbad chain conveyer. Many other types are alsQ^Ti|ilable, and special conveyers for almost any sort of specific material-handling problem can be obtained. Information and advice can be obtained from the leading conveyer manufacturers whenever an installation is contemplated. The main point to be decided upon first is the necessity for the conveyer. If a conveyer is desirable, a suitable type can be found.
Conveyers for Miscellaneous Work.
It is commonly felt that conveyers are applicable only where a standard product is manufactured in quantities. Under certain conditions, however, they may be used successfully to handle a miscellaneous variety of work. Figure 61 shows a conveyer running through a storeroom for finished material. A number of miscellaneous products are kept in this storeroom. When an order is received, material is taken from the shelves of the storeroom and is placed on the conveyer which takes it to a checker. When the order has been checked, other conveyers take it to various packing stations for packing and shipping. In spite of the variety of product handled and the number of ways in which orders are packed and shipped, a large saving was made by convey erizing the stores and shipping department.
Another and perhaps even more striking example of the use of conveyers on miscellaneous work occurred in a machine shop doing milling and drilling operations on small quantities of metal parts. Horizontal milling machines, vertical milling machines, and sensitive, radial, and multiple spindle drill presses were used, and there was a total of 51 machines in the department. Because of the small lot sizes, each machine worked on several different jobs each day. The order in which operations were performed was by no means fixed, for some jobs required drilling before milling, others milling before drilling, and others were milled, drilled, and milled again.
The former layout is shown in the upper half of Fig. 62. Material was moved about by laborers. They brought unfinished material to the various work stations and removed finished material. Material was piled about the machines and, besides occupying floor space, was decidedly unsightly. In addition to the material-handling problems, the matter of proper production control presented difficulties. In every shop, there are always certain jobs that are undesirable from the worker's viewpoint. When a number of jobs are available, the operators will choose the most desirable and will put off doing the least desirable as long as possible. Therefore, the production department has to be continually on the alert to prevent jobs being neglected until they become overdue.
A conveyer installation eliminated the move men and overcame production-control difficulties. All material is sent out from the central dispatch station, The dispatcher has a set of records which show when each job is wanted and what the operations are that must be performed. At the proper time,, he places material on the outgoing conveyer and by means of a control apparatus shunts it off on the proper lateral conveyer which takes it to the machines. When the
operation has been completed, the material is put on a return conveyer located directly below the outgoing conveyer. The job returns to the dispatcher who sends it out to the next operation. In this way, a definite control of the order in which jobs are to be done is obtained. A definite check on the production of each man is available, and certain phases of the clerical routine are simplified.
Material Handling at the Work Station. When material has been brought to the general neighborhood of the work station, the from that point until the operation Is complete is usually done by the operator. When material is brought by truck f move men, or tractor-trailer train, he usually has to walk a varying .distance to the material and transport it to working position himself. Conveyers or overhead cranes usually bring the material close to the operator.
When the material is at the work station, it must be picked up and moved to the working position. The work is done, after which the material is set aside. When the job is finished, the complete lot of material may be removed from the immediate vicinity of the work station by the operator.
The exact procedure followed "will vary considerably with varying conditions and products; but unless the material is brought directly to the operator by conveyer and the work is done on the part while it is still on the conveyer, there will be a certain amount of material handling at the work station. This should be reduced as much as conditions permit. The initial and final moves can sometimes be shortened by rearranging the layout of the department. Material handling at the workplace can be reduced by detailed motion study.
Questions. The discussion of the material-handling problem given here is of necessity rather brief. No particular mention of such transportation devices as overhead cranes or elevators has been .made, for these are usually provided when necessary and are usually installed and working at the time the operation analysis is begun.
As a matter of fact, the analysis of a single operation seldom leads to the installation of a conveyer system or other expensive handling means unless the operation is highly repetitive. Usually it results in the installation of simple handling devices such as the gravity chutes or the development of special tote pans .or racks, which facilitate the handling of the particular job.
At the same time, the desirability of the more elaborate handling devices should be considered. If several analyses indicate that a conveyer system, for example, offers possibilities, then a more general study of material handling may be undertaken. These greater possibilities should be kept in mind during all analyses.
Source: Operations Analysis by Maynard
Full Knol Book on Operation Analysis - Method Study: Methods Efficiency Engineering - Knol Book
Updated 3 July, 28 June 2015
First posted on 23 Nov 2015