UNIT O P E R A T I O N S
Materials Handling
AN
accepted fact is that the 1958 recession has finally run its course. Also a fact is that many large companies held their profit margins during this period of reduced sales volume. This holding-theline technique was not accomplished by converting to automation or investing large sums in new materials handling in order to realize cost reductions, but by reducing the level of capital expenditures and generally cutting the spending policies by operating a t a higher level of internal efficiency. Because of these factors, management found that they could conduct their manufacturing operations a t a new plateau of cost control. S o w that the general business economy has regained the 1957 level, this same management is reluctant to return to the old way of doing business. This new attitude placed a direct challenge in front of the materials handling engineer. Obviously the days of using experience and judgment to accomplish spectacular savings are over. A411 engineers should recognize the fact that materials handling is competing for capital money against all aspects of the total manufacturing process. This conclusion leads to the need for better analysis techniques together with more precise ways of analyzing problem variables. Unless economic justification is basically sound, the momentary trend will probably be toward modernization without automation. Warehouse design trends will probably strive to obtain optimum efficiency through the medium of space control planning, layout, and stock arrangement rather than through mechanization. T h e squeeze will be put on equipment manufacturers to provide more factual data regarding product life with particular emphasis on anticipated maintenance costs. The end result of this trend will be to provide a new and healthier foundation for materials handling. I t will become a science controlled by engineers rather than a n art manipulated by hardware salesmen.
Theory and Training The growing realization that materials handling cost reduction must be firmly based on sound engineering principles has led to considerable growth a t the college level. J. B. Day (8),recently pointed out that over 200 professors are now teaching industrial materials handling courses. From this group, 113 are teaching on a full-time basis and the remainder are teaching these courses in conjunction with other subjects. T h e College-Industry Committee on Materials
Handling Education maintains a n active list of these professors (73) together with an up-to-date review of the material being taught. C I C M H E is also active in the field of cataloging handling methods in a variety of industries. This group has recently announced that it has compiled photographs for use in a new materials handling slide film. T h e Slide Film Subcommittee ( 7 7) reviewed almost 2000 photographs and chose 600 which best illustrate various handling practices. I n the field of materials handling theory, three new books are now available. T h e first book has 1750 pages and required 5 years of work on the part of a joint AMHS-ASME committee (20). While this book is not a complete reference source, it does accomplish the task of gathering together a great deal of information on a complex subject. For the uninitiated, this book provides a n excellent introduction into the field of materials handling. The second publication ( 4 ) contains a discussion of the nature of production techniques and recent progress toward automaticity, and explores management experiences in the evolution of the automation programs in 13 selected firms. This series of studies can be very useful to the engineer who expects a highly integrated and automated manufacturing system. The third book (76) is a companion volume to “Materials Handling Equipment” published in 1957. In addition to giving helpful details on handling all sorts of materials, techniques are presented for adapting both equipment and limited work space to specific problems. In the area of linear programming. a recent article described the situation in which mathematical techniques were helpful in making a decision between handling methods for finished products in a warehouse (79). While this article is well documented, the logic and reasoning which form the basis for the study are not available. The answers to these questions and many more can be found in a recent book entitled, “Mathematical Programming” (28). This book is probably the best in its field and is particularly suited to the practicing engineer who is looking for a simplified route to utilize these valuable tools. Another approach to this problem (2) is expressed in a recent ASME paper which suggests that certain basic concepts of statistical analysis have proved to be extremely useful when applied to materials handling. Such techniques as linear programming, queueing theory. and the like depend upon the data available. T h e everyday decisions re-
garding cost estimating, equipment and packaging specifications, and paper-work systems design also are made on the basis of data available. I t is pointed out that, through the use of statistical analysis, these data are easier to derive and, therefore, more meaningful to the user.
Industrial Trucks T h e materials handling engineer concerned with the field of industrial trucks is often deluged with data which are often meaningless. A thorough analysis of this handbook (78) would tend to alleviate a major portion of these difficulties. I t also examines the industrial truck unit load systcm as related to the science of materials handling. The section on engineering data is particularly informative and presents the user with many facts and formulas to apply to select the right truck for a job. Fork truck stability is a topic that has recently received considerable interest on the part of materials handling engineers as well as from equipment designers and manufacturers’ representatives. This fact points out the value of a recent article which reviews the current thinking on fork truck stability (27) both in the United States and in England. A similar article on the meaning of lift truck specifications (22). should go a long way toward clearing up a subject overburdened with confusing claims. Previous Units Operations Reviews have pointed out the recent developments in driverless tractor trains. A very com~
~~
ROBERT W. WESSON received his B.S. degree in engineering from the United States Naval Academy. For the past 1 1 years he has been employed b y Union Carbide Chemicals Co., and i s currently a member of the staff of the Textile Fibers Department. Wesson i s a member of the American Society of Mechanical Engineers, the American Material Handling Society, and the American Institute of Industrial Engineers.
JOHN R. ARWOOD received his B.S. degree in industrial engineering from North Carolina State College. For the past three years he has been employed b y Union Carbide Plastics Co., and i s currently a project engineer in the Distribution Department. Arwood i s a member of the American Material Handling Society and the American Institute of Industrial Engineers.
VOL. 51, NO. 3, PART II
MARCH 1959
389
UNIT OPERATIONS
F i g u r e 1. attac hme nt
Pul- P a c
Courtesy Clark Equipment Co.
plete analysis of this type equipment (12) gives details of basic selection factors such as weight, speed, grades, and includes a description of various trailer types. Handling long shapes in narrow aisles is always a problem. The British have worked on adapting a narrow aisle truck for this application (23)but recently such a truck has become a commercial reality in this country. T h e 4-D Electric Truck (26) is a straddle-type, rider fork truck which not only moves forward and reverse, raises and lowers its load in the usual manner. but also can travel a t right angles to its normal line of travel. This should be a boon to the chemical industry --would reduce warehouse requirements for heat exchanger tubing and the like. Probably the most productive areas in the design of industrial truck equipment are in the field of attachments and the year 1958 was no exception. One of the most interesting is a carton clamp for palletless handling, with arms only 1-5,’s inches thick. Called the Slndr-Arm ( 6 ) ,it was designed to reduce the arm entry space needed between stacked cartons, thereby increasing usable storage area. Clamping action is provided by two hydraulic cylinders mounted on the unit‘s framework. Clamping arms are made of 6/8-inch steel plate to which are mounted double clamp pads made of ‘/2-inch-thick aluminum alloy. Each clamp pad is rubber mounted to a pivoted support to permit pads to conform to load irregularities. A new Pul-Pac attachment (7) for palletless handling has recently been introduced. This device consists of a load carrying plate. pusher rack, and gripper jaw (Figure 1). Loads are carried on a thin steel sheet instead of conventional pallets thus reducing storage space requirements and replacement of worn pallets. A flap a t the edge of the sheet is gripped by hydraulically-actuated jaws, and the sheet is pulled onto the load carrying plate. Load removal is accomplished by the upright pusher rack which has up to 50 inches of forward travel.
390
Packaging T h e importance of a Packaging Committee (77) has been expressed by one company in terms of dollars saved. Cost reductions for a one-year period amounted to $100,000 as a direct result of package improvement. Savings of this magnitude are available to most companies; however, study and effort are required to search out the potential. Chemical research has played a dramatic part in the advancement of packaging this year. Most notable of the new packaging materials are expansible paper and polyethylene film for industrial products. Long sought after has been a package which would “bounce” and take the abuse of less-than-truckload and lessthan-carload handling (Figure 2 ) . Kraft paper with a n adhesion factor of 10% is now being produced on a broad scale (37), and the cost of packages made from these papers compare favorably with industry standards. The manufacturer claims that the secret of this paper’s toughness is not stretch alone. for it is reported to have a high modulus of elasticity and to be able to stand considerable Ivork before exhausting its stretch. In addition, this paper is claimed to be softer than regular papers a quality which should contribute to a more pliable package with less “paper rattle.” T h e major area of question is whether or not the paper will hold up after the stretch characteristic has been utilized. Only time and use by the packaging industry \vi11 answer this question. Also brand new in the shipping field are industrial shipping bags fabricated from 10-mil polyethylene film. A plastics manufacturer (5)recently announced the commercial availability of these bags immediately follolving the approval by the Railroad Joint Classification Committee for domestic rail shipments of plastic materials. Polyethylene bags have proved tougher than bags fabricated from standard materials in drop tests. Their moisture resistance is unsurpassed in bag packaging. Certain drawbacks to
INDUSTRIAL AND ENGINEERING CHEMISTRY
the package are prevalent; ho\vever: the cost of the package is 15 to 20cc greater than multiwall Kraft bags, and the surface of the polyethylene bag must be treated to reduce the build-up of a static charge and to eliminate slipperiness when stored on pallets. Further information is no\\’ available on the Vredomatic Packer (3)previously reported in the 1957 Unit Operations Review. I t appears that this packer‘s labor saving advantages are its most outstanding feature. Previously, two or three men were required on most open mouth multiwall bag packing lines to fill and sew the bags. For granular products, this packer requires on1)- one attendant for filling the bag feeder with bags about once every 30 minutes. Optional equipment is noiv availableanalysis of identification tags can be automatically sewed under the tape and automatic coding of bags is possible.
Unit l o a d Handling The demand for receipt of materials in unit loads reached a n all-time high during 1958. T h e customer, u.ho is almost always a shipper as well, is no longer content to spend the 12 to 20 man-hours required to unload a freight car of ununitized goods. Receipt of unit loads has cut this receiving time from 1 to ll;z man-hours for fork-lift truck. Emphasis in all industries is increasing on the efficiency of making u p unit loads for shipment. Cost ofexpendable pallets, as well as cost of labor to unitized shipments, is also receiving careful stud).. .4 new pallet made of formed Craveneer (70) made its debut in 1958. Southern hardlvood panels are securely bonded on both surfaces ivith kraft paper then coated to afford moisture resistance. The core is rotary-cut grain \vood lvhich yields greater rigidity and hetter heat forming. These pallets are built for handling with standard fork trucks equipped with tapered forks or for pushpull equipment. A continuous problem in unit load shipping is stability of the stack pattern. Various unitizing glues are sold commercially; however, application of these glues is one additional operation. One company in the multi\vall bag industry has developed antiskid surface coating 1.3) which tends to eliminate the necessity of gluing unit loads. This ne\v antiskid multiwall bag offers improved ease in handling, easy identification (no sticky agents to mar the surface or brand printing on the bag, xvhen removed from a stack), reduction in broken bags due to slippage, and safer stacking qualities than other skid-resistant bags. T h e nonslip quality of the bag is obtained by the application of an antiskid agent to the surface of natural kraft during the papermaking process. The agent has no toxic
All engineers should recognize the fact that materials handling is competing for capital money against all aspects of the tot a I ma nuf act ur ing process effect on the ingredients of the product transported in the bags. ,4 variety of techniques have been introduced to produce a nonslip quality in multiwall bags. Among the most common systems are printing the brands with special inks to increase friction between bag surfaces, spraying the surface or face of the bag \vith a rubber or resin-based compound, applying compounds in bands or strips, and, more recently, spraying a special compound to the surface of the paper to increase surface friction. The manufacturer of this new paper used various techniques to test the nonslip qualities of the paper as compared to other nonslip papers and each indicated the antiskid sheets \cere superior. One test measured the angle of inclination of a plane surface covered Lvith a given paper and on \vhich a g i x n M-eight, with its surface also covered Xvith same paper, rests a t the moment \\.hen the weight starts to move as the plane is inclined. T h e antiskid sheet registered the highest coefficient of friction among the nonslip types tested. Other tests: using a \vide variety of testing techniques. confirmed the “inclined plane method“ findings. Standardization of length and kvidth of multiwall bags used for products with a varying range of bulk density has been hampered by the inability to manufacture polyethylene-lined multiwall bags in pasted-end construction. By forming the end of the bag so that each succeeding ply of the multiwall construction slightly overlaps the previous ply, a “stair step” surface is created. In gluing the end of the bag, better adhesion is obtained, and the problem of gluing natural kraft to the polyethylene-coated internal sheet is minimized (27). Drop and barrel tests of these bags have shown them to be tougher than bags with sewed ends. By varying the thickness of the bag. variable density products can be packaged in a bag of fixed length and width. This allows standardization of pallet size.
Bulk Handling The greatest emphasis on materials handling has again been in the area of bulk handling. Experience has shown that \\.hen large quantities of a single product are received a t one location, the least expensive handling system is bulk handling. Several new bulk trailers appeared this year ( 7 . 9, 74). Both vacuum and positive pressure air conveyor loading and unloading systems are continuing in almost equal importance. and the deciding factor is inevitably the customer‘s preference. A new hopper car which is the granular product counterpart of the Airslide car is currently under a field test program ( 7 5 ) . This car \
