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Labor Requirements in Softwood Plywood Production1 PLYWOOD, a relatively new building material, is the subject of the fourth in a series of studies by the Bureau of Labor Statistics of the labor required to produce the principal types of building materials. Plywood made to special size and shape was used for furniture and other manufactures as early as the middle of the 19th century. However, it was not until 1905 that it was made in stock sizes, and not until about 1920 that the material now known as Douglas fir plywood was first produced. About 153 3 million square feet of the latter was manufactured in 1925, the first year for which data are available. Thereafter production rose to a peak of 1,840 million square feet in 1942, and then dropped for three consecutive years to 1,222 in 1945. In 1946, owing partly to substantial increases in production rates during the last months of the year, output exceeded 1,400 million square feet, about half of which was in what are generally accepted as construction grades. This volume of production was only about enough to meet the estimated minimum requirements for the current housing program and other essential needs.
Plywood board consists usually of an odd number of sheets of veneer so bonded together that the grains of adjacent layers are at right angles to one another. The result is a large, smooth panel which is very strong in proportion to its weight, and which has wide use in both conventional and prefabricated construction. It is used as sheathing, as a covering for partitions, ceilings, and the inner surfaces of exterior walls, for subflooring, and in some cases for siding. To date, it has been the basis of most prefabricated construction, in which it is better adapted than solid lumber for the covering of panels. In addition, it is used in doors and cabinets, and in the construction of concrete forms.
Prepared by Roland V. Murray in the Bureau's Construction and Public Employment Division, under the direction of Brunswick A. Bagdon. The field data were collected by Joe R. Brinkerhoff of the Bureau's San Francisco regional office.
For previous studies, see Monthly Labor Review, issues of September 1946, Labor Requirements in Cement Production; November 1946, Labor Requirements in Production and Distribution of Concrete Masonry Units and Concrete Pipe; and December 1946, Labor Requirements in Southern Pine Lumber Production.
This report will be included in a forthcoming bulletin which will contain a detailed analysis of labor requirements in the production and distribution of lumber and lumber products.
'The standard unit of measure in the industry is a square foot of 3-ply material of a total thickness of 34 inch.
Scope and Method of Survey
For a number of technical reasons, only Douglas fir has thus far been widely used in the production of softwood plywood. The presence of cracks and center rot in other woods, their longer drying schedules, and their unsatisfactory gluing and sanding properties are among the factors which have discouraged their use. Hence, at least 97 percent of the total softwood plywood footage produced in early 1946 was from Douglas fir, the remaining 3 percent being chiefly from Ponderosa pine, with a scattering of other woods. The industry is therefore confined largely to those areas in western Washington and Oregon in which Douglas fir is the predominant species. It comprises only some 35 mills, 2 of which are in northern California and account for the relatively small amounts of plywood produced from woods other than Douglas fir.
In order to obtain data for the current survey, a Bureau representative visited 9 of the Douglas fir plywood plants, selected for study in cooperation with the Douglas Fir Plywood Association. These plants accounted for nearly 43 percent of total softwood plywood production during the first half of 1946, the period covered by this survey. Sixty-nine percent of the sample production coverage was obtained in 7 Washington mills. This, however, only slightly overemphasizes the importance in the industry of that State, which has about two-thirds of the total Douglas fir plywood capacity. At each plant, the representative transcribed from plant records data regarding total amount of production, man-hours worked in each principal plant department, and quantities of materials consumed, during a representative period in the first half of 1946. Observations of plant operations during these visits were supplemented by discussions with technical men in the trade association.
Man-Hour Requirements, 1946
The data obtained indicate that an average of 12.4 man-hours of labor were required in the mill to produce 1,000 square feet of plywood. The range of requirements in the individual mills surveyed was from 9.7 to 15.1 man-hours. The rather wide plant-to-plant variations reflect differences not only in plant efficiency but also in types of products. Plant efficiency is very largely a matter of plant age; the older mills were originally merely the panel departments of door plants, and the subsequent tremendous expansion overtaxed their facilities.
♦ Hardwood plywood is used mostly for furniture, store and office fixtures, and similar products. Its use in construction is largely limited to decorative paneling and ceiling. It will not be an important factor in the current housing program and therefore is not included in the current survey.
The effect of type of product on man-bour requirements is illustrated by the 2 plants at the extremes of the range noted above. The plant with highest requirements manufactured a variety of products, including exterior 5 plywood (which requires closer control in manufacture than the interior type), scarfed panels (giant panels produced by gluing together standard panels in a special hot press), and specialty items; the plant with the lowest requirements produced only standard interior panels, the simplest type of product. Another factor distorting plaat-to-plant comparison arises from the fact that some plants produce for themselves certain essential items which more commonly are purchased. Thus, 4 of the surveyed plants generated their own electric power, and 2 manufactured their own glue.
The total man-hour requirements for the production of 1,000 square feet of plywood were distributed, by department, as follows:
Production departments.-Relatively few man-hours (1.6 per 1,000 square feet) are required in the green end operations, where the veneer sheets are produced. Here, the "peeler" logs (straight, sound logs, usually of a large diameter) are drawn from the pond and cut into lengths (usually 8 feet) determined by the desired length of the plywood panels. The bark is removed, and the log is mounted in a lathe which revolves it against a knife running the entire length of the log. The veneer is thus peeled off in a manner which resembles the unrolling of a large roll of thick paper. It is conveyed over tables to clippers which cut it to panel widths or to widths determined by defects in the log.
In the drying department, which accounts for the same number of man-hours as the green end operations, the individual pieces of veneer are run through a mechanical dryer, which reduces the moisture.
There are two basic types of plywood-the "exterior" and the "interior" (formerly called "moistureresistant")-which differ chiefly in the type of adhesive used. The former is bonded chiefly with phenolic resin by the hot-press process, and represents the maximum in resistance to moisture. The latter is bonded with casein, soy bean, or similar glue, generally in a cold press, and is for use where continuous exposure to the elements is not required.
content to the desired low percentage in a few minutes. The veneer is then ready for the actual process of plywood manufacture.
More than half of the total man-hour requirements, as shown in the above tabulation, are expended in the assembling department, which bonds the veneer sheets into plywood and finishes the panels according to their intended uses. Since many more different processes are used in this department than in any of the others, an attempt has been made to analyze its functions by grouping the processes into three classes as follows:
Owing to differences in production methods and cost systems, the above figures are based on data which may not be strictly comparable from plant to plant. Moreover, only 6 of the 9 sample plants were able to supply readily the detail necessary for this distribution. It is therefore offered only as a rough indication of the allocation of the relatively large number of hours absorbed by the assembling depart
Veneer preparation, as referred to above, consists chiefly of the joining of fractional widths of veneer (their substandard size resulting from defects in the log) into full-size sheets by taping or gluing; the removal of smaller defects by cutting, plugging, and patching; and the selection of veneers appropriate for different uses. Bonding involves spreading glue on the prepared veneer sheets; "laying up" the latter into panels of the desired number of plies; and subjecting the assemblies to pressure (and, frequently, to heat) to set the adhesive. Finishing the panels requires dimensioning on saws; sanding; finish patching, to remove defects which have appeared during the manufacturing; and such treating for special purposes as oiling the faces of concrete-form plywood. A further expenditure of 0.8 hour of direct labor is required for shipping, which includes handling through the storage room and to the shipping facility, and packing.
Nonproduction departments.-The man-hours shown for plant burden, which account for the greater part of the nonproduction labor requirements, represent for the most part the labor needed in the maintenance and protection of the mill and the operation of its power plant. Data from a few of the mills surveyed indicated that maintenance and protection required about 0.8 hour, and power-plant operation 0.4 hour. (Power-plant requirements varied considerably according to whether the mills generated or purchased their electric power.) The additional 0.1 hour represents chiefly general plant
superintendence not chargeable to a specific production department, and a very small amount of laboratory work. Administration and selling, which, with plant burden, make up the nonproduction manhours, include the activities of the central office executive and clerical personnel.
Comparison of Man-Hour Requirements, 1935 and 1946
A previous survey of labor requirements in the production of lumber and allied building materials measured the number of manhours required to produce 1,000 square feet of plywood in 1935 in a sample of 6 mills, representing, as in the current study, about 40 percent of total production. A comparison of the figures developed in the two surveys follows:
Man-hours per 1,000 square feet
(36 inch basis)
A substantial decrease in total man-hour requirements, amounting to a little more than 25 percent, appears to have occurred over the 11-year period. Although the two measures are not strictly comparable because of differences in the samples and methods of data collection, technical men in the industry believe that they reflect with reasonable accuracy the trend over the period.
Since the earlier study attempted only the requirements breakdown as shown above, it is not possible to analyze by department the decrease in "factory production" requirements. A review of some of the improved machines and techniques suggests, however, that labor requirements have decreased to some extent in every department. Among the more widely adopted improvements in the green end operations are mechanical barkers, which replaced the hand-wielded adzes; core lathes, for the rapid production of crossbanding veneers from cores of logs peeled down on the large primary lathes; and automatic clippers, which increase the rate at which an operator can cut veneer sheets from the continuous ribbon flowing from the lathe. Driers, although not basically changed, have been redesigned to permit faster operation. Significant improvements in the dry end operations include the automatic plugger, which cuts out a defect and inserts a tight patch in a single operation, and the edge-gluer or tapeless splicer for joining fractional widths of veneer. Through
Labor Requirements in Lumber Production, Monthly Labor Review, May 1937. (Reprinted as Serial No. R-529.)
'In plywood of 5 or more plies, crossbanding is the veneer used between the core (innermost layer) and the faces.