15. Two types of routing.—From the time sched ule standpoint there are only two classes of manu facture: 1. For stock; that is, the factory turns out the same thing continuously, throwing on the sales department the responsibility of finding a market for the product. This class includes textiles, typewriters, shoes, furni ture, clothing, pianos and most of the ordinary goods which are consumed in quantity. Quantity time schedules are adequate for manufacture for stock.
2. For specific contract; that is, a single object is made to a customer's order. This class includes re pair work on orders from the general shops, but its most important feature is the assemblage of large engineering products such as locomotives, large ma chinery, steamboats and buildings. Making connec tions is the important thing in manufacturing, as it is in railroading, for one late part will stall the entire work. A premature arrival is as bad as a delay. If the steel for a modern skyscraper arrives before the foundations are complete, chaos ensues, for it is con stantly in the way, retarding the work which must be done before the steel can be set. It may take a month or more to straighten out the confusion. It is there fore necessary to figure out the time necessary to manufacture each separate part, and to schedule the starting date of each succeeding operation accord ingly. These time schedules resemble ordinary rail
road time-tables.
For example, in the Thompson-Starrett schedule for the construction of a New York office building, shown in Figure 19, on page 322, it will be noticed that the foundations start 11-1 (November 1) , the day the excavation is finished, and not sooner, and that the steel erection starts 11-24 (November 24), the day the foundations are finished. The supplying of the granite, however, depends not only upon the com pletion of the steel construction, but upon the finish ing of the foundation walls, and so the granite starts as soon as they are brought to grade, 12-8 (Decem ber 8) . The limestone follows the granite 12-10 (De cember 10) and the brick succeeds the limestone 12-15 (December 15) . The floor arches, however, depend again on the steel and follow right behind the rivets before the steel work is complete, and so thruout the building. The difference of a day or two between operations is to allow the time necessary to get the material on the job so as to be able to start at once.