A detailed discussion of all the techniques and procedures of production planning and control is beyond the scope of this book; many complete text books exist on the subject. We have already indicated that planning and control practices will vary widely from plant to plant.
Though no production control function can be entirely eliminated, the least control that results in effective operation of the factory is the best control. It must be remembered that production planning and control systems should be tools of management. The objective is not an elaborate and detailed system of controls and records, but rather, the optimum operation of the plant for maximum profits.
- Production Planning and Control Systems – Because production planning and control places an emphasis on the control of work-in-process, the system will in effect tie together all previous records and forms developed in all planning for the manufacture of the product.
- Market forecast – Its value to production planning and control is that it will indicate future trends in demand for manufactured product. Work shift policies, plans for an increase or decrease in manufacturing activity, or possible plant expansions may often be based upon the market forecasts and in turn affect the planning of the production planning and control group.
- Sales Order – This is the second of the five classes of orders. It is a rewrite of the customer’ order specifying what has been purchased – product and quantity and authorizing shipment of the goods to the customer. Multiple copies are prepared and all interested functions are furnished a copy. Sales orders may be written by marketing, inventory control, or production control.
- Stock Order – This third class of order is not always used. In the preceding paragraph we indicated how it may be used after sales order accumulate to an economical manufacturing lot. It is, of course, the principal order when manufacturing to stock. It will authorize production in anticipation of future sales.
- Shop Order – This fourth class of order deals with the manufacture of component parts. Customer orders, sales orders, and stock orders are for the finished product. By product explosion, the requirements are established for component parts to build assembled products.
- Standard Process sheet – This form is prepared by process engineering and it is the source of basic data as to the type of machine to be used, the time required for processing and the sequence of operations in the manufacture of the product. Routing and scheduling of shop orders, as well as loading of work-stations in advance of scheduling, depend on up-to-date standard process sheets being available to the production planning and control group.
- Engineering Specifications – Blueprints and bills of materials are used by production planning and control when they become a component part of the packaged instructions issued to the shop through the control office. One good planning procedure is to accumulate all necessary data for a shop order in a single package- the standard process sheet, the blueprint, the bill of material (if an assembly operation is involved), the route sheet, and possibly the schedule for the production of the order.
- Route Sheet – This is the form on which the route of a shop order is indicated. In practice, this form is generally combined with one of the other forms in the system. For example, the shop order, the standard process sheet, and the route sheet are often one piece of paper- usually called the shop order or the manufacturing order.
- Load Charts – These charts are prepared to show the productive capacity that has been “sold” – and at the same time the available productive capacity. These charts may be prepared for each workstation or machine in the plant, or they may be for groups of machines or departments.
- Job Tickets – This is the fifth and last type of order in a manufacturing situation. Job tickets authorize the performance of individual operations in the manufacturing process.
- Project Planning Methods – The production planning and control methods deal primarily with the production of consumer or industrial products which could be considered to fall within the area of “repetitive manufacturing”. The products to be produced are often manufactured in quantities of more than one, and their total processing time can be measured in hours, or at most, days. The best –known methods that have been developed are CPM (for Critical Path Method) and PERT (for Program Evaluation and Review Technique). The original PERT technique is now considered, more accurately, PERT TIME, whereas a later development is known as PERT COST. From the optimistic, most likely, and pessimistic times, the expected elapsed time (te) can be obtained by statistical techniques. The relationship of the three estimates to the expected elapsed time is given by the formula
te = (a+4m+b)/6 where, a = optimistic time, b = pessimistic time and m = most likely time
It can be seen from the formula that the most likely time estimate is given four times as much weight as the optimistic and pessimistic estimates when computing the expected time.
Systems Analysis – As with other manufacturing control systems and procedures, production planning, and control lends itself to modern mechanization techniques such as machine accounting and use of computers. Careful study of the control system through procedure analysis will indicate the savings by the utilization of modern equipment. These savings may be in the clerical help required in the administration of the system or in the advantages of quick compilation of data, which in turn results in up-to-date control data.