The literature on processing of plastics usually suggest limits within which the controlling instruments should operate, but seldom do we find explanations for the prescriptions. 

             The setup sheet, which is expected to contain all the needed information for starting ajob and getting ready for a production run, isin itself a very useful explanatory tool. 

             The implementation of this information will be good if one has an understanding of all the items on the list and their variables, as well as the factors surrounding them. It will be the aim of this subsubsection not only to list every item considered vital to successful operation, but also to provide information that will aid in the proper interpretationof  such items. The systematic arrangement and listing of the items is the setup record (Table 2-10). 

             The setup record is made in order to establish the most favorable operating conditions for each mold in a particular press. These favorable conditions pertain to good product quality, minimal rejects, and shortest possible cycles. Once these favorable operating conditions are established and approved by management, they should be faithfully executed. Should any modifications become necessary during some future run, they must be implemented only with the approval of the authorized individual in charge of plant management. In such an event, the setup record should be suitably revised, or an additional one made that indicates the reason for modification and the elements affected. 

             The setup record is a most important document in starting a job. If properly interpreted and precisely carried out, this record should result in the same quality, consistent cycles, and low quantity of rejects every time the job is in operation. For these reasons, it is desirable to describe each column of the record and point  out what  factors enter into the determination of a particular setting. Thus, those filling out the record and those applying it to the setup will have the same understanding of the information at hand. The goal is to acquaint those involved with the setup and the running of the operation with this description so that the job is carried out in a standardized manner leading to good performance. 

              If we consider that 1 sec of machine time alone is worth between 3/4 and 1(1/2) cents (depending on machine size), and each machine produces at least two shots per minute, or 720,000 shots a year, we can see that a single second wasted during one shot can amount to about $7,200 per year. With these kinds of values in mind, the exact reproduction of the settings indicated on the setup record becomes imperative. 

              The most productive setup sheet will implement the basic principles of molding: time, temperature, and pressure (see earlier discussion). Only if these elements are fully explored in relation to machine specifications and material processing  characteristics  can we be assured  that the molding operation has been optimized. For example, if the mold temperature is kept  at the low end of  the range because the part thickness is 0.065 in. (0.165 cm) or less, the material temperature must be in the medium to upper rage, so it can be injected at the full speed of the machine. And the pressure will be just high enough to do the filling of the cavity without opening the mold. 

               Let us look at some of the details connected to the setup sheet specifications.