THE L3 SYSTEM — ^ QUALITY CONTROL IN MANUFACTURE 



1001 



which employed a thermocouple in each heat treating boat, it was 

 established that the final minor axis dimension varied inversely with the 

 heat treating temperature. Temperatures between 850° C and 1000° C 

 could be used satisfactorily with a corresponding shift in process average 

 of 0.0006''. In Fig. 11(a) is shown the variation of grid minor axis with 

 temperature and in Fig. 11(b) the variation of size with tension is 

 indicated. 



A procedure was then set up which resulted in a more uniform grid 

 production. Each time a new spool of mre is used, a group of 25 grids is 

 wound using a standard value of tension. These grids are processed 

 through final sizing using 925° C for heat treatment and the standard 

 sizing blades. The distribution of these 25 grids is then plotted. The 

 position of the average is noted and correction is made for displacement 

 of the average by a change in winding tension, a change in heat treating 



V -2 



o 



o 



§-3 



850 875 900 925 950 975 



FINAL HEAT TREAT TEMPERATURE 

 IN DEGREES C (l5 MINUTES) 



1000 



20 



40 60 80 100 120 140 



LATERAL WIRE TENSION IN GRAMS 



Fig. 11 — Control of grid minor axis in terms of temperature and tension. 



