1132 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1956 



valve in the vacuum line at the right time in the turret indexing cycle to 

 drop the laminations as class "A" or "B" mica. 



Experience with these machines and with others that followed brought 

 into being a more or less orderly body of knowledge as to what features 

 are desirable and what constitutes good design in an automatic test ma- 

 chine. 



If the machine is to have speed, reliability and long life, attention 

 should be paid to the following matters: 



1. Reduction of the test process time to as low a figure as the capabilities 

 and use of the product will permit. Thus, if one of the requirements of a 

 capacitor is a maximum limit on its leakage current measured after a 

 charge time of 60 seconds, and if the material sand manufacturing process 

 are such that a unit is surely good or bad after a 25-second charge, then 

 the machine may be designed to charge for, say, 30 seconds. Frequently 

 the only limitation is the speed of the machine itself. When this is true, 

 it must be worked out so as to satisfy the needed production rate. Obvi- 

 ously the machine should satisfy the rate of the line it serves, or more 

 than one machine should be provided. 



2. Rationalization of the number of test positions in the machine with the 

 production rate and the total test process time. This requires breaking the 

 test time down into bits equal to the desired output cycle. In the example 

 above, if the output needed is a capacitor every 5 seconds then the 30-sec- 

 ond charge will have to extend over 6 positions. 



3. Ruggedness. This must be stressed, even at the expense of space, 

 power consumption, and dollars of first cost. If a project is large enough 

 to justify automatic test facilities, then any down time associated with 

 it will be expensive. A good mechanical design is essential. 



4. Provision of self -stopping and alarm features to serve in the event of 

 certain types of failure. A limited torque clutch in the main drive will pre- 

 vent jamming and damage caused by parts getting into the wrong places, 

 or in certain applications overload cutouts will suffice. Gong and lamp 

 alarms are desirable to attract attention. The point is that allowance 

 must be made for mishaps which, without precautions, could result in 

 shutdowns of the equipment. 



5. Provisions of adequate checking for accuracy. Accessible check points 

 and suitable easy-to-use standards are essential. Checking intervals are 

 determined by experience, but schedules should be laid out to cause as 

 Hi tic interference with use as possible. Where practicable there may be 

 means for self-checking in the regular operation of the machine. In this 

 case, periodic checking of the checking devices themselves is necessary. 



6. Incorporation of features in the product and in the handling methods 



