1124 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1953 



the ventilating roof fans, a switch for removing the magnetic field from 

 the supply-end capstan, a selector switch for selecting the speed of wire 

 passage through the machine, and seven push-button stations which give 

 the operator individual control over various elements of the machine. 

 The push buttons energize relays mounted in a bank within the control 

 console and thus permit a large degree of interlocking. The interlocking 

 is designed to prevent accidents from occurring in the process. For ex- 

 ample, the operator cannot permit the pickling acid to flow over the wire 

 while the wire is stationary; otherwise the acid would dissolve, the wire 

 in a short time. Time delay relays also are used to advantage. They in- 

 sure, for example, that the full length of moving steel core wire has its 

 flash coating of cyanide copper prior to the rise of the acid copper plate 

 solution into the cells and around the wires which, without the copper 

 envelope, would be eaten through in a short time. 



The overall machine control system has been broken down into two 

 parts because of the two-floor design. From his console, the second floor 

 operator controls only those portions of the process which are visible to 

 him on the second floor. He can, for example, permit solution to flow 

 into the plating cells by electrically opening the valves in the circulating 

 system. Actual control of the first-floor pumps which move the solution, 

 however, is in the hands of the first-floor operator who has a control panel 

 strategically located near each storage tank and pumping station. Here 

 he can operate filters, pumps and level control systems. 



WIRE RESISTANCE CONTROL 



There has been provided for each machine in the electroforming plant 

 a control system which automatically adjusts the dc plating current in 

 the acid copper plate section to that value which, under all normal op- 

 erating conditions, will produce a wire meeting the electrical resistance 

 specification for the product. 



Control is necessary because of the number of variable factors which, 

 if uncontrolled, would interfere with the proper flow of plating current 

 and, therefore, with the amount of copper deposited. These variable 

 factors can occur in the physical and chemical properties of the raw 

 materials entering the process, in the plant services feeding the process, 

 and in the process itself. Some of the more important variables are as 

 follows: 



1. Incoming electrical line voltage fluctuations. 



2. Failure of one of the sixteen rectifiers feeding the acid copper plate 

 section. 



