1126 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1953 



The inspection wire contacting device automatically moves from wire 

 to wire across the machine, sampling the resistance of each wire for about 

 fifteen seconds. The chart provides the observer with a complete picture 

 of the behavior of the plating operations at a glance and enables the 

 operator to properly select the controlling pilot wire in such manner that 

 minimum energy and copper are expended. The control wire contacting 

 device is manually set in position against one wire until conditions re- 

 quire selection of a new pilot wire. 



Both contacting devices are located in the position just preceding the 

 take-up capstan from which the wire moves down to the first floor to be 

 taken up on reels. To avoid the by-passing of the bridge current through 

 ground and the building steel, each channel has been completely insu- 

 lated from ground and from other channels between the contacting de- 

 vices and the end of the wire on the take-up spool. The take-up capstan, 

 all sheaves, guide tubes, rollers, and the take-up stands themselves have 

 been designed to provide the required insulation. 



Aside from presenting to the operating personnel a complete chart 

 showing the values of the electrical resistance for each channel, the sen- 

 sitive resistance measuring equipment also gives indication of process 

 difficulties long before they are evident from any other source. For ex- 

 ample, an increase of organic contamination above certain concentra- 

 tions in the acid type plating bath will produce wide variations in the 

 structure and, hence, in the electrical resistance of the copper deposit. 

 These fluctuations can occur in very short sections of the product. While 

 the average value of the resistance may remain constant for long sections 

 of the product, the resistance charts provided by the control and inspec- 

 tion equipment will record the individual wide fluctuations and thereby 

 provide experienced operating personnel with a positive indication of 

 imminent serious trouble. 



SOLUTION HANDLING 



In this plant, all unit processes are similar if not identical in arrange- 

 ment and operation. 



A typical handling system consists of a storage reservoir, mixing and 

 filter station, circulating pumps, heat exchanger, solution supply, and 

 return piping between storage tank and processing area, and a solution 

 temperature and level control. (Fig. 9.) The chemicals of which the elec- 

 trolyte is composed are placed in; the mix tank and agitated. This mix- 

 ture is then transferred through the filter into the storage tank. The 

 filtered solution in the storage tank is first circulated through the heat 

 exchanger and finally delivered to the processing area on the mezzanine 



