Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 349 of 707

dure is required. Tools of suitable size and shape are selected for each step. Tools that cover about 10% of the total area are appropriate for preparing the base material. The plating tools should contact more surface area so plating will proceed faster; consequently, the tool used for plating is selected more carefully. It is larg- er than the preparatory tools, and it covers the full length of the bore. The anode portions of the tools are covered with appropriate covers. Once the tools are selected, suitable amounts of solutions are poured into con- tainers. There is enough plating solution to soak the anode covers and to com- plete the plating operation without stopping. The power pack is then connected as follows: the negative (black) lead to the part (cathode) and the positive (red) lead to the tool (anode). Prior to starting the job, the operator completes the calculation of a set of for- mulas that will help assure the job is carried out properly. Some of the commonly used symbols and definitions used in these formulas are listed in Table V. The formulas used and sample calculations for this job are shown below. 1. Calculate the area to be plated (A) A = 3.14 x diameter x length A = 3.14 x 6 x 2 A = 37.7 in sq. 2. Calculate the ampere-hours required. Amp-hr = F x A x T Amp-hr = 150 x 37.7 x 0.002 Amp-hr = 11.31 3. Calculate the estimated plating current (EPA) EPA = CA x ACD EPA = 6 x 5 EPA = 30 A 4. Calculate the plating time required (EPT). EPT = [Amp-hr x 60] / EPA EPT = [11.31 x 60] / 30/ EPT = 22.6 minutes 5. Calculate the rotation speed (RPM). RPM = [FPM x 3.82] / diameter RPM = [50 x 3.82] / 6 RPM = 31.8 revolutions per minute 6. Calculate volume of plating solution required (V). V = Amp-hr / MRU V = 11.31 / 44.5 V = 0.255 liters Finally, the operator prepares a process chart that includes this information. 348

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