What is racking?
Racking for plating involves using copper wire to rack (suspend/hold the parts within a plating rack) so that it meets the following requirements:
Faces the plating anode
Is rigid and tight within the rack
Makes contact with the plating line
Wires do not stick to any visible sides of the part
How it works:
Diagram 1 above shows the use of "robbers" which you can see is the thicker copper wires that spans the whole ack and is placed in front of the parts. The purpose changes depending on the stage of plating they are used in. The robbers in diagram 1 (the copper stage) are used to steal copper from the parts so that they do not become too thick. Specifically for small parts that will be installed back onto the original project we do not want the inserts to become too thick and not fit once we are done plating. That is the purpose of the robbers.
Diagram 2 showcases the robber post-chrome. The name changes for robbers to an "auxillary anode". Now this anode is used to direct the chrome into shooting towards certain areas. This is used when parts have dips or crosses or areas we call "low-current density areas". These areas need an auxiliary anode to direct the chrome into where the current is low (which is in dips, curved and corners). The anode in diagram 2 was used for another purpose. For smaller parts, this anode can be used to take the current from the parts so that they do not burn. Smaller parts are at risk to intake too much current, resulting in burning from too much electricity. The anode in this case steals the current and protects the part.