Electroplating is a widely used industrial process that involves the deposition of a thin layer of metal onto the surface of a substrate using electrical current. One crucial aspect of electroplating is the racking process, which plays a pivotal role in ensuring a successful and uniform plating outcome. Racking involves the arrangement of items to be plated in such a way that the electroplating process is efficient, effective, and yields high-quality results.
Purpose of Racking:
The primary purpose of racking in electroplating is to facilitate uniform metal deposition on the substrate, ensuring that every part of the item to be plated receives an equal coating. Racking serves several essential functions:
1. Even Distribution:
Racking is designed to hold and position the items in a way that promotes an even distribution of the electric current and plating solution. This helps prevent uneven plating, which can lead to defects such as blistering, pitting, or uneven thickness.
2. Accessibility:
Racking ensures that the plating solution has unobstructed access to all surfaces of the item being plated. This is critical for achieving a consistent and complete coating on intricate or complex geometries.
3. Efficiency:
Efficient racking allows for the simultaneous plating of multiple items, maximizing the throughput of the electroplating process. This is particularly important in industrial settings where large batches of items are plated to meet production demands.
Common Racking Techniques:
1. Normal Racking:
Normal racking involves suspending items vertically or horizontally in a way that ensures optimal exposure to the plating solution. This method is suitable for items with simple geometries and is widely used for uniform plating of flat or easily accessible surfaces.
2. Robbers:
Robbers, also known as thieves or dummy loads, are sacrificial items strategically placed on the rack to attract excessive current. By diverting excess current away from critical components, robbers help prevent overplating and ensure a more even distribution of the plating metal.
3. Jigs and Fixtures:
Jigs and fixtures are custom-designed tools used in racking to securely hold items in place during the electroplating process. These fixtures are especially useful for irregularly shaped items, preventing movement and ensuring consistent exposure to the plating solution.
4. Rack Design for Barrel Plating:
In barrel plating, small items are placed in a rotating barrel, facilitating uniform coating. The barrel contains racks or mesh baskets that hold the items securely and allow for efficient plating without direct contact between individual pieces.
Effective racking is a critical factor in achieving successful electroplating results. Whether using normal racking for flat surfaces, employing robbers to control current distribution, or designing custom fixtures for complex shapes, the goal is to ensure uniform metal deposition on all parts of the item being plated. By understanding and implementing various racking techniques, we can can enhance efficiency, reduce defects, and produce high-quality plated products in diverse applications.
In the video below we can see "Robbers" being used however in an alternative way. When used in a fashion to direct plating to a low current density area robbers are called auxillary anodes. These anodes are crucial for many commonly plated parts.