The rack is the vehicle on which we depend to produce a top-quality, plated part with processing profitability. Once the rack is designed, fabricated and in the process line, it is too late for instant changes. The related issues surrounding rack issues can work together, one dependent on the other, in synergy to reap full value. The degree of success is related to the performance efficiency and other contributing factors, which we will look at in the following segments.

Plating System Design Includes Rack Size Parameters

As a general rule, when a plating facility is designed from the standpoint of origination or revision, along with the appropriate support equipment, the rack size, dimensions and current-carrying capacity is also determined.

Letís assume that we are using a hoist line, plate-through system (racked parts are preplated and electroplated as a straight-through process) with the plating or process tanks measuring 24-in.wide X 60-in.high X 120-in.long.

Predetermined rack dimensions, usually called the "box size," are pegged at 8in. from front to back, 15-in. from left to right, and 42-in. high, top to bottom. These dimensions are set, and an average of seven sq ft (1008 sq in.) per rack will be used as a basic factor in all subsequent calculations. This is important to the extent of knowing how many parts can be loaded onto a plating rack, respecting current requirements.

Plating Rack Design

The Overall Look. Many considerations must be taken into account when designing the rack for plating on plastics. The best performance factor possible is the goals for all areas of production. Taking a long, careful look at the part to be plated, while taking all issues into account, will insure building the best rack for a particular item. Cost-effective Rack Fabrication Rack design must incorporate all applicable facets, but more importantly, the easiest and most cost-effective method used for fabrication.

The easiest way to systematically check each facet of proper rack design is to use a checklist.

The "Rack Survey Sheet" Serves as Guide. Understanding rack design has residual effects. It is suggested that you refer often to this reference to recognize how the various aspects of the plating rack affect the many areas of processing.

Part Positioning

Shelf Roughness. Plating roughness, which results when very fine dirt particles float and settle on the shelf areas of parts while plating is taking place, relates to how the parts are placed on the rack.

Residual Shelf Roughness. Another problem with plating shelf areas, and, in particular, large, flat surface areas that are positioned at the top of the rack, is less brightness and minimal leveling as a result of less air agitation on those surfaces.

Position Parts to Minimize Shelf Roughness. The idea is to minimize the situation of having large, flat surfaces positioned at the top of the rack. At the outset, carefully plan the best possible positioning of the parts onto the rack.

Roughness Emanates From Plating. The plating system has an inherent shelf roughness factor that emanates from fine anode corrosion particles while deplating. This phenomenon is a constant experience and occurs simultaneously with electrodeposition.

Anode bags and the filtration system pick up or remove these anode by-products. How fast or efficient this removal takes place dictates the degree of shelf roughness experienced. The amount of "shelf" is directly proportional to plating time in the tank.

Living with Roughness

As stated, shelf roughness is a constant consideration and correlates to plating deposition time. Copper deposits are more likely to reveal "shelf" as compared to bright nickel because of time and metal thickness factors.

Check for Degree of Roughness. Checking for "shelf" should be a regular part of the plating quality check point system during the day. This particulate surface examination may be a nuisance, but it cant be overlooked.

Use a Doubled-up Hull Cell Panel. Roughness can be checked by taking a Hull Cell brass panel and doubling it up so it looks like a "U" placed sideways. Process it through with the plated parts during the plating cycle. This method works well with copper and nickel solutions.

Solution Roughness Checks

Perform separate tests to know the degree of "shelf" in the copper or nickel solutions. A bent brass panel can be processed straight through the copper and nickel to include the chromium or any other final finish, to simulate the effects or degree of "shelf" on parts in production.

Use Roughness Panel to Check Plating Low Current Densities. There is another significant added plus factor when running a "bent panel test" for shelf. The bent panel will reflect the throwing power efficiency as well as allowing the examination of plating effects on the low current density areas. This test can work on only one solution or straight through the plating system.

Dirt in Solution Creates Roughness. Airborne dust or dirt falling into the plating tank can also lead to roughness. Racks also act as dirt transport vehicles. Continuous good housekeeping is the key to reducing roughness resulting from dust and dirt.

Filter, Filter, Filter! Keep Solutions Clean

Maximizing plating quality through solution cleanliness is an important factor. This can be accomplished by ample filtration and by adhering to a regular filter maintenance plan.