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Improving Plating Performance

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  • Improving Plating Performance

    The science of combining plating chemistries with the art of aesthetics to achieve beautiful,
    jewel-like finishes...
    Fashion often dictates trends in the decorative electroplating industry, with platers scrambling to develop new technologies and exotic finishes to accommodate the market's demands. Traditionally, jewelry designers created these trends. However, others, such as the eyeglass frame, writing instrument, automotive, plumbing, and lighting fixture industries, are requiring jewelry-like finishes on their products. These manufacturers are challenging electroplaters to achieve even more sophisticated, decorative finishes that are both beautiful and durable. An eye wear manufacturer might develop a new frame using titanium, stainless steel or brass alloys, base metals not traditionally plated. A writing instrument manufacturer might want to reduce field returns by adding a protective coating to its product, but the market will not bear a price increase. Expectations are greater than ever for the plating job shop to produce higher quality more sophisticated finishes and quickly. The old combination of art and science needs a new ingredient?methodology.
    Fortunately, there are a variety of disciplines and processes that can enhance a job shop's performance and ultimately its bottom line. These are not processes in the traditional, chemical sense of the word. They are procedural methods that are used to develop, control and verify processes and thereby improve overall plating performance. In addition, the adoption of a documented ISO system will integrate these basic procedures and heighten their positive effect. Using methodical, documented plating procedures will help the decorative finisher to meet the fast-paced demands of the marketplace and at the same time reduce the rejection rate, improve work flow and increase customer satisfaction.
    Developing the Process.
    One of the most important ways to improve plating performance is to develop a method for establishing the electroplating process or recipe. Think of this as preventive medicine that will help avoid the myriad problems that arise during production. Taking the time to carefully develop, test and document the process generally results in a higher yield, an optimum finish and a more satisfied customer.
    It is critical to know at the outset what final finish the customer expects, as well as the base metal of the piece, its geometric design, and how and under what conditions the product will be used.

    The composition of the base material will dictate what cleaning cycles will be used and whether any particular plating solutions must be added or avoided. For example, a zinc die cast piece will corrode when exposed to acid solutions such as nickel, but adding a pre-plate of heavy copper can prevent a reaction. Similarly, a plate will not adhere to a stainless steel alloy base metal. Adding a nickel chloride pre-plate to the process will allow for subsequent plating. The condition of the base material is also a consideration and may require special pre finishing to improve its quality and ultimately that of the final finish.
    An evaluation of the geometric configuration of the product will help to devise the best racking method, either wire or fixture. Since overloaded racks will plate poorly, the maximum number of pieces per rack must be noted. Unique finishes or complex geometric shapes may also require special racking. For example, in the case of a black nickel finish, variations in color may occur depending on part placement on the rack. It will be important to consult with the customer to agree on how much variation is acceptable.
    There are also other considerations such as dimensional requirements and functional use of the product. As an example, an eyeglass frame manufacturer would like to avoid a costly tubbing operation yet wants a hand-polished look. The typical process calls for a heavy plate, but after a sample run the dimensions of the frame have changed making post-operation assembly impossible. A new process will have to be developed for this product. Similarly, an earring receiving a silver/electrocoat process may trap solution in the hinge and become stained during testing. Extra process steps can then be added to eliminate this staining.
    Once the evaluation process is complete and documented, multiple test runs using various plating processes may also be necessary. These test runs will provide more information about how the product will react in production and will ultimately determine the cycle that gives the best results. When the plating cycle and sequence have been established, quality considerations and quality checkpoints should be noted.
    Sharing this information with the customer helps to establish a standard of acceptability that both plater and client agree to. It is essential to maintain this information on file for future production runs. At companies like Tanury Industries, samples are catalogued by customer and finish, and procedures are in place to ensure that standards remain current. The samples are used during in-process inspection to confirm that proper color and brightness (or in the case of matte finishes, dullness) are being achieved. This discipline is often taken one step further with "story boards" that illustrate both acceptable product and typical defects that could cause rejections.
    The final step in developing the process is the creation of a routing ticket. The routing ticket contains all the pertinent information to successfully plate the product: racking method, pieces per rack, time cycle to plate different metals, final finish, quality checkpoints, and special handling instructions. When product arrives at a facility like Tanury Industries, it is assigned a routing ticket that stays with the production run until it is shipped.

    Controlling the Process.
    Once the plating process has been established and documented, and a routing ticket has been assigned, it becomes important to monitor and control the process via quality inspections, personnel training, and plating bath maintenance.
    After a new production run receives a routing ticket, it undergoes a vital "incoming inspection" where the product is examined to make sure that the process on the ticket makes sense for that particular material. It is not unusual for production pieces to differ slightly from the original materials that were sampled. For example, the original samples may have been pre finished by the customer. If the production run has not been pre finished, the prescribed process on the routing ticket will not work and will need to be modified to include a pre finishing cycle. The incoming inspector also checks to see that the racking method makes sense. This is particularly important for jewelry products that may have mixed sizes that require a uniform finish.
    Once the job has been inspected and racked, the cleaning and plating cycles begin. Although the routing ticket provides the plater with cycle guidelines, other variables such as time and amperage can affect the outcome at each stage. A plater who knows his bath's nuances will manipulate them to achieve the best possible plate; herein lies the "artistic" side of the plating science. However, if the plater takes a vacation, a sick day, or even a break, control of the process may go awry. Documenting work instructions for each station helps to take the guess-work out of the system. Work instructions give detailed information for control of these variables, which include temperature, pH levels and various cleaning cycles. In addition, work instructions might be used as a tool for cross-training to ensure that there is adequate and knowledgeable personnel coverage at all times.
    No discussion of controlling plating processes would be complete without mentioning bath maintenance. At companies like Tanury Industries, the analytical chemical laboratory is the focal point of the quality control measures that are used for plating solutions. Hull cell analysis, a diagnostic check, visually monitors brightener levels in the plating bath, while atomic absorption equipment monitors the specific metal concentrations. By analyzing plating baths daily and weekly, chemistries can be maintained to the highest standards.
    Performing an incoming inspection, providing work instructions, cross-training personnel, and maintaining plating chemistries all help control the process. Additionally, they help to avoid many of the production delays and costly replates that decorative electroplaters experience.
    Jim Eaton