Improving Plating Performance

Article From: Products Finishing, , from Tanury Industries

Posted on: 10/1/1997

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 eyewear 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 prefinishing 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 prefinished by the customer. If the production run has not been prefinished, the prescribed process on the routing ticket will not work and will need to be modified to include a prefinishing 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.

Process Verification.

An integral part of improving the plating process comes from verifying, at various stages throughout production, that the process on the routing ticket is being adhered to and the expected results achieved. Spot inspections during the operation help to red-flag any discrepancies. If a process ticket calls for light nickel and poor coverage is observed during an inspection, production on the job is halted while the plater, supervisor, and a member of the quality control team determine possible causes of the problem and potential solutions. A test rack procedure is initiated, and when the racks are successfully plated and consistent with the standard (keep in mind, that after the process was developed color and quality standards were kept on file for reference), the process on the routing ticket is modified and plating begins again.

Products that require a precious metal plate receive an x-ray to ensure that the plating thickness matches the specifications on the routing ticket. Final inspections take place when the product is taken off the racks and wrapped so that the customer is assured of receiving product that conforms to its quality requirements.

Is this a foolproof method for improving plating performance? Not quite. Despite the preventive actions of process development and the pro-active procedures for process control and verification, errors can still occur. For example, if a process is modified during the verification stage, but the routing ticket is not changed, an incorrect process could be assigned to the next order. Or, if an updated color sample is not logged during the development stage, the color match on the next job could be incorrect. Often these errors are a result of poor communication, however, there is a system of checks and balances that integrates all aspects of the operation and improves performance and follow-through. This is the ISO-9000 quality system.

The ISO-9000 Process.

The ISO-9000 system is the glue that holds development, control and verification of the processes together. An ISO-9000 registered company is the industry's most rigorous third-party endorsement of quality. However it is not "quality" in the traditional sense of the word but a quality system. ISO-9000 certification mandates that a company document and adhere to its procedures and identify and solve its problems.

Through a "non-conformance system" a company defines how it will track errors or omissions, identify the root causes of problems, and initiate corrective actions. For example, assume that a product is rejected by internal Quality Control due to roughness in the deposit. The product would be segregated for repair and an evaluation performed as to possible causes of the rough condition. Possible causes would be: material, workmanship, product design or process. If the cause is determined to be process, a non-conformance would be issued to either the plating or lab manager who would then identify the tank that caused the roughness, perform lab testing to determine the root cause, and return the tank to a normal performance level. The actions would be documented and the non-conformance closed. If subsequent test runs yielded satisfactory results, production would then be resumed.

A "preventive action system" analyzes trends for major or repetitive problems. Reviewing information generated from in-process or final inspections can help determine if a certain type of product has a high rejection rate. Other sources of information might be customer complaint or product return logs. Again, material, workmanship, product design and process are examined to determine the root cause of the problem. If in this case it is the product itself, there would be three possible vehicles for corrective action:

  1. improving the process to accommodate the product's quirks;
  2. asking the customer if the product can be manufactured in a manner more friendly to the process; or
  3. asking the customer to change his requirements to accommodate the capability of the process.

The ISO-9000 system is particularly effective in keeping the preventive action and root-cause/corrective-action systems robust and effective. A series of internal system audits, product audits, and external audits takes place regularly to monitor the effectiveness of the system and are conducted by in-house personnel.

External audits are performed semi-annually by the registrar and the audited company is expected to continuously maintain and improve its system. If it passes each audit, the company will continue to be granted ISO-9000 certification.

The Best Investment.

Decorative electroplaters have always taken pride in the beautiful, lustrous finishes they craft. However, the challenges of the 90's marketplace with its new base metals, exotic finish requirements, stringent quality standards, and quick turnaround expectations can make achieving those finishes seem like an up-hill battle. Help is at hand via an arsenal of production tools called process development, process control, process verification and ISO-9000. Together they make a disciplined system of checks and balances that can help improve a platers performance, the customer's satisfaction, and ultimately the bottom-line. Investment in these processes could turn out to be the best investment you will ever make.


Comments are reviewed by moderators before they appear to ensure they meet Products Finishing’s submission guidelines.
blog comments powered by Disqus


Learn More

Zones

Supplier Categories


Technic Inc
Luster-On Products
American Plating Power
Pavco

Suppliers | Products | Experts | News | Articles | Calendar | Process Zones

The Voice of the Finishing Industry Since 1936 Copyright © Gardner Business Media, Inc. 2014

Subscribe | Advertise | Contact Us | All Rights Reserved