Processing Components With Strict Finishing Requirements

Certified Metal Finishers, Muncie, IN, processes components for a product that more than 90 million Americans, and an estimated 500 million adults outside the U.S., use regularly. A product that, 35 years after its heralded introduction on the 1964 Studebaker, is still hotly debated, legislated and litigated. "Click it, or ticket," as they say in North Carolina where intensive, visible enforcement of seat-belt laws recently increased use from 64 to 80%.

Certified processes parts for seat belts. The parts are simple in concept, but requirements are precise and complex in terms of finish and performance, according to Dennis Oaks, plant manager. Among the most critical requirements are those that relate to lubricity and release. Each assembled seat buckle must snap closed and open instantly a minimum of 90,000 cycles.

Certified has a substantial stake in seat belts, since it processes every metal component in the buckle except for the springs. Each day 300,000 assemblies are manufactured for use in Ford, Chrysler, GM, Mercedes, Nissan and other automobiles. The company, founded in 1987, also plates automotive fuel pump housings and coats body mounts for GM.

Certified is heavy on technology, lean in terms of staffing and high-end in terms of quality. The company is among the few that have been certified to QS9000, third edition standards. This new standard, introduced in 1998, encompasses 20 individual elements, four of which are new.

What distinguishes Certified most sharply, however, is speed. When an order is critical, the company can convert "green" steel into a finished order in just six hours.

Plant manager Dennis Oaks founded and built the company and hired all of the original workers. He is largely responsible for the manufacturing and automation systems that have allowed Certified to succeed in an industry known for intense competitive pressures.

Among Mr. Oaks' most important decisions have been those related to parts pretreatment and finishing. To satisfy the company's equipment needs, Mr. Oaks engineered and built a 90-ft-long, 12-stage system. It was designed to operate on true logic rather than ladder logic, a decision that gave it a lot of "brain-power" and extensive flexibility.

Mr. Oaks explained, "One goal was to be able to input part attributes and have the computer calculate the movements of cranes, dwell times, temperatures and maximum throughput rates. We also wanted the ability to flip back and forth between calcium-modified and heavy zinc-phosphate tanks, and make other process changes easily. We needed everything to be weighted and recorded. We wanted to stress conservation at every opportunity."

The system uses both PC and PLC technology. A PC holds all memory and process knowledge; the PLC receives information on a need-to-know basis. Conductivity sensors and pH meters are tied to the computer and, when a tank is about to receive parts, chemical feed is activated.

Operators can change the cycle time in the baths and make other process changes if needed. The system has three security levels: 1) The operator can do some tasks; 2) Engineering can do some tasks; and 3) The master key can change anything. Certified prefers a highly automated system.

All production at Certified begins with green stampings that are processed and austempered on site to achieve a hardness of RC42/49. Parts are emptied from hoppers into barrels. A smart hoist (two run in parallel) already knows its destination and how quickly to move the load.

Austempered parts are subject to a three-stage cleaning cycle. The cleaning chemistry and pretreatment protocol are provided by Heatbath Corp., Springfield, MA. The initial stage uses Uni Kleen^® 117, a heavy-duty alkaline soak that removes machining oils and rust preventives. Originally formulated for electroplating applications, it is also highly effective for use prior to zinc phosphating and black oxiding. It operates for approximately two minutes at 160F.

The next stage, alkaline derusting, employs Uni Kleen^® 1033L at 170F for approximately two minutes. Parts are rinsed and then some are subjected to a phosphoric-acid-based pickling in Destain B to remove residual oxides from the austempering process. This product was the most recent to be added to Certified's line. It is specially inhibited to prevent attack on ferrous substrates and contains surfactants that reduce dragout and facilitate effective rinsing.

Parts that will be heavy zinc phosphated are then immersed in Heatbath's Phos Dip^® BZP5, which becomes part of the phosphate coating, imparting a deep black color that will not rub off. Parts are rinsed a final time before phosphating.

Certified uses two zinc phosphate systems. In selecting a zinc for seat-belt components, the company's first priority was precise control over coating weight, which ranges from 1,200 to 1,500 mg/sq ft. Numerous products the company tested could not be controlled within this narrow range. According to Mr. Oaks, most were too heavy, a situation that would not only raise the cost of everything from chemicals to waste treatment, but cause parts to fall outside specifications.

"What has happened to the market," Mr. Oaks explained, "is that many zinc phosphates have heavy weights and create loads of products for high depositions. However, with seat-belt components, zinc provides a base for subsequent Teflon coating. If you deposit too heavily," he added, "the zinc phosphate crystals, as they shear or abrade, will raise the coefficient of friction and decrease lubricity, the one thing you cannot allow."

Certified required a zinc phosphate that would provide a thin, extraordinarily uniform, fine-crystal base. "And we needed to achieve a total coating thickness of phosphate plus two coats of Teflon® of just 0.0007 inch," he added.

PhosDip^® 1263 is a heavy zinc phosphate that meets all known governmental, automotive and appliance industry specifications. It is highly concentrated for greatest user economy and has a high tolerance for iron in solution. It produces exceptionally consistent coatings and its nitrate-to-phosphate ratio produces minimal sludge.

A second zinc phosphate, PhosDip® R-2 LT process, is used when a highly corrosion-resistant microcrystalline paint base with 300 to 500 mg/sq ft coating weight is required. To maximize the bath's service life, the supplier developed an accelerator and technique for using it, which drops the iron out of solution and rejuvenates the bath, extending substantially the intervals between required dumping and waste treatment.

To accommodate increased demand, Certified has twice enlarged the tank used for this product, adding 200 gal of capacity each time. The system accommodates up to three barrels in various stages of process (one entering, one in process, one outgoing) in each phosphate tank.

Following phosphating, most seat belt components are Teflon coated using the dip/spin method. "In the past," said Mr. Oaks, "customers specified electrocoating, a highly uniform coating, but it does not help with lubricity. The process we developed has been approved by every automaker and has become an industry standard." After phosphating, Certified applies a chromic acid seal or Lab Oil 100, depending on the part.

Lab Oil 100 is a water-soluble emulsion that is different from other products applied for short-term rust prevention. It provides high corrosion resistance (240+ hours per ASTM B117 on zinc-phosphated steel panels). It also has excellent emulsion stability to alkaline or acid contamination encountered in phosphating or black oxide processing cycles.

By contrast, conventional water-soluble and solvent-based rust preventives have extremely poor stability when exposed to alkaline or acid contamination.

The oil has low toxicity, and it is free of barium compounds. It is dry to the touch over phosphate; thus, it offers users advantages in ease of handling.

Certified uses flow restrictors, counterflow rinsing and other techniques throughout the line to minimize chemical use and effluent. "We would have included these items on the line regardless," said Mr. Oaks, "but they are particularly important where we are. In this conservation district, every dollar in water used generates $2.50 in sewage charges. It is a big and visible part of our expenses."

Mr. Oaks also has a personal interest in maintaining a good environment. In October 1997, Certified was acquired by ASII, a family of companies specializing in safety-related businesses. Since that time, Mr. Oaks has focused his energies on sales and all phases of environmental management.

"By making sure every aspect of the process is the best it can be, you serve the quality objective that your customer needs you to do and the environmental objective that you need to do to keep costs under control. This allows growth," noted Mr. Oaks.

Recently, Certified doubled its capacity, adding a second heat-treating line, a second crane to the pretreatment operation and a second dip/spin system for the application of Teflon. It was Certified's third major expansion, which was accomplished during the same time the company was audited for QS9000 certification.

The key to achieving those goals while maintaining full production was strong vendor support. The company's suppliers helped with on-site training, training data and system operation.

Certified has experienced just 12 hours of unanticipated downtime during the 12 months the expanded pretreatment system has been operating. "Now the only inventory is the steel the mill has made. There is no material inventory any place. Everything is in motion. And you had better be as lean as possible," remarked Mr. Oaks.

At Certified the latest wrinkle on being lean has taken its cue from MRP, Management Resource Planning. "In the service industry you cannot really fit the bill with that standard system," said Mr. Oaks. "So we have customized our own. It is called MES, Management Executable System. It is ideal for the service industry where parts go through multiple processes. Where MRP manages material in and out and skips other aspects, MES addresses the important `how do you get it through' questions."

Part of Certified's MES system is what Mr. Oaks calls reservation scheduling. "We schedule the process from start to finish as the steel hits the door." Speed distinguishes Certified. When an order is critical, the company finishes it in just six hours. So, buckle up!

To learn more visit Heatbath Corp..