Part Finishing Solves Customer Delivery Demands

Getting and keeping a competitive edge with automotive customers these days requires ingenuity, hard work and a willingness to change with the times. For DCT's Stature Machining of Warren, Michigan, being more competitive meant doing its own part finishing in-house on two shifts to support its machining and

Case Study From: 2/1/1997 Modern Machine Shop

Getting and keeping a competitive edge with automotive customers these days requires ingenuity, hard work and a willingness to change with the times.

For DCT's Stature Machining of Warren, Michigan, being more competitive meant doing its own part finishing in-house on two shifts to support its machining and fabricating operations. Stature Machining is the parts and tooling department within DCT Welding and Assembly, a supplier of automotive supplier of welding, assembly and material handling systems and components.

Gerald Music, Department Leader at DCT's Stature Machining, says that his company serves a diverse base of customers who produce tooling and components for the automotive industry. Many of these components are made of tool steels and require a non-dimensional form of corrosion protection after heat-treating. Electroplated and painted finishes often are non-uniform and of excessive thickness, making them unusable for precision manufactured components. The accepted practice with these types of parts was to send them outside to a plater for black oxide finishing.

Even though the delivery schedule of its custom plating vendor had been acceptable in the past, Mr. Music said that its automotive customers' delivery demands became shorter. It became increasingly difficult to maintain consistent quality and manage product flow.

"There were times when the black finishes turned out red or brown. On some parts with blind holes or complex shapes, salt leaching would occur. Then there was the occasional lost or damaged part. We could deal with these events when operating a single shift, but the problems were multiplied on two shifts when a just-in-time (JIT) delivery was required. There was no margin for error," Mr. Music said.

DCT's Stature Machining's two shifts a day are totally geared for JIT delivery. Part shipments are often made during the second and third shift so that they arrive at the customer's site early the next morning. On parts requiring outside hot oxide finishing, the vendor operated only one shift. While very responsive with its one-shift operations, the vendor at times found it virtually impossible to satisfy the second shift job requirements. So the shipments to the customers would be delayed and the entire JIT process would get backed up and sometimes halted entirely.

Mr. Music said that the system worked until delivery was required from its second shift. "It's a simple case of what used to work fine, didn't work anymore because customer needs had changed.

After hearing about Birchwood Casey's room temperature finishing process, they decided one of the company's BC40 systems using the Presto Black process would solve many of their finishing problems.

DCT had to be reassured that it wasn't sacrificing quality by going to room the temperature process. The cold Presto Black process in fact withstands up to 200 hours of neutral salt spray (ASTM B117) and produces a uniquely attractive black finish that is even in appearance without the red/brown discoloration or salt leaching problems. With its own BC40 Presto Black system, "quality was better from the start," reported Mr. Music, "and just as important, we were in control instead of delegating to an outside third party."

The cold black finish operates much like the hot oxide in that the rust preventative supplies the corrosion resistance layer while the black finish, with its porous crystal structure, provides an absorbent base for the sealant, holding it in contact with the metal substrate. This produces a non-dimensional barrier against atmospheric humidity and corrosive elements along with an aesthetically pleasing black finish.

The process steps for room temperature Presto Black in the BC40 system take just 10 to 12 minutes as follows: First, the parts must be cleaned and degreased in Presto Kleen at 150°F for 5 minutes. This is followed by a rinse with cold tap water for 15 seconds. Next, parts are cleaned and activated in Presto Prep P2 solution at 130°F for 2 to 4 minutes. This is followed by another rinse with cold tap water for 15 seconds. In the next step, parts are blackened at room temperature in Presto Black solution for 30 to 90 seconds. Another rinse with cold tap water for 15 seconds, and then parts are sealed with the water displacing Dri-Touch rust preventative for 1 minute.

Stature Machining's BC40 system, using the Presto Black process, was ready for operation immediately. Because the system is very compact (16 inches by 24 inches by 24 inches for each of the six process tanks with total overall floor space of 3 feet by 16 feet) and required no drain connections, it allowed DCT to set it up within an existing production line. No connections to floor drains or venting ducts were needed. When new machining centers were added later, DCT was able to move the finishing line quickly with the same ease as the initial installation.

For a blackening line, the only sure way to eliminate pollution concerns is not to discharge any effluent at all. The company liked Birchwood Casey's approach to this issue with its Ion Exchange option. It allowed them to disconnect from the drain entirely, eliminating any pollution problems while it made their system "moveable" when the time came later to reconfigure some of its manufacturing cells.

DCT has a fluctuating need for finishing on two shifts. At times, projects require finishing throughout a shift. At other times, batches of parts are finished every few hours. The BC40 system handles these intermittent needs very well. Since the system takes less than an hour to warm up, it can be ready to finish parts on short notice. On most days, the line is kept at operating temperature round the clock which allows for finishing turnaround time of 10 minutes from the start of the first batch of parts.

Learning to operate the BC40 system was easier than most machine tools, reports Mr. Music. The line is located near machining centers to minimize part and operator movement. The operator can load parts into the BC40 system and alternate at operating other equipment while the parts are being finished. "Factory training was provided by Birchwood Casey at no charge. We were shown how to operate and maintain the line for best performance. Our operators learned to operate the system quickly and recognized how, with imaginative scheduling, it helped to smooth out part flow through the plant," Mr. Music stated. "Our quality is better, delivery problems have been eliminated and our finishing costs are lower." MMS

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