Okay IndustriesNew Britain, CTThermal Diffusion Process Boosts Die Life by 75% While Cutting Scrap and Increasing Productivity

By Steve Chamberlain, Business Development Manager, TD Center, April 2004

Okay Gives Thermal Diffusion the “OK”

Okay Gives Thermal Diffusion the “OK”

300 ton press performing progressive die applications

As a precision stamper, Okay Industries (New Britain, CT) likes to take on the tough jobs, the ones other companies don’t want. However, there are several penalties associated with these jobs: high maintenance cost of reworking dies because of high wear or galling; excessive press downtime, resulting in lower production rates and higher manufacturing costs; and even the inability to manufacture specific unique parts.
Solving these challenges has led Okay Industries to pursue unique solutions with a thermal diffusion process playing a key role.

Okay Industries has been in the stamping business for 35 years. Their facility has 100,000 sq. ft. and 165 employees. Jim DeVecchis Design Engineer said, “To handle the high volume of stamping we do, we have a tool engineering/design staff of ten people. We develop tooling using several software packages, including: AutoCAD, MasterCAM, and Solid Works.”

Okay serves several diverse market segments including medical, automotive, electronics, defense and specialty industrial. Press sizes at Okay Industries range from 10-ton to 800-ton presses with 100 presses in total that allows them to stamp metals with a thickness from 0.001" to 0.5". They have a complete die production tool room with 22 toolmakers and a full complement of machine tools, as well as precision Quality Control instrumentation to suit any measurement criteria their customer may have.

TD Coated rocker arm

A rocker arm part (stamped from a die using thermal diffusion from the TD Center)

An Early Challenge

DeVecchis remarked, “The first job that I worked on as a project manager was to assemble stamped surgical blades. The material is 302 stainless steel in a strip. To feed this machine, we use a hitch feed mechanism. Pawls are spring loaded from the top and they drag on pilot holes in the strip. The stainless steel rapidly wore out the pawls. Solid-carbide pawls would hold up for a while, but unfortunately they would begin to pit and needed to be redressed often. Pawls made of CPM 10V material did not hold up either. We tried everything and nothing would hold up longer than a few days, which led to high downtime costs.”

One of Okay's design engineers read an article in a stamping magazine about the TD Center's (Columbus, IN) thermal diffusion process. Okay decided to send two sets of pawls manufactured with EDM machines to TD Center to have them coated with the thermal diffusion (TD) process. These two sets lasted seven months compared to only five days without the (TD) process.

TD Center's thermal diffusion process is a hot process (1800°F) that combines carbon from the tool surface with the element Vanadium to grow a Vanadium Carbide layer that is ‘welded’ to the substrate metallurgically. This method of thermally diffusing a vanadium carbide layer into the surface creates an incredible adhesive bond far stronger than any deposited coating and better adhesion means longer life. Because of the high temperature TD process, the coating will not chip, peel or spall off the substrate, and it is extremely durable, providing excellent protection from both adhesive and abrasive wear. TD is a layer of super pure, ultra-dense carbide that completely covers the part, and is bonded below the surface. The carbide is 0.0002"–0.0003" thick with a hardness of 3500 to 3800 HvU (Vickers Hardness), well above 90 Rockwell C.

TD Coated EGR Flex Tube

An EGR (Exhaust Gas Recirculation) Flex Tube part (stamped from a die using thermal diffusion from the TD Center — part is not referenced in article)

With this success on the hitch feed system, Okay started utilizing the TD process on their progressive dies with a great deal of success. “We use the TD process on most of our draw dies in pockets where there might be a lot of part galling,” added DeVecchis.

Improving Run Time on Large Lot Size Stampings

“We produce a part that is a 1.25" long draw processed through a series of cups,” stated DeVecchis. The material is 0.08" thick cold-rolled steel running through a 22 station progressive die. “We'll draw some of these multiple times before we get to the final draw. It looks like a top hat after it's drawn. Also, because of the galling, our quality was suffering. It caused surface imperfections that increased the runout to the point that it was no longer in tolerance and produced excess heat which also distorted the part,” remarked DeVecchis. “No matter how smooth and precise the draw die's finish, we were still getting metal galling, which led to worn out tooling and parts that failed our workmanship criteria.”

“Our run time efficiency significantly increased with the TD process. When we started this job, we were taking apart the die constantly to redress the die inserts. The TD process brought up our run time by about 65%. The coating has lasted about 6 months, and this is a high volume part with about 70,000 parts produced per week.”

TD Coated rocker arm punch insert

Rocker arm punch insert – top insert is TD coated and offers longer performance than the non-coated insert.

Die Inserts using the TD Coating Process

(Rocker arm part reference) Die inserts using TD coated (bottom- silvery looking steel) and non-coated (top-bronze colored) methods.

Lubricant Issues Addressed

DeVecchis stated that almost all of Okay's new dies now have TD Center's coating specified for them. They use it primarily for areas of high wear or galling and to reduce lube costs, especially for drawn parts. “We have changed over our lubrication to non-toxic oil and coolant. These lubricants often won't prevent galling where the TD process will.”

He added, “Because of the TD process, we can use a water-based coolant for many of our dies. In areas of the die where the part would normally run hot, it significantly reduces the heat. Otherwise, more expensive coolant or oils would have to be used. This water-based coolant is much cheaper than oil and easier to handle, because it's non-toxic. Before the TD process, we would use water-based coolant and spray the die. The part would come out hot to the touch, and there was no way of knowing if there would be galling, and often we would have to dress the dies. Now with the TD process and our new water-based coolant, we have a part coming off that you can pick up, and we've eliminated any possible galling in the draw sections.”

From Casting and Multiple Secondary Operations To Stamped Parts . . . A Significantly Improved Process

Another automotive part that they produce is a stamped precision roller finger follower (RFF). The part is made of 1008 CRS, 0.098" thick. The traditional manufacturing method for a RFF in the automotive industry was casting and expensive secondary operations such as boring, grinding and lapping. These RFFs performed satisfactorily; however, the high cost needed to be reduced, especially as engines were being designed with more valves.

To reduce cost, the automotive industry moved to a stamped and formed (folded-up side walls) RFF, but this design had several disadvantages. It was heavier and less stiff than the cast version that had an adverse impact on fuel economy and emissions. In addition, because of the folded-up sidewalls, the cross section was wider than the cast version. Finally, these stamped components also required the assembly of a clip in the socket area for final assembly into the engine that also increased costs.

Okay partnered with its customer to understand the critical requirements of the application and developed (and joint-patented) methods for manufacturing a lower-cost stamped RFF that was lighter, narrower, and stronger. Okay's method is to stamp and forward extrude an RFF with the same configuration as a cast part. The parts are net shape stamped, heat treated, and shipped to the customer without adding any additional components or secondary operations.

Okay Industries – Tool engineering

The Okay Industries' Tool Room

There were many challenges to developing a stamped RFF. One was creating valve stem guide sidewalls long enough so the parts would not tip over during assembly. Okay satisfied this requirement by forward extruding material into a die cavity that produced net-shaped valve guide sidewalls that keep the valve stem aligned during assembly.

There were many challenges to developing a stamped RFF. One was creating valve stem guide sidewalls long enough so the parts would not tip over during assembly. Okay satisfied this requirement by forward extruding material into a die cavity that produced net-shaped valve guide sidewalls that keep the valve stem aligned during assembly.

“We experimented with the TD Center coating in this RFF die, and were able to exceed 100,000 cycles using the coating. Before we could only get about 50,000 cycles. The TD process has significantly increased run time. In this die, we have stations that punch, stamp, and form the part. In the forming stations we are pushing the metal around in a radius and the material wants to slide. So we'll have heat build up and galling in these areas. We can't have this, because it distorts the part.”

“Also, a part with galling isn't aesthetically appealing to the customer or us. There are fourteen stations on the die with the TD process used on three of them. It has given us better product quality, less scrap, faster throughput, longer die life, and reduced die dressing.” In addition, “the TD process permits an increased amount of strokes per minute because of our ability to run the tool, while maintaining a noticeable decrease in temperature,” added DeVecchis.

“Now that we've been working with the process for several years, we know that the capabilities of the TD process are endless. We are always experimenting with it to get greater die life and less heat build up in our draw dies.”

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