In effort to expand market share of a high volume product with established competition and firm market price, I led a process development project to extrude a hole though a high strength raw material. The new process applied to the entire product line, eliminating a drilling operation and two subsequent heat treatments–carburizing and annealing. The production cost savings was dramatic and allowed the facility to increase margins and offer the product at a reduced price. This made the facility cost competitive and enabled opportunities for quoting new business with similar product in multiple sizes.
In retrospect this sounds neat and tidy, but new product and process development projects typically hit numerous obstacles. Cross functional teams often have cross functional interests and objectives. Many challenges that have to be resolved, fall outside of the defined project challenge. How the team handles these outside obstacles not only effects project timing but sets the stage for team work and collaboration for the whole project.
Backward extrusion with a piercing step. Left: Backward extrusion before material flows downward. The punch travels downward and the displaced material causes the work piece to grow in length in the opposite direction of punch travel. Right: Piercing. When the punch approaches close enough to the bottom of the work piece, it becomes easier for the piece to shear. In the material used here, that distance was approximately 1.5 times the punch diameter.
The buzz on the manufacturing floor, and amongst the facilities’ tool steel vendors, was that the idea was impossible. Interesting but dream like. Meanwhile, 11 hours drive south of the facility, development and trials were taking place in the corporate R&D facility. The separation of operations and product development in manufacturing is commonly seen even when the functions are co-located. In the corporate materials department, I had access to simulation software, a fully equipped materials lab, tool makers and a precision forging press. After several months of simulation and trials, there was plenty of excitement the first time the carbide punch passed fully through the part without fracturing.
Microstructure of annealed plane, high carbon steel showing finely dispersed carbides in a matrix of ferrite. The blue arrows point to voids, running parallel to the extrusion punch, that were discoved,
I shipped samples to the manufacturing facility hoping for a congratulatory thumbs up and an invitation to start designing the process for the manufacturing floor and equipment, but instead, a quality engineer performed a typical inspection on the samples, which included a metallographic cross section, and observed cracks in the steel. The manufacturing team expected cracks. No surprise—That’s what happens when extruding high carbon steel. For the manufacturing facility, and justifiable so, no further analysis was required. The manufacturing team was busy keeping the customer’s existing product flowing through the shop. When a standard quality check is performed on a new product or process and voids are discovered, a quick decision is simple.
Although development environments provide engineers time to think and consider alternate ideas, as compared to the busy production floor, it is typical that several projects are competing for the same resources. Project funding can shift based on buzz. The target manufacturing facility rejecting the samples can create project obstacles beyond the technical issue at hand.
In the material lab, theoretically speaking, cracks didn’t seem possible. Finite element analysis and common sense indicated the material was under radial compression in the region the cracks were observed. The only tension present was at the end of the stroke when the punch finally passed through the part and sheared out a small slug. Theoretical argument at this point would only have caused tension. The inspection was repeated on several samples and the voids were confirmed.
Thanks to the well equipped corporate materials lab, a SEM (scanning electron microscope) with EDX (energy dispersive x-ray) was available in R&D and indicated the voids had high concentrations of manganese and Sulfur. Manganese sulfur inclusions were present in many locations throughout the microstructure. Could these voids be cracked MnS inclusions? Literature on MnS inclusions indicated that they are highly ductile. A second theory emerge that the inclusions pulled out during metallographic sample preparation. Many soft materials can be challenging to polish without pulling out inclusions. After several attempts of careful preparation, a few samples were outsourced for polishing to a vendor who was looking to sell the lab a new piece of polishing equipment. Careful preparation confirmed the theory. At this point, the pictures and theory of radial compression were shared and all were satisfied. The red flag was removed, and the development effort continued.
This event was only a small obstacle in the larger story of launching this process. However, this event set the tone for how other obstacles were handled, and this event established trust between the two groups. Rather then establishing an argument between theory and practice, the development group took responsibility to research the phenomena, demonstrate it in practice, and share all of the findings. Note that the lessons learned also included the finding that I should have looked closer for the cracks originally.
With this level of honest communication, both groups increased their skills and understanding together. From learning about the characteristics of this new material to sample preparation. Evan the materials lab benefited by using the report to justify investment in the new polishing equipment.
Launching new products requires collaboration between individuals and teams. Collaboration is present when you notice that all members are learning together. Unanswered questions and loosely defined philosophical explanations, delay launches.
The upper two images were taken at 1000x and show MnS inclusions but no voids. Notice that the inclusion snake around the carbides. these were in close proximity to the extrusion punch. The lower image, taken at 1500X and further from the punch, show that two variations of the MnS inclusion. The central inclusion, indicated by the white arrow, appeared to be slightly translucent. In general, all that mattered was that the voids weren’t cracks, but overall, there was a good deal of learning accomplished as well.
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