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Latent Failure: A Manufacturing Supply Chain Problem
If your contract manufacturer is internalizing its surface engineering processes, make sure it’s doing it right.
August 2, 2013
7 Min Read
As OEMs seek to streamline their supply chains, tier 1 contract manufacturers are increasingly expected to internalize more surface engineering related processes. However, improperly internalized surface engineering process can increase latent field failures and adversely impact quality metrics used by OEMs to gauge the performance of their tier 1 contract manufacturers.
To improve quality metrics and to increase profit margins, tier 1 contract manufacturers should consider deploying subject matter experts (SMEs) during the surface engineering implementation process.
Tier 1 Supplier Requirements
With surface engineering processes being executed both in-house and at multiple secondary suppliers, problems can creep up anywhere. And because the tier 1 core competence is in subtractive machining, it becomes harder for tier 1 suppliers to diagnose the root cause of failure. Any missteps by tier 1 manufacturers are magnified under the heightened OEM focus on supplier key performance indicators such as quality (i.e., scrap rate generation) and on-time delivery.
One area that seems especially challenging in root cause investigations is secondary (downstream) surface engineering processes, such as heat-treating, cleaning, passivation, electropolishing, shot peening, thin-coating applications, forming, and cosmetic add-ons (i.e., rubber overmolding). The majority of these secondary processes occur after the initial bulk shaping has been generated and after multiple processes of the manufacturing life cycle. Most of these secondary process—although a specific science in their own right—can be grouped into a study called surface engineering.
Without staff on hand that has core competence in surface engineering processes and a deep understanding of the science of surface integrity to diagnose these issues, it takes a long time to learn enough about the basics, determine what critical process parameters are, and come to a conclusion about the root cause. However, when it comes root cause investigations, the pure lack of time and comprehensive understanding are the main limiting factors. This investigation process is detrimental to contract manufacturer metrics—and thus the OEM—as it takes time away from subtractive machining processes and is a difficult exercise for an engineering staff not equipped with a background in surface engineering processes..
The most frustrating aspect of these latent failures is that fallout occurs at the tail end of the manufacturing life cycle, where secondary processing poses challenges for any product that is made to order. In addition, for tier 1 contract manufacturers working with a specialist in surface engineering processes, it presents several vendor management issues such as the following:
Scheduling conflicts associated with their own contract vendors of secondary surface engineering processes and the associated uncertainty they introduce when it comes to timeline management. For example, heat treatment and passivation specialists must accommodate all jobs coming from different tier 1 suppliers from various fields such as aerospace, automotive, and medical devices at the same time, and this introduces uncertainty in timelines.
Problems related to mismatched quality systems between surface engineering specialist and OEMs. This happens because specialists who are engaged in these secondary surface engineering processes are usually handling similar job requests but with different quality systems requirements due to a number of different industries they service.
Most importantly, tier 1 supplier management teams are under the false impression that they can reduce rejection rates and minimize latent field failures associated with secondary processes by bringing surface engineering processes in-house. In most cases, it is hard to assess the origins of rejection rates associated with surface engineering projects. For example, if the titanium parts from a heat treatment vendor come back tarnished, is it due to poor controls at the heat treatment facility, or because the parts were not cleaned properly prior to shipping it to secondary vendor, or a combination of both factors?Thus, the quality attributes of these secondary processes cannot be directly measured. For instance, processes such as heat treatment, passivation, cleaning, and thin-film technology applications do not change the shape or form of the product, thus making inspection pass-fail criteria difficult to establish, monitor, and validate. All of these factors can negatively affect supplier performance.
A byproduct of bringing secondary processes in-house is profit margin expansion. From a cursory analysis, internalizing surface engineering processes appears to be the right strategy; however, a deeper analysis will reveal that internalizing surface engineering is much more difficult.
Expertise Difference
In tier 1 contract manufacturing, engineers might be experts in subtractive machining processes such as milling, turning, and drilling. However, when it comes to secondary processes, tier 1 contract manufacturers might not be experts in an arena such as surface engineering, which is being performed by subcontractors who are specialists in secondary surface engineering processes. Most suppliers are under the false impression that surface engineering processes are relatively easy to internalize, and management makes a fatal assumption that these processes require the same engineering skill set as their current engineering skill set.
When one compares and contrasts the skill set required for secondary surface engineering processes as outlined in Table I, it becomes apparent that each surface engineering process requires a different type of expertise. In addition, market forces have created space for specialists:
The skill set required for each surface engineering process is different than that of a traditional tier 1 contract manufacturing shop, and tier 1 suppliers cannot afford to keep specialists on staff full time because this secondary surface engineering process is not the dominating part of the business.
These secondary process specialists exist outside gross metal removal machine (i.e., subtractive manufacturing) shops because they need a feeder system of several large OEMs, tier 1 contract manufacturers, and other industries (including aerospace) to maintain business.
Tier 1 contract manufacturers have the perception that once they buy equipment such as passivation equipment or cleaning equipment, internalization of the surface engineering process is relatively straight forward. However, the technical skills required to design fixtures for cleaning and passivation requires in-depth understanding of ultrasonic horn design and chemistry. Setup process parameters such as pH and temperature are also not typically available at tier 1 contract manufacturer engineering groups because the core competence required to comprehend ultrasonic horn design is very different than that required to setup a milling machine.
What’s preventing tier 1 manufacturers from solving the problem of internalizing surface engineering processes? It is lack of acknowledgment from the management that their current engineering resources cannot help them internalize these processes, as the skill set required to conduct secondary surface engineering operations is not easily transferable.
Implementation Sequence
Figure 1. These three sequences are used during internalization of surface engineering processes. |
Tier 1 manufacturers should consider following the sequences as outlined in Figure 1 during internalization of various surface engineering processes. Some surface engineering processes require other processes as a predicate process. To successfully internalize these surface engineering processes, consider having a SME who can lead the process.
All three internalization sequences can proceed in parallel. However, when it comes to the processes mentioned in sequences 2 and 3, pay close attention to surface integrity (white layer formation, introduction of residual stresses, and surface finish). To carry out vertical integration, there must be a strong education component in addition to buying equipment. Internalizing these processes is vastly different than buying additional capital such as a 5-axis milling or Swiss screw machine.
Conclusion
Successful tier 1 contract manufacturers will either change the composition of their engineering workforce, which is financially not a viable option, or rely on SMEs who can provide instant knowledge. Tier 1 contract manufacturer’s can bring SMEs on board only when there is a need, allowing current engineering resources to focus on daily activities and learn from the experts. This will retain tier 1 supplier key performance indicators to increase throughput, reduce scrap, and improve processes.
For OEMs, smooth integration of these processes in the tier 1 contract manufacturer will result in improved timelines and, ultimately, reduced time to market. Most importantly, they will minimize costly latent field failures due to compromised surface integrity and avoid FDA warning letters.
Ajay Kumar is vice president of R&D for Innovadontics (Palmdale, CA). He holds a B.S. in mechanical engineering from Regional Engineering College (Kurukshetra, India), M.E. in mechanical engineering from the University of Southern Illinois, an M.S. in biomedical engineering from Rutgers University, and an MBA from the University of California, Irvine. He has 26 issued patents and 4 pending patents. Reach him at [email protected].
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