Everyone can appreciate that an embedded system design - like a chain - is only as strong as its weakest link. But do we consider that those "links" include more than just the physical components?
Are not the processes used to develop and manufacture the finished system - from the smallest component supplier in the supply chain, all the way through to the ultimate manufacturer - equally important?
Certain industries, such as aerospace and railway, specify their own high quality standards for both the components and processes of mission-critical and safety-critical applications. But beyond meeting industry-specified levels of performance, there are additional business reasons to consider quality management as an integral part of the design discipline.
Obviously, the financial implications of evaluating quality and reliability as part of the design and production processes affect costs as well as benefits. But the return on investment can be more than worth the price, particularly in industries or applications where the cost of failure is high - in terms of either financial repercussions or human safety issues.
The more complex the design, the more complex the process of proving quality assurance (QA) becomes. That can make defining success solely on pass/fail testing at the end of manufacturing a risky proposition in terms of both rejection rates for assembled systems or eventual failures in the field.
So how should a company define the quality of products and services and why do they need one or more quality management systems?
Using Quality as a Strategy
Quality can be defined as the sum of all factors that contribute to the production of a high-grade product. Those factors can include discrete components, complete systems and all the processes involved in bringing the finished solution to fruition.
The basic idea behind quality management is that all those factors be well defined and actively maintained with respect to their required properties. ISO 9001 is the market-independent basic system, but variations based have evolved to account for differences in the processes and requirements of individual markets, resulting in different market-specific standards, some of which are outlined below.
Naturally, quality is not cost-free. Any implementation of one, or even several, quality management systems incurs costs. But a product designed to be "cheap" does not necessarily contribute to cost optimization.
On the contrary, in applications involving safety-critical control or harsh-environment operation (including mobile applications such as railway, bus, airplane, ship, utility vehicle, agricultural equipment and construction), danger to human life or downtime caused by poor quality management can impose excessive penalties.
Once adopted as part of the corporate culture and standard operating procedures, however, quality practices become second nature and can pay big dividends over the long haul.
Costs are amortized at the supplier's end thanks to optimized workflow in development, production, testing and logistics. On the user's end, savings derived from high-quality products include minimizing costly failures, downtime, or dangerous situations.
Equally important to using quality standards is establishing a culture of quality that can also help support expansion into other demanding industries.
Evaluating Product Features ... And Beyond
In component selection, designers typically narrow down their options based on features listed in the product description. As requirements become more specific, the hit rate of potential options becomes smaller. So how do you ensure that the products meet the standards your market or application demands?
First, the product should be documented to deliver all the functionality promised in its data sheet, so don't forget to ask for the substantiating test results. Next, the supplier should be capable of proving its competence in developing, manufacturing and testing components appropriately for your end-use application.
This is particularly important if your industry or application involves stringent reliability and fail-safe requirements for safety-critical applications. Quality factors to consider include:
- Traceability from the incoming components to the outgoing complete system
- Fully automated production equipment with smooth soldering techniques
- Test processes to document that the values for vibration resistance defined during development are actually met
- Documented obsolescence management and lifecycle support programs for applications with anticipated long lifecycles
- Market-specific understanding of the implementation of any appropriate standards (e.g. 50155 for trains, E1 for automotive, DO-254 and DO-178B for aircraft)
Sector-specific Quality Requirements
The objective of a quality management system is to assure quality standards and continuous improvement with the focus on satisfying customer requirements and increasing customer satisfaction.
The globally accepted ISO 9001 standard represents the basis for more detailed norms and standards with sector-specific requirements:
- ISO 13485 (Medical Engineering)
- ISO/TS 16949 (Automotive)
- EN/AS 9100 (Aerospace)
- IRIS (Railway)
Depending on your market focus, these industry-specific standards should be adopted in addition to ISO 9001. For example, a company that works heavily in railway and aerospace applications must adhere to the IRIS and EN 9100 standards, respectively.
Ensuring reliable and safe railway operation
The IRIS standard (International Railway Industry Standard) was derived from cooperation with leading railway system manufacturers (Bombardier, Siemens, Alstom and Ansaldo Breda) and the UNIFE (Association of the European Rail Industry) in order to ensure high quality throughout the entire supply chain of the railway industry. This standard is critical because participating train manufacturers have committed to assigning orders only to suppliers and subcontractors certified according to IRIS.
An important aspect of this framework is its very detailed documentation. IRIS Rev. 02 requires 16 documented procedures and 25 processes. (By comparison, ISO 9001 requires only six documented procedures.) In addition, IRIS prescribes that procedures and processes for defining this quality management system be managed using Key Performance Indicators (KPIs) with the aim to measure, analyze and improve performance. These important activities include:
- Input review (e.g. delivery, reliability)
- Bid management
- Purchasing processes
- Project management
- Cost management
Under IRIS, as in many applications, obsolescence management is an important consideration. Long-term availability is extremely relevant because once railway vehicles pass complex acceptance tests before initial deployment, they are then in use for several decades. Careful planning and selection are required to ensure guaranteed availability of at least 10 years.
During the last few years, the trend to use COTS computer assemblies with standard operating systems (e.g. Intel architecture operating under Windows) for control applications has complicated this issue. Within that platform, it is not uncommon to see components discontinued every three months For this reason, the obsolescence management aspect of IRIS focuses on ensuring the defined and agreed lifecycle of the product as well as the availability of the delivered products and spare parts.
The required discontinuation strategy includes the following items, among others:
- Proactive component selection at the start of development
- Early communication with customers and suppliers
- Preferential cooperation with suppliers that also have obsolescence management processes
- A strategy for second-source suppliers
- Stockpiling for the estimated total demand expected in the future
- Method for achieving compatibility of design, fit and function
One of the most important procedures required by IRIS is RAMS (Reliability, Availability, Maintainability and Safety). RAMS (Fig. 1) is a methodology intended to help avoid costly mistakes in the planning phase. It ensures that systems are defined, risk analyses are carried out, risk rates are determined and detailed checks and safety verifications are made.
- Reliability describes how consistently the product (e.g. a computer system) carries out an assigned function within a given time interval.
- Availability is the capacity of that product to be in a state that makes it possible to fulfill the required function during a given time interval. It is deduced from reliability based on system failure rates, analysis of potential risks, probability that a failure might occur, impact of a failure on the functionality of the system and maintainability based on determined repair times.
- Maintainability is the combination of all technical, administrative and organizational measures during the product's (computer system) lifecycle for sustaining the functional state or returning to it. Maintenance includes inspection and repair.
- Safety describes a product (computer system) that is free from unjustifiable risks and considered to be free from dangers.
RAMS management for standard sub-assemblies, customer-specific solutions or complete systems starts at the earliest stages of the development process. Using an adapted V-model (Fig. 2) helps to achieve high availability and reliability, since verification and validation are repeated on every design and implementation level.
Knockout Criteria & Scoring
Twelve so-called "knockout" (K.O.) criteria are central to the IRIS standard. If a single knockout condition is not fulfilled at the certification audit, the whole process has to be started again with a new application.
Development validation is one such K.O. criterion. A company has to prove that reports, calculations and test results meet the applicable requirements in order to receive development validation.
IRIS evaluation of a quality management system (Fig. 3) is performed through the scoring method of the IRIS Audit Software Tool, with the resulting score intended to help customers compare quality management system performance among suppliers.
In avionics, acceptance of industry standards parallels that of the railway industry, since relatively few major manufacturers dominate in this market as well. Certification according to the avionics standard EN/AS 9100 is an essential precondition for being a supplier in this demanding market.
As with the IRIS railway standard, EN/AS 9100 includes criteria that exceed ISO 9001 requirements. Some of these criteria, such as the First Article Inspection (FAI), are even similar to those found in IRIS. But regardless of your industry application, you can apply the principles behind FAI criteria to your advantage.
First Article Inspection
FAI prescribes the testing, verification and documentation of a product from the first series of a production lot or after a retrofit change. Applying FAI systematically makes it possible to avoid mistakes and resulting re-work later in the production sequence. The requirement is satisfied under a series of conditions that ensure product quality at the same time as proving that processes are being observed.
Another important requirement regarding quality assurance is complete tracking of the entire supply chain for a finished product. This is also found in the ISO/TS 16949, ISO 13485 and IRIS standards. but you don't need to be involved in aerospace applications to realize the benefits of traceability.
One way of integrating traceability is to equip all devices and production equipment with different data acquisition interfaces and maintain all collected data in a database, complete with time stamps. This enables you to determine that a specific board passed the pick-and-place machine at a specific time. When the parameters of the machine at that time are known, you can trace any problem involving a specific board back to its source. This also works for the components involved, so one can trace which component from which delivery was ultimately placed on which product.
In addition to collecting production routing data, you can also collect a variety of machine data. A centralized database server can gather all the information and make it available in real time -- ideally via a company Intranet. This has the major benefit of total transparency throughout the complete production and testing process and therefore shorter reaction times in case of problems. The system can even become an integral part of an ERP system.
While your current quality practices might not require the same level of compliance depending on the industries in which you work, significant quality benefits can be gleaned from each of these standards, no matter what the specific application.
Defining Success: Correlating Quality Management with Business Excellence
In addition to generating qualified bidding opportunities through adherence to ISO 9001 or sector-specific standards like IRIS or EN/AS 9100, there are ancillary advantages to the quality management disciplines they involve.
Any company that adheres to documented principles of quality management can benefit from an improved reputation for business excellence, regardless of the markets they serve. Applying those principles consistently, from initial development through the end of the product lifecycle, results in high-quality products that minimize failures or dangerous situations in the final application.
It also satisfies prerequisites for a smooth workflow, making it easier to get product and project approvals from decision-makers in any application - from avionics and railway, to medical engineering, automotive and automated precision manufacturing.
So, don't begrudge industry standards as "necessary evils" in electronic design. Embracing the same guidelines that improve quality and business efficiency in the short- and mid-term can also help build your reputation and ability to compete in an increasingly competitive global environment over the long term.