Question 3 of 7: Product Design and Simulation

Question 3: Product Design and Simulation (20 marks: 7/6/7)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

(i) Sequential versus Simultaneous (Integrated/Concurrent) Design

• Sequential design ("over the wall") — marketing defines the product, design engineering designs it, then manufacturing engineering, purchasing and production each take over in turn. Each department works in isolation, so manufacturability, cost and service problems are discovered late, forcing redesign loops. Result: long development time, many engineering changes, high cost and adversarial relationships between departments.
• Simultaneous (integrated) design — a cross-functional team (marketing, design, manufacturing, quality, purchasing, suppliers and often customers) works on the product and its production process in parallel from the start, considering the whole life cycle (manufacture, assembly, service, disposal). Supported by tools such as CAD/CAE, DFM/DFA and QFD.
• Comparison — simultaneous design gives shorter time to market, fewer late changes, lower cost and better quality; it demands more coordination, early commitment of resources, team skills and good communication, and works best with a strong project leader.

(ii) Design Criteria

• Function and performance — the product must meet customer requirements and specifications (captured, e.g., through QFD).
• Manufacturability and assembly — can be made economically with available processes (DFM/DFA).
• Quality and reliability — performs consistently over its intended life; robust design that is insensitive to variation.
• Safety and regulatory compliance — safe in use and misuse; meets applicable codes and standards (e.g., CSA certification in Canada) and product-liability expectations.
• Cost — target cost and life-cycle cost acceptable to the market.
• Maintainability and serviceability — easy to repair, with accessible, standard parts.
• Ergonomics and aesthetics — easy and comfortable to use; appealing appearance.
• Standardization and modularity — common parts and modules to reduce variety and cost.
• Environmental sustainability — materials, energy use, recyclability and end-of-life disposal (design for environment).

(iii) Simulation Models in Production

• What they are — computer (usually discrete-event) models of the production system: arrivals of orders, processing-time distributions, machines, operators, buffers, material handling, breakdowns and schedules, validated against actual plant data.
• Tracking processes — the model reports throughput, work-in-process, queue lengths, machine and labour utilization, cycle and lead times over time; when linked to live shop-floor data it can track the actual process and forecast where it is heading.
• Identifying problems — reveals bottlenecks, starved or blocked machines, excessive queues and inventory, capacity shortfalls, scheduling conflicts and the effect of breakdowns or variability.
• "What-if" analysis — tests changes (added capacity, new layout, different lot sizes or schedules, staffing) without disrupting real operations or spending capital, so the best alternative can be selected before implementation.
• Communication — animation helps managers and workers see and agree on the problem; limitation: results are only as good as the input data and model assumptions.