23-Ind-A3 Facilities Planning · May 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — May 2018 — 17-Ind-A3 Facilities Planning. Three-hour, closed-book exam (Casio or Sharp approved calculator only); any five of the seven questions constitute a complete paper and only the first five answered in the answer book are marked — all seven are solved below for completeness.
Reference texts: Tompkins, White, Bozer & Tanchoco, Facilities Planning (4th ed., Wiley) — facilities design alternatives, material flow planning, activity relationships, machine space determination, layout types, computerized layout (CRAFT/CORELAP), buffer design and Muther’s Systematic Layout Planning, material handling systems and the materials handling equation; Niebel & Freivalds, Niebel’s Methods, Standards, and Work Design (13th ed.) — assembly-line balancing (Ranked Positional Weight technique) and operator-paced line speed.
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.
Non-progressive layout (also called process or functional layout) groups equipment by function — all lathes together, all milling machines together, all inspection stations together — and each product/order is routed through whichever departments its own process requires, in whatever sequence and order that product needs. Progressive (product/line) layout instead arranges equipment in the fixed sequence one product (or product family) requires, and every unit flows through the same sequence of stations.
Advantages of non-progressive (process) layout, compared to progressive (line) layout: (1) much greater flexibility — it accommodates a wide variety of products and low, variable, or unpredictable volumes without re-tooling the layout itself; (2) lower vulnerability to disruption — a breakdown at one machine does not stop the whole facility, because work can usually be re-routed to another machine of the same type; (3) lower capital investment per unit of flexibility, since general-purpose equipment serves many different products rather than one dedicated line per product; (4) broader use of a skilled, versatile workforce, since operators work across a wider variety of jobs rather than one narrow repetitive task; (5) better suited to job-shop, made-to-order, or low-volume/high-variety production.
Disadvantages of non-progressive (process) layout, compared to progressive (line) layout: (1) complex, often crossing and backtracking material flow, since each product follows its own route through the functional departments; (2) higher work-in-process inventory and much longer manufacturing lead time, because material queues between departments awaiting the next available machine; (3) higher material handling cost per unit, driven by the longer, more variable travel paths; (4) more complex production planning, scheduling and control (job routing, machine loading, queue management) than a paced line requires; (5) larger total floor space is typically needed for aisles, in-process storage and queuing between departments.
Correspondingly, progressive (line) layout's advantages relative to process layout are the mirror image — smooth, short, predictable flow; low WIP and short lead time; lower handling cost; simple scheduling (the line itself paces production); and effective use of specialized, often automated equipment — while its disadvantages are low flexibility to product/volume change, high capital investment in dedicated equipment, a station breakdown that can propagate and stop the entire line unless buffers or decoupling are provided, an inherent balance delay from imperfect line balancing (Question 3(iii)), and a requirement for high, sustained volume to justify its capital cost. The practical choice between the two is therefore governed primarily by product variety and volume: high variety/low volume favours non-progressive (process) layout, while low variety/high, stable volume favours progressive (line) layout — and manufacturing cells (grouping dissimilar machines around a part family) exist specifically as a middle ground when neither extreme fits well.
Computer-integrated manufacturing (CIM) is the integration of an organization's design, planning and production functions through a shared computer database and communications network, so that information generated at one stage of the product life cycle is directly usable by every other stage without re-entry or translation. A CIM system typically links: computer-aided design (CAD), which generates the product geometry and specification; computer-aided process planning (CAPP), which derives the routing and operation sequence directly from the CAD model; manufacturing resource planning (MRP/MRP II), which schedules materials, capacity and labour against demand; computer-aided manufacturing (CAM), including numerically controlled (NC/CNC) machines, robots and flexible manufacturing systems (FMS) that execute the plan; automated material handling and storage (AS/RS, AGVs, conveyors, Question 2(iii)); and computer-aided quality (CAQ) systems that feed inspection data back into design and process control. The defining characteristic of CIM is not any one of these technologies individually (each can exist standalone) but their integration through a common database, so that a design change in CAD automatically propagates to process plans, NC programs, and material requirements without manual re-entry at each interface. This integration is what enables CIM's practical benefits: shorter design-to-production lead time, better consistency between what was designed and what is produced, more responsive small-lot/high-variety production, and tighter overall process control — the same objectives CRAFT/CORELAP-based layout planning and cellular manufacturing pursue by physical means, CIM pursues by informational integration.
An AS/RS is a computer-controlled storage system — typically a narrow-aisle, high-bay rack structure served by a rail-guided storage/retrieval (S/R) machine (stacker crane) that stores and retrieves unit loads under direct command of a warehouse management/host computer, without a human operator entering the storage aisle. Its impact on manufacturing and warehousing is dramatic along several dimensions:
Cubic space utilization. Because the S/R machine, not a human-driven forklift, travels the aisle, aisle widths shrink to little more than the load's own clearance, and rack height can extend far beyond what a counterbalance forklift can safely reach — typically several times the storage density of conventional wide-aisle racking on the same floor footprint.
Labour and accuracy. Storage and retrieval transactions are executed under computer control against a real-time inventory record, essentially eliminating the picking and location errors inherent in manual, memory- or paper-based put-away/retrieval, and sharply reducing the direct labour hours per transaction.
Speed, consistency and throughput. S/R machine cycle times are consistent and can be scheduled/optimized by the host computer (e.g., dual-command cycles combining a put-away and a retrieval in one trip), giving predictable, high-throughput performance that does not degrade with shift changes or operator fatigue the way manual forklift operation can.
Inventory control and integration. Because every transaction is computer-logged, real-time inventory accuracy is dramatically improved, and the AS/RS host system integrates directly with production scheduling and MRP/CIM (Question 2(ii)) — enabling exact, verified small-lot delivery to point of use, which is what makes AS/RS a practical enabler of JIT manufacturing rather than only a warehousing efficiency measure.
Product and personnel protection. Because no operator enters the storage aisle, AS/RS reduces damage from operator-driven handling errors and removes personnel from the highest-risk zone of a conventional high-rack warehouse (falling loads, rack-collision, and lift-truck incidents).
These benefits come at the cost of high capital investment and reduced flexibility to reconfigure the storage system once installed (rack bay sizes and S/R machine envelopes are fixed at commissioning), so AS/RS is justified where storage volume, transaction rate, or accuracy requirements are high enough to offset that fixed investment — the same capital-vs-flexibility trade-off that governs the progressive/non-progressive layout choice in part (i).
