ENME301
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| 🇬🇧 | 🇬🇧 |
| (Q) influences organisation of people, facilities and procedures. Can be separate into low, med and high | Product Quantity |
| Small differences between products e.g. models on same brand have a lot of common parts | Soft product variety |
| Products differ substantially e.g. small car vs large truck have practically no common parts | Hard product variety |
| Inverse correlation P is much less exact than Q - Differences in design details isn't the same as no. of different designs | Product Quantity and Variety Relationship |
| Yes but significantly less because of human welfare | Is manual labour still relevant long-term? |
| - Low labour rates in some nations - Too complex tasks to automate - Product life cycle - Reduce risk of new product failure | Long term manual labour |
| E.g. processing, assembly, inspection and material handling | Examples of automation |
| - Requires set up time, hence less production - Usually arranged in a process layout | Batch Production |
| - Minimal changeover time - Cellular layout is based on group technology | Cellular Manufacturing |
| - Single parts on single pieces of equipment - Process (functional) layout | Quantity production |
| - Parts/assemblies move through multiple workstations - Flow line (product) layout | Flow line production |
| - Used for high volume/mass production e.g. cars and consumer products | Flow line (product) layout |
| - Processing - Assembly - Material Handling - Inspection and Testing - Coordination and Control | Factory Operations |
| 5% on machine and 95% moving and waiting During the 5% on machine: 30% cutting and 70% positioning, loading etc | Material handling |
| Inspection - check dimensions are within tolerance Test - check the function of the final product | Inspection and test |
| T_c | Cycle time |
| R_p | Production rate - units produced per unit time (typically hour) |
| A | Availability - function of MTBF and MTTR (%) |
| MTBF | Mean time between failure |
| MTTR | Mean time to repair |
| PC | Production capacity - maximum output per unit time (typically week) |
| U | Utilisation - amount of productivity output (Q) relative to production capacity (%) |
| MLT | Manufacturing lead time - time from order to delivery |
| WIP | Work-in-progress - quantity of parts currently in the workshop (inventory) |
| Cycle time eq | T_c = T_o + T_h + T_th Cycle = operation processing + handling (placing product in machine) + tool handling (changing tools in between) |
| Batch production eq | Q = Q |
| High quantity production eq | Q = infinity |
| Production capacity | The maximum rate of output that a production facility is able to produce under a given set of operating conditions. In the context of a plant or factory, this is dubbed plant capacity |
| Assumed operating conditions | - Number of shifts per day - Of hours per shift - Employment levels |
| Plant Capacity eq | See image |
| Adjusting plant capacity short term | - Change number of workers - Change number of shifts per week - Change hours per shift e.g. overtime |
| Adjusting plant capacity intermediate and long terms | - Change number of machines - Change processing technology |
| Costs of manufacturing operations | Fixed costs - Building, equipment, insurance, rates Variable costs - Direct labour, raw materials, power |
| Manufacturing support systems | The procedures and systems used by a firm to manage its production operations and solve the technical and logistics problems associated with: - Designing the products - Planning the processes - Ordering materials - Controlling WIP (inventory) as it moves through the plant - Delivering quality products to customers |
| Types of process planning | Traditional computer aided process planning - retrieval (older) - generative (newer) - dynamic (developing) |
| Process planning | (carried by manufacturing engineers) - Electing appropriate processes and their sequence - Determining tooling requirements - Electing equipment - Estimating costs |
| Production planning | - Logistics of manufacture - Ordering materials - Obtaining resources |
| When determining the most appropriate manufacturing processes to fit the designs of the product, you need to consider: | - Available processing equipment - Technical capabilities in the factory - Parts or subassemblies that cannot be made internally and must be outsourced (i.e. need to work around standards) |
| People required | - Manufacturing engineers to read engineering drawings and are familiar with processes used in the factory using their knowledge, skill and experience - Tool designers - Cost estimators |
| Decision details | - Processes and sequence description - Equipment selection - Tool use for design (delegated) - Methods - Estimating production costs (delegated) - Specifying parameters of cutting tools and cutting conditions |
| Process planning for parts steps | Raw materials - basic processes - secondary processes - property-enhancing processes - finishing operations finished product |
| Raw materials | - Chosen based on functional requirements - Chosen based on limits of possible processes |
| Basic process | Establishes initial geometry e.g. Metal casting, forging, sheet metal rolling - This determines secondary processes |
| Secondary processes | Modifies the initial geometry e.g. machining, stamping, bending |
| Property-enhancing processes | - Treatments to strengthen metal - This step isn't always required |
| Finishing operations | Provide a coating on work surfaces e.g. electroplating, painting |
| Route sheet | - Specifies details of the process plan - "route sheet is to the process planner what the engineering drawing is to the product designer" Lists all the manufacturing operations in order |
| Process planning for assemblies | - Consists of line balancing to allocate work elements to particular stations - For single stations, the route sheet shows a list of the assembly steps |
| Make or buy decision | Even if cost to buy is greater than cost to make, doesn't mean you should buy Need to consider equipment at fixed cost and labour overhead. Only add these costs to the cost to buy if they would also be used in other areas of production, THEN compare cost to buy with cost to make |
| Retrieval (variant) CAPP systems | This is an older CAPP system based on Group Technology and parts classification & coding. Standard process plans are stored in computer files with each part code number - Plans are based on current part routing - For each new part, the standard plan is edited - If file doesn't exist, can search a similar code name and edit it to become the standard plan for the new part - Final step is the process plan formatter which may call on other application programs e.g. design cutting conditions, computing cost estimates |
| Group Technology | - A manufacturing philosophy where similar parts are grouped together to take advantage of similarities in design and production - Similar parts are arranged into part families |
| Generative CAPP systems (newer) | - Newer CAPP system - Process plans are created using rules a human may follow. - In fully generative CAPP systems, process sequences can be planned without any human assistance or predefined standard plans - Expert system required to build generative CAPP systems |
| Components of an Expert system for a generative CAPP system | Knowledge base - Technical knowledge of manufacturing and logic Computer-compatible part description - Description of product needed for the process sequence Inference engine - Algorithm that applies planning logic and process knowledge located in the knowledge base |
| Dynamic, generative CAPP | - Still developing CAPP system - Artificial intelligence is used to produce process plan - Considers plant and machine capacities, tool availability, work centre, equipment loads and status - Smooth blending between process and production |
| Benefits of CAPP | - Process rationalisation and standardisation - Increased productivity - Reduced lead times to prepare process plans - Improved legibility over manually written route sheets - Can be integrated with other applications (e.g. design cutting conditions, computing cost estimates) - CAPP is good for discrete parts with significant numbers of products and steps |
| 70% of product life cycle cost is fixed during design stage, therefore it is important for the manufacturing engineer to work with the design engineer for manufacturability | Product life cycle cost relationship between manufacturing engineer and design engineer |
| This is the approach to product design in which companies attempt to bring a product to market quicker by integrating design, manufacturing and other fields like marketing | Concurrent Engineering |
| - What products are to be products, in what quantities and when - Accounts for current orders, sales forecasts, inventory and plan capacity | Production planning |
| Ensure resources are available for the provided plan. If not, take action to remedy | Production control |
| Raw materials Components WIP Finished products | Types of inventory |
| Independent demand How much to order - typically determined by economic order quantity (EOQ) eq When to order - typically determined by reorder points | Order point system |
| See pic | See pic |
| - Product features (design) - Freedom from deficiencies (manufacturing) | Quality in Design and Manufacturing Aspects |
| - Characteristics that result from design - Functional and aesthetic features that appeal to the customer | Product features |
| - Performance - Ease of use - Reliability - Durability - Availability of options - Serviceability | Examples of product features |
| - Product does what its supposed to do - Product is absent of defects and is within tolerances | Freedom from deficiencies |