Lecture 4 Production Planning and Interchangeable Manufacturing.pdf

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Curtin University
Mechanical Engineering
Alokesh Pramanik

Lecture 4: Production Planning and Interchangeable Manufacturing Sunday, 27 October 2013 10:28 AM • Production Planning: Introduction, Process planning • Interchangeable Manufacturing: Dimensioning and tolerancing, limits and fits, and surface texture • Design for assembly • DVD on Milling Machining Centre basics Production Planning • Raw Materials -> Factory -> Finished goods • Concerned with logistics issues • Deciding which products to make, how many of each and when they should be completed • Scheduling the delivery and/or production of the parts and products • Planning the manpower,raw materials and equipment resources needed to accomplish the production plan • Production systemsinclude: People Money Equipment Materials Supplies Markets Management Manufacturing System All aspects of commerce • Manufacturing systems:Collection of operationsand processes to produce a desired product of component;design or arrangement of the manufacturing processes • Manufacture-to-stock:Products are manufactured before customer's order (eg. TVs, power hand tools, off-the-shelf items) • Assemble-to-order:Products are assembled after customer'sorder, key componentsare stocked in anticipation of customer's order (eg. Cars, office furniture, etc) • Manufacture-to-order:Products are made after customer'sorder, simple or custom variation of similar parts (eg. Industrial punch presses, vehicle chassis, etc.) • Engineer-to-order:Products are made after customer'sorder with significant customisation, custom-designed capital equipment (eg. Space vehicles) • Forecasting: Predicts the future by using data on hand; affects the decisions we make today; use to forecast for demand for products and servicesand availability or need for manpower and inventory and material needs daily • Aggregate Planning (Intermediaterange/production, sale and inventoryplanning): provides overall frame work by integrating demands of marketplacethrough forecasting based on manufacturing place; intermediate-rangecapacity planning, covering 2-12 months; matches the capacity and demand • Master Production schedule: after aggregate plan, top-level managementauthorises the production-planning department to develop master production schedule. Translates aggregate plan into a separate plan for individual items and operates as a part number level • Master Production schedule provides basis for making good use of manufacturing resources, making customerdelivery promises, resolving trade-offs between buy and manufacturing, attaining strategic objectivesin the sales and operations plan • Material Requirements Planning (MRP): Based on MPS, material requirements planning system creates schedules identifying the specific parts and materials required to produce end items, determines exact unit numbers needed, determinesthe dates when orders for materials should be release, based on lead times • Loading and Scheduling: Involvesassignment of start dates and due dates for componentsto be processed through factory. • Machine loading: Allocating jobs to work centres • Machine loading: Allocating jobs to work centres • Shop loading: Allocating jobs to the entire shop ProcessPlanning • Determining the sequence of individual manufacturing processes and operations needed to produce a given part or product • Route sheet: lists manufacturing operationsand associated machine tools for each workpiece (for material handler) • Operation planning sheet: Describes machining or assembly operations done at particular machines (for machinist and assembly personnel) • Interpretation of design drawings: consider work materials, dimensions, tolerances and surface finishes • Processesand sequences: which processes are required and their sequences • Equipment selection:develop plans that utilise existing equipment. Otherwise the component must be purchases or an investmentmust be made in new equipment • Tools, dies, moulds, fixtures and gages: decide what tooling is required • Methods analysis: workplace layout, small tools, hoists for lifting heavy parts, specified hand and body motionsfor manual operations • Work standard: work measurementtechniques are used to set time standards for each operation • Cutting tool and cutting conditions: specify cutting tool and cutting conditions for each machining operation with reference to handbook recommendations Processselection criteria • Size and shape of the geometriccomponentsof the workpiece • Tolerances as applied by the designer • Material from which the part is to be made • Propertiesof material being machined • Number of pieces being produced • Machine tools available for this workpiece Interchangeable Manufacturing • Interchangeable manufacturing consists of machining of parts of a given mechanism with such tolerances that any of the parts will properly function in any of the machines. • Preferred by most modern manufacturers • Suitable for large production volumes • Requires high quality parts with small tolerances • Interchangeable parts: Identical for all practical purposes; made to specifications so that they will fit into any assembly of the same type; one such part can freely replace another without any custom fitting • This interchangeability allows easy assembly of new devices, easier repair of existing devices and minimizes the time and skill for assembly or repair • Interchangeability of parts was achieved by: ○ Combining a number of innovations and improvementsin machining operations ○ Invention of several machine tools such as the slide rest lathe, screw-cutting lathe, turret lathe, milling machine and metal planer ○ Additional innovations including jigs for guiding the machine tools,fixtures for holding the workpiece in the proper position and blocks and gauges to check the accuracy of the finished parts • Dimensioning and tolerancing practice decide interchangeability of parts. The dimensional specifications are expressed through size, form, orientation, location and surface texture Tolerance • The following three methods are usually used for size tolerancespecifications: Bilateral tolerances (either equal or unequal), unilateral or limit of size • Limit of size: The maximum and minimumsizes permitted for a dimension. The difference between the limits of size is equal to the tolerance • Nominal size: the size by which an item is designated as a matter of convenience • Basic size: The theoretical size of a dimension on which the limits of size and design size are • Basic size: The
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