Design Representation 1

Transcription

1 Once a design is conceptualized, it must be represented and communicated to others in a complete and technically accurate fashion. GET130 Intro to Engineering Technology Fall 2016 Communication methods: oral presentations written documents technical drawings demonstration of model / prototype Different engineering fields use different types of representations and symbology. and tools (software packages) to work with them symbology, def: a system of symbols 2 sketch: generally refers to a freehand drawing including artistic implications subjective/ambiguous impressions like you did in the problem solving lab drawing: result of using drawing instruments or technology ruler/compass drafting board computer with CADD software CADD: Computer Aided Design and Drafting civil grading, landscaping, etc. topological & relief maps architectural plan, section, elevation, perspective construction electrical, mechanical (HVAC), plumbing patent General Info Drawing Standards engineering clearly defines requirements for engineered items 3 4 block diagram computer/software engineering: flowchart electrical engineering: schematic mechanical: layout part/detail assembly / exploded view arrangement bill of materials (BOM) high-level presentation of a system to show overall concepts without implementation details aka system diagram used in all engineering fields symbology: blocks denote principle parts or functions of the system lines show relationships between the blocks 5 6 Design Representation 1

2 7 8 a visual diagram tool that shows the sequencing of a process or algorithm to solve a specified problem typically used to design/document/analyze computer programs, program flowchart symbology: blocks describe the steps to be performed lines show the order of the process how it works 9 10 Alternate process (entry) Off-page connector Process Decision Predefined process (subroutine) Data input/output On-page connector Terminator a good (free) diagramming tool: Diagram Designer Design Representation 2

3 car won't start put car in park Scenario: will key turn is car in park A ou jump in your car, hit the key, but your car won t start. does engine crank check battery battery good replace battery got gas get gas! What to do A car start now done, be happy call service technician done, pay da man START i=0 x=10 y=1 from the flowchart given, determine the output of x, y, and i an abstract representation of a system using an appropriate symbology x > y Output i,x,y STOP x y i heavily used in electronics (but not only!) aka circuit diagram x=x/y y=y+i i=i Electronic Design Automation (EDA) computer tools provide for schematic capture and editing ex: ational Insruments Multisim audio power meter: 7-segment display : this schematic done in Multisim Design Representation 3

4 a really nice table of electrical and electronic symbols may be found at RapidTables.com they also have another table of some electronic components with photos! another library of 800+ electronic symbols & photos: include: layout modify detail control assembly interface installation mechanical schematic arrangement electrical schematic are drawn in conformance to industry standards ex: ASME drawing standards Table of Contents required by Department of Defense (DoD) policies shows design requirements of major system components via pictorial, notational, and dimensional data used during development to prepare other engineering drawings not typically used for fabrication provides complete definition of the part or parts shown including dimensioning and tolerances, also identifies the parts includes materials and fabrication info may be either for a single part (monodetail drawing) or multiple parts (multidetail) click drawing to open PDF Design Representation 4

5 otice: dimensioning tolerances title block identification shows how individual parts fit together to form an assembly may be in the form of an exploded view depicts the physical relationship of significant components using appropriate projections or perspective views may include reference dimensions, but not item identification info used to convey general description of the configuration and location of significant items, i.e. ancillary info not normally used to control design Design Representation 5

6 sank 11/01/1995 off Palungitak Island in northern ewfoundland due to loss of situational awareness 3 crew members lost in technical drawings, various views are used to describe an object or item these views basically fall into two categories: Isometric (pictorial) Orthographic (plan) 1 survivor paddled 2 hours to shore shows 3 surfaces of an object in a 2D fashion perspective view attempts to replicate what is seen by human eye or camera lines of depth converge to one or two vanishing points on an imaginary horizon most complex but most accurate isometric view uses only vertical and 30º lines to simulate perspective easy to create and widely used supported by CAD tools illustrates a 3D object via 2D views of two or more of the object surfaces a collection of views of an object formed by projectors onto and perpendicular to the desired plane of projection in English please projection onto the frontal plane projection onto the horizontal plane projection onto the profile plane envision the object contained in a glass box wrapped with paper each of the 6 sides shows its unique projection cut & unfold paper into its 2D form all planes are hinged to the front plane, except for back which is hinged to left side Design Representation 6

7 note that rarely do we need all 6 views 3 views is typical, some objects need only 2 or even 1 as in the previous metal handle a system of standard symbology and conventions used on the detail drawing to convey maximal design details while keeping it neat and uncluttered is a language of communication between designer and fabricator based on ASME 14.5 Dimensioning and Tolerancing standard essential components needed on every drawing to ensure correct interpretation standard symbols for particular items clear lettering (UPPERCASE only) standard drawing views clear consistent lines, dimensions & units appropriate clarification notes title block: drawing title designer/drawer s initials & date material & finish specifications allowable tolerances (variations) tolerance specifications metric dimensions include 0 before decimal point (0.5 mm); inch do not (.25 in) line types: extension lines emanate from object with visible separation gap dimension lines have break for the numbers, 10mm from the object; 6mm for subsequent lines; shortest closest to object and longer lines further away leader lines indicate surfaces & hole diameters; angled & pointing towards hole center hidden (dashed) lines indicate a feature better seen in another view center lines (di-dashed) indicate a cylinder object extension lines cylinder line dimension lines leader line hidden line stacked dimensions Design Representation 7

8 refers to allowable variation of a dimension to accommodate imperfect manufacturing processes indicated with ± notation specify only as tightly as needed because tighter tolerances result in increased manufacturing costs and possibly use of more expensive equipment tolerances are specified: with a dimension line, in a drawing note, or in the title block as a drawing default from the ASME standard grouped by types form, profile, orientation, location, runout ex: a piece thickness spec d at.500±.003 in it could vary between in look for these in CADD software! A bill of materials (BOM) is a list of the raw materials, sub-assemblies, intermediate assemblies, sub-components, parts and the quantities of each needed to manufacture an end product. used for communication between manufacturing partners (external BOM), or confined to a single manufacturing plant (internal BOM) can be used in various contexts: engineering BOM design electronics BOM circuit board components sales BOM ordering/procurement/inventory service BOM maintenance BOMs can be created/maintained with spreadsheet program (Excel) purpose-built applications Diagram Designer flowcharts, illustrations Autodesk Inventor Dassault Systems SolidWorks ational Instruments Multisim circuit schematics and PCB layout American Society of Mechanical Engineers (ASME) Engineering drawing Engineering Drawing and Sketching [tutorial] Engineering Drawing Practices Flowchart GD&T Reference Guide The United States Patent and Trademark Office (USPTO) Technical Drawing %20Class%20Handout.pdf Design Representation 8