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Mechanical Engineering Technology

MEC 1011

MEC 1011 - Design Communication I
Fall 2004 Final Project

Due at the final exam

Background:

This project will closely resemble the mid-term project, but it will include more requirements for presenting your design and the evaluation of tolerances will consider fit. Think of it as the mid-term with assignment 10 and assignment 11 tacked on. You may submit any prior work from the course. For example, someone who made good clean models for the mid-term might further refine the design, buff over the presentation and pitch it again as a final project.

Objectives:

        Produce a concept sketch (freehand pencil on plain 8 x 11) of modest refinements to the design of a simple machine.

        Produce a complete set of working drawings for the refined design using Autodesk Inventor. Set up and use an Inventor project file in V: /MEC/1011/Fall_04/Final/TXA/aaammdd/ that saves your models next to or below itself. Your models should include logical sub-assemblies. Use A-size portrait or B-size landscape sheets.

        Develop a design guide, using Word, to compile the rules of the design, ranging from aesthetics (ex. brushed stainless parts fastened with black socket-head cap screws) to manufacturing process plans and capabilities (capabilities include minimum reasonable tolerances and what geometric restrictions apply, like draft for casting). Your guide should also specify minimum clearances between mating parts. Consider table and outline structures for your design guide (see example). Save your design guide (.doc or .htm) in your Final project V: drive folder.

        Exchange feedback with a peer through a complete set of marked-up paper plots. After making all necessary changes based on feedback, you must indicate who checked the drawings using the 'Checked by' iproperty.

        Turn in a paper package consisting of:

a.                  A flat 3–hole cover (not 3-ring) with your name on it

b.                  A title page including a rendering of your machine in its environment

c.                  Your design guide and your concept sketch(s)

d.                  Your set of working drawings (printed 1:1 with drawing scale of your choice. Fold B-size pages accordion style.

e.                  Your peer’s set of drawings marked-up by you. Be sure to share the set with the author before turning it in.

You must turn in this package to an instructor in person. Make sure the instructor records the delivery by checking your name off a list.

        Produce motion and assembly animation files (5M max each). Animate sub-assemblies separately.

        Produce a PowerPoint slide appropriate for the 36” plotter (17” x 17” sheet of paper). Your slide should feature a rendering of your machine (500 x 500 pixels) surrounded by images of your working drawings, similar to those hanging in the hall outside the mechanical department offices (but smaller).

        Update your electronic notebook to cover the entire semester including the final project.

Conditions:

Each project must include at least 6 custom parts, one sub-assembly, some standard fasteners or components, some mechanical motion.

        You may use your mid-term project as a basis for your final project if it meets the above requirement or if you embellish the scope to meet the above requirement. For example, if you designed a two-part tap wrench for the mid-term, you could add in the taps, threading dies, and die handle to go with the tap wrench. Or perhaps you could design a case for the tap wrench.

or:

        You can start over and develop a new design if it meets the above requirement. You may start with any existing design whose drawings don’t yet exist. Draw from your imagination, experience or the list of examples (see links to projects below).

Priorities:

  1. Completeness: Sketches, each working drawing, and the set of drawings must be complete.

        Sketches: Draw freehand with pencil on plain 8 x 11 paper. Include title at the top, notes that explain your ideas and refinements, name of designer (you), your signature, and the date.

        All Working Drawings: Include formal (consider standard ANSI) title block and border. Title blocks include scale, author, checker and date, title.

        Assembly Drawing(s): Include exploded and assembled views (at least one of each - your choice of ortho, section or iso and consider two sheets) necessary to clearly show (consider detail views) what parts and how they go together. Also, include balloons (on assembled and exploded views), a parts list and good trails on any explosion. The parts list should at least include Item number, Quantity, and a column to name custom parts and clearly specify standard ones. The names of custom parts must match titles given on part drawings.

        Part Drawings: Include all views and dimensions necessary to define the part geometry. Tolerance all dimensions to conform to design guide with respect to minimum reasonable tolerances of relevant processes and minimum clearances vs. mating parts. Note material, and units (perhaps in title block).

        Drawing Set: Include an assembly drawing for each assembly and sub-assembly and part drawings for each custom part.

  1. Quality:

Challenge: Model and dimension in metric units.

Always:

        Avoid Contradictions: Never use the decimal places of the style (appearance) of a dimension (unfortunately Inventor calls this the ‘precision’ of the number) to round off a quantity. For example, if the length of a feature is 1.625, you should not allow its dimension to state 1.6.

        Dimension hole sizes and list characteristics using hole notes (use numerator -like 2X- available under dimension style). This requires the also desirable use of hole features to model holes.

        Dimension a hole’s location by referencing a centermark or centerline.

        Place extension lines with visible ‘gaps’.

        Avoid multiple parts per drawing or multiple drawings per Inventor drawing file (.idw). Also, avoid multiple parts per Inventor part file (.ipt).

        Give meaningful names to your Inventor files.

Generally:

        If you’re stuck designing in English units, think in simple decimal sizes when you design (like 1.6), and use fractional sizes for stock and standard components only. When you use fractional sizes (like 1.625), dimension them with a fractional style (like 1 5/8).

        Choose your sizes of stock or standard components by using the Inventor Library or from among the preferred sizes on this list from Columbia University’s Mechanical Engineering Department.

        Follow dimensioning rules of Figure 12.48 like locating holes in view looking down hole.

        Place dimensions off the views (Figure 12.43).

        Avoid over dimensioning (saying the same thing twice).

        Apply geometric dimensions and tolerances where appropriate to lower manufacturing cost.

        Tolerance consistent with process capabilities as stated in your design guide.

        Delete unused Inventor sketches (it’s easiest to kill them immediately).

        Avoid unused projected geometry in sketches. This is most easily done by confirming the status of Tools/Application Options/Sketch/Automatically Project Face Boundaries.

        All work planes and axes exist for a good reason.

        Holes are placed on a 'Point, Hole Center' (avoid extruding cut circles or placing hole features on sketched circles).

        Holes are tapped by modifying a hole feature (not by adding a thread feature).

        Holes are dimensioned with hole notes

        Specify part finish (using notes or symbols).

        Where a part is symmetrical, indicate symmetry with a centerline and tolerance the symmetry with a note.

  1. Complexity. Notice this is the LAST PRIORITY. Look up at Completeness. Before you make your design more complex, consider having a friend with a sharp eye look over your drawings. Your most insidious foe is the missing dimension.

Advice:

        Add complexity only after you have completeness.

FYI:

Links to Projects:

Landscape Views

Portrait Views