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Mechanical Engineering Technology

MEC 1011

Assignments

MEC 1011 - Design Communication I
T2&T3
Mid-Term Project 2010

Due at the end of our Second meeting in Week 7
Communication consistentent with course policy can extend the due date to the beginning of our second meeting in week 8 (following break)

As usual, create a new folder for your work using your full_name and located in V:\MEC\1011\Fall_10\Mid-Term_Projects/Tx (where Tx is T2 or T3).

Background:

This project will emphasize one of the middle phases of a typical design process. Consider these examples: Landscape Views, Portrait Views of some simple machines. Many of these designs are just at the end of the conceptual design phase. Your job is to build a computer model of a machine, refine the design (considering fit, function, manufacturing, aesthetics etc.) and document the refined design.

Objectives:

·         Produce a concept sketch (freehand pencil on plain 8 ½ x 11) of modest refinements to the design of a simple machine.

·         Produce a complete set of working drawings for the refined design using SolidWorks.

·         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 what tolerances are reasonable and what geometric restrictions apply, like draft for casting). Consider table and outline structures for your design guide (see example). Save your design guide (.doc or .htm) in your Mid-term project V: drive folder.

·         Exchange feedback with a peer through marked-up printed drawings. After making all necessary changes based on feedback, you must indicate who checked the drawings using the 'CheckedBy' file property.

·         Print at 100% and turn your set of A-size drawings (8 ½ x 11) in.

·         Also, turn in your peer’s set of drawings marked-up by you. Be sure to share the set with the author before turning it in.

Conditions:

·         Start with one of the example machines,

or:

·         Develop your own comparably complex design. You may start with any existing design whose drawings don’t yet exist. As a test of complexity, consider that a typical design from the examples has 6 custom parts and some standard fasteners or components. Also, note that each example presents some mechanical motion.

Priorities:

1.    Completeness: Sketch(es), each working drawing, and the set of drawings must be complete.

·         Sketch(es): Draw freehand with pencil on plain 8 ½ x 11 paper. Include title at the top, notes that explain your ideas, refinements, and how the parts will be made, name of designer (you), your signature, and the date

·         Set of Working Drawings (at least one assembly drawing and part drawings of each custom part):
Include formal (consider standard ANSI) title block and border. Confirm stated scale.

·         Assembly Drawing(s): Include any combination of views (ortho, section, iso, exploded or assembled) necessary to clearly show what parts and how they go together. Also, include balloons, a parts list and trails for any explosion. The parts list should at least include Item number, Quantity, and a column to name custom parts and specify standard ones.

·         Part Drawings: Include all views and dimensions necessary to define the part geometry. Tolerance all dimensions except stock sizes (including angles). Note material, units and projection system.

2.    Quality:

Challenge: Model and dimension in metric units.

Always:

·         Avoid Contradictions: Never use the decimal places of the style (appearance) of a dimension 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 callouts. This requires the also desirable use of hole features to model holes.

·         Dimension a hole’s location by referencing a center mark or centerline.

·         Place extension lines with visible ‘gaps’.

·         Avoid multiple parts per drawing or multiple drawings per drawing file. Also, avoid multiple parts per part file.

·         Give meaningful names to your 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, a manufacturer’s catalog (list of Component suppliers on Dept page) or from among the preferred sizes on this list from Columbia University’s Mechanical Engineering Department. If you choose a component from a Manufacturer’s catalog, please include the relevant info (Company, part#, etc.) in your parts list.

·         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 sketches (it’s easiest to kill them immediately).

·         Avoid unused geometry in sketches.

·         All reference planes and axes exist for a good reason.

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

·         Specify part finish (using notes or symbols).

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

3.    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.