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Mechanical Engineering Technology

MEC 1012

Assignments

MEC 1012 - Design Communication II
Assignment 3
Adaptivity, Weldments and Multistage Documentation

This assignment is now due in combination with Assignment 5 at the end of your TXL meeting in week 12.
Each student must meet the conditions and objectives of this assignment in order to earn a passing grade in the course.

Overview:

Much of a parametric solid modeling system’s power comes from its ability to ‘adapt’ to changes based on the designer’s expressed intent. You will demonstrate many of Inventor’s methods of modeling for adaptivity. Weldments are a special form of assembly that allows the addition of weld features. Multistage documentation is used to show preliminary stages of fabrication (such as a part as-cast, but prior to machining).

Conditions:

        Your assembly must follow the basic concept shown in the sketch above.

        Use mm sizing including standard metric clearance holes.

        Your documentation must adhere to the standards of completeness and quality outlined in Priorities 1 and 2 of the MEC 1011 Final Project

        Your tolerances must be consistent with your design guide’s stated process capabilities and minimum clearances (i.e. your parts must fit together and be ‘manufacturable’). Include the minimum clearance between the base’s mount holes and a stated standard fastener presuming an identical set of holes in the ‘table’. This does not require geometric tolerances, but consider using them anyway.

Objectives:

Links to Detailed Descriptions (use this as a checklist)

        Illustration Highlighting Adaptivity by:

a.   Algebraic Equation
1.           Model Parameters
2.           User Parameters
3.           Linked Parameters
4.           Embeded Parameters

b.   Projection

c.    Assembly Constraint

d.   Derived Part or Assembly

        Weldment

        Cast Base

        Full set of working Drawings

        Check Sections

        Design Guide

        Feedback

        Paper Package

Details

        Illustration Highlighting Adaptivity - Make sure it's clear exactly where you have demonstrated what. Consider using a .idw sheet with a labeled view of your assembly or provide a labeled sketch (example)

a.      Algebraic Equation - A relationship that uses variables. Inventor calls its variables 'parameters' and allows you to call on the current value of a parameter by including the name of the parameter in an equation (ex. d0=10in, or Wall=2mm, or Length= 2*Width)

1.        Model Parameters - These are created when you add general dimensions and features to the model (named by default d0, d1 etc.).
2.        User Parameters - These are predetermined numbers/algebraic equations independent of features. These are best for values used repeatedly such as draft, wall thickness and so on.
3.        Linked Parameters -These are laid out on a spreadsheet (Excel) and then linked to one or more models. A value change in the spreadsheet is immediately reflected in the model (after update). This is a permanent relationship so the spreadsheet MUST reside in the workgroup folder. (Or the path must be designated in the project file.)
How to set up the spreadsheet:
        1. Use A1 to label the purpose of the spreadsheet.
        2. Add column labels in a lower row.
        3. Use column A to add parameter names.
        4. Place values and units in the following columns.

When linking or embedding the spreadsheet you MUST designate the first cell which has the label for the first row of values. (In the example A5)

Consider setting up a spreadsheet to drive the casting parameters of your base.

4.        Embedded Parameters - These are initially laid out on a spreadsheet (Excel) and then pulled into the model. The link is then severed to the spreadsheet. Subsequent changes to the original spreadsheet will NOT be reflected in the model. Instead changes must be made to the embedded spreadsheet.

b.      Projection - In sketch mode use 'project geometry' to project an existing edge (or axis or plane from the same or a different part) into the sketch. The line in the sketch will adapt to changes in the edge that was projected.

c.      Assembly Constraint - By leaving some aspect of a part unspecified (like leaving out a length dimension in a sketch), that part can be made to adapt to other parts in an assembly based on assembly constraints. For example, a block (with length unspecified) could be placed inside a box and mated to opposite inside walls of the box. The dimensions of the box would then drive the block. You must have the sketch as well as the feature and part designated as adaptive.
This capability is active when you see the swirling arrow symbol:

d.      Derived Part or Assembly - This allows you to use an existing part as the base for a new part. It allows you to scale an existing part and/or create a mirror image of the original. You cannot modify the derived features, but you can add new features. If you change the parent model these changes will be reflected in the derived part. Derived parts also allow you to make working drawings at various stages of manufacturing (for example, you can show machining features that are added after welding or casting by deriving the final part from a weldment or part that models the cast features. You can also use basic sketch geometry for a derived part to drive several parts.

        Weldment -This is an assembly mode (under the application menu) that allows you to add welds to your parts. Specialized commands:

Prepartions

Here you add chamfers for the welding bead

Welds

You designate the surfaces that touch the bead

Machining

These are post-welding processes that finish the welding stage

        Cast Base - Your base must be designed for the casting process. Specifically, the minimum reasonable tolerance is +/- 1.0% but no tighter than +/- .05 mm. Create and apply User Parameters for cavity draft, core draft, wall thickness, and rib thickness

Cavity Draft

2 degrees min.

Core Draft

1 degree min.

Shut-off and Parting Line Draft

5 degrees min.

Wall Thickness

3 mm

Rib Thickness

Max 60% of Wall Thickness, Min 1 mm

        Produce a complete set of working drawings based on your concept using Autodesk Inventor. Set up and use an Inventor project file in V:\MEC\1012\Spring_05\Assignment2\TXA\username. Use A-size portrait or B-size landscape sheets. Include at least one example of multistage documentation (like base casting and base). If a size of one of your parts is adaptive by assembly constraint, then it may have an odd size (like 3.478564). On the working drawing please show the dimension with many decimals to minimize rounding. Presumably, the size would be ‘cleaned up’ at a later time. See illustration

        Produce the models and drawings necessary to complement the working drawings to show that your design meets requirements. Include ‘check sections’ showing drafts, wall thicknesses, etc.

        Develop a design guide, using Word, to compile the rules of the design, ranging from aesthetics 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 V: drive folder.

        Exchange feedback with a peer. 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 (stapled top left) consisting of:

a.      Design guide

b.      Illustration Highlighting Adaptivity

c.      Set of working drawings (A-size portrait or B-Size landscape printed 1:1 with drawing scale of your choice. Fold B-size pages accordion style).

Related Links: (use the Back button to return to this page)

  1. Apex Fasteners for mechanical designers
  2. More fasteners
  3. Multiple sites for gears of all types
  4. Bearings & Bushings
  5. Thomas Register-The BIBLE of builders of things mechanical
  6. An example of A to Z in new product development
  7. More fasteners BUT check out the engineering knowledge base

Advice

Keep it simple. Completeness and quality are more important than complexity.

Check

Does your set of working drawings fully define an assembly of parts that are consistent with your complete design guide?

See Example of a Positional Tolerance Scheme

Typical stuff you’ve seen before shown in this color

Developed by Mary Waldo and Paul Johnson February 2005