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Mechanical Engineering Technology

MEC 1012

MEC 1012 - Design Communication II, Challenge 2
Adaptivity, Weldments, Redesign for Casting,
and Multistage Documentation

Each student must earn a passing grade on all challenges to earn a passing grade in the course.

Start:

Start by making a folder: V:\MEC\1012\Spring_05\X\Challenge2\TXA\username. Copy the Inventor and .htm contents of V:\MEC\1012\Spring_05\X\Challenge2\ (2 parts, an assembly, three drawings and a design guide) to your folder. Start Inventor and browse to the project file in your folder.

Overview:

        This Challenge is an abbreviated version of Assignment 2 and Assignment 3.

        You must modify the design of a table. Your goal is to redesign the base to be cast, increase the clearance for the fasteners and weld on a name plate.

Conditions:

        You are given the table’s design guide, models (Assembly, Base, and Plate) and drawings (Assembly, Base, and Plate).

        You are given a concept sketch for needed changes.

        Your models must demonstrate the appropriate modification and use of various 3D features as called for. Expect to modify Extrude features to apply a taper by User Parameter, Shell with a wall thickness by User parameter, create a Rib and apply Face Draft (also by User Parameter), and Mirror the Rib.

        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’). This does not require geometric tolerances, but consider using them anyway.

Objectives:

        Redesign the Base to be cast.

        Include draft as appropriate with a parting line at the bottom outside edge. Add ribs as indicated in the concept sketch. Further, remove the holes from the base casting and model them in a later stage (using Derived Component).

        Presume that the casting process is capable of at minimum +/- 1.0% but no tighter than +/- .05 mm.

        Create and apply User Parameters for Cavity_Draft, Core_Draft, Wall_Thickness, and Rib_Thickness based on the following geometric restrictions:

Cavity Draft

2 degrees min.

Core Draft

1 degree min.

Wall Thickness

3 mm

Rib Thickness

Max 60% of Wall Thickness, Min 1 mm

        Confirm that inside corners have radii at least equal to the neighboring thickness.

        Produce an informal drawing necessary to complement the working drawings to show that your design meets requirements. Include ‘check sections’ showing drafts, wall thicknesses, etc. For example, Do your ribs intersect the standard wall at less than or equal to 1.8 mm (60% of 3mm)?

        Increase the minimum clearance between the Plate and the Screws from .15 mm to .2 mm.

        Add a Name Plate (keep it simple – rectangle with engraved letters) to your Assembly and weld it to the center of the Plate.

        Develop a design guide, using Word, to compile rules of the design. Include 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). You may choose to simply modify the given Design Guide. Save your design guide (.doc or .htm) in your V: drive folder.

        Produce a complete set of working drawings using Autodesk Inventor. Set up and use an Inventor project file in V:\MEC\1012\Spring_05\Challenge2\TXA\username. Use A-size portrait or B-size landscape sheets. Include multistage documentation with a drawing of the base as cast and a separate drawing for hole drilling. Feel free to model your main assembly as a weldment to avoid the need for a separate weldment drawing.

        Turn in a paper package (stapled top left) consisting of:

a.      Design guide

b.      Given sketch with tolerance calculation for minimum clearance between Plate and Screws (see below).

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

 

Advice:

        Use section views for clarity where appropriate.

        To control the minimum clearance between the screw fasteners and the clearance holes on the base choose:

        Positional Tolerancing where: T is the diameter of the tolerance zone, H is the MMC hole and F is the MMC fastener with min clearance added to both sides. For a Floating Fastener case T = H – F and for a Fixed Fastener T = (H – F)/2. In the Given design we have a Fixed Fastener with H = 9 - .1 = 8.9, and F = 8 + 2(.15) = 8.3 so T = (8.9 – 8.3)/2 = .3 mm.

OR

        Rectangular Tolerancing where the hypotenuse of a square zone can be presumed to be 40% greater than the side.

Bonus Problem:

        If the top surface on the Base is cast (far from flat) the Plate may wobble or tilt. How could we modify the Base to insure a stable and level Plate?

References

        You shouldn’t need it but, http://www.metrication.com/ is good for metric drill sizes.