VSC Blackboard Portal

Mechanical Engineering Technology

MEC 1012


MEC 1012 - Design Communication II
Assignment 4
Sculpted Form from an Industrial Design Drawing

This assignment is due at the end of your TXL meeting before break (week 10)


Commonly, mechanical designers will receive an outside shape from an industrial designer. The outside shape might come in the form of an ambiguous 2D construction. Since most mechanical design and manufacturing uses 3D models, it sometimes falls on the mechanical designer to model a sculpted form in 3D before proceeding with mechanical details like lap joints, screw bosses, etc.


        You are given an AutoCAD drawing named GivenID.dwg and located in V:\MEC\1012\Spring_05\Assignment4. This generic housing shape is sculpted on the top, but straight forward on the bottom. It could be a vacuum cleaner or a clock radio, but the truth is top secret. You are also given a sketch of mechanical design details.

        Your parts must be designed for the injection molding process.

Cavity Draft

1 degree min.

Core Draft

.5 degree min.

Shut-off and Parting Line Draft

5 degrees min.

Wall Thickness

.090 inches (2.3 mm)

Rib Thickness

Max 60% of Wall Thickness, Min .020 inches (.5 mm)

There are some very good guidelines for injection molding design at efunda.com (note menu items at left) and at protomold.com. Also, there are design guidelines for injection molding at engineersedge.com.


        Set up and use an Inventor project file in V:\MEC\1012\Spring_05\Assignment4\TXA\username.

        Use the given geometry and/or dimensions to model the outside shape of the housing.

a.      Model the parting line in a file that will be used as a Derived Component in both the Top and Base of the housing.

b.      Create a spreadsheet of parameters for cavity draft, core draft and wall thickness and link it to both the Top and the Base.

        Use the given sketch to design a lap joint and set of four screw bosses.

        Produce an informal drawing to show that your design meets requirements. Include ‘check sections’ showing wall thickness at screw bosses, drafts, wall thicknesses, etc.

Typical stuff you’ve seen before shown in this color

Developed by Mary Waldo and Paul Johnson March 2005