Engineering Drawings ME 161 One of the important methods to create solid models is feature based modeling. In addition to feature based model, using sketch is another method to create solid models. Sometimes, a sketch is more flexible than a feature. In many cases, sketch is the only way to create a solid model. Drafting is a technique to create 2-D engineering drawings which are used for manufacturing. We are going to discuss the fundamental principles and concepts of sketch and drafting. On Wed and Thu we will teach you how to use UG to create sketches, how to create a solid model from sketches, and how to create engineering drawings from a solid model. ME 161

Drafting The drafting application is creating 2D drawings with different views from a solid model. You have a solid first, and then drawings. You will learn how to Create a drawing Add orthographic and section views Add dimensions and annotations

ORTHOGRAPHIC VIEWS Orthographic Views: 2-D views of objects where the viewpoint of the object is at right angles to surfaces.  Let’s discuss sketch first. What is a sketch? A sketch is a collection of 2D curves. A sketch is a group of curves and lines. A sketch can be closed like the profile on the left or unclosed like the profile on the right. The primary purpose of using a sketch is to create solid models.

An object inside a box with its surfaces "projecting" on to the sides of the box.  Unfold the box to project the views on a flat surface.

Drafting Example (cont.) Add more views Orthographic view Front view TFR-ISO view Orthographic view

How Many Views? Three-view drawing is most commonly used. Avoid using views more than needed.

Isometric or Trimetric Views Included to help visualization. Should not be used to define object. Optional

Isometric & Trimetric Views TFR-ISO TFR-TRI

Auxiliary Views Use to show true view of important features. Dimensions should be in true view.

Section Views

Dimensioning Rules There are multiple ways to specify the dimensions, but they will not all represent the identical manufactured part. There should only be one way to interpret the dimensions and tolerances. Choose to dimension features to maintain the critical locations and tolerances. A redundant dimension should be denoted with (ref), indicating it is only included for reference. Every dimension has a tolerance.

Some Dimensioning Tips Avoid putting dimensions on top of the part. Avoid dimensioning to hidden lines. Always dimension in a “true” view. Choose to dimension in the view that shows the feature most clearly. Holes should be dimensioned in the view where the cross-section is seen. Minimize crossing of leader lines. Large dimensions are positioned outside of small dimensions.

Tolerances All dimensions must have a tolerance. Can show defaults with a note Dimension tolerances: Fractional +/- 1/16 x.x +/- 0.01 x.xx +/- 0.001 x.xxx +/- 0.0001

Tolerance Accumulation Chain Dimensioning 10±0.05 10±0.05 10±0.05 10±0.05 Overall length = 30.80 to 40.20 Baseline Dimensioning 40±0.05 30±0.05 20±0.05 10±0.05 Overall length = 30.95 to 40.05

Tolerance Accumulation Direct Dimensioning 40±0.05 20±0.05 10±0.05 20±0.05

Line Types Visible - are continuous lines used to depict edges directly visible from a particular angle Hidden - are short-dashed lines that may be used to represent edges that are not directly visible Center - are alternately long- and short-dashed lines that may be used to represent the axes of circular features A variety of line styles are used to graphically represent physical objects. Types of lines include the following: visible - are continuous lines used to depict edges directly visible from a particular angle. hidden - are short-dashed lines that may be used to represent edges that are not directly visible. center - are alternately long- and short-dashed lines that may be used to represent the axes of circular features. cutting plane - are thick, medium-dashed lines, or thick alternately long- and double short-dashed that may be used to define sections for section views. section - are thin lines in a parallel pattern used to indicate surfaces in section views resulting from "cutting." Section lines are commonly referred to as "cross-hatching."

Title Blocks

In Your Design Project In the engineering drawings: Use dashed lines for hidden lines. Use center lines for the axis of symmetry of a part or feature. In the title block, include the information of part name, designer’s name, general tolerance, material, date, units, etc.

Example of Working or Detail Drawings (1)

Example of Working or Detail Drawings (2)

Example of Working or Detail Drawings (3)

Example of Exploded View or Assembly Drawing