Week 9:- 2D Detailing Challenge

1) What are drawing templates ?

Drawing templates are the files of frames and title block which convey the design information that are used to generate 2D drawing from 3D part.

Neat and detailed drawing template convey more information from designer to manufacturer. So we can avoid misunderstanding and make a very effective parts, which saves time and money.

Drawing template are change as per the company standards.

Drawing templates are provided by the customer at the starting of project, if not then we should finalise at starting of project.

Drawing templates has n number of information such as:

1. Company name

2. Project name

3. Sheet size

4. Sheet number

5. Angle of projection

6. Revision number / letter (if its revision drawing)

7. Signature or name of drawn by, checked by, responsible engineer and approved by

8. Part detail

9. Quantity

10. Additional notes (surface finish, heat treatment, material detail etc.)

11. Scale, date, unit of measurement.

2) What do you understand by angle of projection ?

The define an object, technical drawings use 2D views. This is called as orthogonal projection. The projection of the plane is viewed by the observer. The quandrant it should be only rotated in a clockwise direction.

The angle of projection are basically the view formats for orthogonal views of assemblies or panels. First and third angle of projection are majorly used in automotive standards. Understanding the angle of projection helps us to derive the actual image of 2D drawing.

The orthographic projection system is used to represent a 3D object in a 2D plane. The orthographic projection system utilises parallel lines, to project 3D object views onto a 2D plane. According to the rule of orthographic projection, to draw a projection view of a 3D object on a 2D plane. The horizontal plane is rotated in the clockwise direction.

There are two angle of projections used in drawings:

• First angle of projection
• Third angle of projection

Basic differences of first and third angle of projections are :

3) What is the first angle and third angle projection? and why can't we use the 2nd and 4th angle of projection?

First angle projection :

In the first angle projection, the object is placed in the 1st quadrant. The object is positioned at the front of a vertical plane and top of the horizontal plane. First angle projection is widely used in India and European countries. The object is placed between the observer and projection planes. The plane of projection is taken solid in 1st angle projection.

Third angle projection :

In the third angle projectuion, the object is placed in the third quadrant. The object is placed behind the vertical planes and bottom of the horizontal plane. Third angle projection is widely used in the United States. The projection planes come between the object and the observer. The plane of projection is taken as transparent in 3rd angle projection.

why we can't we use the 2nd and 4th angle of projection:

In second quadrant, vertical plane (VP) lies in between object and observer. Therefore, front view of the object will lie on vertical plane where as top view will lie on the horizontal plane. As per rule of projection when horizontal plane is rotated 90degree in clockwise direction, top and front view will overlap.

Overlapping projection views create confusion in the drawing. Therefore 2nd angle projection system is not used.

Similarly, when object is placed in 4th quadrant both top and front view will overlap. TYherefore, fourth angle is also not used.

To sum up, because of overlapping of front and top views 2nd and 4th angle projections are not used. First and third angle projection systems are recommended for orthographic projections.

4) What is GD & T? What are the benefits of GD&T ?

Geometric dimensioning and tolerancing (GD&T) is a design approach and manufacturing mechanism that helps engineers and designers communicate how to bring a part design to life. When documented correctly using GD&T, it is possible to build a part that exactly matches its on-paper plans.

GD&T uses a symbolic language to indicate how significantly part features can deviate from the geometries listed in the design model. This language contains all relevant details involved in fabrication, including dimensions, tolerances, definitions, rules, and symbols that communicate a components functional requirements.

Engineers and designers look to GD&T to design critical aspects of a parts features, including a specific features desired location, form, profile and orientation. It is common practice to use the profile designation tied to the datum structure that is related back to the solid CAD model. This allows manufacturing to use a best fit protocal.

GD&T is a feature based system and parts are composed of features geomertric tolerance are applied to features by features control frames. The most frequently used tolerances categories are form, orientation and locaton. Therefore, the ten associated symbols are the most utilised of the fourteen total GD&T symbols.

Benefits of GD&T :

• A standardised design language.
• A clear and precise way for the customer, supplier and production team to communicate.
• A method for calculating the worst case mating limits.
• Production and inspection processes are repeatable.
• Standardised, international system
• More flexibility, particularly for complex shapes
• Allows cylindrical toleerance zones
• Datums are clearly defined
• Based on the fit and function of a part or assembly
• Eliminates the need for many notes
• Allows for more tolerance

Five Major advantages

GD&T, a vital part of complex machining offers a number of major advantages:

Saving Money - GD&T enhances design accuracy by allowing for appropriate tolerances that maximise production. For many projects, the process provides extra or bonus tolerances further increasing cost effectiveness.

Ensuring Dimensional and tolerance requirements - By explicitly stating all design requirements, a thorough GD&T process guarantees accurate fulfillment of all dimensional and tolerance specifications.

Assisting digital design methods - Clear, concise, GD&T data is readily adaptable to digital design programs, including nearly universally used 2D and 3D CAD files.

Offering uniformity and convenience - As a single, consistent language, GD&T reduces guesswork and interpretation while ensuring consistent geometries across design and manufacturing.

Providing accurate communication - Today's intricate designs demand the most accurate and reliable communication. GD&T enables designers, manufacturers, and inspectors to communicate clearly with one other, saving time and making the proceess more efficient.

When to use GD&T :

• While many application benefit from GD&T, there are certain situations in which the process provides fundamental assistance, including scenarios in which critical or interchangeable parts fit into a larger assembly, tolerance analysis needs simplification or the project requires functional gauging techniques.
• GD&T replaces complex description notes with a single symbol or set of symbols, allowing for effortless reference and fast, precise communication. The process provides additional clarity when clients are working without a standard interpretation or tolernace, making even the most in-depth and complicated projects easier to complete.

5) Explain all the symbols used in GD&T ?

• Form tolerance : Controls the shape of features and are often used refinememt of size.

Straightness - Controls the straightness of a feature in relation to its own perfect form.

Flatness - Controls the flatness of a surface in relation to its own perfect form.

Circularity - Controls the form of a reolved surface in relation to its own perfect form by independent cross sections.

Cylindricity - Like circularity, but applies simultaneously to entire surface.

• Orientation tolerance : Controls the tilt of the features and are always associated with basic angle dimensions. If applied to surfaces, orientation tolerances also control form.

Perpendicularity - Controls the orientation of a feature which is nominally perpendicular to the primary datum of its datum reference frame.

Angularity - Controls orientation of a feature at a specific angle in relation to the primary datum of its datum refrence frame.

Parallelism - Controls orientation of a feature which is nominally parallel to the primary datum of its datum refrence frame.

• Locatiion tolerance : Controls location and are always associated with basic linear dimensions.

Position - Controls the location and orientation of a feature in relation to its datum refrence frame.

Concentricity - Controls concentricity of a surface of revolution to a central datum.

Symmetry - Controls the symmetry of two surfaces about a central datum.

• Profile tolerance : Locates features surfaces. Profile is the most powerful characteristics of all and also controls orientation and form.

Profile of a surface - Controls size and form of a feature. In addition it controls the locaton and orientation when a datum refrence is used.

Profile of a line - Similar to profile of a surface, applies to cross section of a feature

• Runout tolerance : Runout is how much one given refrence feature or feature vary with respect to another datum when the part is rotated 360 degree around the datum axis.

Circular runout - Controls circularity and coaxiality of each circular segment of a surface independently about a coaxial datum.

Total runout - Controls circularity, straightness, coaxiality, and taper of a cylindrical surface about a coaxial datum.