Week 9:- 2D Detailing Challenge

AIM

To Provide detailed answers to the questions asked with suitable examples and images.

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 templates convey more information from designer to manufacturer.
• We can avoid misunderstanding and make very effective parts, which saves time and money by giving a proper detailed 2D drawing.
• Drawing templates can be changed from customer to customer and standard templates are also available as per the customer.
• Drawing templates are provided by the customer at the start of the project.

Drawing templates has n number of information such as

• Company name
• Project name
• Sheet size
• Sheet number
• Angle of projection
• Revision number/ latter (if its revision drawing)
• Signature or name of drawn by, checked by, responsible engineer and approved by
• Parts detail
• Quantity
• Additional notes (Surface finish, Heat treatment, Material detail, etc.)
• Scale, date, unit of measurement.

2) WHAT DO YOU UNDERSTAND BY ANGLE OF PROJECTION

• Technical drawing usually consists of various 2D views to define an object and this is known as orthogonal projection.
• The two orthogonal projection methods used internationally are First angle projection and Third angle projection.
• If some detailed view can be inferred from another, then you don’t bother to draw that view.
• The angle at which an observer drawn an object to convert it from 3D to 2D plane such as real object image to a plane is known as angle of projection.
• It shows the 3D object on a 2D image in paper with different sheet size.

ORTHOGRAPHIC REPRESNTATION

• According to the rule orthographic projection, Horizontal plane is rotated in the clockwise direction to draw a projection view of 3D object on 2D plane.
• Orthographic projections are 3D representation of 32D objects.
• Features of 3D parts are presented on flat plane, though the outline of part had been projected onto a screen.

• From the above image, the viewing angles are splint into quadrants of first angle, second angle, third angle and fourth angle.
• First angle quadrant and third angle quadrant are used as they are the pure and proper views of the design,
• The Second angle quadrant and Fourth angle quadrant are combination of first and third angle projection and can cause confusion to the reader.
• The Principle of first angle projection is shown below. In that image the observer looks at the 3D shape and projects the image onto a screen behind the component.

• The Principle of third angle projection says the observer looks at the 3D shape and projects the image onto a screen in front of the component.

3) WHAT IS THE FIRST ANGLE AND THIRD ANGLE PROJECTION? WHY CANT WE USE THE SECOND ANGLE ANF FOURTH ANGLE OF PROJECTION?

FIRST ANGLE PROJECTION

• In the 1^st angle projection, objects are placed in the First quadrant and it lies between the observer and the plane of projection.

SYMBOL

FRONT AND TOP VIEW IN FIRST ANGLE PROJECTION

• To drawn front and top views, object’s front and top views are projected on vertical and horizontal planes respectively.
• According to the rule of projection, the horizontal plane is rotated in the clockwise direction.
• Horizontal plane rotation brings top view in the bottom of projected front view whereas the left side view is projected on the right side of the front view.

THIRD ANGLE PROJECTION

• In 3^rd angle projection, objects are placed in the third quadrant and projection plane lies in between observer and the object.

FRONT AND TOP VIEW IN THE 3^rd ANGLE PROJECTION

• To drawn front and top views in 3^rd angle projection, Object’s front and top views are projected on vertical and horizontal planes respectively.
• As per rule of projection, the horizontal plane is rotated in the clockwise direction. This rotation brings top view on top of the projected front view.

RIGHT AND LEFT VIEW

• Right and left views of an object are projected on vertical right and vertical left planes respectively.
• To drawn the right side view on a 2D plane, Right plane is unfolded towards the right side.
• As a result, Right side view is projected on the right side of the front view.
• Similarly, the left side view is projected on the left side of the front view.
• Bottom view is projected on the bottom plane and placed on bottom of front view.

WHY SECOND AND THIRD ANGLE OF PROJECTION IS NOT IN USE?

• Second and Fourth angle of projection system has some limitations in it and so 1^st and 3^rd angle of projection are used to prepare engineering drawings.
• The concept behind the orthographic projection system helps us to understand why 2^nd and 4^th angle are not used.

HOW PROJECTION SYSTEM WORKS.

• Let’s consider a point in A and B in 1^st and 3^rd quadrant respectively.
• As per rule of projection to bring drawing views from three dimensional to two dimension planes, Horizontal plane (HP) is rotated in the clockwise direction.

• As shown, Point A in 1^st quadrant lies in between observer and projection plane. Therefore, front view of point A will be in vertical plane (V.P) and top view will be on horizontal plane.
• Similarly in point B in 3^rd quadrant can be projection on horizontal and vertical plane.
• To understand why the 2^nd and 4^th angle projection system are not used.

PROJECTION SYSTEM IN 2^nd AND 4^TH ANGLE OF PROJECTION

• Let’s consider rectangular parts X and Y are placed in 2^nd and 4^th quadrant respectively.
• In the second quadrant, vertical plane (VP) lies in between object X and observer.
• Therefore the front view of object X will lie on vertical plane whereas top view will lie on horizontal plane.
• As per rule of projection when horizontal plane is rotated 90 degree in clockwise direction, top and front view will overlap.
• Overlapping projection views create confusion in the drawing. Therefore the 2^nd angle projection is not used.
• Similarly when the object is placed in 4^th quadrant both top and front view will overlap. Therefore 4^th angle projection is also not used.

4) WHAT IS GD&T? WHAT ARE THE BENEFITS OF GD&T?

GEOMETRIC DIMENSIONING AND TOLERANCING (GD&T)

• GD&T is a design approach and manufacturing mechanism that helps engineers and designers communicated how to bring a part design to life.
• When documented correctly using GD&T, It is possible to build a part that exactly matches it on-paper planes.
• The drawing is the controlling document that ensures the vendor is creating precisely what the customer’s design requires.
• Machinists and quality engineers will use GD&T, Print dimensions and drawing notes to develop a manufacturing process and inspection methodology that will construct high- precision components matching the designer’ original vision.
• Proper Print detailing will also help with measurement coorelation to aid in the communication between customer and vendor.
• 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 component’s functional requirements.
• GD&T currently follows the standard of ASME Y14.5M-2009 (Previously ASME Y14.5M-1994).
• Engineers and designers look to GD&T to design critical aspects of part’s features, including 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 protocol.

MAJOR ADVANTAGES

GD&T, a vital part of complex machining, offers a number of major advantages and they are as follows.

SAVING MONEY: GD&T enhances design accuracy by allowing for appropriate tolerances that maximize production. For many projects the process provides extra or bonus tolerances, further increasing cost effectiveness.

Enhanced Communication:

• The vital role of communication in the manufacturing process cannot be overstated.
• Today’s complex part designs require accurate communication across the various disciplines.
• The use of a single and standardized GD&T language ensures engineering, design, production, and quality teams are able to communicate clearly and accurately with each other, saving time and increasing efficiency.

ASSISTING DIGITAL DESING METHODS

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

OFFERING UNIFROMITY AND CONVENIENCE

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

ENSURING DIMENSIONAL AND TOLERANCE REQUIREMENTS

By explicitly starting all design requirements a thorough GD&T process guarantees accurate fulfillment of all dimensional and tolerance applications.

5) EXPLAIN ALL THE SYMBOLS USED IN GD&T

There are a total of fourteen GD&T characteristics and the symbols that represent them are shown in the symbol below.

FORM TOLERANCE

It controls the “shape” of features and often used as refinement of size.

ORIENTATION TOLERANCE

• It controls the “tilt” of features and always associated with basic angle dimensions, often used as a reinforcement to location.
• If applied to surfaces, orientation tolerances also control form.

LOCATION TOLERANCE

• Location tolerances control location and are always associated with basic linear dimensions.
• Position locates and orients the median plane or axis of features of size.
• Profile locates feature surfaces.
• Profile is the most powerful characteristic of all, and also controls orientation and form.

RUNOUT

• Runout is how much one given reference feature or features vary with respect to another datum when the part is rotated 360 degree around the datum axis.
• It is essentially a control of circular feature and how much variation it has with the rotational axis.
• Runout can be called out on how much “wobble” occurs in the one part feature when referenced to another.

LEAST MATERIAL CONDITION (LMC)

The condition where the feature contains the least material within the stated limits of size (ex. Smallest pin or largest holes)

MAXIMUM MATERIAL CONDITION (MMC)

The condition where the feature contains the maximum material with the stated limits of size.(e.g. largest pin or smallest hole)

PROJECTED TOLERANCE ZONE

• The projected tolerance zone applies to a feature’s protrusion.
• In most cases, the zone to which geometric tolerance is applied is limited to the range of the feature specified in the drawing.
• In contrast to this, indications using the projected tolerance zone can specify a virtual zone for the specified feature’s mating part.

BASIC DIMENSION

• Basic dimensions are theoretically exact numerical values used to define form, size, orientation, or location of a part or feature.
• It is usually shown on a drawing enclosed in a box, but they can also be invoked by referencing a standard or by not on the drawing.

FREE STATE

• Free state modifier is added to indicate that the geometric tolerance applies in the unrestrained condition.
• This modifier is only applicable for non-rigid parts for which there is a note that indicates that tolerances are specified for the restrained state.