Week 9:- 2D Detailing Challenge

2D Detailing Challenge

1.Q) What are the Drawing templates?

Ans:

• Drawing template are basically the drawing standard as per customers specification.
• Drawing Templates are format that are used for detailing of different parts or units of the fixture.
• There are n numbers of details that are already available on the template and are useful for various manufacturing processes, such as, machining finish, tolerances, surface treatment, material, name of the parts, name of assemblies etc.
• Preparing a drawing template at the start of the project can help us save time, as these templates can be used as a start model of detailing for different parts.
• Drawing templates also gives information about the angle of projection to be used, views to be considered scaling of the drawing as per the part or unit.

Drawing templates contains a lot of information about the drawing as given below:

• Scale
• GD&T
• Roughness Symbols and standards
• Quantity
• Tolerances
• Sheet size and sheet number
• Type of projection (1st angle or 2nd angle)
• Notes about surface hardening and stress relieving
• Project code
• Part number
• Project name
• Company name
• Title
• Designed and checked by who
• Date
• Mass and density
• Allowance
• Tolerance range
• Some of the testing criteria

2.Q) What do you understand by Angle of projection?

Ans: 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 quadrants 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.

3.Q) What is the First angle & Third angle projection? and why can't we use the 2nd and 4th angle of projection?

Ans:

The First angle: The First Angle Projection schema imagines the object in the first quadrant. One can place an object on the top of the horizontal plane and at the front of the vertical planes. The first angle projection is utilized mostly in India and various European countries. It places the object between the projection planes and the observer. You can take the plane of projection to be solid in the first angle projection.

Third Angle Projection: The Third Angle Projection schema imagines the object in the third quadrant. One can place an object on the bottom of the horizontal plane and behind the vertical planes. The first angle projection is utilized mostly in the United States. It places the object between the observer and the object. You can take the plane of projection to be transparent in the third angle projection.

Parameter	First Angle Projection	Third Angle Projection
Method of Projection	When you divide a plane into four quadrants, you can place any object in the first quadrant in a first angle projection schema.	When you divide a plane into four quadrants, you can place any object in the third quadrant in a third angle projection schema.
Placement of Objects	It places the object between the observer and the plane of projection for the first angle projection.	It places the object between the observer and the object for the third angle projection.
Sequence of Views	In the first angle projection schema, the views come in the following sequence- top left, then clockwise, the Right view, Front view, and the Top view.	In the third angle projection schema, the top view sits at the top of the front view, and the right view sits on the right side of the front view.
State of Projection Plane	You can take the plane of projection to be opaque (solid) in the first angle of projection.	You can take the plane of projection to be transparent in the third angle of projection.
Uses	Widely used in India, Europe, Canada.	Widely used in Australia and the United States.
Identification	You can identify a drawing of the First Angle Projection by the symbol of the first angle projection. This symbol of the angle of projection typically appears near the Title block in the angle of projection block.	You can identify a drawing of the Third Angle Projection by the symbol of the third angle projection. This symbol of the angle of projection typically appears near the Title block in the angle of projection block.

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

Ans: Second and fourth angle projection system are not used to draw engineering drawing because of the limitation of overlapping projection View. In this article we will discuss in details the limitation of the 2^nd and 4^th angle projection system.

To understand why 2^nd and 4^th angle projection are not used. Firstly we need to understand the concept behind the orthographic projection system.

To understand why 2^nd and 4^th angle orthographic projection system are not used to draw engineering drawing. We will repeat the above experiment of creating engineering drawing views in the second and fourth quadrants.

Let’s consider rectangular parts x and y are placed in the 2^nd and 4^th quadrant respectively.

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

Overlapping projection views create confusion in the drawing. Therefore the 2nd angle projection system is not used to draw engineering drawings. Similarly, when the object is placed in the 4th quadrant both the top and front view will overlap. Therefore, fourth angle projection is also not used.

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

Ans:

• Ans: 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 component functional requirement.
• 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 protocol.
• GD&T is a feature-based system and parts are composed of features geometric tolerance are applied to features-by-features control frames. The most frequently used tolerances categories are form, orientation and location. Therefore, the ten associated symbols are the most utilized of the fourteen total GD&T symbols.

Benefits of GD&T :

• A standardized 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.
• Standardized, international system
• More flexibility, particularly for complex shapes
• Allows cylindrical tolerance 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 maximize 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 process more efficient.

When to use GD&T :

While many applications 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 tolerance, making even the most in-depth and complicated projects easier to complete.

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

Ans:

Position Tolerance: True Position, or just Position as the ASME Y14.5 standard calls it, is defined as the total permissible variation that a feature can have from its “true” position. The “True Position” is the exact coordinate, or location defined by basic dimensions or other means that represents the nominal value. In other words, the Geometric Dimensioning and Tolerancing “Position” tolerance is how far your feature’s location can vary from its “True Position”.

Position is one of the most useful and most complex of all the symbols in GD&T. The two methods of using Position discussed on this page will be RFS or Regardless of Feature Size and under a material condition (Maximum Material Condition or Least Material Condition). However, since this is such a useful symbol, we will continue to add content and examples for other uses of this nifty little symbol in the coming months.

Application:

Although incorrect, we title this page and sometimes refer to the symbol as “True Position” since this is typically the term people are referencing when they are looking for the position tolerance. However, it is correctly termed in the ASME Y14.5 standard as simply “Position”. For clarity on these two terms check out our article and video here.

Datum Feature: Datums are theoretically exact points, axes, lines, and planes or a combination thereof that are derived from datum features. A datum feature is the tangible surface or feature of size (comprised of multiple surfaces or revolved surfaces) that is indicated by the datum feature symbol. You can think of them as anchors for the entire part. They are the surface or feature where the other features are referenced from. It is usually an important functional feature that needs to be controlled during measurement as well.

Datums are theoretical and only simulated by Measurement Equipment (Gauge pins, Granite slabs, angle plates, computer-generated planes, etc)

Datum Features are real, tangible features on a part where the measurement equipment would physically touch or measure.  They are usually important functional surfaces.

Profile of a surface: Profile of a surface describes a 3-Dimensional tolerance zone around a surface, usually which is an advanced curve or shape. If it is called out on a curved surface, like a fillet on a welded part, the entire surface where the radius is has to fall within the tolerance zone. Profile controls all the points along the surface within a tolerance range that directly mimics the designed profile. Any point on the surface would not be able to vary inside or outside by more than the surface profile tolerance. Usually, when surface profile is required, there are no tolerances on the dimensions that describe the surface and use the GD&T callout to give the acceptable range.

Application:

Profile is the catch-all symbol for surface control in Geometric Dimensioning and Tolerancing. If it cannot be controlled with another symbol, profile is your best bet. When used with datums it can control every aspect of a feature’s geometry which includes size, location, orientation, and form.

Flatness: Flatness is very straight forward. It is a common symbol that references how flat a surface is regardless of any other datums or features. It comes in useful if a feature is to be defined on a drawing that needs to be uniformly flat without tightening any other dimensions on the drawing. The flatness tolerance references two parallel planes (parallel to the surface that it is called out on) that define a zone where the entire reference surface must lie. Flatness tolerance is always less than the dimensional tolerance associated with it.

Used: When you want to constrain the amount of waviness or variation in a surface without tightening the dimensional tolerance of said surface. Usually, flatness is used to give a surface an even amount of wear or for sealing properly with a mating part. Commonly used on a fixture that must mate flush with another part without wobbling, but where orientation is not important.

Concentricity:

Concentricity, (called axiality in the ISO Standard), is a tolerance that controls the central derived median points of the referenced feature, to a datum axis.Concentricity is a very complex feature because it relies on measurements from derived median points as opposed to a surface or feature’s axis.

Used: Due to its complex nature, Concentricity is usually reserved for parts that require a high degree of precision to function properly. Transmission gears, which need to always be coaxial to avoid oscillations and wear, may require concentricity to ensure all the axes line up correctly. Equal mass or inertial concerns are one of the leading causes for the concentricity callout, however are often better designed with runout. In fact, in most cases, the use of runout or position should replace the need for concentricity and be much easier to measure.

Perpendicularity:

Perpendicularity is measured using a height gauge, similar to flatness, however, the gauge (or part) is locked to a 90° datum to measure how perpendicular the surface is. The entire surface has to be measured if it is a flat feature.

Used: Whenever two surfaces needing a constant 90° angle, Perpendicularity is effective. Flange bearings and critical square edges usually reference it. Perpendicularity is also commonly called out on the corners of cylinders where the flat bottom must be perpendicular with the curved sides.

Runout:

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