Week 9:- 2D Detailing Challenge

1. what are the Drawing templates?

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

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

Drawing templates are change as par the company standards,

Drawing templates are provide by the customer at the starting of the project ,if not then we should finalize 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/latter(if its revision drawing)
7. Signature or name of drawn by, checked by, responsible engineer and approved by
8. Parts 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 angle at which an observer draw an object to convert it from 3D to 2D plane such as real object image to a plane paper is known as angle of projection. We usually use two angle of projection in the automotive industry:

• 1st angle of projection
• 3rd angle of projection

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

When we talk about planes of projection, we have 2 planes viz. horizontal plane (HP) and vertical plane (VP). When these planes are extended beyond their intersection line, we get 4 quadrants as shown in below image.

This means that we can assume that our object is placed in any one of these quadrants for the projection. The position of the object in the quadrant gives the name to the angle of projection. We can say that:

• Object in first quadrant: First angle projection
• Object in second quadrant: Second angle projection
• Object in third quadrant: Third angle projection
• Object in fourth quadrant: fourth angle projection

NOTE: To obtain the projection, we have to rotate the HP by 90deg in clockwise direction.

First angle projection: In this, we assume that the object is placed in the first quadrant or above HP and in front of VP. We obtain the top view below the reference line and front view above the reference line after rotating the HP by 90deg.

Third angle projection: In this, we assume that the object is placed in the third quadrant or below HP and behind VP. We obtain the top view above the reference line and front view below the reference line after rotating the HP by 90deg.

We usually use first angle and third angle projection method in the industry even though second angle and fourth angle projection methods are possible because, as mentioned earlier we have to rotate the HP by 90deg in clockwise direction to get the projection. So when an object is placed in second quadrant that is above HP and behind VP and we rotate HP by 90deg in clockwise direction, we end up getting top view and front view together above the reference line. Similarly in fourth angle projection we get top view and front view below the reference line. In industry we come across crucial drawings of the products which will become complex to understand if they were drawn using these two projection methods.

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

A design model is an idealized representation of a part design. However, the design model by itself does not fully define the design. Due to imperfections in manufacturing and inspection processes, physical parts never match the design model exactly. An important aspect of a design is to specify the amount the part features may deviate from their theoretically exact geometry (as defined in the design model).

Geometric dimensioning and tolerance, often referred to as GD&T, is a symbolic language used on engineering drawings and models to define the allowable deviation of feature geometry. The language of GD&T consists of dimensions, tolerances, symbols, definitions, rules, and conventions that can be used to precisely communicate the functional requirements for the location, orientation, size, and form of each feature of the design model. Thus, GD&T is an exact language that enables designers to “say what they mean” with regard to their design models. Production can then use the language to understand the design intent and inspection looks to the language to determine set up requirements.

The language of geometric dimensioning and tolerancing can be intimidating at first, but when used properly, it can yield many advantages:

• Standardized, international system
• More flexibility, particularly for complex shapes
• Allows cylindrical tolerance zones
• Datum are clearly defined
• Based on the fit and function of a part or assembly
• Eliminates the need for many notes
• Allows for more tolerance

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

According to ASME Y14.5M 2009 standard there are 14 symbols which we usually use but two symbols are scrapped off in ASME Y14.5M 2018. These symbols are categorized into 3 types:

• Form tolerances: Controls the shape of features and are often used as refinement of the size.
• Orientation tolerances: Controls the tilt of the feature and are always associated with basic angle dimensions. If applied to surfaces, orientation tolerances also control form.
• Location tolerances: Controls location and are always associated with basic linear dimensions.
• Profile tolerance: Locates feature surfaces. Profile is the most powerful characteristics of all and also controls orientation and form.

Straightness: Straightness actually has two very different functions in GD&T depending on how it is called out. In its normal form or Surface Straightness, is a tolerance that controls the form of a line somewhere on the surface or the feature. Axis Straightness is a tolerance that controls how much curve is allowed in the part’s axis. This is usually called out with an included call to maximum material condition. Both callouts are very different from each other!

Flatness: GD&T Flatness is very straight forward. It is a common symbol that references how flat a surface is regardless of any other datum 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.

Circularity: The circularity symbol is used to describe how close an object should be to a true circle. Sometimes called roundness, circularity is a 2-Dimensional tolerance that controls the overall form of a circle ensuring it is not too oblong, square, or out of round. Roundness is independent of any datum feature and only is always less than the diameter dimensional tolerance of the part. Circularity essentially makes a cross-section of a cylindrical or round feature and determines if the circle formed in that cross-section is round.

Cylindricity: The Cylindricity symbol is used to describe how close an object conforms to a true cylinder. Cylindricity is a 3-Dimensional tolerance that controls the overall form of a cylindrical feature to ensure that it is round enough and straight enough along its axis. Cylindricity is independent of any datum feature the tolerance needs to be less than the diameter dimensional tolerance of the part. Cylindricity essentially forms a perfect cylindrical boundary around the object that the entire 3-Dimensional part must lie in.

Profile of a line: Profile of a line describes a tolerance zone around any line in any feature, usually of a curved shape. Profile of a line is a 2-Dimensional tolerance range that can be applied to any linear tolerance. If it is called out on a surface, like a radius on a part – profile of a line would specify how much that cross-section could vary from a true curved radius. Profile of a line takes a cross section at any point along the surface and sets a tolerance zone on either side of the profile. The profile of a line callout can also be set with an all-around leader or given a specific range.

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.

Angularity: Angularity is the symbol that describes the specific orientation of one feature to another at a referenced angle. It can reference a 2D line referenced to another 2D element, but more commonly it relates the orientation of one surface plane relative to another datum plane in a 3-Dimensional tolerance zone. The tolerance does not directly control the angle variation and should not be confused with an angular dimension tolerance such as ± 5°. In fact, the angle, for now, becomes a Basic Dimension, since it is controlled by your geometric tolerance. The tolerance indirectly controls the angle by controlling where the surface can lie based on the datum.

Parallelism: Parallelism actually has two different functions in GD&T depending which reference feature is called out. The normal form or Surface Parallelism is a tolerance that controls parallelism between two surfaces or features. The surface form is controlled similar to flatness with two parallel planes acting as its tolerance zone. Axis Parallelism is a tolerance that controls how parallel a specific parts central axis needs to be to a datum plane or axis. The axis form is controlled by a cylinder around a theoretical perfectly parallel axis. Parallelism is most commonly called out as surface parallelism.

Perpendicularity: Perpendicularity in GD&T can mean two very different things depending on which reference feature is called out. The normal form or Surface Perpendicularity is a tolerance that controls Perpendicularity between two 90° surfaces, or features. Surface Perpendicularity is controlled with two parallel planes acting as its tolerance zone. Axis Perpendicularity is a tolerance that controls how perpendicular a specific axis needs to be to a datum. Axis Perpendicularity is controlled by a cylinder around a theoretical perfectly parallel axis. Pay close attention if a hole or pin is referenced since axis perpendicularity is commonly called out on these features.

Position: The Position tolerance is the GD&T symbol and tolerance of location. 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 GD&T “Position” Tolerance is how far your features location can vary from its “True Position”.

Concentricity: Concentricity, sometimes called coaxially, is a tolerance that controls the central axis of the referenced feature, to a datum axis. The axes for the datum and referenced feature are derived from the median points of the part or feature. Concentricity is a very complex feature because it relies on measurements from a derived axis as opposed to tangible surface or feature.

Symmetry: Symmetry is a 3-Dimensional tolerance that is used to ensure that two features on a part are uniform across a datum plane. An established “true” central plane is established from the datum and for the symmetry to be in tolerance, the median distance between every point on the two surface features needs to fall near that central plane. Each set of points on the reference features would have a midpoint that is right between the two. If you take all the midpoints of the entire surface, this must lie within the tolerance zone to be in specification. Symmetry is not a very common GD&T callout since it has very limited functional uses (centering location is done with Position) and the verification and measurement of symmetry can be difficult.

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.

Total Runout: Total Runout is how much one entire feature or surface varies with respect to a datum when the part is rotated 360° around the datum axis. Total runout controls both the amount of variation in the surface as the part is rotated, but the amount of variation in the axial dimension. Both radial variation and axial variation are measured and held within the tolerance. Total Runout is usually called on a part that is rotated about an axis where the entire surface is critical to be in spec.

Some other symbols which are used: