Week 14 challenge

AIM : To assemble the Butterfly Valve by using the sub parts created and apply the GD&T to the Butterfly Valve assembly drawing.

Introduction:

Butterfly Valve:

• A butterfly valve is a valve that isolates or regulates the flow of a fluid. The closing mechanism is a disk that rotates. A butterfly valve is from a family of valves called quarter-turn valves. In operation, the valve is fully open or closed when the disc is rotated a quarter turn.
• The "butterfly" is a metal disc mounted on a rod. When the valve is closed, the disc is turned so that it completely blocks off the passageway. When the valve is fully open, the disc is rotated a quarter turn so that it allows an almost unrestricted passage of the fluid. The valve may also be opened incrementally to throttle flow.The image of Butterfly Valve is shown below

Applications of Butterfly Valve :

A Butterfly valve can be used in many different fluid services and they perform well in slurry applications. The following are some typical applications of Butterfly valves:

• Cooling water, air, gases, fire protection, etc.

• Slurry and similar services.

• Vacuum service.

• High-pressure and high-temperature water and steam services.

Geometric Dimensioning and Tolerancing (GD&T): 

• Geometric Dimensioning and Tolerancing (GD&T) is a system for defining and communicating engineering tolerances. It uses symbolic language on engineering drawings and computer-generated three-dimensional solid models that explicitly describe nominal geometry and its allowable variation. It tells the manufacturing staff and machines what degree of accuracy and precision is needed on each controlled feature of the part.
• GD&T is used to define the nominal (theoretically perfect) geometry of parts and assemblies, to define the allowable variation in form and possible size of individual features, and to define the allowable variation between features. There are several standards available worldwide that describe the symbols and define the rules used in GD&T. One such standard is the American Society of Mechanical Engineers (ASME) Y14.5.
• Any product is first designed by a design engineer, manufactured by a manufacturer, and is inspected by an inspector of the metrology department. For this process to work, all the professionals in this process must communicate effectively and efficiently in every step of the process in order to reduce the failure of parts and increase the accuracy. A CAD is perfect but there is no such manufacturing method that can replicate the exact CAD file into the physical world with perfection. This may lead to failure or disqualification of many parts during the inspection.
• To meet the design intent of the design engineer and make the process of manufacturing and inspection faster, proper communication is required. A CAD is perfect but the reality is not, which is why need to define by how far and in what ways our physical product can vary from the CAD model. GD&T is, therefore, applied to every engineering drawings before it goes to a manufacturer. Trying to get the perfect result or very tight tolerance increases the cost, so it is discussed with the customers on how much tolerance to provide for the parts.

Advantages of applying GD&T: 

• 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.

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

• 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.

• 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.

• 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.

Design procedure:

The Butterfly Valve consist of following components

• Body
• Shaft/Stem
• Disc
• Retainer
• Lever/Handle
• Nut

These parts are created separately and finally assembled in the assemble file. The creation of each parts and their application of GD&T are shown below

Body:

• The body is the housing for the internal components and it is the main part of the butterfly valve.
• The body connects to two pipes on its two sides and it regulates to flow.
• For the creation of this part, simple features like revolve, extrude, and move objects are used in the modeling application of NX. The image of Body is shown below.

Application of GD&T:

• For the application of GD&T on the part body, it is better to apply it once the parts are assembled it because will be connected to two pipes once the assembly is completed.

Shaft/Stem:

• It is another important component of the butterfly valve. It inserts into the body of the valve and sits perpendicular to the direction of flow.
• It holds the disc inside the body and is clamped with the lever outside the body.
• It is created using simple features like revolve and extrudes features in the NX modeling environment. The image of Shaft/Stem is shown below

Application of GD&T:

• After the part creation is completed, the drawing is created in the drafting application of NX, and GD&T is applied using the features of NX.
• For this shaft, position tolerance should be given to the holes which hold the disc.
• Then Profile of the surface should be applied to the surface where the disc sits.
• Then Position tolerance for the cylindrical body of the shaft with respect to the defined datums.
• Composite position tolerance is applied in the case of disc positioning holes as it repeats creating a pattern. The image of application of GD&T for Shaft/Stem is shown below.

Disc Plate:

• This disc plate is the main component of the butterfly valve which regulates the flow in the valve.
• The orientation of this disc determines the flow rate of the fluid. It is not perfectly circular, rather it is elliptical in profile.
• The holes in it help to position it properly on the shaft created earlier. A simple feature like extrude can create this part in NX. The image of Disc Plate is shown below

Application of GD&T:

• In order to apply GD&T for this part, the primary datum is defined on the surface where it comes in contact with the surface of the shaft.
• Then Perpendicular tolerances are applied as per the requirement.
• As the cost increases, while machining the entire contact surface, small circular datum targets are created and GD&T is applied in order to reduce the manufacturing cost.The image of application of GD&T for Disc Plate is shown below

Retainer:

• This part helps to retain or to fix the shaft with the body of the butterfly valve.
• It prevents the shaft from coming out of the body and keeps it in position for the proper functioning of the disc inside the body.
• The creation of the retainer plate involves only a simple feature like extrude in NX. The image of Retainer is shown below

Application of GD&T:

• For the GD&T application in the retainer plate, similar steps are followed as in the case of the disc.
• Primary, secondary and tertiary datums are defined properly as per the design intent.
• Then Datum Targets are applied to the holes.
• Perpendicular and position tolerances are applied in order to lock the DOF of the retainer in position.
• A profile tolerance is also applied to control the upper surface of the retainer. The image of application of GD&T for Retainer is shown below.

Lever:

• A lever is a handle that is used to rotate in order to regulate the flow. It is attached to the shaft with the help of a key to fixing it in position with respect to it.
• So when it is rotated, the shaft rotates which in turn rotates the disc and regulates the flow inside the pipe.
• It is created using simple features like extrude in NX after the proper base sketch is created. The image of Lever is shown below

Application of GD&T:

• For the application of GD&T on the lever, a section view is also created to show how different datums are defined and tolerances are provided.
• Position tolerance is applied to the proper holes.
• Then Perpendicular tolerance is applied to the first hole.
• In order to control the key slot, small tolerance is applied to the width of it.
• Profile tolerances are provided to the surfaces which come to contact with other parts as per the requirement. The image of application of GD&T for Lever is shown below.

Nut:

• It is the last part that helps to fix the lever in position with the stem.
• It allows to keep it in position or to disassemble whenever required.
• It is created using simple extrude and revolve features in NX. The image of Nut is shown below

Application of GD&T:

• In order to apply GD&T for this nut, the primary datum is defined on the surface which comes in contact with the lever.
• Perpendicular tolerance is applied to the hole or the thread and is defined as datum B.
• Size tolerance is also applied to the thickness of the nut. The image of application of GD&T for Nut is shown below.

SCREW:-

       This Screw helps to retain or to fix the Disc with the Shaft of the butterfly valve. It prevents the shaft from coming out of the body and keeps it in position for the proper functioning of the disc inside the body. 

Assembly:

• The assembly is created by first adding all the sub parts in assemble sheet in NX.
• Then the shaft and disc are joined together with the screws in place to create a sub-assembly.
• Then that shaft disc assembly is then assembled to the body.
• Then retainer plate is assembled with the body and screws are used to fix them.
• Then the lever is assembled to the shaft in a position that is then fixed.
• Then the nut is assembled with the shaft.The image of Butterfly Valve Assembly is shown below.

Isometric View:

Front View:

Top View:

Side View:

Application of GD&T:

• To apply the GD&T to this assembly, we need to apply it to the features which come in contact with the other parts and contribute to the positioning of the valve.
• In this case, all the required GD&T for individual parts have been applied already. Now it is applied to the assembly. Here, only the 3 holes on each side of the body come to contact with two pipes.
• So, the primary datum is defined as the surface containing 3 holes with the application of circular datum targets.
• Perpendicular tolerance and Position tolerances are applied to the respective holes in order to define secondary and tertiary datum and also a sub-datum D in this case.
• As the holes on the other sides should be aligned with the holes on one side, Position tolerance is applied to each hole with respect to the datum of the opposite holes.
• Flatness tolerance is applied to the primary datum.
• Then profile tolerance is applied to the other side of the body to control the Thickness of the body.The image of application of GD&T for Butterfly Valve Assembly is shown below

CONCLUSION:  Therefore, the Butterfly valve is created and the Geometric Dimensioning and tolerances are applied with the help of using NX 12 software.