Week 14 challenge

Objective:     

• To design of Butterfly Valve in appropriate dimension with the application of GD&T - ASME Y14.5 2009.
• To assemble all the individual parts of the butterfly valve by assigning suitable constraints.
• To understand the concept of geometric tolerance and dimensioning. 

Softwares Used

• Siemens NX 2019

Introduction

        Siemens NX 2019: NX, formerly known as "Unigraphics", is an advanced high-end CAD/CAM/CAE, which has been owned since 2007 by Siemens PLM Software in 2000.

It is used, among other tasks, for:

Design (parametric and direct solid/surface modeling)
Engineering analysis (static; dynamic; electro-magnetic; thermal, using the FEA method; and fluid, using the finite volume method).
Manufacturing finished design by using included machining modules.

     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.

        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 

Parts of Butterfly Valves

• Butterfly valve body 
• Shaft
• Disc Plate 
• Lever
• Retainer 
• Nut

Commands Used

• Line: This feature allows us to create a straight line. The line can be a solid line or a construction line.
• Circle: This feature allows us to create circles.
• Rectangle: This feature allows us to create squares or rectangles.
• Arc: This allows us to create an arc.
• Trim: This is used to trim sketches.
• Extrude Bose: This feature allows us to create solid bodies.
• Revolve: Revolves add or remove material by revolving one or more profiles around a centreline. You can create revolved boss/bases, revolved cuts, or revolved surfaces. Axis of revolution can be 3d sketch.
• Circular Pattern: This allows us to create a pattern in a circle
• Fillet: This is used to create circular edges.
• Hole: A Hole feature is used to create holes on the model.
• Unite: Unite is used to convert two or more solid bodies into one solid body.

assembly

After the design, all the models should assemble with appropriate constraints. The assembly is created by first placing the body in position and mating other parts to it with the application of different joints provided in NX. First, the shaft and disc are joined together with the screws in place to create a sub-assembly which is then joined to the body in position. The retainer plate is then mated with the body and screws are used to fix them. After that, the lever is mated to the shaft in a position that is then fixed after the nut is mated with the shaft.

Features used to Assembly 

• Infer Axis/center
• Touch Align
• Concentric 
• Move Component 

Methodology

The Assembly file is opened in NX CAD.

The above parts are added to the assembly file.

Now, one by one part is assembled using the Move part command and assembly constraint command.

Different constraints are used to assemble butterfly valve, such constraints are Infer Axis, Touch, Align.

Finally, the assembly of the butterfly valve is saved in the folder where all the other parts are saved.

Drafting Methodology

• Datum target area A1,A2 and A3 is given to the ears of the butterfly valve.
• Datum target area A2 and A3 is given with perpendicular tolerance and Position tolerance respectively.
• Sub datum D is given to the third ear.
• Finally, other tolerances are given to the surfaces and features of the Butterfly Valve.

Conclusion

In this project, a butterfly valve is designed and assembled in parametric CAD software, Siemens NX. GD&T according to ASME Y14.5 is applied at every stage of the part design process in order to make the communication with the manufacturers effective and efficient. Hence, a design process in a real industrial manner is followed in this design of butterfly valve understanding the design process more with the application of GD&T with industrial standards.