Project

Assemble and apply GD&T to the butterfly valve assembly drawing

UUlsa Sandeep28 Mar 2023

OBJECTIVE

The objective of this project is to design a butterfly valve and apply GD&T to it's components and final assembly using CATIA V5.

INTRODUCTION

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 shaft. 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.There are different kinds of butterfly valves, each adapted for different pressures and different usage.

Here after modelling various components of the Butterfly valve, GD&T (Geometric Dimensioning & Tolerancing) is applied to each component and final assembly.Geometric Dimensioning and Tolerancing (GD&T) is a system for defining and communicating engineering tolerances. It uses a 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 American Society of Mechanical Engineers (ASME) Y14.5. This article is based on that standard, but other standards, such as those from the International Organization for Standardization (ISO), may vary slightly. The Y14.5 standard has the advantage of providing a fairly complete set of standards for GD&T in one document. The ISO standards, in comparison, typically only address a single topic at a time.

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.

Application of GD&T:

General Approach to Applying GD&T to a Design Model

In order to understand a qualitative application of GD&T to a production environment, one must understand the design model. A design model consists of a collection of geometric shapes, referred to as features. In a completed design, the geometry of the feature must be defined and the deviation of its geometry attributes (e.g., location, orientation, size, and form) must be constrained. There are two common approaches to constraining the deviation of the geometry attributes of the features in the design model. GD&T may be applied to each feature based on how the part functions or it may be based on how the part is manufactured. It is generally considered best practice for application of GD&T based on part function.

Step 1: Application of GD&T with established Datum Reference.

The first step in applying GD&T to a design model is to establish a datum reference frame (DRF). The first datum reference frame that is established is called the predominant datum reference frame. In a functional approach to GD&T, the surfaces that orient and locate the part in its assembly are typically used as the datum features that are used to establish the predominant DRF. There are also additional considerations for datum feature selection:

Manufacturing considerations – You may choose to select the surfaces that orient and locate the part in the machining fixture as the datum features.
Inspection considerations – You may choose to select the surfaces that orient and locate the part during the inspection process as the datum features.

Step 2: Application of GD&T to constrain attributes of features

Once the predominant DRF has been established, you can use GD&T to constrain the geometry attributes of each feature in the model with respect to that DRF based on function. In complex parts it may be necessary to establish multiple DRFs, but ultimately all features in the part must be constrained, either directly or indirectly, to the predominant DRF.GD&T Advisor software by Sigmetrix, provides convenient tools for defining the features on your part, applying GD&T to those features, and then evaluating each feature and the applied GD&T on the feature to determine whether all of the geometry attributes of the feature are fully constrained.

The table below shows the geometric characteristic symbols that are used to specify the geometric limits of deviation for a feature in the ASME Y14.5M-1994 standard.

COMPONENTS OF BUTTERFLY VALVE

Various components of butterfly valve and GD&T applied to them are shown below.

1. BODY - BUTTERFLY VALVE

Butterfly valves are usually fixed between two pipleines using flange couplings. Body of our Butterfly valve and GD&T applied to the same using CATIA V5 are shown below.

2. STEM - BUTTERFLY VALVE

The disc/plate, lever and nut are assembled to this shaft.

3. DISC - BUTTERFLY VALVE

When valve is fully opened or closed the disc is rotated a quarter turn.Disc is mounted on shaft. 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.

4. LEVER - BUTTERFLY VALVE

Lever is mounted at an end of shaft outside the body. Hand lever is usually used in small sized Butterfly valves. It is used to open or close the valve.