Drawing Standards

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School of Aerospace, Mechanical and Manufacturing Engineering

E

NGINEERING

D

RAWING

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TANDARDS

After creating parts and assembling them, you need to generate their drawing views. A 2D drawing is the life line of all the manufacturing systems because on the shop floor or tool room, a machinist mostly needs the 2D drawings for manufacturing.

This drawing standard establishes the conventions to be adhered to by engineering and drafting staff and students in the preparation, revision, and completion of engineering drawings. This manual sets forth the minimum requirements acceptable for the preparation of engineering drawings in RMIT University.

Below are the A3 and A4 drawings formats available in CATIA V5. These drawing templates will be translated into compatible formats and then loaded into CATIA default drawing files, for use in the relative environments.

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School of Aerospace, Mechanical and Manufacturing Engineering

D

RAWING TYPES

Assembly Drawing:

An assembly drawing is needed for all products that have more than one part. These drawings list all parts and sub-assemblies that make the final product. Each component is given item numbers and a BOM (Bill of Materials) on the drawing is created, listed each part number, part name, and part quantity.

Some of these drawings provide instructions on how to assemble the product at a manufacturing. Instructions may include information such as how to fasten parts together, or what types of lubricant to use. Part/Detail Drawing:

A detail drawing is the most important drawing in your fabrication work. A detail drawing gives all the dimensions, fabrication methods and types of materials required to manufacture the part.

When there is more than one component on a detail drawing the individual components are given item or part numbers ie Item 1, Item 2 etc. A BOM on the drawing is also necessary to specify

T

ITLE

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LOCK

The title block displays all the necessary and sufficient information for the exploitation of the document in the SAMME Engineering workshop.

The information required shall be as specified or referenced by items 1 through 12, below.

1) TITLE: The title should be as brief as possible but should contain sufficient information to categorize the

part properly and to distinguish it from other similar parts.

2) DRAWING NUMBER: Each drawing for detail part, assembly, etc., shall be identified by a number.

Start with the initials of the title followed by a dash, then add a P or a A (P and A stand for Part Drawing and Assembly Drawing respectively) and the revision number (001, 002, etc.)

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School of Aerospace, Mechanical and Manufacturing Engineering Example: You wish to make a drawing for a pressure vessel made up of pipes and flanges. The assembly drawing number would be: PS-A001 and the Top flange part drawing number would be TF-P001.

3) REVISION: After submitted your drawing and when modification is necessary, you need to increment

the revision number. You also should fill a row in the revision block. Thus, the drawing number will have to be updated accordingly.

4) NEXT ASSY: Enter drawing number on which the part is next utilized, modified, or assembled. In the

case of tooling drawings, in the Next Assembly block refer to a general note that states “This drawing is used to fabricate: (drawing number).”

5) “SH _ OF _”: Enter sheet number as applicable. (i.e. if a part or assembly drawing is made up of more

than one page)

6) SCALE: Enter scale.

Drawings shall be made to full scale unless the parts (or assembly) are too large to permit it or so small and complex that drawing to an enlarged scale is essential for clarity. When the main views of large parts are drawn to a reduced scale, the detail views “taken” to clarify detail should be made to full scale whenever possible. When the part has been drawn to an enlarged scale for clarity, it is not necessary to make an actual-size view. The scales preferred for engineering drawings are full actual-size 1/1, reduced 1/2, 1/4, 1/10, 1/20, and enlarged 2/1, 4/1, 10/1, 20/1.

7) DESIGNED BY: Enter designer's printed name.

8) CHECKED BY: Enter design analyst's printed name. This name shall be an independent name from all

other names on the drawing. It represents that the drawing has been checked against the parameters of this drawing manual and, where possible, to form, fit, function, and feasibility.

All drawings for issue to the SAMME workshop need checking by the Technical Design Officer prior to submission.

9) DOCUMENT TYPE: Assembly Drawing or Part Drawing as to be mentioned.

10) FINISH and HEAT TREATMENT: The finish surface and the heat treatment of the part shall be

identified here.

11) QUANTITY: Indicate here the quantity of parts needed.

12) ANGLE PROJECTION: The standard use of Third Angle projection is in place in

Australia.

Note: CATIA is a French software using European Standard projection (i.e. First Angle projection). You will need to change the projection method in the properties of the drawing sheet.

13) GENERAL TOLERANCING: If you don’t specify tolerances to your dimensions,

then these standards will apply. (See dimensioning and tolerancing)

Note: The use of the general tolerancing ISO 2768 – mK are in place in RMIT.

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School of Aerospace, Mechanical and Manufacturing Engineering

15) BILL OF MATERIALS: A bill of materials is a list of the raw materials, sub-assemblies, intermediate

assemblies, sub-components, components, parts and the quantities of each needed to manufacture an end product.

R

EVISION

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LOCK

Revisions in the field of drawings are made by deletion, either by erasure or crossing out (a series of parallel lines placed on the face of drawing over the deleted portions of drawing), by addition, or by redrawing (all delineations shall be made to scale). For each revision you have to enter the description of the modification, the date and the signature of RMIT staff assigned to approve.

DIMENSIONING AND TOLERANCING

The dimensions and tolerances that are placed on product design drawings are a necessary part of the language of technical drawing. They are the means by which a designer specifies and communicates details of the size and shape requirements of a product, to those who will manufacture the design, and to those who will inspect the product to determine its conformance to the design specification.

The three principal objectives of a system for dimensioning and tolerancing are:

- to enable designers to clearly and unambiguously specify the functional requirements of their design, - be consistent and compatible with the technology and practices in current use for design, manufacture and inspection and quality control, and

- enable products to be designed and produced efficiently and at minimum cost. Fundamental rules for dimensioning and tolerancing

- Each necessary dimension of an end product shall be specified. No more dimensions than those necessary for complete definition shall be given. The use of reference dimensions on a drawing shall be minimized. - Dimensions shall be selected to suit the function and mating relationship of a part and shall not be subject to more than one interpretation. Such dimensions are termed functional dimensions.

- The drawing should define a part without specifying construction and inspection methods. Thus, only the diameter of a hole is given without indicating whether it is to be drilled, reamed, punched, or made by any other operation.

- Dimensions should be arranged to provide required information for optimum readability. Dimensions should be shown in true profile views and refer to visible outlines.

- A 90º angle is implied where centre-lines and lines depicting features are shown on a drawing at right angles and no angle is specified.

- Each dimension should have a tolerance, except for those dimensions specifically identified as basic, auxiliary, maximum or minimum. The tolerance may be applied directly to the dimension (or indirectly in the case of basic dimensions), indicated by a note, or located in a supplementary block of the drawing layout.

- Dimensions for size, form, orientation, and location of features shall be complete to the extent that there is full understanding of the characteristics of each feature. Neither scaling (measuring the size of a feature directly from a technical drawing) nor assumption of a distance or size is permitted.

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School of Aerospace, Mechanical and Manufacturing Engineering - Geometry tolerances shall be specified where essential, i.e. in light of functional requirements, interchangeability, and probable manufacturing circumstances.

Geometric tolerancing

Geometric dimensioning and tolerancing (GD&T) is used to define the nominal (theoretically perfect) geometry of parts and assemblies, to define the allowable variation in form and possibly size of individual features, and to define the allowable variation between features. Dimensioning and tolerancing and geometric dimensioning and tolerancing specifications are used as follows:

- Dimensioning specifications define the nominal, as-modeled or as-intended geometry. One example is a basic dimension.

- Tolerancing specifications define the allowable variation for the form and possibly the size of individual features, and the allowable variation in orientation and location between features. Two examples are linear dimensions and feature control frames using a datum reference (both shown in the part drawing example).

Standards

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