The world over, industries recognize the importance of standardization. Correspondingly, today, there are thousands of standards, authored and approved on an industry-wide basis or developed by individual organizations. The wave of standardization has not missed the computer-aided design (CAD) space. Here, there are tens of CAD standards whose deployment has proven beneficial to both large and small engineering, architectural, and design firms.
The consensus of opinions and experiences points to factors such as efficiency, uniformity, and continuity as some of the drivers behind the decision to adopt such standards. But the benefits are much more. And while CAD standards offer numerous advantages, their implementation can be challenging, too. So, in navigating the world of CAD standards, this comprehensive guide will discuss what CAD standards are, their history, benefits, and challenges. This article will also discuss the commonly adopted CAD standards worldwide.
Table of Contents
History of CAD Standards
Formative Years of Engineering Drawing Standards
Just as hand-made drawings paved the way for computer-aided design (CAD), so too did they create the necessity for standardization. As George Dunham, a member of the Society of Automobile Engineers (SAE) (which later became the Society of Automotive Engineers), lamented in a 1913 paper, “There are probably not five men in the whole Society who use the same system of drawings.” His lamentation was against a backdrop of several problems he had come to associate with a lack of a standardized system.
He had observed that drafting technicians and members of the Society would constantly move from one automobile or parts manufacturing factory to another. And every time they made this shift, they would have to learn and adopt the new factory’s way of producing engineering drawings, effectively changing what they had previously become used to. Unfortunately, this meant that they used (or perhaps more accurately, wasted) a lot of time learning the new system. And obviously, the chances of committing errors were high. The abundance of numerous systems also meant that they crammed a lot of unnecessary information into their brains.
Early Standardization Suggestions
Dunham, however, went beyond lamentations. He expounded on a suggestion – which he had made earlier – on how the SAE should go about standardizing automobile drawings. After all, he wrote, he had already practically deployed his suggested system as an employee at a factory. The suggestion covered the following 15 items:
- Size and arrangement of sheets
- Arrangement of views on the drawing and method of projection
- Character and weight of the lines on a drawing
- Style and size of lettering and numerals
- Abbreviations for names of materials
- Method of making records of alterations
- Style of letter and placing of finish marks on drawings
- Methods of dimensioning
- Methods of noting working limits or tolerance
- Location of general notes on the sheets
- Positioning of the diameter and length of undercut notations
- Nomenclature of parts
- A standard note for tap and die sizes
- Checking instructions
Of course, there is a preponderance of discussions on standardization of parts in early – pre-20th century – literature. However, Dunham’s is the earliest documentation we could find of the standardization of engineering drawings. Years later, and even with technological advancements, his suggestions form the basis of today’s CAD standards.
Fragmentation of Engineering Standards
Concurrent with Dunham’s pursuit for standardization, the American Society of Mechanical Engineers (ASME), founded in 1880, was also hard at work. In 1914, ASME published the first national standard for engineering drawings called the Standards for Cross Sections. It then followed that up with the 1915 publication of the Standards for Engineering Drawings. (We did not find evidence showing that SAE came up with its in-house set of standards for engineering drawings.)
Across the Atlantic, European countries were also working on standardization. In 1922, Germany’s standards body, DIN, published DIN 6, a standard that contained guidelines on engineering drawings concerning views, sections, and special representation methods. DIN 5-10 also contained rules on technical drawings, primarily around projections and terms. In Britain, Europe, the British Standard Institute (BSI) published the first British Standard for Engineering Drawing Officer Practice, BS 308, in September 1927.
Thereafter, these national standards were individually revised to reflect updates. But even then, they were largely only recognized as national standards. As years wore on, however, the national standards bodies started joining the International Organization for Standardization (ISO), which was formed in 1947, as members. (ISO has been publishing its standards since.)
Harmonization under ISO Standards
Thus began a trend whereby the bodies withdrew some standards relating to technical drawings in favor of implementing ISO drawing standards. But the withdrawal was not immediate.
The BSI, for instance, resolved to transfer the UK totally to the ISO standards base in 1999. Currently, in Germany, DIN standards are only used in cases where no ISO standards exist. Additionally, members of the CEN (the European Committee for Standardization) and CENELEC (the European Committee for Electrotechnical Standardization) can approve the adoption of ISO standards, with conflicting in-house standards withdrawn.
The passage of time also birthed innovations that drawing standards could not ignore. In January 1995, ASME published the Y14 5.1M Mathematical Definition of Dimensioning and Tolerancing, which created explicit definitions for use in CAD and computer-aided manufacturing (CAM). Later, in August 2000, BSI created and published BS 8888, designed to accommodate all technical changes in development and any future changes.
Understanding CAD Standards
CAD standards are sets of rules that govern how professionals or students create, document, and deliver CAD drawings. They specify drawing requirements and techniques, appearance, and record-keeping methods. CAD standards can also include how-to instructions and technical definitions directed at designers, manufacturers, engineers, and users. They eliminate the unnecessary.
For simplicity and in layperson’s terms, you can think of a CAD standard as an agreed-upon, uniform way of creating and presenting 2D drawings and 3D models using CAD systems. The standard codifies the process of creating these plans and design documents. It also builds a standardized library of symbols and templates that professionals can easily access, increasing efficiency and consistency.
There are two types of CAD standards:
- Those that have an industry-wide reach and are developed by recognized/accredited standards bodies such as ASME, ISO, DIN, and more
- Localized CAD standards that companies or learning institutions develop to meet their unique needs. (If you intend to pick this second option, Autodesk has created a complete guide to developing CAD standards, outlined the stages of developing CAD standards, and discussed how to build BIM standards.)
Regardless of the choice, the bottom line is that everyone producing CAD drawings should use CAD standards.
CAD standards encompass a variety of areas, including:
- Uniform file naming conventions
- Organization and naming of layers
- Standardized detail block assets, e.g., title blocks, approval, and revision blocks,
- Various forms of documentation, such as document types, terms relating to technical drawings, and design for manufacturing, assembling, disassembling, and end-of-life processes
- Font styles and sizes
- Method of recording revisions
- Methods of dimensioning
- Notes and checking instructions
- Size and arrangement of sheets
- Weight of the lines on the drawing
- Part nomenclature
- Annotation rules
- Color of lines
- Units of measurements
- Plot styles and plotting
- Graphical symbols
Commonly Adopted CAD Standards
1. ISO CAD Standards
The International Organization for Standardization (ISO) is an international nongovernmental body comprising 168 national standards bodies. It develops and publishes international standards for use in numerous industries, including CAD. Examples of ISO drawing standards include:
- ISO 5455:1979, which indicates recommended scales, gives definitions for scale types and relevant terms and designates their use in any engineering field
- ISO 5456 Parts 1 to 4, which cover projection methods used in technical drawings
- ISO 128 Parts 1 to 20, which outline the general principles of presenting technical drawings. It was first published in 1982 and revised severally between 1996 and 2003. As a result of the revisions, Part 1 of the standard, ISO 128-1:2003, could be applied to both manual and computer-based drawings. ISO 128-1:2003 has since been revised by ISO 128-1:2020, which gives rules for the execution of technical 2D and 3D drawings.
- ISO 13567 Parts 1 and 2, which establishes the general principles of layer structuring within CAD files
- ISO 29845, which defines document types, including drawings prepared in CAD systems
2. American National Standards (ANS)
In the United States, the American National Standards Institute (ANSI) is mandated with the development of standards. The body was founded in 1916 when ASME, the American Institute of Electrical Engineers (now the Institute of Electrical and Electronics Engineers), the American Society for Testing and Materials (now ASTM International), and the American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME) came together to form an impartial national body to oversee the development of national consensus standards.
ANSI accredits the procedures of standards-developing organizations such as ASME and IEEE and approves their documents as American National Standards (ANS). The body is also a member of ISO and promotes the use of US standards internationally. In addition to ASME and IEEE, ANSI has also accredited bodies such as the American Welding Society (AWS) and SAE to develop ANSs.
American Society of Mechanical Engineers (ASME) Standards
Some examples of CAD standards developed by ASME include:
- ASME Y32.18, Symbols for Mechanical and Acoustical Elements as Used in Schematic Diagrams, contains symbols and definitions used in creating schematic diagrams for mechanical and acoustical systems
- ASME Y14.1, Decimal Inch Drawing Sheet Size, and ASME Y14.1M, Metric Drawing Sheet Size and Format, contain information on the border and what can be included in the title block. This standard can be used in electrical, electronic, mechanical, structural, and architectural drawings.
- ASME Y14.31-2014, Undimensioned Drawings, provides the requirements for undimensioned drawings that graphically define objects with true geometry views and predominantly without dimensions.
- ASME Y14 5.1M, Mathematical Definition of Dimensioning and Tolerancing,
- ASME Y14.35, Revision of Engineering Drawings and Associated Documents, which defines the practices for revising drawings
- ASME Y14.4M, Pictorial Drawing, defines and illustrates the different 3D views and representation practices used on engineering drawings
- ASME Y14.5, Dimensioning and Tolerancing, establishes uniform practices for stating and interpreting dimensioning, tolerancing, and other related requirements when creating or using engineering drawings
- ASME Y14.3, Multi and Sectional View Drawings, governs sectioning techniques
- ASME Y14.2, Line Conventions and Letterings, which covers, among others, principles of section and cutting plane lines
- ASME Y14.6, Screw Thread Representation, outlines thread design guidelines
- ASME Y14.8 gives guidelines for the drafting of castings and forgings
Institute of Electrical and Electronics Engineers (IEEE) Standards
Examples of IEEE CAD standards are:
- IEEE 315, Graphical Symbols for Electrical and Electronic Diagrams, which defines symbols used in the design of electrical and electronic diagrams. Usually, CAD systems come with a symbol library or template designed to IEEE standards.
- IEEE 690:2018, Design and Installation of Cable Systems for Class 1E Circuits in Nuclear Power Generating Stations
American Welding Society (AWS) Standards
Below are two examples of AWS CAD standards:
- AWS A2.4, Standard Symbols for Welding, Brazing, and Nondestructive Examination, which covers welding and weld symbol sizes, which you can use to design a weld symbol library using CAD software
- AWS ARE-5 Design for Welding
United States National CAD Standard
In 1997, a group of organizations comprising US Coast Guard, the National Institute of Building Sciences (NIBS), the Sheet Metal and Air Conditioning Contractors National Association (SMACNA), the Construction Specifications Institute (CSI), the American Institute of Architects (AIA), and the CADD/GIS Technology Center (CGTC) formed US National CAD Standard (NCS).
The NCS simplifies and streamlines the exchange of building design and construction data throughout the life of a facility. It comprises layer and plotting guidelines and a uniform naming system. The US National CAD standard primarily applies to the architectural and construction disciplines.
An important point to remember is that ANSI has not accredited or approved NCS. It is, therefore, not an ANS.
3. European Standards (EN)
National members of CEN and CENELEC implement European Standards as national standards. What this means is that a proposal to develop an EN is made through the members, accepted by the relevant Technical Body or the Technical Board, drafted, passed through a public inquiry, adopted by way of a weighted Formal Vote, and, finally, published. Then, all member countries give the published EN the status of a national standard.
Such a standard will, therefore, bear the member country’s acronym, such as DIN (Germany), BS (British), or OENORM (Austria), etc., the EN designation, and the standard’s numerical classification. To illustrate this, take the example of the European standard EN 9300-012:2013, which covers Long Term Archiving and Retrieval of digital technical product documentation such as 3D, CAD, and PDM (product data management) data. The standard is published as DIN EN 9300-012:2013, BS EN 9300-012:2013, UNE EN 9300-012:2013, and NBN EN 9300-012:2013 in Germany, Britain, Spain, and Belgium, respectively.
Importance of Implementing CAD Standards
The following benefits back the implementation of CAD standards:
- CAD standards increase efficiency and save time, as users do not waste time learning new systems of designing or modeling, or interpreting designs created using systems with which they are not familiar.
- They reduce the chances of making mistakes because they define every important detail
- They ensure all parties easily understand the contents of design documents. For instance, users can easily interpret graphical symbols for electronic and electrical systems, welds, and mechanical and acoustical systems because of the uniformity that accompanies using CAD standards.
- The standards promote compatibility with existing CAD documents
- CAD standards ease collaboration between various parts manufacturers and original equipment manufacturers (OEMs)
- The standards promote consistency and continuity in that the drafting and design style is unimpacted even when a group of employees leaves the company and is replaced by a new group
Challenges in Implementing CAD Standards
While CAD standards are beneficial, their implementation can present a few challenges, including:
- CAD standards are regularly revised, with the previous versions withdrawn. But why do standards organizations revise the standards? The revisions ensure the standards stay relevant to technology developments and user expectations. However, this often means that you have to constantly check whether the standards your company or school has adopted have been revised.
- Industry-wide CAD standards are not free. They are available for sale through the national or international standards organizations or approved agents. Given that you may require a number of CAD standards to compile your company’s or school’s standards, the cost can add up quite considerably.
- Coming up with localized organization-oriented standards involves a lot of hard work
Engineers, architects, designers, contractors, and other professionals agree that everyone who produces CAD designs or models should use CAD standards. The choice of the exact CAD standard to employ will, of course, vary from organization to organization based on location and industry. Often, it is confined to the primary standards, which include international standards like the ISO or IEC, or regional/national standards, e.g., EN, BS, ASME, IEEE, DIN, AWS, and NCS. Organizations can, however, choose to develop their own CAD standard.
Regardless of what you end up selecting, the benefits will more or less be the same. CAD standards increase efficiency and save time, reduce the chances of making mistakes, promote continuity, enhance compatibility, and make designs easy to understand. But the implementation is not without a few challenges, including cost, regular revisions, and the hard work involved in developing localized standards.