1) Introduction to Technical Drawings
What are the technical drawings?
Technical drawings also known as drafting or simply as drawing is an act and discipline of composing one or more drawings that act as means of visual communication for the reader to know how a system works or is constructed. Technical drawings are extremely important and essential in our modern world due to the non-stopping rise of the things that are being manufactured and created. However, this raises the question that with more people creating things, and creating technical drawings it gets harder for people to quite understand it. This was true until something called ISO 128 came out. So what is ISO 128?
ISO 128 is an international standard that focuses on the general principals of presentation in technical drawings. This made drawings easier to understand thanks to the familiar symbols, perspectives, measuring units, page layout, notation systems, and the overall visual style. Therefore, regardless of where the engineer is, what language he speaks, he would probably be able to read the technical drawing as long as he is familiar with the standard that is used in the drawing.
How are technical drawings made?
There are various ways of creating a technical drawing such as:
– Sketching: which is probably the easiest and least accurate way of drafting a technical drawing; however, this does not mean that this method is not important. The freehand drawing is not intended as a finished work; rather, it is regarded as a quick way of recording an idea or making a simple presentation of what the final project would generally look like.
– Manual drawing (using instruments): this may seem similar to sketching; however, it is much more accurate, while using such engineering tools instruments as technical pens, rulers, drawing board…
– Computer-Aided Design (CAD): with the ever-growing technology, it is now possible to create a technical drawing using a CAD software. There are two types of computer-aided design systems that are used for the creating of technical drawings 2D and 3D.
Types of technical drawings
Technical drawings can be classified into two categories based only on the graphical projection:
- 2D representation: which uses orthographic projection in order to create an image where only two of the three dimensions of the object is seen.
- 3D representation: obviously it represents all of the 3 dimensions of the object. A three-dimensional representation is also sometimes referred to as a pictorial representation.
2) Examples of technical drawings
An engineering drawing is a type of technical drawing. It is also commonly referred to as engineering graphics. It is the manipulation of the designs of various components for example in a machine or a car. The engineering graphics mostly consists of engineering related components, the sketching of the exact dimensions all while using a scale if the image does not fit the page layout. In order to develop the design or the assembly of the machine, an engineering drawing is necessary, and that is why it is one of the most parts in mechanical engineering and modeling.
Fabrication drawing is a very special type of engineering drawing, and is still considered as a technical drawing; however, it is used for certain purposes and tasks. For example, after creating the design of a machine, it is the time to make the engineering drawing related to the machine. It includes creating separate drawings of each engineering part and component that makes the machine such as bolts, rods, pistons, cover… It should be mentioned that a fabrication drawing focuses only on the assembly of the machine. In other words, a fabrication drawing is an assembly drawing. The fabrication drawing includes all the materials necessary to assemble a product or machine. All the necessary weldments are represented in the form of universal weldment symbols on the top of the referenced documents that represent the stress relieving requirements for the fabrication process.
The items that would be used to make up the fabrication will also be identified with leader lines to balloons with their references and standard codes. Even though a fabrication drawing is associated with assembly, it can be divided into two categories:
- Single part drawing: which focuses on the cutting of metals and lists all necessary information.
- Assembly drawing: which provides all the necessary information for the welder in order to assemble the product or machine.
A shop drawing is a technical drawing that focuses on and speaks directly to the fabricator, manufacturer or constructor. A shop drawing includes a set of drawings required for prefabricated components such as dimensions, manufacturing and fabrication standards and other important details for the manufacturer, fabricator or supplier.
3) Advantages of and Disadvantages of technical drawings
Advantages of Technical drawings
There are plenty of pros and benefits of using technical drawings or any other form of drawing in general such as:
- It enhances the ability to understand what a product is, rather than relying on the memory to visualize how the product looks like.
- It breaks the language barrier between two or more engineers since technical drawings are using standards such as ISO, the speaking language of an engineering graph is no longer an obstacle.
- It provides the ability to see details that cannot be simply explained.
Drawbacks of technical drawings
- Creating technical drawings can be sometimes a dull task; especially without the use of a CAD software, it can be pretty challenging for new engineers and students.
- Correcting mistakes can be a challenging task without using the proper tools and equipment.
- A technical drawing made according to the ISO standard may not be easy to understand for an engineer who is used to ANSI standards.
In conclusion, all technical drawings are important. The choice of each drawing depends on the user’s requirements. If a user or customer only wants to see an overview of what the product would look like, then a simple sketch is enough. and if the product would be fabricated or manufactured, then other technical drawings such as fabrication drawing or engineering drawing are necessary.