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There are two methods of producing engineering drawings. The most common way of drawing in engineering used to be done by hand on a piece of paper. These drawings were time consuming; they needed precision and skilful draftsman. They are still used because this is a quick method if we talk about simple sketches. On paper we can draw in different techniques that include isometric, oblique and orthographic.
During my first assignment I had to use the manual technique. In this paragraph I will explain what they are.
Oblique- This technique is based on showing the front of the object in 2D and the side and top in 3D. If we have a cube we will need to draw a square and to its right side measure 45°. This is where lines will go to create the side. Generally, I did not find it very difficult from my point of view. Oblique involves simple equipment such as pencil, ruler and a protractor. A drawing that is usually drawn in oblique contains its benefits and limitations such as we can see the full front of the object (advantage) or that it isn't good enough in architecture where most drawings are isometric which is harder (inconvenience).
Architectural drawing in Isometric (google.com)Isometric- Technique is slightly more complicated as it involves two 30° angles and if we want to draw an Isometric circle it appears to be quite hard. We will need the same equipment as in oblique however to draw an isometric circle we need a compass as well. The benefit is that we will see 3 Dimensions in more detail and it is suitable for architectural drawings. The limitation is that to draw some components in isometric more work needs to be done and it isn't easy for a beginner.
Orthographic- Orthographic involves 1st and 3rd angle projections however it is easy to draw because it is in 2 dimensions. The equipment is the same as in case of Isometric. The drawing itself is very nice and simple however more details are needed such as hidden lines or sections etc. Typical Orthographic drawing shows plan, front and the side. An advantage is that it contains a lot more details and it is therefore used in manufacturing for plans. The disadvantage is that you will not be able to see how it looks as a 3D object.
BELOW: equipment that can be used in the manual technique (google.com) Manually produced drawings are good because the drawer can develop his/her skills and it is suitable for quick sketching. We can just sit down with a piece of paper and a pencil and make an instant drawing. If we think back to the times where blue prints were used they were still done by hand. Manual drawings were very good however the drawer needed and still needs a lot of patience when producing a drawing not to make errors which may be disastrous for the project. Precision plays a big part in this type of drafting. We are in a higher risk of getting things wrong and if for instance the line is very thick rubbing it out will leave marks and the drawing will look not as professional. This may only spoil the neatness of drawing but we will look like an unprofessional drawer which is why it is so important to spend time and do something very well.
Drawings produced manually have an advantage because when an error is made then it can be rubbed out. During my assignment work where I was asked to produce engineering sketches done manually, I found that a drawing needs to be thought through rather than rushed. This gives the drawer more calmness and so he can do it in a very short time with minimum of mistakes. The manual technique is suitable for different paper formats but with any type of formats there need to be some scaling. If we were to produce a drawing of a car's engine it will be hard to put it on A4 paper so as finding paper that is big enough to draw the engine. Scaling is simply making the picture smaller by dividing the actual size by a number that will allow us to fit the engine on paper. Could be by 8 or 25 this will depend on the engine and the paper format as well. Personally, I have used scaling for few components such as the machine vice because the actual size wouldn't fit on A4 paper. The scaling may be used with all of the manual techniques which is a big advantage.
Manual technique is suitable for people without the knowledge of computers and software. It is therefore used in many cases. It is not used by professional companies mainly because if an error occurs which can happen within the manual technique then big sums of money can be lost. Another reason may be that everyone wants to be distinguished as a professional company who can afford a CAD drawer and so they hire a person to work on a computer rather than on paper. In fact any design starts with a paper drawn concept so originates from pencil and paper.
Drafting companies don't use manual drawing because of the fact that the customer requires a formal drawing in a simple format with many details and as much clearly as possible. It is a harder task in manual drawing because it will need to be though through several times and the drawing will require lot more time.
Summarising the manual technique is a good way to sketch things. The equipment needed to draw in this technique is simple to use and not expensive. The method gives us the opportunity to sketch in both 2 and 3 dimensions up to the choice. One thing that is a big unfriendly is the use of paper. This may or may not be a good reason but we need to remember about the environmental impact. The technique isn't going to be hard once we get used to it and practice as much as it is possible. It isn't a very popular technique amongst professionals one because they want to save time and the time is the money, they also want to look professional both in the eyes of their customers and the competition. Manual drafting offers flexibility to mistakes which can be corrected at any time but a problem may be that a CAD drawing can be carried on a memory stick or a CD. In terms of manual technique this isn't possible and the whole drawing needs to be carried around.
CAD is a short version of Computer aided drafting. The term can be used to describe software with which it is possible to produce engineering drawings. Producing drawings using CAD was one of my tasks for assignment 2. In this explanation I will try and talk about many different advantages and disadvantages of this technique.
CAD software is nowadays a vital tool for company with their own design department. It can also be used by individuals who understand how the software works. The main difference between manual drafting and using CAD is that there is no need for manual skills. Anybody with sufficient training can begin drawing variety of things in CAD. In the software we can draw in 3 Dimensions with the same projections as in manual technique. The software we have been using had a simple interface and after enough guidance by our experienced lecturer the software became very easy to use. Alternatively, there are many books which include details of options and FAQ.
ABOVE: Autodesk inventor screenshot (google.com) Software works by following user's commands. We have a library of standard components drawn and available to use. The commands include the very basic copy and paste and more complex such as chamfer or fillet. We can draw arcs and lines or circles and polygons. There are dimensions which we will have to enter or play around with a mouse. Before producing a drawing it is worth to set up a page of sufficient size. We can produce a template using this function.
An advantage of CAD software is that they don't take up space and carrying them can be done electronically. Program is stored on a computer and any produced drawings can be carried on memory stick rather than a bunch of other drawings. The drawing can then be printed out of any printing station to the desired format. Above all that there is the accessibility. The drawing can be emailed in an electronic form to any other device. It is very good because this way a lot of time is saved if any changes need to be made to the drawing. This is another aspect I found very useful at the time of using this software.
CAD software is very useful in making civil engineering plans. In mechanical and manufacturing sector, computer or a laptop can be connected to CAM manufacturing device and the plan will automatically be manufactured by the CAM machine. This minimises the costs of production. Software is expensive because it may cost up to £10.000 for a year plus qualified person who can use this program and in some cases providing training to the personnel. With time the investment will turn into profit. Mainly because high accuracy and flexibility and on the top of that there is time saved on data transfer and any changes amended.
Due to the fact that there are many CAD software on the market there is no easy answer on how the program works. As I have mentioned previously it works based on commands. These can be used to set up the layout of our page, the dimensions of the template and any other configuring options.
Set up can include things such as:
Extents- Setting up extents will limit the program to work to the page dimensions that we choose. If we want to work on A3 paper this needs to be slightly smaller than A3 paper itself so that it will be able to print the work afterwards.
Grid- We have a guidance of reference points in form of a grid. This is a set of dots which can be enabled or disabled when there is a need. With aid of this it becomes very simple to draw lines and angles.
Snap- Used to equalise the snap and grid to the same value, it is possible to turn it off. The function works by moving cross hairs on the screen.
The drawing command is very simple; it can be anything from drawing lines to circles. Usually for lines we specify a start point and the direction and using the numerical pad we enter the length or angle. In circles we can specify to choose the diameter or radius and enter its data.
Editing is also very simple so we can copy and paste, move rotate or trim or extend. The functions will vary depending on the software but these are usually the basic functions that all software contains.
Businesses use CAD software because of its profitability. It is reasonable for companies to invest money into software and hire personnel who know how to operate it. It may seem costly but there are many advantages and turnouts. We look more professional and the company is time efficient. There is no impact on the environment by not using bunches of paper. The drawing itself is more eco-friendly.
ABOVE: Architectural Drawing produced using CAD (google.com) The CAD software I have used for my assignments had many features that are needed in professional engineering. It contains a library of common devices such as a spring. There are also many types of gears and links. This is very significant because a feature can be picked out from the library and copied to our drawing. This way the time is saved because some components are already drawn.
We can solve problem of time consuming isometric drawing using CAD. This is because we have a protractor saying the angles of each line. We will get the exact angle and length of the line. If we were to make something of a round shape we can draw arc's which are simple to do using a program. In addition to that we can label many things on the drawing or annotate it automatically. Using labelling on an engineering drawing we can draw any text which could be the standards, name of the company and the draftsperson and so on and so forth.
Architectural companies may want software such as Autodesk inventor which is more suitable for their area of interest and could be used to create interactive plans and visualisations of buildings. For mechanical there is a special program called AutoCAD Mechanical which I have used personally. These programs are all related however they have different functions which are specific for the area of engineering such as the architecture. This is why a manufacturing company will not need software which will not be useful for them although it may be suitable for a specific product drawing.
There are negative points to CAD as there were to manual drafting. One of them is that to get this an investment must be made and if there is no turnout, then there is no need for it. If the company has it is treated more professionally however the software isn't just totally reliable because a skilled draftsman is needed which also costs money. Mistakes can happen and so they can be made using CAD as well. Wrong labels or symbols can have a major effect on the business.
We can see that both manual and CAD drafting techniques have good and bad points. CAD is more professional way of drawing however an idea starts from a piece of paper and a pencil which is manual so there are established connections between the two. Nothing is perfect and so these two techniques may not be suitable for something but they will do better in another task. The described CAD method does not require drawing skill from the user and it is more tolerant to mistakes because it will not be seen. Manual drawing requires more skills and uses paper which is gained from chopping down trees so it has an impact on the environment. The fact is that we are now in the 21st century and the world will develop as it started as a blueprint and developed to a piece of paper, from piece of paper it became more virtual. We will not predict what can happen to drawing techniques in future and we don't know how much time it will take to develop something new, something that is as popular as the two mentioned above. For the mean time the two ways of producing engineering drawings does its job very well.