Unit 16 Report
Benefits and limitations
CAD has many reasons as to why it is now used so heavily in design and manufacturing, this is due to the precision, flexibility, established drafting standards, efficiency and the ability to modify the drawings. All these are great tools compared to manually drawing , this can cut out a lot of time and using CAD also ensures that the drawings are drawn 1:1 and with no tolerance, this means that for the manufactures it is a lot easier to make as there is no faults in the drawing and it can provide many views with all the dimensions required, it can also show assembly drawings of the parts that you are making, showing how it all fits together with key just the key dimensions making it easier for whoever is manufacturing the product.
One of the main reasons that CAD is a big advantage over drawing by hand when designing products is that you can change the dimensions of your products and modify it if it goes wrong, this gives an advantage over drawing it by hand because if you dimension the product wrong you have to start all over again whereas on CAD you can just undo what you did and correct the mistake, CAD also allows you to draw perfectly at a 1:1 scale. This is an advantage for the people modelling the product as they don’t need to think about fitting it on one page and if they have to scale up or down to make sure that it fits on the page. As CAD can get 100% accuracy on all the measurements it could help the company save a lot of time as it wouldn’t take anywhere near as long as it would to draw up the model with correct measurements and dimensions this can save money for companies if you’re running against a deadline or need to get a drawing into a meeting to be shown and this is why CAD is used a lot more frequently over drawing manually.
With the use of CAD you can manipulate the view of the product as you can spin it round to see all aspects of the products to make sure that everything is correct on the product. This allows you to see every aspect of the drawing and in 3D so when presenting your ideas to a company instead of showing them 2D formal and informal drawings you can show them what it is actually going to look like by spinning the model round and rendering it on CAD to show them what the product would look like when actually manufactured. It is good to use drawings and modifications because if it goes wrong you can modify the drawing instead of starting again which will save you time when producing a drawing of a product, which is a benefit compared to if you were drawing it by hand because if it went wrong when drawing it by hand, you would either have to start again or rub it all out this can create smears and make the drawing messy and could make it hard to read as people could confuse different lines and then it could end up getting made wrong, this is why the use of modification is so useful for companies to have . It’s also a lot faster to create the drawings on CAD and with better accuracy than drawing it by hand. CAD also has many features that can allow the program to give the same level of detail on the model compared to drawings such as the section view tool which allows you to virtually cut open your model to see what it the parts are going to look like inside the model, this can help designers visualise what the part is going to look like and help them understand what they need to be doing when making it, this can also be done whilst on the 3D model so the manufactures can actually see how all the parts look and fit together rather than just on a drawing.

Limitations of CAD are that the software often consumes large amounts of computer processing power. This requires high-quality computer hardware that can be costly, the cost of hardware is a significant disadvantage of CAD. Software Complexity is another disadvantage of CAD because as CAD software advances, it becomes more flexible and adaptable. However, this comes at the cost of making the software more complex. This complexity makes it more difficult for first-time users to learn the software, combined with the cost of training personnel in CAD it can be very costly for a company and if they are only a small company, they may not have enough money to buy the packages so it would be better for them to draw their products, although it may take longer to produce the models it would be beneficial in the long run as it would get the company started off. Most of the CAD programs also have to be renewed monthly to allow the company to keep the licences this can be another few grand on top of the payment at the start. Another disadvantage of CAD is that with the many updates that it comes with the staff need constantly training to keep up to date with the program and so that the company can keep up to speed with all the other competition. CAD also struggles with some shapes, which are a bit obscure, this can limit the designs that companies might want to produce and this can lead to CAD leading the designer because CAD can only do certain objects and produce them in certain ways it can make the designer change the way he might want to of modelled the product and letting CAD take over the design this is a disadvantage compared to drawing manually because when you draw manually you can draw every shape and produce more fluent shapes which are not heavy influenced by CAD, this allows designs to be more unique and individual, as they are not limited to a number of shapes, this could influence the company to produce the product more if they are unique to them, which is an advantage of drawing over using CAD.
Advantages of informal drawings are that they can be used
Importance of working to recognised standards
ISO B8888
It is always better to make the drawings as per some recognised standard. The engineering drawings normally use letters, symbols and short forms to make the drawing more readable. To avoid any confusions to an external party (a component supplier company - it could be even from another country, or even the customer) regarding the meaning of these symbols, notations short forms etc. Also, making a standardised format for drawings make it easy for anyone to understand the drawing. They can easily understand where to look for the Title block, Notes general tolerances etc…
Many objects have complicated interior details which cannot be clearly shown by means of front, top, side, or pictorial views. Section views enable the engineer or detailer to show the interior detail in such cases. Features of section drawings are cutting-plane symbols, which show where imaginary cutting planes are passed to produce the sections, and section-lining (sometimes called cross-hatching), which appears in the section view on all portions that have been in contact with the cutting plane.
Very important as in CAD system it is often easy to see part of the drawing on the monitor but when drawing is printed in hard copy the print can be too small to read. People can be prevented from using multi-coloured lines to mean something on the drawing. Again does not print well and may be interpreted wrongly by other people. The point at which an assembly drawing needs to be broken down into more detailed drawings will be better controlled. Parts lists will be in accordance with one type of system for appointing parts numbers on the drawings. This will support the concept of one integrated well managed company, not a group of uncoordinated people.
Different component drawings coming from different design engineers will be consistent, readable and understandable for the reasons given above. This will reduce manufacture of wrong or faulty components with consequent loss of profit.
Another reason why it is important to work to recognised standards is that different component drawings come from different design engineers and using standards means that all drawings will be consistent, readable and understandable for the reasons given above. This will ensure that one consistent inspection regime will be able to handle many types of different components, resulting in economies of scale and saving in inspection times resulting in better profit margins.
Also departments will have confidence in quotations from subcontractors as they will know that each sub-contractor has received the same type of drawings that are consistent within themselves. There should be reduced errors in misunderstandings leading to claims by subcontractor for more money. A question on detail from one contractor will apply to all. There will not be many different questions because of different types of drawing layouts or content. It also allows much better traceability or changes over time. One system will support the tracking and recording of changes much better than if there was no system in operation. The management of change over time is critical and is possible only with one consistent standard being used over time.
How formal drawings would be used The main purpose of formal drawings is that they are given to the manufacturers to produce the part or product from the drawing. A formal drawing provides the manufacturer with all the information that they need in order to make the product such as the dimensions, the material, finish and tolerance. All of these features are added onto the drawing to make it as seamless as possible for the manufacturer when extracting information from the drawing to make the product.
The main drawing gives the manufacturer an idea of what the product should look like, most drawings are drawn with several views usually a drawing has a view of each different angle of the product for example a front facing view, side, top and bottom. Formal drawings can be drawn in two different projections, first angle or third angle. Each projection provides the same views of the drawing it’s just how the views are laid out that changes. As you can see from the picture the when drawing first angle you look as what you see on the left side of the product which in this case is the circle and then you draw that view the opposite side, third angle is where you look at the side you want to draw and draw it on that side. Drawings can be denoted by that symbol letting the manufacterer know which projection the drawing was produced in, this can help them when making the product as they can see which way round the product needs to be and it ensures that the produt is made correctly.
When using the formal drawings the manufacture should be able to see what tolerance there is on the product, this is found in the title block which is shown by a ± symbol followed by the number the drawings must also follow the tollerance so that it provides an accurate representation of the product. This means that there is no error when producing the product as the tollernace will be specified in the title block and they can also see it in the drawing. The formal drawing should also be drawn to a scale, scales are usually decided on depending on whther or not they drawer can fit the product on the page. If it is a small product and they have plenty of room on the page, it makes sense to draw the product at a scale of 2:1 making it twice as big, this ensures that whoever needs to read the drawing can see it and hs a clear view of what it looks like. However all drawings must have the correct 1:1 dimensions on even if drawn 2:1 otherwise the product would be made twice as big as meant its to be.
Dimensions is another part of the drawing when being used to create the product. Dimensions are the key element to the drawing as without them the maunfactures wouldnt be able to make the product as they wouldn’t know what the sizes where for each part. Dimensions also follow rules when using them in which you lay out the arrows and numbers and the way the arrows and numbers are drawn themselves for example the arrows must be twice as long as they are thick and the dimensioning lines must nt touch the acctual drawing, this is because when handed down to the manufacturer they might mistake the dimensioning line for a part of the product, so there must always be a slight gap. Also when stating the dimensions the numbers must always be in the middle of the line so that it is easy to read and depending on the scale to which you have drwn they must be a certain height. There are different symbols used when dimensioning to denote certain features to a drawing for example this symbol Ø is used when specifing a diameter of a circle and a Ɍ is used when specifying a raduis, if these where not used the maunfacturers would not know whether the dimension you put down was for the diametre or the radius. Staying to correct dimensioning means that it is easy to read them and people don’t have to work out which dimension is for which part and it is also crutical for them to be able read it correctly as it ensures that the product is made correctly to which it is specified.
The title block is one of the main features to producing the product from the drawing, it gives all the essential information as to what materials need to be used with the finish, it alos provides informaion as to who drew it and cheked it along with any notes or when the drawing was changed. All these help when the drawing is passed down as it means that the manufactures don’t need to ask many questions about the product and if the title block supplies the right information they should just be able to make it. It is usful for the maunfacturer to know who drew the product and who check and apporved it as if they have any questions about the product they know who they can go and speak to about it, however if they find something with the drawing that may be wrong or incorrect they can go speak to whoever checked it and check against them, this is useful for them as it can cut out a lot of time going round trying to fins who checked the drawing. They can then add in any changes made to the drawing in the title block so that no one else makes that mistake if its then passed on to someone else. This stops people making the same mistake as they can see when the mistake was changed so they know whether it ws a recent mistake so they know to make sure not to include whatever was changed when produing the drawing. The title block also gives information such as materials which is needed to start to make the prodcuct and the finish which is used afterwards, if this information wasn’t shown on the title block the maunfacturer wouldn’t know what material to use and wouldnt be able to produce the product, this could use up a lot of time trying to produce the product and the company may miss the deadline. This is why a titleblock is crutial when producing a drawing as withut it there wouldn’t be a lot of information to go off when making the product.
Methods of producing drawing

Informal drawings are used to sketch down ideas by the designer that may be used in production, they are good for giving customers and designers an idea when in a meeting pitching new ideas to them as it gives them an idea of the scaling and overall look of the product, they can be produced in two methods isometric and orthographic. Isometric drawings are used more of a sketch, but using the isometric angle, using these sketches are good as they can be used to get feedback on whether they like the design, this feedback can then be used to remodel the design or take it further in production the good thing about informal is that the designer can remodel the design right there in front of them as it is just a quick sketch, this way the designer can get live feedback from the whoever is in the meeting about the product and whether they are going to take it further into production. From this the designer can take it down to the shop floor and show the manufactures, they can then do a more detailed sketch of the product showing them different angles and with the dimensions of the product, the advantages of using informal’s is that if someone doesn’t understand the product they can sketch it again from another perspective and show them in different ways until they understand, you can also show them what is inside the product and the interiors of the product with how it works, it also shows how you can change the product and what the difference is, for example the most famous informal drawing was produced by Alec Issigonis who drew an informal of the mini he showed how then engine could be rotated by 90 degrees so that the engine would fit in a smaller sized car, this revolutionised the car design just from a quick sketch from someone who had an idea, this shows how far drawings can be taken from a small informal sketch on a piece of paper.
Orthographic drawings gives a more detailed look at the product showing different views and projections of the product, orthographic drawings are a closer draft to a formal drawing as they can be used as a plan to lay out the view of where everything is going on the page and how it will all fit on the page, from these drawings the designer can shift the views about in order to fit the drawing on the page. This is a good way for the designer to figure out the scale they have to draw to and allows them to accommodate all features of the drawing making sure that they have enough room for a title block and dimensions, it can also be shown to the manufacture showing them all the different view from which they can then get feedback as to how the product looks and also they may have changes they need to make in order for them to successfully make the product. Some of the main people that use it are design and construction industries who often use orthographic drawings to communicate dimensions and shape. Real estate agents and realtors commonly use floor plans to show prospective buyers the layout and square footage of buildings. Engineers and architects use various plans, sections and elevations to depict designs and detail constructions of objects and buildings. The advantages of using orthographic drawings is that it can be used to determine accurate dimensions and roughly show how the formal drawing will look in the end result. However Orthographic drawings do not show depth or realistic views. A single-view orthographic drawing represents every object as having only two dimensions. However, there are some disadvantages to using orthographic drawings, by assembling two or more drawings with overlapping features or by using line weight and shading, orthographic drawings can depict the depth of objects. Additionally, the human eye views the world in perspective, not in the two dimensions of orthographic drawings. Also curvilinear shapes and diagonals that exist in three dimensions represent an example of distortion created by orthographic drawing. These shapes appear distorted and shortened because their entirety does not sit parallel to the view frame.
Another method of producing drawings is using CAD, programs such as draftsight and AutoCAD these programs enable designers to produce precise formal drawings by using a range of commands in the task bar to draw lines and any other objects they need. The good thing about CAD is that they all have a taskbar at the bottom which can be used to produce the drawings so no matter what version or program the designers use they will always no how to use it because they can just type in their commands compared to using the buttons. There are many benefits to using CAD over drawing by hand. One advantage is that it allows 0 tolerance on drawings which reduces the amount of mistakes that can be made as there is no way the manufactures can get confused on the dimensions because they know that there is 0 tolerance on the drawings. Another massive benefit of using CAD is that it is a lot faster compared to drawing by hand. If you are properly trained using CAD you are able to produce drawings in hours whereas if you were drawing it and it was a big product it could take a few days, this is a benefit as they can meet deadlines much faster so then they can suggest shorter deadline times for the company which is useful for them as they can get the product out faster and they also have more time to recover from any mistakes that may happen when producing the product. Another benefit of producing drawings using CAD is that it is a digital copy, so instead of going round with a paper version that could easily get destroyed or ruined when taken down to the shop floor, they can just send a copy of the drawing round to everyone, so each department has their own version and there is less chance of the drawing getting destroyed. You can also add on layers to your drawing when using programs such as draftsight, this is useful as people don’t have to see all the guidelines and how you produced the drawing they just get to see the final product with nothing else around it, this can also make it easier to read the drawing especially if someone is not used to looking at drawing, it would make it a lot easier if there were no guidelines around to confuse the drawing as it may end up getting made wrong if they struggle to read it. You can also produce title blocks in CAD which can be filled in and placed where you need them to be. The benefit of CAD is that you can also use other programs such as solid works where you can produce 3D models of the drawings and then produce them as an outline which can then be seen as an informal sketch, you can also render these models to see what the product will look like once it’s been made as you can add on different materials and finishes to make it look as realistic as possible, from this you can also make a formal drawing from the model which can be used instead of drawing it you can then smart dimension this drawing and it will give you all the dimensions of the product and you can also change the projection of the drawing to third and first angle depending on which projection you prefer. All these features and programs help to produce exact drawings of the product that you are making with al dimensions and title blocks the same as a drawing would be if it was drawn by hand, but cutting down the time massively depending on your skill level. Which can be a disadvantage as to produce complex drawings on CAD it takes a lot of training or skilled workers which can cost the company a lot of money.
The final method of producing drawings and the one that has been used throughout the production of many products until the release of CAD is formal drawings. Formal drawings are used by producing several angles and projections of your product in order for the manufacturer to make the product. Formal drawings are created by using a drawing board and a set squares to ensure that all lines are drawn perfectly straight, this stops any confusing when producing the product as to whether the line should be curved. Designers use guidelines in order to perfectly line up the different view that they have produced, by doing this all the view match up and they should all be the same distance away from each other and all follow the same projection. It takes a long time to produce complex products using formal drawings as you have to be skilled in order to present the accuracy of intricate details. Advantages of using formal drawings to make products is that you can separate a product into many parts, so that you are able to scale up the intricate parts of the drawing to be able to draw them. You can then put all the part together into an assembly drawing to show what the product should look like when it’s all fitted together. By doing this you can send different drawings to different departments in the company so all the part can be made at the same time and then they can be fitted together, this cuts down time and makes sure that all the parts are made with accuracy because the drawings will specify how It needs to be made. Formal drawings can also be used to show what’s going on inside the product by showing section views these are produced next to the part which you are showing the inside of, by doing this the manufacturers can see how it works and what’s going on inside the product to piece it all together. You can also get a lot of information from the formal drawings which has been stated above in how formal drawings are used. However, with the rise of CAD formal drawings are not widely being used anymore as it is much easier after training to use CAD as it is quicker and more precise and is a lot easier to use because if you go wrong you don’t have to start all over again you can just simply undo any mistakes. But formal drawings will always be a skill which have been used for many years and will still keep going in many places for a long time.

Bibliography:
http://www.ehow.co.uk/about_6595856_meaning-orthographic-drawing_.html