Thermoforming

Thermoforming is a set of processes for forming a thermoplastic sheet or film around the mold by applying heat and pressure. In this process, the sheet is heated in the oven until softened but not to the melting point. Sheet is then removed from the oven, spread out around the mold and then the sheet is sucked by the vacuum process. Because the mold at room temperature, then the formation of the plastic mold will be in accordance with smoked During sheet in contact with mould. That the types of products generated with this process are Billboards, packaging, household applications. Product-open or hollow products can not be formed Because the pressure can not be maintained During the formation. Since thermoforming is the process of withdrawal and toning, as well as sheet metal forming, the material must have a high uniformity of strain, if not Will there be a failure. -Mould for thermoforming molds are usually made ​​from aluminum Because of the high fracture strength is not required. Tooling is not too expensive and quality considerations, including wear, unequal thickness is not too significant. (bid / multiple sources)

First angle projection

The other standard orthographic projection method is first angle projection. The only difference between first angle and third angle projection is the position of the views. First angle projection is the opposite to third angle projection. The view, which is seen from the side of an object, is placed on the opposite side of that object as if one is looking through it. Figure 2.13 shows the first angle projection layout of the bracket shown in Figure 2.12. The labelling of the views (e.g. front view, plan, etc.) is identical in Figures 2.12 and 2.13. Note that in first angle projection, the right-side view is not placed on the right-hand side of the front view as in third angle projection but rather on the left-hand side of the front view as shown in Figure 2.13. Similarly, the left-side view appears on the right-hand side of the front view. The other views are similarly placed. A comparison between Figures 2.12 and 2.13 shows that the views are identical but the positions and hence relationships are different. Another first angle projection drawing is seen in the title box in Figure 2.13. This is the truncated cone. It is the standard ISO symbol for first angle projection (ISO 128:1982). It is this symbol which is placed on drawings in preference to the phrase 'first angle projection'. First angle projection is becoming the least preferred of the two types of projection. Therefore, during the remainder of this book, third angle projection conventions will be followed. 

Engineering Drawing for Manufacture
by Brian Griffiths
Publisher: Elsevier Science & Technology Books

Rotational molding

Most thermoplastics and thermosets can be formed into products with a large cavity with Rotational molding process. Mould with thin metal walls are made in two pieces and is designed to rotate in two mutually perpendicular axes. Plastic powder that has been measured previously placed in a warm mold. Mould then heated in an oven usually large, while the mold is rotated in two axes. This process makes the powder pressed into a mold where the mold surface will heat the powder without melt. The types of products made with this process are tanks with a variety of sizes, trash, baket, housing, ball. The liquid polymer called plastisol (usually used vinyl plastisol) can also be used in slush molding process. Mold simultaneously heated and rotated. After contact with the wall of the mold material to melt and mold wall wrap. Products to be cold when it was still spinning and removed by opening the mold.

Third angle projection of a bracket

Figure 2.12 shows a third angle projection drawing of a small bracket. In this case, the plan view and the inverted plan view are projected from the front face. Note that the arrangements of the views are still in third angle projection but they are arranged differently from the views in Figure 2.11. Another example of third angle projection is seen in the truncated cone within the title box in Figure 2.12. Here, the cone is on its side and only two views are shown yet they are still in third angle projection. The reason the cone is shown within the box is that it is the standard symbol for third angle projection recommended in ISO 128" 1982. The standard recommends that this symbol be used within the title block of an engineering drawing rather than the words 'third angle projection' because ISO uses symbology to get away from a dependency on any particular language. Third angle projection has been used to describe engineering artefacts from the earliest of times. In the National Railway Museum in York, there is a drawing of George Stephenson's 'Rocket' steam locomotive, dated 1840. The original is in colour. This is a cross between an engineering drawing (as described above) and an artistic sketch. Shadows can be seen in both orthographic views. Presumably this was done to make the drawings as realistic as possible. This is an elegant drawing and nicely illustrates the need for 'engineered' drawings for the manufacture of the Rocket locomotive. Bailey and Glithero (2000) state, 'The Rocket is also important in representing one of the earliest achievements of mechanical engineering design'. In this context, the use of third angle projection is significant, bearing in mind that the Rocket was designed and manufactured during the transition period between the millwrightbased manufacturing practice of the craft era and the factory-based manufacturing practice of the industrial revolution. However, third angle projection was used much earlier than this. It was used by no less than James Watt in 1782 for drawing John Wilkinson's Old Forge engine in Bradley (Boulton and Watt Collection at Birmingham Reference Library). In 1781 Watt did all his own drawing but from 1790 onwards, he established a drawing office and he had one assistant, Mr John Southern. These drawings from the beginning of the industrial revolution are significant. They illustrate that two of the fathers of the industrial revolution chose to use third angle projection. It would seem that at the beginning of the 18th century third angle was preferred, yet a century later first angle projection (explained below) had become the preferred method in the UK. Indeed, the 1927 BSI drawing standard states that third angle projection is the preferred UK method and third angle projection is the preferred USA method. It is not clear why the UK changed from one to the other. However, what is clear is that it has changed back again because the favoured projection method in the UK is now third angle. 

Engineering Drawing for Manufacture
by Brian Griffiths
Publisher: Elsevier Science & Technology Books