Manufacturing Processes

1. Manufacturing Processes Dr N K Singh Associate Professor (Workshop) Department of Mech Engg I S M Dhanbad

2. Importance of the subject Involved in conversion of raw material into useful product.

3. Basic manufacturing process Casting process Forming process Machining process Powder metallurgy Joining process, assembly and finishing

4. Carpentry

5. Timber • Timber is the basic material used for any class of woodworking. • Growth:-–The growth of the tree trunk happens upwards and outwards, and in general, growth is directed to maximize the light on the leaves.

6. Growth rings • As a tree grows, the wood is laid down in concentric rings. Where a definite growing season exists (temperate climates) • The growth pattern for each season gives light coloured wood closer to the centre of the tree and darker coloured wood nearer the outside. The disparity between these two types of wood gives a ring for each growing season. At least one such ring is laid down each year. 

7. Growth rings

8. The wood growth cells are in a thin layer between the bark and the sapwood. This thin layer is called the cambium. • It lays down new bark on the outside, and new wood cells on the inside. As the tree grows, each layer of wood cells remains in its original position except the cambium. It is continually moving outwards.

9. Sapwood is the newest wood in a tree. When the wood cells are first laid down, they have very thin walls and large hollow voids in the middle. The outermost wood carry sap from the leaves to the cambium where it is used to manufacture new cells.

10. The mature cells blocked, and carrying extractives no longer grow in wall thickness and are now known as “heartwood” or “truewood”. • It has the colour of the mature wood because of the extractives. As cells are converted from sapwood to heartwood, the boundary between sapwood and heartwood is steadily moving away from the centre of the tree at roughly the same rate as new cells are being formed.

11. Darker wood is heartwood, lighter wood is sapwood

12. Classification of WOOD • Hardwoods and softwoods • The main differences between hardwoods and softwoods are botanical, and relate to the way the tree grows and the timber is laid down.

13. Hardwoods and softwoods

14. Seasoning of Wood  Water is stored in wood in two main forms: • As free water in the vessels and/or cells, used to move nutrients within the tree. • As cell (or bound) water, which is an integral part of the cell walls.

15. Seasoning Process • The process of seasoning removes all of the free water and most of the bound water. In the removal of the bound water, the wood cells change in size and shape, so this part of the process must be carried out with careful control over drying rate.

16. Advantage of Seasoning • Tends to have superior dimensional stability • Increasing stiffness, • Bending strength and compression strength • Lighter in weight

17. Methods of Seasoning • Air seasoning • Kiln seasoning • Chemical seasoning

18. Air seasoning • The traditional method of seasoning timber was to stack it in air and let the heat of the atmosphere and the natural air movement around the stacked timber remove the moisture.

19. Air seasoning • Air-drying is necessarily a slow process, particularly for hardwoods, typically taking 6 to 9 months to reach a moisture content in the range 20% to 25%.

20. Kiln seasoning • Kiln seasoning accelerates the process of seasoning by using external energy to drive the moisture out.

21. Kiln seasoning • The timber is placed inside a chamber in which the conditions can be varied to give best seasoning results. Air is circulated around the charge (stacked timber) and the temperature and humidity can be varied to give optimum drying. • Typically the timber may be in the kiln for a period of between two days to one week.

22. Chemical seasoning • The process involves soaking the green timber (as soon as it is cut) in a hygroscopic chemical for about a day, which slows down the rate of moisture loss and minimizes the risk of inducing the internal stresses which cause checking to occur during the subsequent air-drying.

23. Chemical seasoning • Chemical seasoning is used for very high value applications such as rifle butts, golf club heads and carvings, where the timber is required to be completely free of surface checks.

24. Preservation of Wood • Keep timber dry • Protect timber from sun • Isolate timber from pests

26. CARPENTARY TOOLS • Marking and measuring tools • Cutting tools • Planing tools • Boring tools • Holding and miscellaneous tools

27. Marking and measuring tools • Measuring tools are used to mark and check work for size and alignment. • These tools include • The steel tape or rule: • The folding wood rule

28. Marking and measuring tools • The square and the tri-square are used to align or test right angles

29. Marking and measuring tools • Spring divider is used for making arcs and circles

30. Marking and measuring tools • Marking Gauge is used to mark lines parallel to a edge.

31. Cutting tools • Saws: - • A saw is specified by : • Length of its blade measured along the toothed edge • pitch of teeth (mm)

32. 1. Rip Saw • Use for woodcutting with the wood grain. • Usually 24" to 26" long with 4 to 7 teeth per inch (tpi) • Cut very aggressively and leave slightly rough edge

33. 2. Cross Cut • Use for woodcutting across the wood grain • Usually 24" to 26" long with 8 to 11 tpi • Don't cut as aggressively as rip saws but leave a much smoother edge

34. 3. Panel Saw (Short cut or box Saw) • Use for woodcutting across the wood grain • Usually shorter than regular cross cut saws, for easy portability

35. 4. Bow Saw • Use for woodcutting in any direction • Have a tubular steel frame with a ribbon-like, high-tension steel blade

36. 5. Coping Saw • Use for fine woodcutting, coping joints • Have deep steel tension frames and very thin blades to allow the user to make intricate cuts at extreme angles

37. 6. Back Saw • Use for fine woodcutting, molding and trim. • Have a rigid piece along the back to prevent the saw from kinking during use.

38. 7. Dovetail Saw • Use for wood joint cutting • Have rigid backs like backsaws, but are usually smaller and have finer teeth

39. 8. Keyhole Saw • Use for circle and curve cutting in wood • Have very thin, pointed blades for cutting small, tight radius curves and holes

40. Chisels

41. Types of Chisels • BEVEL edged chisels are slightly undercut making them easy to push into corners. • They are normally used for finishing dovetail joints.

42. Types of Chisels • FIRMER chisels have a blade with a rectangular cross-section. • This means that they are stronger and can be used for tougher /heavier work.

43. A PARING chisel is a longer, thinner chisel which can be pushed into long joints such as housing joints. It is used for cleaning up the joint and to make it an accurate fit. Types of Chisels

44. Use of Bevel Chisel

45. Types of Chisels Mortise chisel: • Thick, rigid blade with straight cutting edge and square sides to make mortises and similar joints. • Blades vary in width from 3-16 mm.

46. Types of Chisels Gouges: • Used for cutting CURVED sections

47. Planning tools • Plaines are used to smooth and shape wood by means of a sharp steel blade (housed in a wood or metal casing) set at an angle to the surface to be planed. • The depth of the cut can be varied by adjusting the distance the blade protrudes beneath the bottom surface of the plane.

48. Planning tools • Planes are made in many sizes, and special planes are sometimes used to cut channels. Files of various shapes are also used to smooth and shape wood

49. Planning tools

50. Types of planes Jack plane • A general-purpose bench plane, used for general smoothing of the edges and sizing of wood. • Jack planes perform both the work of smooth planes and trying planes.