Mechanical Manufacturing: 104 Essential Knowledge Points | MachineMFG

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Mechanical Manufacturing: 104 Essential Knowledge Points

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1. The manufacturing process includes technical preparation, machining, heat treatment, assembly, etc., commonly referred to as the manufacturing process.

2. Mechanical processing is composed of several workshops. The process can be further divided into installation, workstation, step, and tool movement.

3. Depending on the degree of production specialization, production can be divided into three types: single-item production, batch (small, medium, large) production, and mass production.

4. Material removal forming processing includes traditional cutting processing and special processing.

5. The methods of metal cutting processing include turning, drilling, broaching, milling, grinding, and shaping.

6. There are three constantly changing surfaces on the workpiece: the surface to be processed, the transition surface (cutting surface), and the already processed surface.

7. The cutting amount is the sum of the following three.

(1) Cutting speed, the speed of the main motion.

(2) Feed rate, the relative distance moved between the tool and the workpiece along the feed direction in one cycle of the main motion.

(3) Backlash, the vertical distance between the surface to be machined and the already machined surface on the workpiece.

8. Generatrices and guide lines are collectively referred to as the lines of formation for surfaces.

9. Formation of generatrices can be accomplished through methods such as shaping, tracking, unfolding, and tangential.

10. The forming motion of the surface is the movement that ensures the required surface shape of the workpiece.

11. Classification of machine tools:

(1) By versatility: general machine tools, specialized machine tools, and dedicated machine tools.

(2) By precision: ordinary machine tools, precision machine tools, and high-precision machine tools.

(3) By automation level: standard machine tools, semi-automatic machine tools, and automatic machine tools.

(4) By weight: instrument machine tools, standard machine tools, large machine tools, and heavy machine tools.

(5) By the number of main working parts: single-tool machine tools, multi-tool machine tools, single-axis machine tools, and multi-axis machine tools.

(6) By CNC functionality: standard machine tools, general CNC machine tools, machining centers, flexible manufacturing units, and others.

12. Components of a machine tool: power source, forming motion executors, variable speed transmission devices, motion control devices, lubrication devices, electrical system components, support components, and other devices.

13. Motions on the machine tool:

(1) Cutting motion (also known as surface forming motion), including:

1. The primary motion makes the tool and workpiece move relative to each other, which is the basic motion for cutting off excess metal on the workpiece.

2. The feed motion continuously places the excess layer of metal into the cut to ensure the continuous progress of cutting. (Can be one or several)

(2) Auxiliary motions. Indexing motion, feeding and clamping motion, control motion, other various idle motions.

14. Tool classification:

(1) According to the tool, it is divided into cutting tools, hole processing tools, milling cutters, broaches, threading tools, gear tools, automatic processing tools.

(2) According to the number of main cutting edges on the tool, it is divided into single-edge tools and multi-edge tools.

(3) According to the complexity of the cutting part of the tool, it is divided into standard tools and complex tools.

(4) Depending on the relationship between the size of the tool and the size of the workpiece being processed, it is divided into fixed-size tools and non-fixed-size tools.

(5) According to the construction of the cutting part of the tool itself, it is divided into single tools and complex tools.

(6) According to the structural relationship between the cutting part of the tool and the clamping part, it is divided into integral tools and assembly tools.

15. Cutting tools mainly include turning tools, planing tools, parting tools, and knives.

16. Hole processing tools include twist drills, center drills, reamers, and countersinks.

17. The most commonly used tool materials are high-speed steel and cemented carbide steel.

18. High-speed steel is divided into standard high-speed steel and high-performance high-speed steel.

19. High-performance high-speed steel is divided into cobalt high-speed steel, aluminum high-speed steel, and vanadium high-speed steel.

20. The reference system of the tool is divided into a static (marked) angle reference system and a working angle reference system.

21. The static (marked) angle reference system is determined by the primary motion direction, and the working angle reference system is determined by the composite cutting motion direction.

22. The reference planes constituting the tool marking angle reference system include the base plane, cutting plane, orthogonal plane, normal plane, assumed working plane, and back plane.

23. The structural elements of the external circular turning tool cutting part: front tool face, back tool face, secondary back tool face, main cutting edge, secondary cutting edge, and tool tip.

24. Orthogonal plane reference system:

(1) The base plane T is a plane vertical to the main motion direction passing through the selected point of the cutting edge.

(2) The cutting plane is a plane tangent to the cutting edge at the selected point and perpendicular to the base plane.

(3) The orthogonal plane is a plane that passes through a selected point on the cutting edge and is perpendicular to both the base plane and the cutting plane.

(4) The normal plane is a plane that passes through a selected point on the cutting edge and is perpendicular to the cutting edge.

25. Assume that the working plane is a plane that passes through a selected point on the cutting edge, parallel to the feed direction, and perpendicular to the base plane.

26. Tool angles:

(1) The rake angle, clearance angle, and wedge angle marked within the orthogonal plane. The rake angle is the angle between the front cutting face and the base plane measured within the orthogonal plane. The clearance angle is the angle between the primary clearance face and the cutting plane measured within the orthogonal plane. The wedge angle is the angle between the front cutting face and the back cutting face measured within the orthogonal plane.

(2) The auxiliary rake angle and auxiliary clearance angle marked within the auxiliary plane.

(3) The edge inclination angle marked within the cutting plane. The edge inclination angle is the angle between the primary cutting edge and the base plane measured within the cutting plane.

(4) The primary relief angle, secondary relief angle, and point angle marked within the base plane. The primary relief angle is the angle between the projection of the primary cutting edge on the base plane and the feed motion direction. The secondary relief angle is the angle between the projection of the secondary cutting edge on the base plane and the opposite direction of the feed motion. The point angle is the angle between the primary edge and the secondary edge measured within the base plane.

27. Principles for Choosing Rake Angle

(1) For workpiece materials with low strength, low hardness, and high plasticity, a larger rake angle should be selected. When processing brittle materials, a smaller rake angle should be chosen.

(2) The stronger and more resilient the tool material, the larger the rake angle should be.

(3) For rough cutting, choose a smaller rake angle. In cases of poor process systems, opt for a larger rake angle.

28. Principles for Choosing Clearance Angle

(1) For rough cutting, a smaller clearance angle can be chosen. For fine cutting, select a larger clearance angle.

(2) When the rigidity of the process system is poor or tools requiring dimensional accuracy are used, choose a smaller clearance angle.

29. Principles for Choosing Major Cutting Edge Angle

(1) For rough machining, semi-fine machining, and hard alloy turning tools, choose a larger major cutting edge angle.

(2) When processing very hard materials, select a smaller major cutting edge angle.

(3) For good process rigidity, choose a smaller major cutting edge angle. For turning slender shafts, opt for a larger major cutting edge angle. For single or small batch production, the major cutting edge angle should be 90 degrees or 45 degrees.

30. Principles for Choosing Minor Cutting Edge Angle

(1) Generally, choose a smaller minor cutting edge angle for tools.

(2) For fine machining tools, select an even smaller minor cutting edge angle.

(3) When processing high-strength, high-hardness materials, or during interrupted cutting, choose a smaller minor cutting edge angle.

31. The Function of the Rake Angle: Increasing the rake angle can reduce cutting deformation and friction, lower cutting forces and temperature, reduce tool wear, and improve surface quality.

32. The Function of the Clearance Angle: Increasing the clearance angle can reduce the friction between the flank of the tool and the machined surface, and it can also reduce the cutting edge radius, making the edge sharper.

33. The Function of the Inclination Angle: It affects the direction of chip flow, the sharpness of the cutting edge, the strength of the blade, and the cutting forces.

34. The Function of Major and Minor Cutting Edge Angles

(1) They affect the roughness of the machined surface.

(2) They affect the size and proportion of cutting forces, and influence the elasticity variation and vibration of the process system.

(3) They directly affect the strength of the tool tip and the dissipation of cutting heat.

(4) The major cutting edge angle affects the shape of the chip layer, the chip breaking effect, and the direction of chip removal.

35. Types of chips include ribbon chips, segment chips, granular chips, and shattered chips.

(1) Ribbon chips form at high speeds, with lower cutting thickness, and larger tool rake angles when cutting plastic materials.

(2) Segment chips form at lower cutting speeds, smaller rake angles, and larger cutting thickness when cutting plastic metals such as steel.

(3) Granular chips form at even lower cutting speeds, larger cutting thickness, when cutting metals with lower plasticity.

(4) Shattered chips are formed when cutting brittle materials.

36. The cutting layer at the cutting edge area is divided into three deformation zones: the first deformation zone (shear slip zone), the second deformation zone (friction zone), and the third deformation zone (extrusion zone).

37. The cutting force is decomposed into three components.

(1) The main cutting force is the component along the cutting speed direction.

(2) The feed resistance is the component in the feed direction.

(3) The cutting depth resistance is the component in the cutting depth direction.

38. Factors affecting cutting force include workpiece material, cutting quantity, tool angle, and others.

39. Factors influencing cutting temperature include cutting quantity, workpiece material, tool angle, and others.

40. Tool wear stages are divided into three stages: initial wear stage, normal wear stage, and rapid wear stage.

41. Forms of tool wear include rear tool face wear, front tool face wear, and simultaneous wear of both front and rear tool faces.

42. Reasons for tool wear include abrasive wear, adhesive wear, diffusive wear, and oxidative wear.

43. Types of tool breakage include brittle fracture and ductile fracture. Brittle fracture can be further divided into chipping, cracking, peeling, and thermal fracture.

44. Measures to prevent tool breakage include the rational selection of tool material, angle, and cutting volume.

45. Factors affecting tool life include cutting volume, workpiece material, tool material, tool geometric angle, and others.

46. When choosing the cutting volume, one should first choose the maximum possible back-cutting volume, then a large feed volume, and finally, based on the determined back-cutting and feed volume, choose a reasonable cutting speed within the limits of tool life and machine power.

47. Grinding tools are composed of abrasives, binders, and pores.

48. The characteristics of a grinding wheel include abrasive, grain size, hardness, binder, structure, shape, and size.

49. The hardness of a grinding wheel refers to the ease with which abrasive grains break away from the wheel during operation.

50. Grinding motion is divided into the main motion and feed motion (radial, axial, circumferential), total of four motions.

51. The quality of the grinding surface includes the roughness of the ground surface, surface burns, and residual stress in the surface layer.

52. Residual stress refers to the stress remaining within a part after the effects of external forces and heat sources.

53. High-efficiency grinding methods include high-speed grinding, strong grinding, and belt grinding.

54. Generally, for metals with high hardness, a soft grinding wheel should be chosen for rough grinding; for soft metals, a hard grinding wheel should be chosen for fine grinding.

55. Workpiece clamping is divided into direct alignment clamping, line-finding alignment clamping, and utilizing special fixture clamping.

56. Positioning ensures that the workpiece is in the correct position within the processing system.

57. A datum is a point, line, or surface used to determine the geometric relationship between the geometric elements of a part. It is divided into design datum and process datum (including operation datum, positioning datum, measurement datum, assembly datum).

58. The principle of restricting the six degrees of freedom of a workpiece to position it is called six-point positioning.

47. The grinding tool consists of abrasive, binder, and pores.

48. The characteristics of the grinding wheel include abrasive, grain size, hardness, binder, structure, shape, and size.

49. The hardness of the grinding wheel refers to the ease with which the abrasive falls off the grinding wheel during work.

50. Grinding movements are divided into main movement; feed movement (radial, axial, circular movement), for a total of four movements.

51. The quality of the grinding surface includes the surface roughness of the grinding, surface burn, and surface residual stress.

52. Residual stress refers to the stress that exists within the part after the action of external forces and heat sources.

53. High-efficiency grinding methods include high-speed grinding, heavy-duty grinding, and belt grinding.

54. Generally, when machining hard metals, soft grinding wheels should be chosen for rough grinding; when machining soft metals, hard grinding wheels should be chosen for precision grinding.

55. Workpiece clamping is divided into direct alignment clamping, line alignment clamping, and using special fixture clamping.

56. Positioning ensures the workpiece is in the correct position within the process system (including process datum, positioning datum, measurement datum, assembly datum).

58. The method of restricting the six degrees of freedom of the workpiece to position is called the six-point positioning principle, six-point positioning.

59. Do not confuse positioning and clamping; positioning is to put the workpiece in the correct position, clamping is to ensure correct positioning.

60. Full positioning restricts the six degrees of freedom of the workpiece.

61. Incomplete positioning (reasonable positioning) restricts less than six degrees of freedom but can still ensure processing requirements.

62. Under-positioning restricts the degrees of freedom of the workpiece to less than a reasonable number, which cannot guarantee processing requirements.

63. Repeated positioning (over-positioning) is when the same degree of freedom is repeatedly restricted by the same positioning element.

64. Common planar positioning elements include fixed supports, adjustable supports, self-positioning supports (limiting one degree of freedom), and auxiliary supports.

65. Workpieces are positioned using cylindrical pins, dowel pins, and centering spindles for round hole positioning elements.

66. Workpieces are positioned using conical centering spindles and centering points for tapered hole positioning elements.

67. Workpieces are positioned using positioning sleeves, spring chucks, and Y-blocks for outer cylindrical surface positioning elements.

68. Short cylindrical pins restrict 2 degrees of freedom, long cylindrical pins restrict 4 degrees of freedom, and diamond pins restrict 1 degree of freedom.

69. Conical pins used for unprocessed holes can restrict 3 degrees of freedom, while floating conical pins restrict 2 degrees of freedom.

70. A centering spindle with clearance fit restricts 5 degrees of freedom, an interference fit centering spindle restricts 4 degrees of freedom, and a small taper centering spindle restricts 4 degrees of freedom.

71. In planar positioning, one support pin restricts 1 degree of freedom, two support pins restrict 2 degrees of freedom, and three support pins restrict 3 degrees of freedom.

72. V-blocks

(1) Fixed long V-blocks restrict 4 degrees of freedom, short V-blocks restrict 2 degrees of freedom.

(2) Movable V-blocks restrict 1 degree of freedom.

73. Conical centering spindle positioning restricts 5 degrees of freedom.

74. Dead centers restrict 3 degrees of freedom, while live centers restrict 2 degrees of freedom.

75. Three-jaw chuck positioning restricts 2 degrees of freedom for short workpieces and 4 degrees of freedom for long workpieces.

76. The three essential elements of clamping force: point of application, direction, and magnitude.

77. Clamping power (device) systems: pneumatic, hydraulic, electro-pneumatic, electric, magnetic, and vacuum power systems.

78. Workpiece machining quality includes:

(1) Mechanical machining precision refers to the degree of conformity between the actual geometric parameters of the workpiece after machining and the ideal geometric parameters.

(2) Machining Surface Quality

79. Mechanical machining precision includes dimensional accuracy, shape accuracy, and positional accuracy.

80. The causes of positioning errors are due to the non-coincidence error of the datum and the displacement error of the datum.

81. The calculation formula for positioning error.

82. Process documents that prescribe the manufacturing process and operation methods of a product are called process procedures.

83. Filling the content of process procedures into a specific format card creates the process document, which is the basis for production preparation and construction.

84. Commonly used process documents include comprehensive cards for mechanical machining process, cards for mechanical machining process, and cards for mechanical machining operation.

85. The design of the machining process should properly address the selection of positioning datum, the drafting of the process route, the determination of process dimensions and tolerances, and the design of machining operations.

86. Positioning references are divided into rough references and precise references.

87. Economic machining accuracy refers to the machining precision that can be achieved under normal processing conditions.

88. The stages of machining are divided into rough machining, semi-precision machining, precision machining, finishing machining, and ultra-precision machining.

89. The arrangement of mechanical processing procedures prioritizes the basic surface, rough before precise, main before secondary, surface before hole.

90. The arrangement of heat treatment procedures includes preparatory heat treatment and final heat treatment.

91. Machining allowance is divided into operation allowance and total machining allowance.

92. The operation allowance is the difference between the sizes of two successive operations.

93. Operation sizes are marked with limit deviations according to the principle of inclusion, i.e., the operation size of the included surface takes the upper deviation as 0, and the operation size of the including surface takes the lower deviation as 0.

94. The minimum operation allowance = basic size of operation allowance – tolerance of the previous operation size.

a) The maximum operation allowance = basic size of operation allowance + tolerance of this operation size.

i= minimum operation size + tolerance of the previous operation size + tolerance of this operation size.

95. The included surface refers to the shaft, and the including surface refers to the hole.

96. Machining allowances are divided into bilateral allowances and unilateral allowances.

97. For external circles and holes and other rotating surfaces, machining allowance refers to bilateral allowance, which is considered from the diameter, and in actual metal cutting, it is half of the machining allowance. The machining allowance of a plane refers to a unilateral allowance, equal to the actual cut metal layer thickness.

98. In the part machining process, the closed dimension combination formed by a series of interrelated dimensions arranged in a certain order is called a process dimension chain.

99. Each constituent dimension in the circular process dimension chain is called a loop.

100. The closed loop is the dimension that is naturally formed or indirectly obtained in the machining process. There is only one closed loop in each dimension chain.

101. All dimensions that impact the closed loop in the process size chain make up the loop.

102. The components of the loop are divided into increasing and decreasing loops. This section was not covered by the teacher in class, it may not be tested, but it still needs to be mastered.

103. When the size of other constituent loops increases, the size of the increasing loop also enlarges. This constituent loop is known as the increasing loop.

104. When the size of other constituent loops remains unchanged and the enlargement of one constituent loop results in a reduction of the closed loop, this constituent loop is referred to as the decreasing loop.

Supplement:

(1) Draw the transmission structure diagram of the machine tool according to the machine tool’s transmission chain diagram, and perform speed calculations.

(2) The selection of the change gear.

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