77 technical requirements for mechanical drawing design

As for mechanical design, I believe everyone can read and draw the drawings, but you should also know that the most difficult part of mechanical drawings is dimensioning and technical requirements. So, today, I’d like to introduce some experience that Xiaobian has summed up in his career of mechanical design in the past few years. No more nonsense, empty talk will harm the country, do solid work to prosper the country, and directly start dry goods

1. Remove scale from parts.

2. There shall be no scratch, scratch and other defects damaging the surface of parts on the machined surface of parts.

3. Remove burrs and flash.

4. After quenching and tempering treatment, HRC50 ~ 55. 5. Parts shall be subject to high-frequency quenching, tempering at 350 ~ 370 ℃, and hrc40 ~ 45. 6. Carburizing depth: 0.3mm.

7. Carry out high temperature aging treatment.

8. The unmarked shape tolerance shall meet the requirements of gb1184-80.

9. The allowable deviation of unmarked length and dimension is ± 0.5mm.

10. The casting tolerance zone is symmetrical to the basic dimension configuration of the blank casting.

11. Unspecified fillet radius R5.

12. The unmarked chamfer is 2 × 45°。

13. Blunt acute angle.

14. All seals must be soaked with oil before assembly.

15. When assembling rolling bearings, it is allowed to use oil heating for hot assembly, and the oil temperature shall not exceed 100 ℃.

20. After the gear is assembled, the contact spots and backlash on the tooth surface shall comply with the provisions of GB10095 and gb11365.

21. When assembling the hydraulic system, it is allowed to use sealing filler or sealant, but it shall be prevented from entering the system.

22. The parts and components (including purchased parts and outsourced parts) entering the assembly must have the certificate of inspection department before assembly.

23. The parts must be cleaned and cleaned before assembly, and there shall be no burr, flash, oxide skin, rust, chips, oil stain, colorant and dust.

24. Before assembly, recheck the main fitting dimensions of parts and components, especially the interference fitting dimensions and relevant accuracy.

25. Parts shall not be knocked, bumped, scratched or rusted during assembly.

26. When fastening screws, bolts and nuts, it is strictly prohibited to strike or use inappropriate screwdrivers and wrenches. After fastening, the screw groove, nut, screw and bolt head shall not be damaged.

27. For fasteners with specified tightening torque requirements, torque wrench must be used and tightened according to the specified tightening torque.

28. When the same part is fastened with multiple screws (bolts), all screws (bolts) shall be tightened crosswise, symmetrically, step by step and evenly.

29. The conical pin shall be painted with the hole during assembly, and its contact rate shall not be less than 60% of the fitting length, and shall be evenly distributed.

30. The flat key shall be in uniform contact with the two sides of the keyway on the shaft, and there shall be no gap on its mating surface.

31. The number of tooth surfaces in contact with spline assembly at the same time shall not be less than 2 / 3, and the contact rate shall not be less than 50% in the length and height direction of key teeth.

32. After the sliding fit flat key (or spline) is assembled, the phase accessories can move freely without uneven tightness.

33. After bonding, the excess adhesive flowing out shall be removed.

34. The semicircular holes of the bearing outer ring, open bearing seat and bearing cover shall not be stuck.

35. The outer ring of the bearing shall be in good contact with the semicircular hole of the open bearing seat and the bearing cover. During color inspection, it shall be in uniform contact with the bearing seat at 120 ° symmetrical to the center line and with the bearing cover at 90 ° symmetrical to the center line. When checking with a feeler gauge within the above range, the 0.03mm feeler gauge shall not be inserted into 1 / 3 of the width of the outer ring.

36. After the bearing outer ring is assembled, it shall be in uniform contact with the end face of the bearing cover at the positioning end.

37. After the rolling bearing is installed, it shall rotate flexibly and stably by hand.

38. The joint surfaces of the upper and lower bearing shells shall be close to each other and cannot be checked with a 0.05mm feeler gauge.

39. When fixing the bearing bush with the locating pin, drill, ream and match the pin while ensuring that the opening and closing surface and end face of the bush are flush with the opening and closing surface and end face of the relevant bearing hole. The pin shall not be loose after being driven in.

40. The bearing body and bearing seat of spherical bearing shall be in uniform contact, and the contact shall not be less than 70% when checked by coloring method.

41. When the surface of alloy bearing liner is yellow, it is not allowed to be used. There shall be no nucleation within the specified contact angle. The nucleation area outside the contact angle shall not be greater than 10% of the total area of non-contact area.

42. The reference end face of the gear (worm gear) shall fit the shaft shoulder (or the end face of the positioning sleeve), and it cannot be checked with a 0.05mm feeler gauge. The perpendicularity between the gear reference end face and the axis shall be ensured.

43. The joint surface of gearbox and cover shall be in good contact.

44. Before assembly, strictly check and remove the sharp corners, burrs and foreign matters left during part processing. Ensure that the seal is not scratched during installation.

45. Cold lap, crack, shrinkage cavity, penetrating defect and serious incomplete defect (such as under casting, mechanical damage, etc.) are not allowed on the casting surface.

46. The casting shall be cleaned without burrs and flash. The pouring and riser on the non machining indication shall be cleaned and flush with the casting surface.

47. The cast words and marks on the non machined surface of the casting shall be clear and legible, and the position and font shall meet the requirements of the drawing.

48. The roughness of non machined surface of casting, sand casting R, shall not be greater than 50 μ m。

49. The pouring riser, flying thorn, etc. shall be removed from the casting. The residual amount of pouring and riser on the non machined surface shall be leveled and polished to meet the surface quality requirements.

50. The molding sand, core sand and core bone on the casting shall be removed.

51. If there is an inclined part of the casting, its dimensional tolerance zone shall be configured symmetrically along the inclined plane.

52. The molding sand, core sand, core bone, fleshy, sticky sand, etc. on the casting shall be shoveled, ground and cleaned.

53. The alignment and staggering, boss casting deviation, etc. shall be corrected to achieve a smooth transition and ensure the appearance quality.

54. The depth of the wrinkles on the non machined surface of the casting shall be less than 2mm, and the spacing shall be greater than 100mm.

55. The non machined surface of machine product castings shall be shot peened or roller treated to meet the requirements of cleanliness SA2 1 / 2.

56. Castings must be subject to water toughening treatment.

57. The surface of the casting shall be flat, and the gate, burr, sand sticking, etc. shall be removed.

58. Casting defects such as cold shuts, cracks and holes that are detrimental to use are not allowed.

59. Rust, scale, grease, dust, soil, salt and dirt must be removed from the surface of all steel parts to be painted before painting.

60. Before derusting, remove grease and dirt on the surface of iron and steel parts with organic solvent, alkali liquor, emulsifier and steam.

61. The time interval between the surface to be coated after shot peening or manual rust removal and the primer shall not be more than 6h.

62. The surfaces of riveted parts in contact with each other must be coated with a thickness of 30 ~ 40 before connection μ M antirust paint. Lap edges shall be closed with paint, putty or adhesive. The primer damaged due to processing or welding shall be repainted.

63. All pipes shall be deburred and chamfered before assembly. Remove the sundries and floating rust attached to the inner wall of the pipe with compressed air or other methods.

64. Before assembly, all steel pipes (including prefabricated pipes) shall be degreased, pickled, neutralized, washed and antirust treated.

65. During assembly, the parts fixed by threaded connection such as pipe clamp, support, flange and joint shall be tightened to prevent loosening.

66. Pressure test shall be conducted for the welded parts of prefabricated pipes.

67. When piping is replaced or transferred, the pipe separation port must be sealed with adhesive tape or plastic pipe to prevent any sundries from entering, and labels must be attached.

68. The defects must be completely removed before repair welding. The groove surface shall be flat and smooth without sharp corners.

69. According to the defects of steel castings, the defects in the repair welding area can be removed by shovel excavation, grinding, carbon arc air gouging, gas cutting or machining.

70. Sand, oil, water, rust and other dirt within 20mm around the repair welding area and groove must be thoroughly cleaned.

71. During the whole process of repair welding, the temperature in the preheating zone of steel castings shall not be lower than 350 ° C.

72. If conditions permit, welding shall be carried out at the horizontal position as far as possible.

73. During repair welding, the welding rod shall not swing laterally.

74. When stacking welding on the surface of steel castings, the overlap between weld beads shall not be less than 1 / 3 of the weld bead width.

75. The nozzle and riser of each steel ingot shall have sufficient cutting amount to ensure that the forging has no shrinkage cavity and serious deflection.

76. The forging shall be forged on a forging press with sufficient capacity to ensure full penetration in the forging.

77. Forgings are not allowed to have visible cracks, folds and other appearance defects that affect the use. Local defects can be removed, but the cleaning depth shall not exceed