How many technical requirements do you know about mechanical parts processing?

Contour processing of parts

1. The unmarked shape tolerance should meet the requirements of GB1184-80.

2. The allowable deviation of the unmarked length dimension is ±0.5mm.

3. No fillet radius R5.

4. All unfilled chamfers are C2.

5. The sharp angle is obtuse.

6. The sharp edge is dull, and the burr and flash are removed.

Surface treatment of parts

1. There should be no scratches, abrasions and other defects that damage the surface of the parts on the processing surface of the parts.

2. The surface of the processed thread is not allowed to have defects such as black skin, bumps, random buckles and burrs. Before painting the surface of all steel parts that need to be painted, rust, oxide scale, grease, dust, soil, salt and dirt must be removed.

3. Before rust removal, use organic solvents, lye, emulsifier, steam, etc. to remove grease and dirt on the surface of steel parts.

4. The time interval between the surface to be coated by shot blasting or manual derusting and the primer coating should not be more than 6h.

5. The surfaces of the riveting parts in contact with each other must be painted with anti-rust paint with a thickness of 30-40μm before connecting. The lap edges should be sealed with paint, putty or adhesive. The primer damaged by processing or welding must be repainted.

Heat treatment of parts

1. After quenching and tempering, HRC50～55.

2. Medium carbon steel: 45 or 40Cr parts are subjected to high frequency quenching, tempered at 350～370℃, HRC40～45.

3. The carburizing depth is 0.3mm.

4. Carry out high temperature aging treatment.

Technical requirements after finishing

1. The finished parts should not be placed directly on the ground when placed, and necessary support and protection measures should be taken.

2. The machined surface is not allowed to have defects such as rust, bumps and scratches that affect performance, life or appearance.

3. The surface processed by rolling shall not peel off after rolling.

4. There should be no oxide scale on the surface of the parts after heat treatment in the final process. Finished mating surfaces and tooth surfaces should not be annealed

Sealing of parts

1. All seals must be soaked in oil before assembling.

2. Strictly check and remove the sharp corners, burrs and foreign objects left during parts processing before assembling. Ensure that the seal is not scratched when it is installed.

3. After bonding, remove the excess adhesive flowing out.

Gear technical requirements

1. After the gear is assembled, the contact spots and backlash of the tooth surface should meet the requirements of GB10095 and GB11365.

2. The reference end surface of the gear (worm gear) and the shaft shoulder (or the end surface of the positioning sleeve) should fit together and cannot be checked with a 0.05mm feeler gauge. And should ensure the verticality requirements of the reference end face of the gear and the axis.

3. The joint surface of the gear box and the cover should be in good contact.

Bearing technical requirements

1. Assembling rolling bearings is allowed to use oil heating for hot charging, and the temperature of the oil should not exceed 100°C.

2. The semi-circular holes of the bearing outer ring and the open bearing seat and bearing cover are not allowed to jam.

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

4. After assembly, the outer ring of the bearing should contact the end face of the bearing cap of the positioning end evenly.

5. After the rolling bearing is installed, it should be flexible and stable to rotate by hand.

6. The joint surfaces of the upper and lower bearing bushes should be closely attached and cannot be checked with a 0.05mm feeler gauge.

7. When fixing the bearing bush with locating pins, drill the reaming and distributing pins while ensuring that the opening and closing faces and end breads of the bushing surface and the end face of the relevant bearing hole are flush with each other. Do not loosen the pin after driving in.

8. The bearing body of the spherical bearing and the bearing seat should be in uniform contact, and the contact should not be less than 70% when inspected by the coloring method.

9. The alloy bearing lining is not allowed to be used when the surface is yellow, and the nucleation is not allowed within the specified contact angle, and the nucleation area outside the contact angle shall not be greater than 10% of the total area of the non-contact area.

Technical requirements for screws, bolts and nuts

1. When tightening screws, bolts and nuts, it is strictly forbidden to strike or use inappropriate screwdrivers and wrenches. The screw grooves, nuts and screws, and bolt heads shall not be damaged after tightening.

2. The fasteners with the specified tightening torque must be tightened with a torque wrench and tightened according to the specified tightening torque.

3. When the same part is fastened with multiple screws (bolts), each screw (bolt) needs to be tightened crosswise, symmetrically, gradually and evenly.

4. The flat key and the two sides of the keyway on the shaft should be in uniform contact, and there should be no gap between the mating surfaces.

Repair welding technical requirements

1. Defects must be completely removed before repair welding, and the groove surface should be repaired smoothly and without sharp corners.

2. According to the defects of the steel castings, the defects in the repair welding area can be removed by shoveling, grinding, carbon arc gouging, gas cutting or mechanical processing.

3. Dirt such as sticky sand, oil, water, rust, etc. within 20mm around the repair welding area and the groove must be thoroughly cleaned up.

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

5. When conditions permit, weld as much as possible in a horizontal position.

6. When repairing welding, the welding rod should not make excessive lateral swing.

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

Technical requirements for castings

1. The casting tolerance zone is symmetrical to the basic size configuration of the rough casting.

2. No cold partition, cracks, shrinkage holes, penetrating defects and serious incomplete defects (such as under-casting, mechanical damage, etc.) are not allowed on the surface of the casting.

3. The castings should be cleaned up without burrs or flashes. The pouring riser on the non-processing indication should be cleaned and flush with the surface of the casting.

4. The casting characters and marks on the non-machined surface of the casting should be clear and identifiable, and the position and font should meet the requirements of the drawing.

5. The roughness of the non-machined surface of the casting, sand casting R, is not more than 50μm.

6. Castings should be clear of pouring risers, spurs, etc. The remaining amount of the pouring riser on the non-processed surface should be leveled and polished to meet the surface quality requirements.

7. The molding sand, core sand and core bone on the casting should be cleaned.

8. The casting has inclined parts, and the dimensional tolerance zone should be arranged symmetrically along the inclined plane.

9. The molding sand, core sand, core bone, fleshy, sticky sand, etc. on the castings should be smoothed and cleaned up.

10. The right or wrong type, casting deviation of the boss, etc. should be corrected to achieve a smooth transition and ensure the appearance quality.

11. The wrinkles on the non-processed surface of the casting should be less than 2mm deep, and the spacing should be greater than 100mm.

12. The non-machined surface of the machine product castings needs to be shot peened or roller treated to meet the requirements of the cleanliness Sa2 1/2 level.

13. Castings must be treated with water toughness.

14. The surface of the casting should be smooth, and the gate, burr, sticky sand, etc. should be removed.

15. Castings are not allowed to have casting defects such as cold partitions, cracks, holes, etc. that are detrimental to use.

Technical requirements for forgings

1. The nozzles and risers of each steel ingot should be removed enough to ensure that the forgings are free from shrinkage and serious deflection.

2. The forging should be forged on a forging press with sufficient capacity to ensure that the forging is fully forged.

3. Forgings are not allowed to have visible cracks, folds and other appearance defects that affect use. Local defects can be removed, but the cleaning depth should not exceed 75% of the machining allowance. The defects on the non-machined surface of the forging should be cleaned and smoothly transitioned.

4. White spots, internal cracks and residual shrinkage holes are not allowed in forgings.

Assembly technical requirements

1. When assembling the hydraulic system, it is allowed to use seal packing or sealant, but it should be prevented from entering the system.

2. The parts and components (including purchased parts and outsourcing parts) entering the assembly must have the certificate of the inspection department before they can be assembled.

3. The parts must be cleaned and cleaned before assembling, and there must be no burrs, flashes, oxide skins, rust, chips, oil stains, colorants and dust, etc.

4. The main matching dimensions of parts and components, especially the interference fit dimensions and related accuracy should be reviewed before assembly.

5. The parts are not allowed to knock, bump, scratch and rust during the assembly process.

6. When assembling the taper pin, the hole should be painted and checked, and the contact rate should not be less than 60% of the mating length, and should be evenly distributed.

7. The number of tooth surfaces contacted by the 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 direction of the length and height of the key teeth.

8. After the flat key (or spline) with sliding fit is assembled, the relative parts can move freely without unevenness of tightness.

9. Before assembling, all the pipes should be free of flashing, burrs and chamfering. Use compressed air or other methods to remove debris and rust attached to the inner wall of the pipe.

10. Before assembly, all steel pipes (including prefabricated pipes) must be degreasing, pickling, neutralization, water washing and anti-rust treatment.

11. When assembling, tighten the pipe clamps, supports, flanges and joints to prevent loosening.