Summary of "Technical Requirements" for Mechanical Parts Processing

01 Parts contour processing

1. The shape tolerance of unmarked parts shall comply with the requirements of GB1184-80.

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

3. The radius of unmarked fillets is R5.

4. All unmarked chamfers are C2.

5. Sharp corners are blunted.

6. Sharp edges are blunted and burrs are removed.

02 Parts surface treatment

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

2. The processed thread surface is not allowed to have defects such as black skin, bumps, random buckles and burrs. All steel parts that need to be painted must be free of rust, scale, grease, dust, dirt, salt and dirt before painting. 3. Before rust removal, use organic solvents, alkali solutions, emulsifiers, steam, etc. to remove grease and dirt on the surface of steel parts.

4. The time interval between the surface to be painted and the primer after shot blasting or manual rust removal shall not exceed 6 hours.

5. The surfaces of the riveted parts in contact with each other must be coated with anti-rust paint with a thickness of 30-40μm before connection. The overlapping edges should be sealed with paint, putty or adhesive.

Primer damaged by processing or welding should be repainted. One Hour is a global energy-saving activity proposed by the World Wildlife Fund to respond to global climate change. It is advocated at 20:30 local time on the last Saturday of March each year.

03 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. Carburizing depth 0.3mm.

4. High temperature aging treatment.

04 Technical requirements after finishing

1. After finishing, the parts shall not be placed directly on the ground, and necessary support and protection measures shall be taken.

2. The processed surface shall not be rusted and have defects such as bumps and scratches that affect performance, life or appearance.

3. The surface of the finished rolling shall not peel after rolling.

4. The surface of the parts after heat treatment in the final process shall not have oxide scale. The mating surface and tooth surface after finishing shall not be annealed

05 Sealing treatment of parts

1. Each seal must be soaked in oil before assembly.

2. Before assembly, strictly check and remove the sharp corners, burrs and foreign matter left during the processing of the parts to ensure that the seals are not scratched when installed.

3. After bonding, the excess adhesive should be removed.

06 Technical requirements for gears

1. After the gear is assembled, the contact spots and side clearances of the tooth surface shall comply with the provisions of GB10095 and GB11365.

2. The reference end face of the gear (worm gear) should fit with the shaft shoulder (or the end face of the positioning sleeve). Check with a 0.05mm feeler gauge to make sure it does not penetrate. The verticality requirement between the reference end face of the gear and the axis should be ensured.

3. The joint surface between the gearbox and the cover should be in good contact.

07 Bearing Technical Requirements

1. When assembling rolling bearings, it is allowed to use oil heating for hot installation. The oil temperature shall not exceed 100℃.

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

3. The outer ring of the bearing shall be in good contact with the semicircular holes of the open bearing seat and the bearing cover. When checking with color, it shall be in uniform contact with the bearing seat within the range of 120° symmetrical to the center line and with the bearing cover within the range of 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 outer ring width.

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

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

6. The joint surface of the upper and lower bearings should be tightly fitted, and it should be checked with a 0.05mm feeler gauge.

7. When fixing the bearing with a locating pin, the bearing mouth surface and the end surface should be drilled and pinned while ensuring that the opening and closing surface and the end surface of the relevant bearing hole are flush. The pin must not be loose after being driven in. 8. The bearing body and the bearing seat of the spherical bearing should be in uniform contact. The contact should not be less than 70% when checked by the color coating method. 9. Alloy bearings are not allowed to be used when the surface of the lining is yellow. There is no core separation phenomenon within the specified contact angle, and the core separation area outside the contact angle shall not be greater than 10% of the total area of ​​the non-contact area.

08 Technical requirements for screws, bolts and nuts

1. When tightening screws, bolts and nuts, it is strictly forbidden to hit or use inappropriate screwdrivers and wrenches. After tightening, the screw slot, nut and screw and bolt heads shall not be damaged.

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

3. When multiple screws (bolts) are used to tighten the same part, each screw (bolt) must be tightened crosswise, symmetrically, step by step, 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.

09 Technical requirements for repair welding

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

2. According to the defects of the steel casting, 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.

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

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

6. When repairing welding, the welding rod should not swing too much horizontally. 7. When welding on the surface of steel castings, the overlap between welds shall not be less than 1/3 of the weld width.

10 Technical requirements for castings

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

2. No cold shut, crack, shrinkage cavity, penetration defect or serious defect (such as undercasting, mechanical damage, etc.) is allowed on the surface of the casting.

3. The casting should be cleaned and no burrs or flash should be allowed. The pouring and rising on the non-machined surface should be cleaned and flush with the casting surface.

4. The casting characters and logos on the non-machined surface of the casting should be clearly 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, shall not exceed 50μm.

6. The casting should be clear of pouring and rising, burrs, etc. The residual amount of the pouring and riser on the non-machined surface should be scraped 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 dimensional tolerance zone of the inclined part of the casting should be symmetrically arranged along the inclined surface.

9. The molding sand, core sand, core bone, fleshy, sticky sand, etc. on the casting should be scraped and polished flat and cleaned.

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

11. The wrinkles on the non-machined surface of the casting should be less than 2mm in depth and the spacing should be greater than 100mm.

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

13. The casting must be water-toughened.

14. The surface of the casting should be flat, and the gate, burrs, sticky sand, etc. should be cleaned.

15. Casting defects such as cold shut, cracks, holes, etc. that may harm the use of castings are not allowed.

11 Technical requirements for forgings

1. The nozzle and riser of each steel ingot should have sufficient removal to ensure that the forgings have no shrinkage holes and serious deflection. 2. Forgings should be forged on a forging press with sufficient capacity to ensure that the forgings are fully forged through.

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

4. Forgings are not allowed to have white spots, internal cracks, and residual shrinkage holes.

12 Technical requirements for assembly

1. When assembling the hydraulic system, it is allowed to use sealing fillers or sealants, but they should be prevented from entering the system.

2. Parts and components (including purchased parts and outsourced parts) entering the assembly must have a certificate of conformity from the inspection department before they can be assembled.

3. Parts must be cleaned and washed before assembly, and there must be no burrs, flash, oxide scale, rust, chips, oil, colorant and dust.

4. Before assembly, the main matching dimensions of parts and components, especially the interference fit dimensions and related precision, should be reviewed.

5. Parts are not allowed to be knocked, hit, scratched or rusted during assembly.

6. The cone pin should be checked with the hole during assembly, and the contact rate should not be less than 60% of the matching length and should be evenly distributed.

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

8. After the sliding fit flat key (or spline) is assembled, the matching parts move freely and there should be no uneven tightness.

9. All pipes should be free of flash, burrs and chamfered before assembly. Use compressed air or other methods to clear the debris and floating rust attached to the inner wall of the pipe.

10. Before assembly, all steel pipes (including prefabricated pipes) must be degreased, pickled, neutralized, washed and rust-proofed.

11. During assembly, the threaded connection fixing parts of pipe clamps, supports, flanges and joints must be tightened to prevent loosening.