Sheet Metal · 2021年11月6日

Commonly used techniques and precautions for machined parts

What technical requirements must be observed when machining parts? Only by adhering to these technical requirements, can the processed finished products be more standardized and reasonable.

  • (1) The scale of parts is reduced.
  • (2) The surface of the part must be mechanically processed, and there must be no scratches or other defects that may damage the surface of the part.
  • (3) The unmarked shape tolerance meets the requirements of GB1184-80, and the dimensional tolerance must be ±0.5mm.
  • (4) The casting tolerance is symmetrical with respect to the basic dimensional composition of the rough casting.
  • (5) Assemble rolling bearings can be charged at high temperature by heating oil, and the oil temperature shall not exceed 100°C.
  • (6) When assembling the hydraulic system, seal packing or sealant is allowed.
  • (7) The parts entering the assembly must be inspected and qualified before assembly.
  • (8) The parts should be cleaned before assembling, and there should be no burrs, burrs, oxide scale, rust, chips, oil stains, colorants and dust.
  • (9) Before assembling, confirm the main mating dimensions of the parts, especially the accuracy related to the tight-fitting dimensions.
  • (10) Do not scratch, bump, scratch or rust parts during assembly.
  • (11) When tightening screws, bolts and nuts, it is strictly forbidden to knock or use inappropriate screwdrivers or wrenches. Do not damage the thread grooves, nuts, screws, and bolt heads after tightening.
  • (12) Fasteners with tightening torque requirements are torque wrenches, which must be tightened according to the specified tightening torque.
  • (13) Excess adhesive needs to be removed after bonding.
  • (14) The outer ring of the bearing, the semicircular hole of the open bearing seat, and the bearing cover will not be blocked. The outer ring of the bearing must be in good contact with the semicircular opening on the bearing seat and the bearing cover. During the color inspection, the bearing housing must be evenly contacted within the range of 120° from the center line and 90° from the center line of the symmetrical bearing cover. When using the tactile gauge within the above range, do not insert the 0.03mm tactile gauge into 1/3 of the outer ring width.
  • (15) After the outer ring of the bearing is assembled, evenly contact the end face of the bearing at the positioning end.
  • (16) The rolling bearing must be flexible and stable after being installed by hand.
  • (17) The joint surfaces of the upper and lower bearing bushes must be tightly installed and checked with a 0.05mm feeler gauge.
  • (18) When fixing the bearing bush with positioning pins, drill holes on the hinges and pins so that the opening and closing surfaces of the mouth and the end face are flush with the end of the relevant bearing hole. After inserting the pin, do not loosen it.
  • (19) If the surface of the alloy including the lining is yellow, it cannot be used. It is stipulated that nuclear separation is not allowed within the contact angle, and the nuclear separation area outside the contact angle shall not exceed 10% of the total area of ​​the non-contact area.
  • (20) The reference end surface of the gear (worm gear) and the shoulder (or the end surface of the positioning sleeve) must be aligned and checked with a 0.05mm feeler gauge. The verticality requirements of the reference end surface of the gear and the shaft must be guaranteed.
  • (21) Strictly check and remove the sharp corners, burrs and foreign objects remaining in the process of parts processing before assembly. Make sure that the seal is not scratched during installation.
  • (22) No insulation, cracks, shrinkage, penetration defects and serious defects are allowed on the surface of the casting.
  • (23) Clean the casting to avoid burrs and flushing. Not working means that the riser should be clean and flush with the surface of the casting.
  • (24) The casting and markings on the unprocessed surface of the casting should be easy to read, and the position and font should meet the requirements of the drawing.
  • (25) Castings must be cleaned of pouring risers, thorns, etc. The remaining risers on the unprocessed surface must be leveled and polished to meet the surface quality requirements.
  • (26) The foundry sand, core sand and core bone of the casting must be removed.
  • (27) Castings should have inclined parts, and their dimensional tolerances should be arranged symmetrically along the inclined plane.
  • (28) Correct the right and wrong types, boss castings, etc., to achieve a smooth transition and ensure the appearance quality.
  • (29) The unprocessed surface of machine product castings needs to be shot peened or drum treated to achieve Sa2 1/2 cleanliness.
  • (30) Smooth the surface of castings, remove gates, burrs and sand particles.
  • (31) Castings cannot tolerate casting defects such as cold partitions, cracks, and holes that are harmful to use.
  • (32) Remove rust, scale, grease, dust, dirt, salt and dirt on all steel parts that need to be painted before painting.

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