Precision Gear Reducer Assembly: A Step-by-Step Guide to Quality Control

I. Purpose

This document applies to assembly fitters during the assembly process of gear reducers to ensure quality control of the assembly.

II. Content

To ensure the quality of gear reducer assembly, a designated assembly area and assembly platform must be equipped, and professional assembly personnel must perform the assembly.

Preparations Before Assembly

First, clean the assembly site and platform. Obtain all machined and standard parts according to the detailed assembly drawing and arrange them categorically on workbench tools. For parts with a high surface roughness, place them on soft materials. For easily deformable parts, consider the placement of support points.

1. Cleaning
   1. Remove burrs and flash from all parts before assembly.
   2. Wash all parts with kerosene at least three times until they are thoroughly cleaned.
   3. Bearings can be washed with gasoline. If the rust-proof grease is thick, it can be cleaned by heating clean oil (oil temperature not exceeding 100°C) to dissolve the grease, then cooling and cleaning thoroughly.
   4. Remove all debris inside the housing. Apply two layers of oil-resistant paint to the inner walls. Clean all oil holes, screw holes, air holes, and machined surfaces. Seal oil and air holes with tape or plastic plugs to prevent contamination.
   5. Apply clean lubricating oil to the surfaces of gear engagements, bearing fits, and pin-to-hole fits before assembly.
   6. Soak all sealing felt rings and gaskets in oil before assembly. Soften soft steel cardboard with hot oil. Copper gaskets should be annealed (heated to 600°–650°C and then cooled in water).
   1. Recheck the dimensional tolerances of all parts. Select appropriate components according to the assembly interference fit required by the drawing and mark them by group.
   2. Verify that chamfers and fillets on mating holes and shafts match to avoid interference and irreversible assembly gaps.
   3. Check the fit dimensions of shaft journals, housings, and bearings, and confirm that the bearing models match the drawings.
   4. Verify that the specifications and models of sealing parts match the drawings and are undamaged.
2. Inspection

1. Recheck the dimensional tolerances of all parts. Select appropriate components according to the assembly interference fit required by the drawing and mark them by group.
2. Verify that chamfers and fillets on mating holes and shafts match to avoid interference and irreversible assembly gaps.
3. Check the fit dimensions of shaft journals, housings, and bearings, and confirm that the bearing models match the drawings.
4. Verify that the specifications and models of sealing parts match the drawings and are undamaged.

Assembly

1. Place the housing on the platform for assembly. Level the housing along its horizontal split plane. If shims are needed, they should be placed at the anchor bolt holes.
2. Assemble gears and shafts using thermal or press fitting. For thermal fitting, eliminate assembly gaps during cooling. After assembly, the reference face of the gear should press tightly against the shaft shoulder, leaving no clearance for a feeler gauge at the shaft shoulder’s end face. The axial position of gear engagement can be adjusted using the bearing’s outer-end locating sleeve. Align bevel gears by their small ends.
3. For rolling bearings, use thermal fitting with a heating temperature of 80°–100°C. Ensure the bearing inner ring is tightly seated with no clearance at the shaft shoulder’s end face.
4. Apply liquid sealant to the split plane of the housing and shaft end covers per the relevant standards.
5. Tighten the split-plane bolts using a torque wrench per the specified pre-tightening force. Tighten bolts uniformly and symmetrically, applying 40% of the pre-tightening force in the first round, 70% in the second round, and 100% in the third round.

Pre-tightening Force and Torque Values for Bolt Strength Grades

Post-assembly Inspection

• Backlash Inspection: Use lead wire compression, feeler gauges, or dial gauges.
• Tooth Contact Pattern Inspection: Use a coloring agent to check the tooth surface. The contact area should be toward the middle of the tooth surface, slightly biased toward the exit end, with no contact on the tooth top or edges. The contact rate must meet the drawing specifications.
• Bearing Clearance Inspection: Measure directly with a feeler gauge. Bearings should rotate smoothly without jamming.
• Gear Modification:
  • For grade 6 or 7 gears, individual hard spots can be removed with a fine file, then polished with an oilstone to remove traces.
  • For grade 8 or 9 gears, scraping tools or polishing wheels can be used, followed by oilstone polishing with slight traces allowed. Grinding wheels are prohibited.
• Gear Lapping: When the tooth contact rate does not meet the requirements, particularly in tooth length, scraping can be used. For a contact rate below 15% of the tooth length, machining is required. Lapping is allowed only when the contact rate is close to the requirement or slightly below.

Perform a sequential inspection of the accuracy of all component positions and the reliability of fastener tightening. After installation, ensure flexible rotation of the assembly.

Lubrication and Testing

Gear reducers use splash lubrication. Before operation, replace the vent plug with a breather plug. Open the oil level plug and add oil until it overflows from the oil level hole. Tighten the oil level plug, confirm no errors, and proceed with factory testing.

Thank you for reading. We are looking forward to serving you with our exceptional gear solutions. #BeyondGears

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