Industrial Robot Diaphragm Coupling Precision Machining Technology and Process Case

A precision robot manufacturer required high-performance couplings for its newly developed six-joint industrial robot, demanding transmission accuracy of ±0.01mm and service life of at least 30,000 hours. Traditional couplings had minimal backlash during high-speed reversing motion, affecting robot repeat positioning accuracy. We undertook the precision machining task for this diaphragm coupling.

This processing faced three major technical difficulties:

1. Thin-walled Part Deformation Control: Diaphragm thickness only 0.2mm, prone to deformation during processing
2. High-precision Hole Position Requirements: 12 mounting hole index error requirement ≤0.005mm
3. Surface Integrity Requirements: Product needs to withstand 16,000rpm high-speed rotation, surface roughness needs to reach Ra0.2

Select 304 stainless steel bar material, first conduct chemical composition analysis to confirm material qualification. Use solution treatment (1050°C 30 minutes water quenching) to optimize material processing performance.

Use Swiss Star turn-mill center for preliminary forming:

• Rough turning: Use Kennametal KC5010 tool, speed 1200rpm, feed rate 0.15mm/r
• Semi-finish turning: Switch to Sandvik GC1125 tool, speed 1800rpm, feed rate 0.08mm/r
• Finish turning: Use diamond tool, speed 2500rpm, feed rate 0.03mm/r, ensure dimensional tolerance within 0.003mm

Use Trumpf laser cutting machine for diaphragm processing:

• Use 400W fiber laser, focal diameter 0.01mm
• Nitrogen protection cutting, pressure 0.8MPa
• Cutting speed 12m/min, smooth cut without burrs

Use German DMG five-axis machining center for hole processing:

• Use carbide drill, speed 5000rpm
• First drill guide holes, then use reamer for finish processing
• Each hole completed in three steps, final hole tolerance controlled within ±0.002mm

Perform low-temperature aging treatment:

• 280°C 4 hours, eliminate processing stress
• Liquid nitrogen deep cold treatment (-196°C 2 hours), improve dimensional stability

• Electrolyte temperature 60°C, current density 15A/dm²
• Processing time 3 minutes, surface roughness improved from Ra0.4 to Ra0.1

Perform correction on Schenck balancing machine:

• Balance G2.5 standard
• At 16,000rpm working speed, vibration value less than 1.0mm/s

Comprehensive inspection after processing completion:

• CMM measurement showed hole position index error ≤0.004mm
• Projector inspection showed diaphragm thickness uniformity deviation <0.003mm
• Torque test showed transmission efficiency reached 98.2%
• Fatigue test passed 100,000 cycles without failure

After applying this batch of couplings to customer's robot products:

• Robot repeat positioning accuracy reached ±0.008mm, exceeding design requirements
• Production line cycle time shortened by 40%, production efficiency significantly improved
• Operating noise reduced by 15dB, working environment significantly improved
• 18 months of fault-free operation, reliability verified

Through this case, we established standard process specifications for diaphragm coupling precision machining, successfully overcoming key technical difficulties such as thin-walled part deformation control, high-precision index machining, and surface integrity assurance, providing reliable technical accumulation and practical experience for similar precision transmission parts processing.