I. Blank Pre-treatment: Avoiding Potential Problems in Subsequent Machining
1. Material Confirmation
This part is made of 45# steel. The hardness of the blank must be tested first (180-220 HBW is acceptable; exceeding this hardness requires annealing).
2. Rough Turning Datum
First, turn the outer diameter/inner hole, leaving a 3mm machining allowance;
The end face must be machined flat (flatness ≤0.05mm) as the positioning datum for subsequent clamping.
II. Core Details of Tooth Profile Machining (CNC Milling)
1. Clamping and Positioning
Use a three-jaw chuck to clamp the turned outer diameter, positioning it with the end face as the datum (alignment requires a dial indicator; radial runout ≤0.02mm); for thin-walled structures, copper shims must be placed between the chuck jaws and the workpiece to prevent damage/deformation caused by clamping.
2. Cutting Tools and Parameters
Use a carbide end mill (6-flute, cutting length adjusted according to tooth depth);
Cutting parameters: Spindle speed 8000 rpm, feed rate 500 mm/min, depth of cut 0.3 mm per layer (to prevent tool chipping).
3. Tooth Profile Accuracy Control
Turn on high-pressure cutting fluid during milling (to flush away chips and prevent tooth surface scratches);
Pause after machining 5 teeth to check the tooth pitch error (tolerance ≤ 0.03 mm). If the error exceeds the tolerance, adjust the tool compensation.
III. Internal Hole and End Face Finishing
1. Internal Hole Boring
Change the boring bar, first rough bore the internal hole (leaving a 0.5 mm allowance), then finish bore to the drawing dimensions (roundness ≤ 0.01 mm);
After finish boring, recheck with an inside micrometer to ensure the clearance with the mating shaft is between 0.02-0.04 mm.
2. End Face Finishing
Using the machined inner hole as a reference, machine two end faces (parallelism ≤ 0.02 mm); the edges of the end faces must be chamfered to C0.5 (to avoid sharp edges scratching assembly personnel).
IV. Post-processing and Quality Inspection
1. Deburring
Remove burrs from the tooth root and inner hole with a nylon brush (do not use a file to avoid damaging the tooth profile accuracy); lightly polish the tooth surface with fine sandpaper (800 grit) to ensure a surface roughness Ra ≤ 1.6 μm.
2. Final Inspection Items
Tooth Profile: Radial runout ≤ 0.03 mm, measured using a gear runout meter;
Dimensions: Outer diameter and inner hole dimensions measured with a micrometer, tolerances conforming to IT7 grade requirements;
Appearance: Surface free of scratches, nicks, or cutting fluid residue.