Circulation Modes of Ball Screws
I. External Circulation
In external circulation, the return methods of ball screw nuts differ, mainly including three types: spiral groove type, pipe insertion type, and end cover type.
1. End Cover Type
The nut is provided with a longitudinal hole to allow the balls in the ball screw kit to return to their original position smoothly. Therefore, an opening is made on the cover plate for the ball return. The balls achieve circulation with the help of these two measures.
2. Pipe Insertion Type
A curved pipe is used, and this design process can stably ensure ball return. For this type of ball screw, it should be noted that the radial diameter of the curved pipe must be increased to ensure that it protrudes outside the nut.
3. Spiral Groove Type
The spiral groove type nut has a spiral groove milled on its outer surface, which can be identified visually.
II. Internal Circulation
In internal circulation ball screws, the use of a reverser is crucial as it ensures the precondition for ball circulation. Typically, there are two types of reversers: cylindrical convex key type and flat circular insert type.
The repair methods for the raceway of ball screws:
1. Slight local wear on the raceway
Use a diamond file or oilstone to locally trim and smooth the worn and raised areas.
2. Slight overall wear on the raceway
Place the ball screw between the two centers of a thread grinding machine.
Strictly control the grinding amount (should not be too large), and restore its function and accuracy by adjusting the clearance or replacing larger ball bearings.
3. Severe wear on the raceway
Use the above method to grind the ball screw on a thread grinding machine. The grinding amount is determined based on the degree of wear, and finish grinding is carried out according to the size of steel balls with the same diameter.
The pitch diameter, tolerance, and pitch remain unchanged, and only the "R" value of the raceway is modified. Replace the steel balls according to the new "R" value and manufacture a new nut. The repaired screw should be as good as new.
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