Tapping Head Slip Joint and Clutch for Excessive Lead Compensation
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Solution Overview
Problem
CNC machines experience vibration and misalignment during tapping operations due to the acceleration, deceleration, and direction reversal of axis feed drive and spindle motor, leading to damage to taps and workpieces.
Innovation Solution
A tapping head with a slip joint and adjustable clutch pack that introduces axial play and frictional forces to compensate for excessive lead, allowing for adjustable feed rates and optional lockup feature to prevent damage, featuring a drive coupler, thrust springs, friction discs, and a clutch cover for controlled engagement and disengagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rigid coupling between tap and drive mechanism is used, then precision of thread formation is improved, but vulnerability to damage from motor acceleration and reversal increases
Solution Approach 1:
The clutch pack friction characteristics are adjusted by changing the number of friction discs, their material composition, and the compression force applied by springs. This allows optimization of the slip threshold to permit normal machining precision while allowing slip under excessive load conditions caused by motor acceleration and reversal.
Solution Approach 2:
The clutch pack acts as an intermediary between the rigid drive mechanism and the tap. It transmits torque under normal conditions while allowing controlled slip when excessive forces occur, thereby protecting the tap and workpiece from damage while maintaining precision during stable operation.
2Reliability
If slip joint with play is introduced, then protection against excessive lead damage is improved, but precision of feed rate control deteriorates
Solution Approach 1:
The clutch pack friction parameters are carefully selected and adjusted so that the slip threshold is set above normal machining variations but below damage-causing excessive lead forces. This allows the system to maintain precise feed rate control during normal operation while protecting against damage when motors accelerate or reverse unexpectedly.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces vibration and misalignment, minimizing damage to taps and workpieces by allowing for adjustable feed rates and controlled engagement, ensuring reliable operation across various tap sizes.
Implementation Method 1
Extending between the bottom surface of the drive coupler and the upper end of the driver is a plurality of axially aligned thrust springs. During operation, the thrush springs force the driver down rom the drive coupler that forces the driver and the tap into the workpiece.
Implementation Method 2
The clutch pact includes one center support plate that slides longitudinally into the base and includes lugs that engage slots to hold the support plate in a fixed radial position on the base. Located on opposite sides of the support plate is at least one friction disc.
Implementation Method 3
A tapping head is configured to hold and drive different taps with a slip joint that introduces a small amount of play between the tap head and the tap to compensate for excessive lead that may damage the tap or the workpiece.
Data Source
AI summary
A tapping head configured to hold and drive different size taps with a slip joint that introduces a small amount of play bet ween the tap head and the tap to compensate for excessive lead that may damage the tap or the workpiece. The tapping head includes a base, a drive coupler, a drive sleeve, a driver, a clutch pack, a pressure ring, a clutch cover, a drive cover and a lock nut. The driver and drive sleeve are longitudinally coupled by splines that form a slip joint. The clutch pact includes discs that against the inside surface of the base and lower surface of the pressure ring. Mounted on the lower surface of the pressure ring are a plurality of clutch springs that force the pressure ring upward against the clutch pack. Disposed between the drive couple and the driver are thrust springs that exert downward forces on the driver. The clutch cover includes internal threads configured to attach to external threads formed on the base. By tightening the clutch cover on the base, the force exerted by the thrust springs on the pressure ring can be adjusted to change the amount of frictional forces exerted by the clutch pack.