Self-Centring Collet Clamping With Rapid Ring-Nut Changeover
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Solution Overview
Problem
Existing self-centring chucks in machine tools face issues with jaw wear leading to misalignment, lengthy setup times, and limited cutting speeds, which hinder high precision machining and production capacity.
Innovation Solution
A self-centring clamping unit with a collet-holder base and a couplable/decouplable ring nut allows for easy and rapid collet replacement, eliminating the need for multiple bolts and enabling faster setup and higher cutting speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional self-centring chucks with jaws are used, then clamping capability is achieved, but jaw wear leads to misalignment and loss of concentricity over time
Solution Approach 1:
The chuck is divided into separate modular components: the body, the collet, and the ring nut. The collet can be independently replaced without replacing the entire chuck or requiring jaw realignment, thus maintaining concentricity while reducing setup time.
Solution Approach 2:
Instead of making the clamping jaws adjustable and realignable (as in conventional chucks), the invention uses a collet that is pushed axially to engage and disengage. The alignment is maintained by the precise fit between the collet and body, eliminating the need for periodic realignment operations.
2Speed
If conventional self-centring chucks are used, then workpiece clamping is achieved, but installation is complicated and cutting speed is limited due to high moment of inertia
Solution Approach 1:
The invention employs a collet with thin-walled flexible structure that can expand and contract axially to grip and release the workpiece. This flexible design reduces the overall mass and moment of inertia of the rotating assembly, enabling higher cutting speeds while simplifying installation through the modular collet replacement system.
3Productivity
If known collet chucks are used, then reduced weight and higher cutting speeds are achieved, but collet replacement requires multiple bolts and is time-consuming
Solution Approach 1:
The fastening function is extracted from the collet replacement process. The ring nut with threaded engagement provides a simple rotational locking mechanism that secures the collet to the body, allowing for rapid collet changes without requiring multiple bolts or complex fastening operations.
Solution Approach 2:
The invention changes the fastening parameter from multiple bolt engagements to a single threaded rotational engagement. The ring nut's threads engage with corresponding threads in the body, converting the replacement operation into a simple rotational motion that is much faster and easier to perform than bolting operations.
Data Source
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Figure 3a~3b
AI summary
The present invention relates to a self-centring clamping unit (1) for a machine tool (100), configured to clamp a workpiece (P) around a clamping axis (A-A), comprising: - a collet-holder base (2) configured to be mounted on the machine tool (100); - a collet (3), removably mountable on the collet-holder base (2), comprising a plurality of clamping elements (30) arranged around the clamping axis (A-A); - actuation members (4) configured to act on the collet (3) so as to move the clamping elements (30) away from/towards the clamping axis (A-A) to engage/disengage the workpiece (P); - a self-centring ring nut (5) couplable to the collet-holder base (2) for mounting the collet (3) on the collet-holder base (2) so that the actuation members (4) can act on the collet (3), wherein: - the collet-holder base (2) and the self-centring ring nut (5) have respectively a first and a second coupling portion (6, 7) that can be mutually coupled, for example in a threaded manner, so as to fix the self-centring ring nut (5) to the collet-holder base (2) along an axial direction (X-X) parallel to the clamping axis (A-A) - the first and second coupling portion (6) have a first and second ground surfaces (61), respectively, configured to abut against each other to ensure the correct mutual positioning of the self-centring nut (5) and the collet-holder base (2) when coupled.