Grinding Spindle Wobble Compensation via Hydrostatic Bearings
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Solution Overview
Problem
Existing tool grinding machines face challenges in achieving high precision due to limitations in repeatability of workpiece clamping and bearing tolerances, leading to potential deformation and inaccuracies during machining.
Innovation Solution
A spindle design with a bearing system that allows for wobble compensation and radial offset between the spindle head and the drive shaft, enabling precise alignment and support of the workpiece through independent linear tilting and radial displacement, while transmitting torque and axial forces effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrostatic bearings are made soft to compensate for wobble movement, then concentricity accuracy is improved, but radial stiffness to receive machining forces deteriorates
Solution Approach 1:
The bearing system is divided into two independent hydrostatic bearings: a first hydrostatic bearing that provides radial support with high stiffness to receive machining forces, and a second hydrostatic bearing that provides axial support and allows wobble compensation. This segmentation enables each bearing to be optimized for its specific function without compromise.
Solution Approach 2:
A magnetic coupling device is introduced as an intermediary between the drive shaft and the spindle head. This magnetic coupling transmits torque while allowing relative movement and wobble compensation, enabling the bearing system to maintain both stiffness and accuracy without direct mechanical constraints.
2Manufacturing precision
If precision bearings are used to maintain alignment, then machining precision is improved, but device cost and complexity increase
Solution Approach 1:
Hydrostatic bearing technology is used to replace complex precision mechanical bearings. The hydrostatic bearings provide precise positioning and support through fluid pressure, achieving high machining precision while simplifying the overall bearing system design and reducing mechanical complexity.
Solution Approach 2:
The magnetic coupling device replaces traditional mechanical torque transmission mechanisms with a magnetic field-based system. This substitution eliminates the need for complex mechanical connections while maintaining torque transmission and allowing for wobble compensation.
3Manufacturing precision
If the collet clamping repeatability is improved, then workpiece positioning accuracy is improved, but the need for steady rests and alignment adjustments increases
Solution Approach 1:
The bearing system and magnetic coupling are designed to automatically compensate for misalignments and wobble movements during operation. This self-compensation mechanism eliminates the need for complex motorized alignment interfaces and manual steady rest adjustments, as the system self-corrects positioning errors.
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
This design enhances machining precision, reduces setup times, and eliminates the need for expensive precision bearings, allowing for accurate positioning and handling of workpieces with improved accuracy and ease of adjustment for different dimensions.
Implementation Method 1
The bearing (11) consists of two partial bearings, which form a front partial bearing and a rear partial bearing. The rear partial bearing has two opposite and mutually displaceable bearing surfaces (24, 34). Between the bearing surfaces (13, 33 and 24, 34) of the front and rear partial bearing, there is at least one hydrostatic bearing.
Implementation Method 2
The hydrostatic bearing is bridged by a rotating coupling, which is formed by a magnetic coupling device with struts.
Data Source
AI summary
The positioning of a cylindrical workpiece (that has to be machined by grinding) can be performed particularly precisely if the workpiece abuts to at least one, preferably two, static supporting elements and is fixed in a collet of a spindle, which allows a wobble compensation as well as a radial displacement of the spindle axis relative to the longitudinal axis of the workpiece.