One-Sided Workpiece Carrier Layout for Stiff, Lightweight Machine Tools
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Solution Overview
Problem
Prior machine tools with three guide rails suffer from reduced stiffness due to one-sided bearing, leading to compromised machining accuracy and quality, and result in static overload and increased weight.
Innovation Solution
A machine tool design with three parallel guide rails, where the workpiece positioning device is supported by two carriages connected via a rotary drive, allowing vertical support and pivot motion, reducing static overload and enabling better force distribution, and utilizing rolling element revolving shoes for enhanced stability and reduced friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If only two guide rails are arranged on the two sides of the linear motor (omitting the third guide rail beyond the chip channel), then the machine structure becomes more compact and accessibility is improved, but the stiffness of the freely projecting workpiece support is reduced
Solution Approach 1:
The workpiece positioning device is divided into two separate moving carriages: a first moving carriage supported by two guide rails and a second moving carriage supported by one guide rail. The workpiece carrier connects both carriages, distributing the support function across multiple segments rather than relying on a single rigid structure. This segmentation allows compact design while maintaining adequate stiffness through the distributed support system.
2Strength
If a workpiece positioning device is moved on a machine bed with three guide rails and supported by six rolling element revolving shoes, then a reliable and stiff workpiece support is achieved, but the device weight and complexity increase
Solution Approach 1:
The support system is segmented into two independent carriage units, each with its own rolling element revolving shoes. The first carriage has shoes on two guide rails, and the second carriage has shoes on one guide rail. This segmentation reduces the total number of shoes from six to five, decreasing weight while maintaining support reliability through the distributed configuration.
Solution Approach 2:
Different parts of the system have different support configurations optimized for their specific functions. The first moving carriage, which carries the drive device, has more robust support with two guide rails and multiple rolling element revolving shoes. The second moving carriage, which is passively dragged along, has simpler support with one guide rail and fewer shoes. This local differentiation reduces overall weight while maintaining stiffness where most needed.
3Adaptability or versatility
If the workpiece carrier is pivotally supported by the second moving carriage with a radial bearing, then pivot motion about the horizontal axis is enabled, but forces acting on the guide rails increase
Solution Approach 1:
The pivot support function is segregated to the second moving carriage, which is specifically designed to handle the pivotal workpiece carrier. By separating the pivot support function from the drive carriage, the guide rail forces are distributed more evenly. The second carriage absorbs the pivot-related forces through its radial bearing configuration, preventing concentration of forces on any single guide rail.
4Speed
If the first moving carriage is driven by a linear motor arranged between the first and second guide rails, then the carriage can be moved in the moving direction, but static overload occurs on the guide rails
Solution Approach 1:
The drive function is localized to the first moving carriage, which is supported by two guide rails and equipped with rolling element revolving shoes for smooth movement. The linear motor is positioned between these two guide rails, creating a balanced force distribution during acceleration and deceleration. This segmented drive arrangement prevents static overload by distributing the driving forces across two guide rails rather than concentrating them on one.
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 accuracy and quality, reduces weight by up to 30%, allows for greater accelerations, and improves accessibility, while minimizing forces on guide rails and tolerance specifications.
Implementation Method 1
The first moving carriage (20) has, on the first and on the second guide rail (18, 19), at least two, in particular two, rolling element revolving shoes (21, 22, 23, 24)
Implementation Method 2
The workpiece carrier (31) is supported by a radial bearing (44) provided on the second moving carriage (45)
Data Source
AI summary
The machine tool (10) has an asymmetrically constructed workpiece positioning device (16) which runs on three guide rails (17, 18, 19). It comprises two carriages (20, 45) which are connected together by a workpiece carrier (31) that is mounted so as to be rotatable about the A axis. While the first carriage (20) serves for the longitudinal and rotary positioning of the workpiece carrier (31), the second carriage (45) is provided merely for supplementary weight support. This results in a mechanically slimline, low-weight structure with high positioning accuracy. High dynamic loadability and thus a high machining rate and particularly high vibration resistance is allowed.