Machine Tool Structural Testing Under Rotating and Static Loads
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining structural characteristics of machine tools, such as those used in milling processes, are prone to prediction errors due to differences between measurement conditions and actual machining conditions, particularly regarding static loads and rotational speeds, leading to inaccurate stability lobes diagrams.
Innovation Solution
A system comprising an excitation device, a preloading device, and a sensing device that simulates machining conditions by applying both dynamic and static loads to the tool, even during rotation, using magnetic forces and an automatic impact hammer to accurately determine structural characteristics, thereby improving measurement accuracy and automation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard impact hammer measurement is used, then the measurement process is simple and safe, but the measurement conditions differ significantly from actual machining conditions leading to prediction errors
Solution Approach 1:
The measurement system transitions from static impact hammer testing to dynamic excitation during actual spindle rotation and machining operations. The excitation device generates forces while the spindle rotates at operational speeds, and the tool remains clamped in the spindle throughout measurement, accurately replicating real machining conditions and eliminating prediction errors caused by condition mismatches
Solution Approach 2:
The measurement system integrates multiple functions into a single comprehensive setup: the excitation device provides dynamic forcing, the spindle provides rotation, the machining process provides static loading, and the tool remains in its operational clamped position. This multi-functional integration eliminates the need for separate static and dynamic testing phases while maintaining all relevant operational conditions simultaneously
2Measurement precision
If manual impact hammer operation is used, then the equipment is simple, but the magnitude and location of impact vary significantly leading to measurement uncertainty
Solution Approach 1:
The system eliminates manual operator intervention by using an automatic excitation device that generates dynamic forces through controlled vibration or impact mechanisms. The device automatically positions and applies excitation forces consistently, removing human variability from the measurement process while maintaining operational simplicity through automated control systems
Solution Approach 2:
The system incorporates sensors that continuously monitor the actual excitation forces applied and the resulting tool responses. This feedback enables real-time verification and correction of measurement conditions, ensuring consistent excitation magnitude and location while providing data for automated analysis and validation of frequency response functions
3Reliability
If impact testing is performed with non-rotating tool, then safety is improved, but the rotational influence on tool tip dynamics is not captured
Solution Approach 1:
The system uses the spindle's own rotational capability and the tool's clamped position during normal machining operations to perform the measurement. The tool remains securely held in the spindle throughout the process, and the excitation is applied through the tool holder or tool body, eliminating the need to remove or loosely hold the tool, thus maintaining both safety and measurement accuracy
Solution Approach 2:
The measurement system captures tool dynamics under actual rotational conditions by exciting the tool while it rotates at operational speeds within the spindle. This dynamic measurement approach records the true tool tip behavior including centrifugal effects, gyroscopic moments, and bearing stiffness variations with rotation, providing accurate structural characteristics that static testing cannot capture
4Measurement precision
If impact testing without static load is used, then the testing setup is simplified, but the bearing stiffness and contact angle are not accurately represented
Solution Approach 1:
The measurement system combines static and dynamic loading capabilities in a single integrated setup. The machining process itself provides the static load through cutting forces on the tool, while the excitation device simultaneously applies dynamic forces. This multi-functional approach captures the true bearing stiffness and contact angle under combined static and dynamic conditions without requiring separate loading mechanisms
Solution Approach 2:
The system uses the machining process itself to generate the necessary static loading conditions on the tool and bearings. The cutting forces naturally applied during machining operations create the appropriate preload on angular contact ball bearings, eliminating the need for external static loading devices while accurately representing real operational bearing conditions
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 approach allows for precise simulation of machining conditions, reducing prediction errors and enhancing the accuracy of stability lobes diagrams by accounting for both static and dynamic loads, resulting in more reliable frequency response functions and improved process optimization.
Implementation Method 1
using magnetic forces and an automatic impact hammer to accurately determine structural characteristics
Implementation Method 2
An instrumented impact hammer is a device that introduces an excitation force pulse into the test structure by hitting the test structure
Data Source
AI summary
The present invention is directed to a system for determining the structural characteristics of a machine tool. The system comprises an excitation device configured to induce a dynamic excitation in a tool of the machine tool, a preloading device configured to generate a static force on the tool, and a sensing device for acquiring a set of data based on which the structural characteristics of the tool can be determined.