Machine Tool Structural Testing Under Rotating and Static Loads
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Solution Overview
Problem
Existing methods for determining structural characteristics of machine tools fail to accurately account for the influence of static loads and rotational speeds during machining, leading to prediction errors in stability lobes diagrams due to differences between measurement and actual machining conditions.
Innovation Solution
A system comprising an excitation device for dynamic excitation, a preloading device to generate static forces, and a sensing device to acquire data, which simulates machining conditions by combining dynamic and static loads, allowing for precise determination of structural characteristics, especially during tool rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If impact testing with a manually operated hammer is used to determine structural characteristics, then the measurement process is simple and equipment is basic, but the magnitude and location of impact vary significantly leading to large measurement uncertainty
Solution Approach 1:
The patent replaces the manually operated mechanical hammer with an automated impact generation system that uses a piezoelectric actuator to generate controlled impact forces. This substitution eliminates operator variability while maintaining the basic impact testing concept, thereby reducing measurement uncertainty without significantly complicating the setup.
Solution Approach 2:
The system automatically positions the impactor and generates impact forces without requiring manual operation. The automated positioning system and controlled impact generation allow the system to serve itself, eliminating the variability introduced by human operators while keeping the overall system relatively simple.
2Ease of operation
If impact hammer testing is performed with a non-rotating tool for safety reasons, then the measurement setup is simple and safe, but the measurement conditions differ significantly from actual machining conditions where the tool rotates
Solution Approach 1:
The patent transitions from static impact testing (non-rotating tool) to dynamic impact testing (rotating tool) by implementing an automated impact system that can safely apply impacts to rotating tools. This allows the measurement conditions to match the actual machining conditions while maintaining safety through automation and controlled impact generation.
Solution Approach 2:
The manual hammer operation is replaced with an automated impact generation system using piezoelectric actuators, enabling safe impact testing on rotating tools. This substitution removes the safety constraint that previously prevented rotating tool testing, thereby improving prediction accuracy without compromising operator safety.
3Device complexity
If standard impact hammer testing is used without static load, then the measurement process is straightforward, but the bearing stiffness and tool dynamics differ from machining conditions where static loads are present
Solution Approach 1:
The patent merges the static load application with the dynamic impact testing by integrating a preload mechanism that applies static forces through the bearing system while the impactor generates dynamic excitation. This combination allows simultaneous application of static and dynamic loads, accurately representing machining conditions without significantly increasing process complexity.
Solution Approach 2:
The static preload is applied before the dynamic impact testing to establish the correct operating conditions. By pre-loading the bearing system with static forces that simulate machining conditions, the system ensures that the structural characteristics are measured under representative load states, improving accuracy while keeping the measurement process organized and systematic.
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 enhances the accuracy of structural characteristic determination and stability lobes diagram prediction by replicating machining conditions, reducing measurement uncertainty and operator variability, and enabling more automated setups.
Implementation Method 1
an automatic impact hammer based on a piezoelectric actuator is applied to generate an adjustable and accurate dynamic excitation on the rotating tool
Implementation Method 2
a preloading device including a permanent magnet is configured to act a static force on the tool
Data Source
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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.