Dynamics modeling and analysis of feed drive system for a frame saw machine considering time-varying load
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-01-01 |
| Journal | Mechanics & Industry |
| Authors | Depeng Sun, Jinsheng Zhang |
| Institutions | Shandong University |
| Citations | 5 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study presents the dynamic modeling and analysis of a novel, heavy-duty Feed Drive System (FDS) designed for frame saw machines used in cutting dimension stone (granite).
- Core Value Proposition: The proposed FDS, utilizing a servo-driven rotary-nut lead screw, achieves significantly higher stiffness and stability compared to traditional asynchronous motor/chain systems, directly reducing diamond tool wear.
- Performance Improvement: Simulation results show the new FDS exhibits a faster response feed and substantially less velocity fluctuation, bringing the maximum undeformed chip thickness closer to the ideal state.
- Dynamic Modeling: A six Degree-of-Freedom (DOF) dynamic model was established using the Lumped Parameter Method (LPM) to predict system behavior under time-varying loads.
- Load Sensitivity: The natural frequencies of the FDS vary nonlinearly with stone mass removal. The first-order natural frequency (f1) range increased by 57.2% (from 20.05 Hz to 31.2 Hz) as the load decreased, demonstrating high sensitivity.
- Resonance Risk: Modal testing confirmed that the first two natural frequencies of the saw blade (22 Hz and 44 Hz) fall within the FDS operating frequency range, highlighting a critical risk of resonance that could increase the sawing gap and affect product quality.
- Design Guidance: The analysis provides essential data for optimizing FDS design parameters to mitigate vibration, reduce diamond wear, and improve overall processing quality (flatness).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Stone Material Hardness | 6-7 | Mohs scale | Granite processing. |
| Acceptable Slab Flatness | 1.5 | mm/m | Geometrical accuracy requirement. |
| Screw Mass (ms) | 160 | kg | Component mass. |
| Stone Platform Mass (mt) | 750 | kg | Baseline load mass. |
| Axial Stiffness of Screw (Ksa) | 8.4 x 107 | N/m | Key stiffness parameter. |
| Elastic Modulus (E) | 2.06 x 105 | MPa | Screw material property. |
| Transmission Ratio (ir) | 3.18 | Dimensionless | Nut-screw system ratio. |
| First Natural Frequency (f1) Range | 20.05 to 31.2 | Hz | Shift due to load variation (57.2% change). |
| Second Natural Frequency (f2) Range | 216.5 to 265.8 | Hz | Shift due to load variation (22.8% change). |
| Saw Blade First Natural Frequency | 22 | Hz | Experimental modal test result. |
| Saw Blade Second Natural Frequency | 44 | Hz | Experimental modal test result. |
| Screw Pitch (p) | 10 | mm | Helical pitch of trapezoidal screw. |
Key Methodologies
Section titled âKey Methodologiesâ- System Configuration: A novel FDS was designed using a servo motor to drive a rotary nut on a vertical trapezoidal screw, replacing the traditional chain and asynchronous motor system to achieve higher stiffness and speed control.
- Dynamic Modeling (LPM): The FDS was modeled as a six Degree-of-Freedom (DOF) system using the Lumped Parameter Method (LPM), accounting for the torsional stiffness of the coupling, bevel gear shaft, and nut, as well as the axial stiffness of the screw and supporting bearings.
- Equation Derivation: Lagrangeâs energy method was applied to formulate the kinetic energy (T) and potential energy (V) of the system, leading to the dynamic equation of motion in matrix form (Mq + Kq = Q).
- Frequency Response Analysis: The dynamic equation was converted into state-space form (X = AX + BU) to solve for the natural frequencies and acceleration amplitudes under varying conditions.
- Time-Varying Load Simulation: The analysis investigated the frequency response characteristics of the FDS as the stone mass (load) decreased from 6000 kg to 3000 kg, simulating material removal during processing.
- Velocity Fluctuation Comparison: The velocity characteristics of the new FDS were simulated using Simulink-Simscape and compared against the performance of the traditional FDS.
- Modal Testing: Experimental modal tests were performed on the tensioned saw blade (using a hammer and acceleration sensor) to determine its first two natural frequencies and verify the potential for resonance with the FDS operating range.
Commercial Applications
Section titled âCommercial Applicationsâ- Dimension Stone Processing: Direct application in optimizing frame saw machines for cutting hard materials like granite, improving slab quality and reducing scrap rates.
- Tooling and Consumables: Reduction in diamond particle wear and extension of saw blade life due to stabilized feed speed and minimized maximum undeformed chip thickness.
- Heavy-Duty Machine Tool Design: Provides a validated dynamic model for designing high-stiffness, high-load feed systems, particularly those requiring precise vertical movement (e.g., large CNC gantries, specialized grinding machines).
- Vibration Mitigation Engineering: The analysis of resonance between the FDS and the cutting tool guides the selection of component stiffnesses and operating speeds to avoid instability and increase processing efficiency.
- Servo Control Systems: Implementation of the novel nut-driven system enables the use of semi-closed loop servo control, enhancing speed controllability and eliminating hysteresis nonlinearity inherent in traditional chain drives.
View Original Abstract
Frame saw machine is one of machine tools that is used to process dimension stone. The velocity fluctuation of traditional feed drive system (FDS) lead to excessive wear of diamond particles. The dynamic performance of the FDS has time-varying characteristics during the processing of stone with a large material removal rate. In this paper, a novel FDS was proposed. Firstly, the dynamic modeling of FDS was set up on account of lumped parameter method (LPM). Then the speed of the new FDS was compared with that of the traditional FDS. Finally, the frequency response characteristics of the system were solved by Lagrange and state space method. Results showed that the new FDS has a faster response feed and less velocity fluctuation. The natural frequency and the amplitude of acceleration increase with decreasing load. With the time-varying load, the range of the second-order natural frequency increased by 50 Hz, which was larger than that of the first-order. The modal test verified that the first two natural frequencies of the saw blade are within the range of the natural frequencies of FDS. The proposed FDS can guide for design, reduce the wear of diamond, and improve processing quality.