Laser Machining Control for Constant Pulse Interval Accuracy
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Solution Overview
Problem
Laser machining devices face limitations in maintaining constant pulse intervals due to discontinuous changes in pulse cycle, leading to reduced accuracy and defects in machined portions, especially at higher frequencies where the device's resolution constraints prevent smooth hyperbolic changes in pulse frequency.
Innovation Solution
A numerical control device that includes a speed command generation unit, a laser command generation unit, a change rate computation unit, and a speed adjustment unit to adjust the speed command and generate a changed cycle command, ensuring constant pulse intervals by reflecting the device's performance limitations and adjusting the speed command to maintain a target pulse interval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the pulse frequency is increased to maintain constant pitch at higher feeding speeds, then the machining speed is improved, but the pulse cycle changes discontinuously due to device resolution limitations, causing bumps in the pulse cycle graph and non-constant pulse intervals
Solution Approach 1:
The patent changes the control parameter from pulse frequency to pulse cycle. By directly controlling the pulse cycle (time interval between pulses) instead of frequency, the system can maintain constant pulse intervals even at high feeding speeds, avoiding the discontinuous changes that occur when controlling frequency at the device resolution limit.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the actual pulse cycle and adjusting the pulse generation timing to compensate for deviations. This ensures that the pulse interval remains constant despite variations in feeding speed or device limitations.
2Manufacturing precision
If the pulse frequency is changed according to feeding speed to maintain constant pitch, then the machining accuracy is improved, but the device cannot follow the frequency change smoothly at high frequencies, resulting in discontinuous pulse cycle changes
Solution Approach 1:
The patent transforms the control approach by switching from frequency-based control to cycle-based control. This parameter change allows the system to maintain reliable, continuous pulse cycle changes even when operating at high frequencies where frequency control becomes unreliable due to resolution limitations.
3Manufacturing precision
If the pulse frequency is controlled to follow feeding speed changes, then the constant pitch machining is achieved, but the resolution limitation prevents smooth hyperbolic pulse cycle changes, causing step-like bumps
Solution Approach 1:
The patent changes the controlled parameter from frequency (which suffers from resolution limitations) to pulse cycle time. This allows for smooth, continuous adjustment of the pulse timing without the step-like bumps that occur when trying to control frequency at high values with limited resolution.
Solution Approach 2:
The patent transitions from controlling the reciprocal parameter (frequency) to controlling the direct parameter (cycle time). This dimensional change in the control space allows for smoother, more precise control without the resolution issues that plague high-frequency operation.
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
The solution ensures constant intervals of pulsed laser irradiation spots on the machining surface, even with discontinuous changes in pulse cycle, thereby improving the accuracy of laser machining by maintaining a consistent pulse interval.
Implementation Method 1
a pulsed laser emitted from a laser machining head while moving the laser machining head and the workpiece relative to each other
Data Source
AI summary
A numerical control device for controlling a laser machining device that machines a workpiece by means of a pulse laser emitted from a laser machining head while moving the laser machining head and the workpiece relative to each other, said numerical control device being provided with: a speed command generation unit for generating a speed command for controlling the speed of the relative movement on the basis of a machining program; a laser command generation unit for generating a laser output command value that includes at least the frequency and duty of the pulse laser, in accordance with the speed command; a change rate calculation unit for calculating a period command for the pulse laser on the basis of the frequency, and calculating a change rate of a changed period command changed by a limitation for the performance of the laser machining device; and a speed adjustment unit for using the change rate to adjust the speed command generated by the speed command generation unit.