A method and device for online monitoring of part dimensions during machine tool milling.
By using optical 3D reconstruction technology to monitor the dimensions of parts in real time during machine tool processing, the problem of precision loss caused by thermal deformation and mechanical wear is solved, achieving efficient closed-loop control and precision improvement.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INST OF CHEM MATERIAL CHINA ACADEMY OF ENG PHYSICS
- Filing Date
- 2024-12-18
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies struggle to monitor and compensate for machining accuracy losses caused by thermal deformation and mechanical wear in real time during machine tool processing, especially regarding temperature changes and tool wear during the transition between drilling, roughing, and finishing.
Optical 3D reconstruction technology based on pulsed light source, beam expansion and collimation optical path, diffuser, projection lens and area array camera is adopted. By projecting a speckle illumination pattern with alternating light and dark and using stereo vision algorithm, the size of the parts can be monitored and fed back in real time, forming a closed loop control.
It enables real-time dimensional monitoring during parts processing, effectively compensating for errors caused by machine tool thermal deformation and mechanical wear, thereby improving processing accuracy and production efficiency.
Smart Images
Figure CN119566970B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of CNC machine tool processing technology, and more specifically to a method and device for online monitoring of part dimensions during machine tool milling. Background Technology
[0002] High productivity and high machining accuracy have always been important technological development directions for CNC machine tools. The thermal stability of machine tools and the wear of transmission mechanical structures are significant factors restricting machining accuracy and efficiency. On the one hand, the constantly changing machining tasks make it difficult for machine tools to achieve thermal stability. The continuous switching between drilling, roughing, and finishing operations causes constant changes in machine tool temperature. Under these conditions, thermal deformation of the machine tool's lead screw, guide rails, and bed structure significantly affects machining accuracy, thus necessitating a reduction in productivity to meet the requirements of machine tool thermal stability. On the other hand, wear of the drive mechanism and machining tools also causes deviations between the machined parts and the design dimensions. Current closed-loop system control machine tools can achieve full monitoring and feedback of the feed mechanism through position detection using linear encoders, encoders, and displacement sensors, ultimately achieving closed-loop control and eliminating positioning errors caused by drive component backlash and lead screw thermal expansion. However, such technologies cannot completely compensate for the loss of machining accuracy caused by overall bed thermal deformation and mechanical wear.
[0003] In recent years, non-contact high-precision 3D reconstruction technology based on optical measurement has developed rapidly. In particular, active optical 3D reconstruction technology, with its advantages of high stability and high precision, has been widely used in various fields of production and life, such as industrial inspection, reverse engineering, cultural relic protection, clinical medicine, virtual reality, and autonomous driving, providing conditions for direct online monitoring of part dimensions during CNC machine tool machining. However, the current mainstream phase-based fringe profile measurement technology usually requires a long data acquisition time and is mainly used for the 3D measurement of static objects. However, parts in machining processes often have large rotational or displacement velocities, requiring rapid 3D profile measurement, which current technology cannot meet. Summary of the Invention
[0004] The purpose of this invention is to provide a method and apparatus for online monitoring of part dimensions during machine tool milling, in order to solve the technical problems in the background art.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] An online monitoring device for part dimensions during machine tool milling includes: a pulse light source, a beam expander and collimator, a diffuser, a projection lens, and an area array camera; the pulse light source, the beam expander and collimator, the diffuser, and the projection lens are located on the same projection optical axis; the positional relationship from upstream to downstream is pulse light source, beam expander and collimator, diffuser, and projection lens; there are two area array cameras, located on opposite sides of the projection optical axis.
[0007] In some embodiments, the angle between the optical axes of the two area scan cameras is not less than 15°; the spatial angle between the optical axis of any area scan camera and the projection optical axis is not less than 10°.
[0008] In some embodiments, the relative positions of the pulsed light source, diffuser, projection lens, and area array camera remain constant.
[0009] In some embodiments, the pulsed light source is a laser or LED light source device that can continuously generate light pulses with a pulse width of 10ns-10μs, a pulse frequency of 0.1Hz-100Hz, a single pulse energy of 1μJ-500mJ, and a wavelength of 400nm-700nm.
[0010] In some embodiments, the diffuser is a frosted glass lens made of quartz or resin, and the transmittance of the pulsed light signal is greater than 10%.
[0011] In some embodiments, the beam-expanding collimating optical path outputs light that is projected onto the part in the form of a cone beam, forming a speckle illumination pattern with alternating bright and dark areas and uniform distribution on the surface of the part.
[0012] In some embodiments, the area scan cameras are equipped with imaging lenses, and the spatial resolution of the final image is better than 0.1 mm / pixel.
[0013] This embodiment also provides a method for online monitoring of part dimensions during machine tool milling, implemented based on any of the aforementioned devices, including the following steps:
[0014] 1) Multiple area array cameras obtain their intrinsic and extrinsic parameter matrices through calibration;
[0015] 2) Pulsed light source projection illumination of the target area;
[0016] 3) Two area scan cameras capture images of the target area respectively;
[0017] 4) Use relevant algorithms to perform pixel-by-pixel stereo matching based on speckle features;
[0018] 5) Use camera calibration data and image stereo matching information to perform 3D reconstruction, obtain the 3D contour information of the part test area, and calculate the dimensional values;
[0019] 6) The obtained real-time part dimension data is fed back to the machine tool control system for deviation compensation, thereby realizing closed-loop control.
[0020] The present invention has the following beneficial effects:
[0021] Using the method and apparatus proposed in this invention, optical three-dimensional measurement technology can be employed to avoid contact with the parts and achieve online dimensional monitoring during the part processing. Furthermore, the method and apparatus proposed in this invention directly monitor and feed back real-time dimensional measurement data of the processed parts to the machine tool control system. Compared to the feedback of parameters such as position, speed, and acceleration in traditional closed-loop control strategies, this approach better reflects the comprehensive processing deviations caused by multiple error sources such as thermal strain and mechanical wear, enabling better compensation and correction, and improving processing accuracy. Attached Figure Description
[0022] Figure 1 This is a structural diagram of this application.
[0023] Diagram description: 1-Pulse light source, 2-Beam expander and collimator optical path, 3-Diffuser, 4-Projection lens, 5-Projection optical axis, 6-Area scan camera, 7-Area scan camera optical axis. Detailed Implementation
[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The described embodiments are some, but not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0025] The embodiments of this application will now be described in detail with reference to the accompanying drawings.
[0026] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0027] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.
[0028] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or display that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or display.
[0029] The following will combine Figure 1 This application provides a detailed description of a method and apparatus for online monitoring of part dimensions during machine tool milling, as described in the embodiments of this application. It is worth noting that the following embodiments are merely illustrative of this application and do not constitute a limitation thereof.
[0030] Example 1:
[0031] This invention provides a method and device for online monitoring of part dimensions during machine tool milling based on pulse projection illumination stereo vision. To monitor the loss of machining accuracy caused by overall thermal deformation of the machine bed and wear of the transmission mechanical structure, and to achieve real-time measurement and feedback of part dimensions, this invention provides a method and device for online monitoring of part dimensions during machine tool milling, employing the following technical solution:
[0032] An online monitoring device for part dimensions during machine tool milling includes: a pulse light source, a beam expander and collimator, a diffuser, a projection lens, and an area array camera; the pulse light source, the beam expander and collimator, the diffuser, and the projection lens are located on the same projection optical axis; the positional relationship from upstream to downstream is pulse light source, beam expander and collimator, diffuser, and projection lens; there are two area array cameras, located on opposite sides of the projection optical axis.
[0033] The pulsed light source can be a laser, LED, or other light source device, capable of continuously generating light pulses with a pulse width of 10ns-10μs, a pulse frequency of 0.1Hz-100Hz, a single pulse energy of 1μJ-500mJ, and a wavelength of 400nm-700nm.
[0034] The diffuser is a frosted glass lens made of quartz or resin, with a transmittance of more than 10% for pulsed light signals.
[0035] A further technical solution is that the projection lens has a focusing mechanism to adjust the projection magnification.
[0036] The beam-expanding and collimating optical path outputs light that is projected onto the part in a cone-beam form, forming a speckle lighting pattern with alternating bright and dark areas and uniform distribution on the surface of the part.
[0037] A further technical solution is to use at least two area scan cameras. The spatial angle between the optical axes of any two area scan cameras is not less than 15°, and the spatial angle between the optical axis of any area scan camera and the optical axis of the projection is not less than 10°.
[0038] A further advanced technical solution is that each area scan camera is equipped with an imaging lens, resulting in a spatial resolution better than 0.1mm / pixel.
[0039] A further technical solution involves maintaining the relative spatial positions of the optical axes and projection optical axes of multiple area scan cameras, and obtaining the intrinsic and extrinsic parameter matrices of the multiple area scan cameras through calibration. Images captured by any two area scan cameras are used to perform pixel-by-pixel stereo matching based on speckle information using relevant algorithms. 3D reconstruction is then performed using camera calibration data and image stereo matching information to obtain the 3D contour information of the part's test area.
[0040] A further technical solution is to feed the aforementioned three-dimensional contour information back to the machine tool control system for deviation compensation, thereby achieving closed-loop control.
[0041] This invention employs optical 3D measurement technology, enabling real-time dimensional monitoring and feedback of parts without physical contact. During high-speed cutting, short-pulse speckle illumination combined with an area array camera is used to rapidly image and reconstruct the target area of the part, achieving real-time acquisition of its external dimensions during machining. The measuring device primarily comprises a pulse light source, a beam expander and collimator, a diffuser, a projection lens, and an area array camera. Its compact structure allows for adjustment of the device's pose and lens parameters based on the size and shape of the monitored part, achieving high-precision and rapid dimensional measurement. The acquired dimensional information is fed back to the machine tool control system, forming a closed-loop control mechanism that corrects machining errors caused by thermal deformation and mechanical wear of the machine tool's mechanical structure, thereby improving machining accuracy.
[0042] The present invention provides a method for online monitoring of part dimensions during machine tool milling, comprising the following steps:
[0043] 1) Multiple area array cameras obtain their intrinsic and extrinsic parameter matrices through calibration;
[0044] 2) Pulsed light source projection illumination of the target area;
[0045] 3) Two area scan cameras capture images of the target area respectively;
[0046] 4) Use relevant algorithms to perform pixel-by-pixel stereo matching based on speckle features;
[0047] 5) Use camera calibration data and image stereo matching information to perform 3D reconstruction, obtain the 3D contour information of the part test area, and calculate the dimensional values;
[0048] 6) The real-time dimensional data of the parts obtained in the above steps are fed back to the machine tool control system for deviation compensation, thereby realizing closed-loop control.
[0049] The above description is merely a preferred embodiment of the present invention and is intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A device for online monitoring of part dimensions during machine tool milling, characterized in that, include: Pulsed light source, beam expander and collimator optical path, diffuser, projection lens, area array camera; The pulsed light source, beam expander and collimator optical path, diffuser, and projection lens are all on the same projection optical axis; The positions of the components from upstream to downstream are: pulsed light source, beam expander and collimator optical path, diffuser, and projection lens; there are two area array cameras, located on opposite sides of the projection optical axis. The online monitoring device for part dimensions during the machine tool milling process employs the following monitoring methods, including: 1) Multiple area array cameras obtain their intrinsic and extrinsic parameter matrices through calibration; 2) Pulsed light source projection illumination of the target area; 3) Two area scan cameras capture images of the target area respectively; 4) Use relevant algorithms to perform pixel-by-pixel stereo matching based on speckle features; 5) Use camera calibration data and image stereo matching information to perform 3D reconstruction, obtain the 3D contour information of the part test area, and calculate the dimensional values; 6) The obtained real-time part dimension data is fed back to the machine tool control system for deviation compensation, thereby realizing closed-loop control.
2. The online monitoring device for part dimensions during machine tool milling as described in claim 1, characterized in that, The angle between the optical axes of the two area scan cameras shall not be less than 15°; the spatial angle between the optical axis of any area scan camera and the projection optical axis shall not be less than 10°.
3. The online monitoring device for part dimensions during machine tool milling as described in claim 1, characterized in that, The relative positions of the pulsed light source, diffuser, projection lens, and area array camera remain constant.
4. The online monitoring device for part dimensions during machine tool milling as described in claim 1, characterized in that, The pulsed light source is a laser or LED light source device that can continuously generate light pulses with a pulse width of 10ns-10μs, a pulse frequency of 0.1Hz-100Hz, a single pulse energy of 1μJ-500mJ, and a wavelength of 400nm-700nm.
5. The online monitoring device for part dimensions during machine tool milling as described in claim 1, characterized in that, The diffuser is a frosted glass lens made of quartz or resin, with a transmittance of more than 10% for pulsed light signals.
6. The online monitoring device for part dimensions during machine tool milling as described in claim 1, characterized in that, The beam-expanding and collimating optical path outputs light that is projected onto the part in a cone-beam form, forming a speckle lighting pattern with alternating bright and dark areas and uniform distribution on the surface of the part.
7. The online monitoring device for part dimensions during machine tool milling as described in claim 1, characterized in that, All area scan cameras are equipped with imaging lenses, and the spatial resolution of the final image is better than 0.1mm / pixel.