In this paper there is a presentation of a simple and reliable solution used for the clamping and unclamping of the tool holders used on the heavy, horizontal and vertical lathes. The solution is ...used on new machine tools or rebuilded machine tools. The hydraulic unit acts independent or like a part of the total unit. It is very efficient on CNC machine tools.
We present an automated turning insert wear detection system developed for aeronautical Low Pressure Turbines (LPT) casing machining process based on a binary classifier using Convolutional Neural ...Networks (CNN). This method involves acquiring the image on the machine itself. During this process, removing the insert from the tool holder is not necessary, and the wear assessment is performed before the next workpiece is mechanized. Since datasets in tool wear prediction are often imbalanced, a multi perspective camera technology as well as data augmentation and class weighting are utilized to address both the number of worn parts considered and the cost of image acquisition. In this study four different insert types and two CNN architectures (specific and universal models) are considered and evaluated. The effects of data augmentation and training set size are discussed. While the models trained perform well on round inserts, they fail on rhombic insert types. An accuracy up to 97.8% (Matthew’s correlation coefficient of 0.955) is achieved by the machine learning model. Additionally, it can detect defects on a variety of insert types.
•We developed a classification computer vision model for turning tool wear detection.•Our model achieved an accuracy of 97.8% (Matthew’s coefficient of 0.955).•By using a specialized optic we reduced the number of samples to build the dataset.•A minimum number of 2000 images is required to achieve acceptable accuracy.
This article presents an analysis of thermal deformations in a large-scale vertical Lathe, examining the sources of heat and their impact on the machine's thermal deformations. The analysis was ...conducted using both experimental measurements and numerical simulations based on the finite element method. The study highlights the critical role of geometric accuracy, stiffness, and thermal distortions in machine tool design, affecting machining errors. Several machine tool manufacturers implement systems that minimize the impact of thermal distortions using numerical control. However, custom production lacks extensive possibilities, posing challenges in achieving requirements for predictable thermal distortions. This article analyzes the thermal distortions of a custom-produced machine tool and examines their values and consistency with the machine tool's working components' movement. The study emphasizes the predictability and directionality of thermal distortions in large-sized machine tools to maintain geometric accuracy and stiffness. Additionally, the study identifies non-technical aspects related to the division of the worktable into component parts, disrupting the axial symmetry of the construction and causing potential deformations of the workpiece due to thermal deformations.
The machining error of heavy-duty vertical lathes is significantly affected by geometric errors. Thus, this paper investigates the measurement and modeling of heavy-duty vertical lathes for error ...tracing. Specifically, the heavy-duty vertical lathe geometric error is measured by a laser interferometer, its error value is identified, and the polynomial model of the error value is established using a polynomial high-order fitting method. After that, based on the multi-body system theory, the heavy-duty vertical lathe bed and cutting tool topology is created to describe the pose relationship of each component of the heavy-duty vertical lathe. Then, the geometric error model of the heavy-duty vertical lathe is established using a homogeneous transformation matrix, and the virtual machined rotary surface model is constructed by combining the cutting tool trajectory and the eccentric installation of the workpiece. Each geometric error is input into the virtual model to compare its effect on the machining error of the workpiece. Among the 19 errors traced, the
X
-direction positioning error of the horizontal slide, the
X
-direction straightness error of the vertical slide, the
X
-direction straightness error of the workbench spindle, the
X
-direction installation eccentricity error of the workpiece, the rotation angle error of the horizontal slide around the
Y
-axis, and the rotation angle error of the workbench spindle around the
Y
-axis are the key errors heavily impacting the machining error of the heavy-duty vertical lathe. According to the influence of each key error term, the mapping relationship between the error term and the machining error of the workpiece is established to complete the error tracing.
The structural design for worktable stiffeners plays an important role in determining dynamic characteristic of heavy-duty vertical lathe which directly affects the machining performance. In this ...paper, a stiffener design method for worktable stiffeners combining modal analysis and topology optimization is proposed to improve the static and dynamic performances. The dynamic characteristics of worktable are analyzed by modal analysis, and the weak part of the worktable base is determined by combining the results of modal analysis and vibration signal processing. An initial optimal structure of the worktable base is obtained by solid isotropic material with penalization (SIMP) based on topology optimization. Then, the layout of stiffeners is remodeled according to the initial optimal structure by number and size optimization. Finite element analyses are implemented to evaluate the performance of the newly designed structure. The natural frequency of the worktable base is increased by 7.59% with a decrease of 11% in the mass. Experiments are carried out to verify the validity of the proposed stiffener design method. The experimental result also shows that the natural frequencies of the worktable base have increased by more than 10%.
Alignment turning system for precision lens cells Huang, Chien-Yao; Ho, Cheng-Fang; Wang, Jung-Hsing ...
International journal of advanced manufacturing technology,
02/2019, Letnik:
100, Številka:
5-8
Journal Article
Recenzirano
This research increases the ability and value of a traditional vertical lathe and applies to manufacture a precise lens cell for the optical industry. The optical performance is limited by the ...residual centration error and position accuracy of conventional assembly methods. Recently, the development of a poker-chip assembly system with high-precision lens barrels has overcome these limitations and provided a solution for ultra-high-performance optical systems. To develop a high-precision lens cell by using poker-chip assembly, an alignment turning system (ATS), is developed based on a vertical lathe and equipped with tactile and optical measurement modules. Inside the ATS, the building-in the vibration/temperature monitoring sensors, which help to self-monitoring and network communication with the intelligent manufacturing techniques, to understand and master the reliability and efficiency of ATS. This system can manufacture precise lens cells, applied for optical metrology, high numerical aperture objective lenses, and lithography projection lenses. This paper describes the design and development of the ATS and its capabilities. The ATS is composed of measurement, alignment, and turning modules. After the ATS completes the measurement, alignment, and turning processes, the centration error of a lens cell, which is 200 mm in diameter, can be controlled to within 10 arcsec. Here, a lens cell with three subcells was assembled through the poker-chip method; each subcell was measured and then it underwent alignment and turning processes. The lens assembly test was performed five times by three technicians, and the average transmission centration error of the assembly lens was 12.45 arcsec. The results demonstrate that the ATS can achieve considerable assembly efficiency for high-precision optical systems.
Purpose
The purpose of this paper is to study thermal-fluid-solid coupling deformation and friction failure mechanism of bearing friction pairs under the working conditions of high speed and heavy ...load.
Design/methodology/approach
The deformation is simulated based on thermal-fluid-solid coupling method, its deformation distribution law is revealed and the relationships of deformation of friction pairs, rotational speed and bearing weight are obtained.
Findings
The results prove that the oil film temperature rises sharply, the lubricating oil viscosity decreases rapidly, the film thickness becomes thinner, the deformation increases, the whole deformation is uneven and the boundary lubrication or dry friction are caused with the increase in rotational speed and bearing load.
Originality/value
The conclusions provide theoretical method for deformation solution and friction failure mechanism of hydrostatic thrust bearing.
Purpose
The purpose of this study with the rapid development of the heavy/large mechanical equipment, the heavy computer numerical control (CNC) vertical lathe has become the ideal processing ...equipment for the parts of those mechanical equipments. The main factor which affects the machining quality and efficiency of heavy CNC vertical lathe is the mechanical properties of the hydrostatic thrust bearing.
Design/methodology/approach
This paper did the research based on the large size sector oil pad’s lubrication performance of the hydrostatic thrust bearing in the heavy/large equipments, establishing the lubrication performance distribution mathematical model of the velocity field, flow field, pressure field and so on, analyzing the bearing behavior of the large size sector oil pad.
Findings
The results show that the oil flow generated by the plate relative motion will be greater than that generated by the pressure difference in area B, with the rotational speed’s increasing of the hydrostatic thrust bearing, and the direction is opposite. The oil flow generated by the centrifugal force will be greater than that generated by the pressure difference in area C, with the rotational speed’s increasing of the hydrostatic thrust bearing, and the direction is opposite. When the rotational speed of the hydrostatic thrust bearing is too high, the friction heat will be not easy to be sent out. The bearing rotating speed should be lower than the comparatively smaller one of ω1 and ω2, which can help avoid the rise of too high temperature.
Originality/value
The research provides powerful theoretical foundation for practical application of the large size sector oil pad hydrostatic thrust bearing, its structure design and operating reliability, realizing the lubrication performance prediction of the large size hydrostatic thrust bearing.
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