Abstract
Machining Centres have been major production units for many decades with desired levels of accuracy, economy in costs of production and ease of control. Though new disruptive technologies ...such as rapid manufacturing, near net shape manufacturing technologies are replacing these machining units, still small and medium Indian Industries go with the conventional ways of large-scale production using conventional and classical machining approaches. With huge setups in place, such machines with high productivity demands, require stringent parts alignment tests frequently from time to time, referred to as Geometrical or Alignment tests to enable accurate finishing and machining of parts and smooth and uninterrupted production. This paper puts forth some basic Geometrical Tests performed on SB CNC 60 Lathe Machine Tool unit, identifying major deviations measurements and reconditioning the machine parts. The main objective of running such tests is to prevent breakdown of the machine and ensure safety working when handling older and heavier conventional machines.
This paper presents a thermal error model for a lathe CNC machine using temperature on moving parts, which is usually a difficult measurement. Different working conditions are performed to obtain ...temperature and thermal displacement of the machine. A multi-linear regression model is applied for modelling relationship between temperatures and thermal errors. Data of two constant working conditions are implemented to find out the fitting function. Through analysis, it shows that thermal errors for X- and Z-axes can be estimated based on only four temperature points (T
2
, T
3
, T
10
and T
12
for the X-axis and T
4
, T
6
, T
7
and T
11
for the Z-axis). Results reveal that using movable part temperature data (T
12
), the average and maximum error in the predicted thermal displacement of the X-axis can be reduced about 1/3 and 2/5 compared to without using T
12
, while the movable temperature point on Z-Screw (T
8
) has a tiny effect on the average and maximum error of predicted thermal displacement of the Z-axis. Results herein can provide useful information to develop a thermal compensation for the CNC lathe machine.
•An electro-mechanical actuator system for CNC-Lathe is proposed•Electro-mechanical actuator aims to substitute the traditional hydraulic CNC lathes•A whole mechatronics system operation with ...different modes are proposed•Different tests are performed to validate applicability of the actuator
A superior model of a novel electromechanical actuator for the computer numerical controlled (CNC) lathe has been proposed. The proposed actuator aims to achieve a high thrust of 50 kN and a spindle speed of 6000 RPM. Furthermore, a ball screw drawbar is used in the proposed model to reduce friction losses and improve mechanical efficiency. The clutch, which decides the operation mode transition in the actuator is designed by combined operation of friction plates and solenoid operated air-piston. The improved mechanical efficiency of the drawbar has helped in the reduction of the torque-speed rating of the actuator drive motor. Moreover, In terms of system power consumption, the proposed actuator consumes 90% lower power than its hydraulic counterpart. Different tests are performed on the prototype to validate its performance and machining precision.
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Thermal error of spindle is critical to the slant bed CNC lathe towards high machining precision. The heat generated by the spindle itself contributes to the thermal error indeed. However, the ...thermal error is also influenced by the thermal deformation of other components such as the turret and lathe bed, especially in complex structured slant-bed CNC lathes where error coupling commonly exists. In order to achieve robust modeling of thermal error, a decomposition method was proposed in this paper to separate the contributions of spindle, turret and lathe bed from the overall measured thermal deformation. The thermal error coupling relationship was established from the perspective of machine tool construction. A specific testing scheme was designed to determine the parameters of decoupling model. Additionally, a comparative experiment was carried out by placing the sensor support horizontally and vertically to verify the effectiveness of thermal error decoupling. Taking T65-750 high-precision CNC lathe as the object, the relationship between thermal error and tilt angle in the X-direction of the headstock, bed, and other components was revealed, achieving robust prediction of thermal error irrespective of the ambient temperature subject to change. Finally, the thermal error model built based on error decomposition was applied to improve the machining accuracy of cylindrical parts dramatically in practice.
This article proposes the design and driving mechanism of a single drive motor integrated electromechanical actuator system for the application in computer numerical control (CNC) lathe machines. The ...electromechanical actuator is designed in such a way that it can replace the conventionally used hydraulically powered headstocks of the lathe machine. To achieve a drawbar thrust of 50 kN and a spindle speed of 4000 r/m, a detailed design with an explanation of different internal parts of the electromechanical actuator is presented. The production ready model was simulated to select the safety factor of the whole system and to enquire the amount of deformation when 50 kN thurst is generated. A prototype is manufactured based on the analysis model and is tested for different modes of operation. The experimental results validate the capability of the electromechanical actuator to produce the require drawbar thrust of 50 kN and spindle speed of 4000 r/m.
A machining center is a common machine tool that can machine complex free-form surfaces such as the press mold, automobile’s cam profile. When these curved surfaces are machined by the conventional ...machining center and/or the grinding machine, it takes lot of time to complete with enough accuracy. In order to solve this problem, this study aims not only to improve the machining accuracy of this curved surface but also to make it possible to shorten the machining time using a CNC lathe. In this study, the NACS-Turning (Non-axisymmetric curved surface turning) method that we proposed originally was used. The spindle of C-Axis, the moving table with the cutting tool of X1-Axis, the other counter moving table of X2-Axis (without involved in shape creation, only used to suppress inertial force), the head stock of Z-Axis, and the tool rotation axis of B-Axis are adapted. In this 4-Axis machining method, all the axes are controlled with the synchronized manner. This method can machine the same rotational position of workpiece with the same cutting edge of the rotary tool. As an experiment, we compared 4-Axis machining with synchronized spindle and tool rotation, 3-Axis machining, and machining without synchronous rotation. Our new 4-Axis machining method with synchronized spindle and tool rotation reduced the form error from 323 ㎛ to 247 ㎛ and the surface roughness from Rz 9.6μm to Rz 3.7μm. Moreover, the repetitive machining resulted in error of 99.6μm and a surface roughness of Rz2.9μm.
A machining center is a common machine tool that can machine complex free-form surfaces such as the press mold, automobile’s cam profile. When these curved surfaces are machined by the conventional ...machining center and/or the grinding machine, it takes lot of time to complete with enough accuracy. In order to solve this problem, this study aims not only to improve the machining accuracy of this curved surface but also to make it possible to shorten the machining time using a CNC lathe. In this study, the NACS-Turning (Non-axisymmetric curved surface turning) method that we proposed originally was used. The spindle of C-Axis, the moving table with the cutting tool of X1-Axis, the other counter moving table of X2-Axis (without involved in shape creation, only used to suppress inertial force), the head stock of Z-Axis, and the tool rotation axis of B-Axis are adapted. In this 4-Axis machining method, all the axes are controlled with the synchronized manner. This method can machine the same rotational position of workpiece with the same cutting edge of the rotary tool. As an experiment, we compared 4-Axis machining with synchronized spindle and tool rotation, 3-Axis machining, and machining without synchronous rotation. Our new 4-Axis machining method with synchronized spindle and tool rotation reduced the form error from 323 ㎛ to 247 ㎛ and the surface roughness from Rz 9.6μm to Rz 3.7μm. Moreover, the repetitive machining resulted in error of 99.6μm and a surface roughness of Rz2.9μm.
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