Informatics Publishing Limited

K. T. Navya ¹, V. Shanmugaraj ¹, G. C. Mohan Kumar ², P. V. Shashikumar ³

Affiliations
1 National Institute of Technology, Karnataka, Surathkal, IN
2 Mechanical Dept., National Institute of Technology, Karnataka, Surathkal, IN
3 Central Manufacturing Technology Institute, Bengaluru, IN

Abstract

The proposed paper aims at designing a real time precision positioning control circuitry for a numerical control device used to control a machine tool with encoder type feedback. More particularly it is intended to design a digital compensating circuit for modifying a position control signal to effect a correction for repeatable linear errors such as the dimensional changes in the machine structure due to changes induced into the structure by operating temperature ranges. The error correction is performed by modifying encoder type position feedback signals supplied to the machine tool controller. This provides real time compensation for thermal errors in positioning of computer numerically controlled machine tools, coordinate measuring machines (CMMs), robots, assembly systems, and the like.

The error correction being accomplished by the Error Correction Circuit(ECC), which adds or subtracts a predetermined number of pulses to the pulses coming from a feedback device such as encoder to compensate for over shoot or under shoot of the machine tool respectively.

Keywords

Elongation of Ball Screw, Encoder Feedback Pulses, Pulse Addition and Subtraction, Thermally Induced Errors.

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Nitin K. Nandeshwar ¹, V. Shanmugaraj ², Vijay Desai ¹, P. V. Shashikumar ³

Affiliations
1 National Institute of Technology, Karnataka, Surathkal, IN
2 Central Manufacturing Technology Institute, Bengaluru, IN
3 Central Manufacturing Technology Institute, Bengaluru

Abstract

Among the factors affecting machine tool accuracy, thermally induced errors are considered to be significant. Thermal effect on machine tools is a well-recognized problem in an environment of increasing demand for product quality. Machine tool thermal distortion accounts for 75 percent of the total machining error. Thermal error models are derived based on the temperature variations data collected from the specified temperature sensors. As a result there has been a great deal of interest in techniques for reducing thermal errors. Error compensation technique is widely used to reduce the thermal errors. The performance of a thermal error compensation system typically depends on the accuracy and robustness of the thermal error model. The general practice is that temperature sensors are mounted at different locations on important elements of machine tool and temperature rise or fall is monitored at a constant interval of time. Based on the temperature measurements, the correction value to be given for each and every slide is computed. This correction value is used to either modify the tool offset table directly or passed on to the servo controller for further action. In the present work a fast and low cost thermal error measurement and compensation system developed and the simulation results are verified through experiments.

Keywords

Machine Tool, Real-Time, Temperature Measurement, Error Compensation, Embedded Controller.

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C. Rajesh Kumar ¹, V. Shanmugaraj ¹, Prakash Vinod ¹, P. V. Shashikumar ¹

Affiliations
1 Central Manufacturing Technology Institute, Bangalore, IN

Abstract

In Ultra precision machining best results are obtained with on-line monitoring and adaptive control of various process parameters during machining. For a reliable on-line process monitoring and error compensation system, it is necessary to have accurate sensor readings. However, sometimes sensors may become faulty and due to failure it gives erroneous or constant values throughout the process. The problem of sensor validation is therefore a critical part of effective process monitoring. The objective of this study is to develop a sensor fault detection module which will be useful for different error compensation /diagnostic techniques needed for the ultra precision machine. A procedure based on Principal Component Analysis (PCA) is developed, which enables to perform detection and identification of sensor failures. PCA is a data driven modelling that transforms a set of correlated variables into a smaller set of new variables (principal components) that are uncorrelated and retain most of the original information. This new index is proposed in order to detect simple and multiple faults affecting the process and diagnose abnormalities in the original system in a robust way. The PCA model maps the sensor variables into a lower dimensional space and tracks their behaviour using Hot teling T² and Q statistics.

Keywords

PCA, Scores, Faulty Sensor, HottelingT², Artificial Drifts, Q Statistics.

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N. Balashanmugam ¹, K. Ankit ¹, K. Niranjan Reddy ¹, V. Shanmugaraj ¹, P. V. Shashi Kumar ¹

Affiliations
1 Central Manufacturing Technology Institute, Bangalore, IN

Abstract

Productivity in manufacture of high aspect ratio cylinders depends on how quickly the inspection parameters are measured and corrective actions are token. Long cylinders undergo a series of processes including bend removal and machining. These processes undergo a series of iterations consuming considerable amount of time for the measurement of straightness of cylinder. In this paper, a concept is proposed, where, the straightness of the bore of a cylinder (barrel) is measured in-situ on the machine. In this method, the barrel diameter and thickness are measured at number of planes using touch trigger probe and ultrasonic transducer respectively. Ultrasonic transducer assembly and the touch trigger probe are mounted on the turret of the CNC Turn Mill Centre. The setup for ultrasonic based measurement includes a nozzle for the supply of stream of liquid on the work piece, an ultrasonic transducer and a data capturing unit. Echo from ultrasonic waves is obtained back from the stream enabling the measurement of the relative position from the outer profile of the work piece to its internal profile. By orienting (rotating) the work piece at different locations in the same plane, thickness and diameters are measured. Straightness is measured by continuing to measure along the length of the cylinder. The thickness and diameters obtained are then used for the evaluation of straightness of the bore.

Keywords

Straightness, Cylinder, Touch Trigger Probe, Ultrasonic Transducer.

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Melvin George Ampattu ¹, V. Shanmugaraj ², G. Shruthi ², J. Pradyumna ²

Affiliations
1 Karunya Institute of Technology and Science, Karunya Nagar, Coimbatore, IN
2 Central Manufacturing Technology Institute, Bangalore, IN

Abstract

Smart manufacturing plays a vital role in modern industry. This involves a collection and analysis of data from the machine tool. Also, it requires to study the behaviour of the machine tool. Since the thermal behaviour is critical, machine tool thermal distortion accounts to 60-70% of machining errors, due to which precision and accuracy will affect. The major factor is the thermo-mechanical deformation. Hence, there is a necessity to study the thermal behaviour of the machine tool to reduce thermal errors which results in better machining accuracy. The major thermal sources of the machine tool are internal and external heat sources from spindle and axis movements. In order to study & analyse the influence of thermal sources on the machine tool, this paper focuses on the thermal error modelling approach using FEM (Finite Element Model) analysis. SOLIDWORKS 2016 & ANSYS Workbench 18.1 is used for modelling and to analyse the thermal behaviour mapping.

Keywords

Thermal Behaviour Analysis, Error Compensation, Thermal Error, Finite Element Analysis, Smart Manufacturing.

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