scholarly journals Study on Machine Tool Positioning Uncertainty Due to Volumetric Verification

Sensors ◽  
2019 ◽  
Vol 19 (13) ◽  
pp. 2847 ◽  
Author(s):  
Aguado ◽  
Pérez ◽  
Albajez ◽  
Santolaria ◽  
Velázquez
Keyword(s):  
Machine Tool ◽  
Measurement System ◽  
Kinematic Model ◽  
Laser Tracker ◽  
Geometric Errors ◽  
Optimization Strategy ◽  
Tool Positioning ◽  
Uncertainty Sources ◽  
Linear Behavior ◽  
The Monte Carlo Method

Volumetric verification is based on the machine tool (MT) kinematic model, along with its geometric errors. Although users often ignore the uncertainty of verification, the use of the MT as a traceable measurement system in the manufacturing process has increased the need for professionals to be aware of it. This paper presents an improvement in the MT kinematic model, introducing in it the influence of verification uncertainty sources. These sources have been classified into four groups: the MT, the measurement system itself, the measurement strategy, and the optimization strategy. As the developed model exhibits non-linear behavior, the Monte Carlo method was used to determine the influence of the measurement system on verification uncertainty using synthetic tests. In this manner, an improved estimation of the MT uncertainty can be obtained. Therefore, if the MT is used as a traceable measurement system, its accuracy should not be higher than the laser tracker (LT) verification influence. It hence shows the importance of LT influence.

scholarly journals Volumetric Verification of Multiaxis Machine Tool Using Laser Tracker

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Sergio Aguado ◽  
David Samper ◽  
Jorge Santolaria ◽  
Juan José Aguilar
Keyword(s):  
Machine Tool ◽  
Measurement System ◽  
Kinematic Model ◽  
Regression Function ◽  
Indirect Measurement ◽  
Extensive Study ◽  
Optimization Techniques ◽  
Laser Tracker ◽  
Rotational Axis ◽  
Rotary Axes

This paper aims to present a method of volumetric verification in machine tools with linear and rotary axes using a laser tracker. Beyond a method for a particular machine, it presents a methodology that can be used in any machine type. Along this paper, the schema and kinematic model of a machine with three axes of movement, two linear and one rotational axes, including the measurement system and the nominal rotation matrix of the rotational axis are presented. Using this, the machine tool volumetric error is obtained and nonlinear optimization techniques are employed to improve the accuracy of the machine tool. The verification provides a mathematical, not physical, compensation, in less time than other methods of verification by means of the indirect measurement of geometric errors of the machine from the linear and rotary axes. This paper presents an extensive study about the appropriateness and drawbacks of the regression function employed depending on the types of movement of the axes of any machine. In the same way, strengths and weaknesses of measurement methods and optimization techniques depending on the space available to place the measurement system are presented. These studies provide the most appropriate strategies to verify each machine tool taking into consideration its configuration and its available work space.

scholarly journals Configuration Optimisation of Laser Tracker Location on Verification Process

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 331 ◽  
Author(s):  
Sergio Aguado ◽  
Pablo Pérez ◽  
José Antonio Albajez ◽  
Jorge Santolaria ◽  
Jesús Velázquez
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Laser Tracker ◽  
Uncertainty Sources ◽  
The Monte Carlo Method ◽  
Nonlinear Optimisation ◽  
Improve Accuracy ◽  
Distribution Of Points ◽  
Systematic Behavior ◽  
Verification Process

Machine tools are verified and compensated periodically to improve accuracy. The main aim of machine tool verification is to reduce the influence of quasi-static errors, especially geometric errors. As these errors show systematic behavior, their influence can be compensated. However, verification itself is influenced by random uncertainty sources that are usually not considered but affect the results. Within these uncertainty sources, laser tracker measurement noise is a random error that should not be ignored and can be reduced through adequate location of the equipment. This paper presents an algorithm able to analyse the influence of laser tracker location based on nonlinear optimisation, taking into consideration its specifications and machine tool characteristics. The developed algorithm uses the Monte Carlo method to provide a zone around the machine tool where the measurement system should be located in order to improve verification results. To achieve this aim, different parameters were defined, such as the number of tests carried out, and the number and distribution of points, and their influence on the error due to the laser tracker location analysed.

A Strategy for Geometric Error Characterization in Multi-Axis Machine Tool by Use of a Laser Tracker

2014 ◽  
Vol 615 ◽  
pp. 22-31 ◽  
Author(s):  
Sergio Aguado ◽  
Jorge Santolaria ◽  
David Samper ◽  
Juan Jose Aguilar Martín
Keyword(s):  
Machine Tool ◽  
Kinematic Model ◽  
Kinematic Chain ◽  
Geometric Error ◽  
Laser Tracker ◽  
Geometric Errors ◽  
Kinematic Chains ◽  
Error Characterization ◽  
Machine Tool Accuracy ◽  
The Relationship

This paper aims to present different methods of volumetric verification in long range machine toll with lineal and rotary axes using a commercial laser tracker as measurement system. This method allows characterizing machine tool geometric errors depending on the kinematic of the machine and the work space available during the measurement time. The kinematic of the machine toll is affected by their geometric errors, which are different depending on the number and type of movement axes. The relationship between the various geometrical errors is different from relationship obtained in machine tool whit only lineal axes. Therefore, the identification strategy should be different. In the same way, the kinematic chain of the machine tool determines determines the position of the laser tracker and available space for data capture. This paper presents the kinematic model of several machine tools with different kinematic chains use to improve the machine tool accuracy of each one by volumetric verification. Likewise, the paper thus presents a study of: the adequacy of different nonlinear optimization strategies depending on the type of axis and the usable space available.

A kinematic approach for error modelling in drilling

2019 ◽  
Vol 36 (4) ◽  
pp. 1364-1383 ◽  
Author(s):  
Wilma Polini ◽  
Andrea Corrado
Keyword(s):  
Machine Tool ◽  
Reference Frame ◽  
Kinematic Model ◽  
Model Parameters ◽  
Geometric Errors ◽  
Volumetric Error ◽  
Machined Surface ◽  
Content Type ◽  
Practical Applications ◽  
Source Errors

Purpose The purpose of this paper is to model how geometric errors of a machined surface (or manufacturing errors) are related to locators’ error, workpiece form error and machine tool volumetric error. A kinematic model is presented that puts into relationship the locator error, the workpiece form deviations and the machine tool volumetric error. Design/methodology/approach The paper presents a general and systematic approach for geometric error modelling in drilling because of the geometric errors of locators positioning, of workpiece datum surface and of machine tool. The model can be implemented in four steps: (1) calculation of the deviation in the workpiece reference frame because of deviations of locator positions; (2) evaluation of the deviation in the workpiece reference frame owing to form deviations in the datum surfaces of the workpiece; (3) formulation of the volumetric error of the machine tool; and (4) combination of those three models. Findings The advantage of this approach lies in that it enables the source errors affecting the drilling accuracy to be explicitly separated, thereby providing designers and/or field engineers with an informative guideline for accuracy improvement through suitable measures, i.e. component tolerancing in design, machining and so on. Two typical drilling operations are taken as examples to illustrate the generality and effectiveness of this approach. Research limitations/implications Some source errors, such as the dynamic behaviour of the machine tool, are not taken into consideration, which will be modelled in practical applications. Practical implications The proposed kinematic model may be set by means of experimental tests, concerning the industrial specific application, to identify the values of the model parameters, such as standard deviation of the machine tool axes positioning and rotational errors. Then, it may be easily used to foresee the location deviation of a single or a pattern of holes. Originality/value The approaches present in the literature aim to model only one or at most two sources of machining error, such as fixturing, machine tool or workpiece datum. This paper goes beyond the state of the art because it considers the locator errors together with the form deviation on the datum surface into contact with the locators and, then, the volumetric error of the machine tool.

Laser Tracker Based Volumetric Verification of Machine Tools

2012 ◽  
Vol 498 ◽  
pp. 151-156 ◽  
Author(s):  
S. Aguado ◽  
David Samper ◽  
J. Santolaria ◽  
Juan-José Aguilar-Martín
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Large Scale ◽  
Kinematic Model ◽  
Measurement Instrument ◽  
Laser Tracker ◽  
Transformation Matrices ◽  
Linear Optimisation ◽  
Working Principle ◽  
Optimisation Techniques

Different techniques of volumetric verification for long range machines are presented in this paper. Its working principle is based on captured points that can be distributed or not, through laser tracker (LT) or a measurement instrument that is generally of large scale. The developed model allows us to characterize the different errors in the machine tool to study, depending on its kinematics and geometry. Obtaining the transformation matrices that define the kinematics of the machine tool (MT) including the measurement system in the kinematic model, it is possible to relate the coordinates of the tool with the coordinates of LT. The best combination of parameters, techniques and models were obtained through the realization of a large number of synthetic tests based on non linear optimisation techniques

scholarly journals An Analysis of Joint Assembly Geometric Errors Affecting End-Effector for Six-Axis Robots

Robotics ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 27
Author(s):  
Chana Raksiri ◽  
Krittiya Pa-im ◽  
Supasit Rodkwan
Keyword(s):  
Industrial Robot ◽  
Kinematic Model ◽  
Measurement Data ◽  
Geometric Error ◽  
Laser Tracker ◽  
Geometric Errors ◽  
Actual Measurement ◽  
End Effector ◽  
Position Errors ◽  
Joint Assembly

This paper presents an analysis of the geometric errors of joint assembly that affect the end-effector for a six-axis industrial robot. The errors were composed of 30 parameters that come from the Geometric Dimensioning and Tolerancing (GD&T) design, which is not the normal way to describe them. Three types of manufacturing tolerancing—perpendicularity, parallelism and position—were introduced and investigated. These errors were measured by the laser tracker. The measurement data were calculated with an analysis of the circle fitting method. The kinematic model and error model based on a combination of translations methods were used. The experiment was carried out in order to calculate the tolerancing of geometric error. Then, the positions of the end-effector in the actual measurement from laser tracker and exact performance were compared. The discrepancy was compensated by offline programming. As a result, the position errors were reduced by 90%.

Tool path error prediction of a five-axis machine tool with geometric errors

2002 ◽  
Vol 216 (5) ◽  
pp. 697-712 ◽  
Author(s):  
Y A Mir ◽  
J R R Mayer ◽  
C Fortin
Keyword(s):  
Machine Tool ◽  
Computer Aided Design ◽  
Tool Path ◽  
Kinematic Model ◽  
Dimensional Accuracy ◽  
Geometric Error ◽  
Geometric Errors ◽  
Computer Aided Process Planning ◽  
Computer Aided ◽  
Five Axis

Predicting the actual tool path of a machine tool prior to machining a part provides useful data in order to ensure or improve the dimensional accuracy of the part. The actual tool path can be estimated by accounting for the effect of the machine tool geometric error parameters. In computer aided design/computer aided manufacture (CAD/CAM) systems, the nominal tool path [or CL (cutter location) data] is directly generated from the curves and surfaces to be machined and the errors of the machine tool are not considered. In order to take these errors into consideration, they must first be identified and then used in the machine tool forward kinematic model. In this paper a method is presented to identify the geometric errors of machine tools and predict their effect on the tool-tip position. Both the link errors (position-independent geometric error parameters) and the motion errors (position-dependent geometric error parameters) are considered. The nominal and predicted tool paths are compared and an assessment is made of the resulting surfaces with respect to the desired part profile tolerance. A methodology is also suggested to integrate this tool within a CAD/CAPP (computer aided process planning)/CAM environment.

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