Most manufacturing machine tools are utilized for mass production or batch production with high accuracy at a
deterministic manufacturing principle. Volumetric accuracy of machine tools depends on the positional accuracy of the
cutting tool, probe or end effector related to the workpiece in the workspace volume. In this research paper, a
methodology is presented for volumetric calibration of machine tools by on-line measurement of an artifact or an object
of a similar type. The machine tool geometric error characterization was carried out through a standard or an artifact,
having similar geometry to the mass production or batch production product. The artifact was measured at an arbitrary
position in the volumetric workspace with a calibrated Renishaw touch trigger probe system. Positional errors were
stored into a computer for compensation purpose, to further run the manufacturing batch through compensated codes.
This methodology was found quite effective to manufacture high precision components with more dimensional accuracy
and reliability. Calibration by on-line measurement gives the advantage to improve the manufacturing process by use of
deterministic manufacturing principle and found efficient and economical but limited to the workspace or envelop
surface of the measured artifact's geometry or the profile.
In this particular research authors have made an effort to investigate the relationships between linear and angular
elemental errors through a pragmatic way and analyzing them. Correlation between the errors was considered by the case
study of the coupling mechanism between the joint kinematic angular and straightness errors of a prismatic joint of a
machine tool, and was validated through measurement. The laser interferometer was employed in conjunction with its
optics under controlled environmental conditions for validation purposes. Prismatic joint of a 5-axis grinding machine
was used for error characterization and its quantification by establishing the relevance between linear (straightness) and
angular (pitch and yaw) errors. Results exhibited a quite agreement to the relationship while compensation factor added
with the methodology. It was investigated whether the methodology is beneficial for reducing the elements of parametric
calibration which provides an efficient characterization and error evaluation, or is just better for an estimation and quick
check of a machine tool error.
A double ball bar (DBB) system is an imperative device for measuring contouring accuracy, error characterization and
interpretation of machine tool performance in volumetric workspace. The advantage that makes it popular and widely
used by machine users is its quick performance checking, easy to use, portability and minimizing the down time of
machine tools. Periodic calibration of this system is vital to ensure its correctness by providing its accuracy information.
An in-situ calibration method is devised by the authors to calibrate DBB for ensuring correct indication and its
metrological characteristics. Direct calibration method is adopted and laser interferometer is engaged for this purpose.
Calibration is carried out under controlled environment and results are reported and compared against its required
accuracy, calibration curve is drawn for its further utilization.
A novel technique is developed and implemented for error quantification in a rotary joint of a multi-axis machine tool by
using a calibrated double ball bar (DBB) system as a working standard. This technique greatly simplified the
measurement setup requirement and accelerated the calibration of rotary joints. In addition it is highly economical by
reducing the complex optics and eliminating the usage of various tooling, instrumentation and accessories. This
methodology is capable of measuring the five degree of freedom (DOF) errors out of 6DOF of a rotary joint by using the
calibrated DBB system and a point locating fixture. The methodology is implemented on rotary joints of a five axis CNC
machine tools. Equation solvers and error modeling technique are implemented and validity of the methodology and
authenticity of the results obtained are tested through simulation in UG and Matlab software. The methodology is found
extremely feasible pragmatic, quite simple, efficient and easy to use for error characterization of rotary joints of multi
axis machine tools.
Squareness plays a vital role for accuracy of multiaxis machine tools. A slight error in squareness exhibits a significant
inaccuracy at end effectors, measuring probe or cutting tool of a multiaxis machine tools. The inaccuracy of machine tool
badly influences the product quality. In this paper authors try to investigate the possible methodologies, techniques and
approaches which are viable for quantification or predication of squareness error in different joints and various topology
of multi-axis machine tools. Besides classical or conventional methodology, up to date modern methodologies are also
considered and their implementation is discussed. A comparison between the methodologies is made and squareness data
is obtained on a multiaxis CNC machine tool by implementing different approaches. The results obtained are treated,
compared and reported for its further utilization.
Calibration refers to the system of quantity value determination of instruments, equipments and test devices according to
industrial requirement, based on metrological characteristics. In present research critical parameter which affects the
accuracy and product quality of a CNC milling machine, was investigated and quantified by using direct method. These
parameters consist of position dependent or position independent parameters, like linear displacement errors, angular
errors of linear axes, straightness error of linear axes and squareness error between the axes. Repeatability, lead screw
and resolution error of the CNC milling machine were also quantified to provide additional information to the user,
because in absence of this additional information a misconception persists causing a major contributor to the inaccuracy
and quality of the product. Parameters were measured and quantified by using a laser interferometer and artifacts as
working standards under controlled environmental conditions on a manufacturing CNC milling machine. Polynomial
regression analyses were carried out for finding the coefficients to predict the errors at each and every desired position
which is quite useful for compensation and enhancing the accuracy of a machine system. Machine accuracy detailed
chart was also made to assess and assure the accuracy, capability or for accuracy monitoring of the CNC milling machine
A methodology was implemented to evolve the volumetric errors of multiaxis machine tools through a parametric way.
The volumetric error was calibrated and evaluated in the workspace arbitrarily by implementing parametric methods and
techniques. In parametric method linear displacement errors and angular displacement errors were measured through a
laser interferometer with combination of a newly developed three-line measuring method to measure the prismatic joints
for efficient and quick error meterage. Besides these, squareness errors between the axes were also quantified by using
reversal method. Volumetric accuracy portrayed the real error picture between the workpiece and cutting tool or end
effectors or a measuring probe. So positional errors, straightness errors, angular errors and squareness errors were
quantified and transformed into volumetric accuracy by using generalized homogenous transformation matrices, whereas
forward kinematics technique was used as a tool. Measured results can be used to compensate the volumetric errors to
achieve high precision in manufacturing and measurement through physical compensation, making correction,
adjustment or improvement through software. Reported here is the volumetric accuracy results carried on a multi-axis
CNC milling machine under controlled environmental conditions and as per the standard procedure and practice.
A three line calibration method for error quantification in a prismatic joint of a machine tool was proposed and
implemented by using a laser interferometer as a working standard. It greatly simplified the measurement setup
requirements and accelerated the calibration of prismatic joints. Moreover, it was highly economical by reducing the
calibration time and eliminating the use of complex optics. The methodology was implemented on prismatic joints of a
three axis CNC machine tool as per standard procedures and guide lines. Cubic spline technique was implemented as
error modeling and results obtained were reported for its further use to compensate the errors for improving the accuracy
in prismatic joints.
Calibration of machine tools refers to the process of determining the relation between output and the value of input
quantity. It refers to the system of conformity testing based on metrological characteristics. Parametric calibration is the
only comprehensive indicator which depicts a detailed picture regarding accuracy of machine tool. In this paper the most
important parametric errors of coordinate measuring machines (CMMs) were calibrated through transfer standards and
by implementing conventional methods and techniques, in the sense that modern sophisticated instrument like laser
interferometers are expensive and beyond the economical range of small industries besides they need comprehensive
training and strong background knowledge for error prediction and analysis. In this scenario it is imperative to develop
and implement some easy to use and cost effective efficient methods by exploiting the available resources. The
methodology was implemented on a three coordinate measuring machine as per standard procedures of error
measurement under controlled environment. Obtained results were reported for its further use to compensate the
parametric errors, either physically compensation or correction in the measurement results.