Page 97

GRANT

journal

ISSN 1805-062X, 1805-0638 (online), ETTN 072-11-00002-09-4

EUROPEAN GRANT PROJECTS | RESULTS | RESEARCH & DEVELOPMENT | SCIENCE

Fig. 1:Zeiss Prismo Navigator, Fixed and Rotating head

[5][6][7]

where the calculation is related to the width of the specification field
T. In both cases, sp is the standard deviation of the process and sg is
the standard deviation of the measured values.

The second eligibility indicator is Cgk. Cgk indicators can also be
determined in various ways. A method related to process variance or
specification field width is used. The relation to process variance is:

When using the method for calculation according to the variance of
the process, the relations are similar. Instead of the variable T, the
selection standard deviation of the process 6sp is used. The relation
to the specification field width is:

2.2

Ford

The variant according to Ford takes into account a bandwidth of
15%. In this method of calculation, measuring devices are
recognized as eligible if the values of Cg and Cgk are greater than 1.
The relationships for the calculation of the indicator Cg are as
follows:

where the calculation is related to the width of the specification field
T. In both cases, sp is the standard deviation of the process and sg is
the standard deviation of the measured values.

To determine the indicator Cgk, the relation related to the variance
of the process is used:

The relationship related to the width of the specification field occurs
after adjustment similarly to the Bosch variant:

DESCRIPTION OF MEASURING EQUIPMENT

The aim of the experiment was to compare the limits of the
tolerance fields of two types of measuring systems. A fixed and
rotating measuring head, which can be used with the Zeiss Prismo
Navigator, was used as the measuring system.

3.1

Zeiss Prismo Navigator

PRISMO enables maximum accuracy for high-speed scanning. It
automatically sets the maximum measurement speed when scanning
- with guaranteed accuracy. All functionally important machine
components are perfectly matched to one another. This is achieved
by using functionally relevant components produced in-house.
Because it is equipped with a multiapplication sensor system from
ZEISS as standard, it allows contact and contactless measurements
on one machine. It is possible to use two different measuring heads
for measuring. One is a fixed head and one is a rotating head. [5]

3.2

Fixed head VAST Gold

The fixed measuring head is a sensor for active scanning with high
dynamics thanks to optimized moving weights and high rigidity due
to improved articulation. It is extremely robust thanks to integrated
collision protection. Dynamic damping allows use in continuous
operation. The sensing force can be adapted to the geometry of the
sensor and the material of the part and is still constant - it can be
programmed in the range of 50 to 1000 millinewtons. [6]

3.3

Rotating head VAST XXT

The VAST XXT swivel head is ideal for measuring tasks where it is
necessary to use a combination of swivel head flexibility with
scanning capability. The compact and lightweight design of
scanning sensors on the swivel head requires various sensor
modules. VAST XXT covers with three modules the range of
typical sensor lengths for this sensor design. Side sensors up to 65
millimetres in length can be attached to this sensor. [7]

DESCRIPTION OF MEASURING

The process of measuring was
the same for both heads. The
stylus for measuring was a ruby
ball with a diameter of 2 mm and
contact measuring was used.
Measurements were performed in
50 cycles by one worker, under
constant environmental
conditions.

The calibration ring was
measured by contact scanning at

a speed of 8 mm/s with the step between points 0.1 mm (approx.
400 points). The diameter of the calibration ring was evaluated. The
nominal size of the calibration ring is 39.9979mm.

Fig. 2: The calibration ring

Vol. 9, Issue 1