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# 5-axis machine tool calibration: volumetric and tool tip position measurement ensures accuracy. (machine alignment).

by：Sinowon     2020-03-21
Calibration 5-
The shaft machine tool can be a very complex, time-
Consuming and expensive processes, especially when considering machine downtime and external service costs.
Even find the amachine tool service provider with the device and experience toperform 5
Axis calibration can be difficult.
However, for the use of 5-
Axis machining center tools and CMMs, especially aerospace parts, calibration is essential if not required by the customer.
We have developed a new calibration method with a reduction of 5-using laser Doppler technology-
Axis calibration.
Portable equipment can be easily used by mechanics and machine tool service technicians, allowing stores to purchase their own equipment and arrange calibration at a convenient time. For a 5-
Axis machining center, calibration of volume positioning of X, Y and z axis and two axis of rotation and B is critical
Linear calibrations of X, Y, and Z, and axes A and B, respectively and independently of each other, are time-intensive, ignoring the linear and square errors along each of the three linear axes, and deviation
Orthogonal and non-orthogonal
Intersection of Axis and non-axis
Intersection of the center line of the spindle with the Z axis.
These errors ensure that 5-
Shaft machine tool or CMM.
The solution offered by Optodyne is a three-step process. Step1--
Volume calibration: the volume error is calibrated by laser vector method, including three linear displacement errors, six linear errors, and three square errors.
By measuring the volume error, the whole volume of the machine can be compensated, and the overall accuracy can be improved, not just linear displacement.
ASME B5 and ISO 230 recommended measurement of Diagonal displacement of body
6 as an effective inspection standard for volume accuracy.
The diagonal measurement of the body is done by moving the tool\'s tips along the diagonal line at the same time, inX, Y and z axes.
This method can only indicate whether the machining center is accurate.
It does not point out the source of the error and can therefore correct the error.
The laser vector or sequential diagonal method indicates whether the machining center is accurate and the cause of the error.
For this measurement, the tool tip follows X-
Axis, then stop the measurement along the Y axis
Finally stop measuring along the Z axis
Axis and stop the measurement until the whole volume is measured.
Since the laser head is mounted on the work table and not on the atrium, the sheet metal casing, fixtures and tools do not have to be disassembled.
This saves a lot of time.
In fact, the volume calibration of one to 2 m³ is 5-
The machining center can be completed in about two or three hours.
The software automatically generates compensation files for leading controllers. Step 2--
Static measurement of A and B (rotational)
Non-axis determination of tool tip displacement error
Contact laser spindle tester.
Install the precision metal ball on the spindle, and install the laser head with a focused lens on the table. A 4\" focal-
The length lens is used to focus the laser beam on the surface of the sphere.
The distance is large and only two components can be alignede.
The laser head assembly and precision metal ball, the system setup is very fast and easy.
The laser head is in X-
Align the axis direction and sphere with the laser beam by moving the spindle.
By rotating the or B axis, the distance change between the laser head and the surface of the sphere is measured, thus measuring the angle error. (Figure 2)Step 3--
Dynamic measurement of A and B (rotational)
The shaft uses a variety of tool paths to determine the knife tip positioning error with anon-
Contact spindle tester.
Dynamic measurement of tool tip positioning errors along a fixed direction using various tool paths to determine angle, dynamics and tool tip positioning errors.
Used for these tests is a rotating tester with a precision sphere.
First, the precision sphere is mounted on the spindle.
Then install the laser head in the position corresponding to the test.
The laser beam is aligned with the focusing lens, focusing on the surface of the precision sphere and perpendicular to its surface. (Figure 3)
5-positioning formula on
Machine tool coordinates are defined (
Xm, Ym, Zm, A, B).
The rotation center of A and B is defined (Xp, Yp, Zp).
The tool tip position is defined (Xt, Yt, Zt).
Relationship Xp = Xm Cx, Yp = Ym Cy, Zp = Zm Cz where Cx, Cy, and Cz are constants.
Xt = Xp RsinBcosA, Yt = Zt rcosbina, Zt = Zp RcosAcosB, where R is the distance between the center rotation and the tool tip.
Static measurement of-
Accuracy of shaft angle (Step 2]
The laser head is installed in position 3 (see figure 3).
The starting position is Yp = Zp = A = B = 0, move-
At the same time as maintaining the position of the tool tip, increment the axis at 5 degrees.
For example: Yp =-RsinA Zp = -R(1-cosA), where A = 0[degrees], 5[degrees], 10[degrees]. . . . . 90[degrees].
So dA =-dYp/(RcosA)
Where dA is the angle error of the Adegrees, dYp is the measurement deviation of the degree.
A sample part program based on moving along a circle and by rotating-
Axis, measurement deviation in X-
Figure 1 shows the direction, and Figure 2 shows the calculation angle error.
Dynamic measurement of-
Accuracy of Axis angle]Step 3]
Measurement of dynamic knife tip positioning error by continuous moving-Axis from 0 [+ or -]
Come back five times at B = 0 90 degrees.
Repeat the same action at 30 and 60 degrees.
Continuous Mobile BAxis from 0 [+ or -]
90 degrees come back 5 times at A = 0.
Repeat the same operation at 30 degrees and 60 degrees.
For complete measurements, data were continuously collected using 2D time bases, and the above measurements were repeated with laser heads at positions 1, 2, 3 and 4.
Laser system error of knife tip positioning measurement error: 0.
000010 \"precision sphere: 0.
000025 \"machine positioning: 0.
Horizontal coupling of 000500 \": 0. 000070\" * * (
Assume that the maximum lateral movement is less than 0. 010\" and1.
Sphere with a diameter of 5\".
The maximum error is 0. 0005\".
Therefore, any improvement in the positioning accuracy of the machine will improve the accuracy of the tool tip positioning measurement. Optodyne Inc. ,www. rsleads. com/210tp-
212 or circle 212 【Figure 1 slightly][Figure 2:
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