Reference number ISO 13041 2 2008(E) © ISO 2008 INTERNATIONAL STANDARD ISO 13041 2 First edition 2008 10 15 Test conditions for numerically controlled turning machines and turning centres — Part 2 Geo[.]
Units of measurement
In ISO 13041, linear dimensions, deviations, and tolerances are specified in millimeters, while angular dimensions are given in degrees Angular deviations and their tolerances are expressed as ratios, with occasional use of microradians or arc seconds for clarification It is important to always consider the equivalence between these different measurement expressions to ensure accurate interpretation.
Machine levelling
Prior to conducting tests on a machine, the machine should be levelled according to the recommendations of the supplier/manufacturer (see ISO 230-1:1996, 3.11).
Test sequence
The order of tests outlined in ISO 13041 does not prescribe a specific practical sequence for carrying out the tests To facilitate easier mounting of instruments and measurement devices, the tests can be performed in any preferred order, offering flexibility in the testing process.
Test to be performed
When testing a machine, it is often unnecessary or impractical to perform all the tests outlined in ISO 13041 For acceptance testing, the user, in collaboration with the manufacturer, should select specific tests related to the machine’s components or properties that are relevant to their needs These selected tests must be clearly specified at the time of order Merely referencing ISO 13041 for acceptance tests without detailing which tests to conduct or agreeing on the associated costs is not binding for either party.
Measuring instruments
The measuring instruments mentioned in the tests are examples; other devices capable of measuring the same quantities with equivalent measurement uncertainty can be used Linear displacement sensors must have a resolution of 0.001 mm or better to ensure accurate results.
Diagrams
In this part of ISO 13041, for reasons of simplicity, the diagrams associated with geometric tests generally illustrate only one type of machine.
Minimum tolerance
When setting the tolerance for a geometric test on a measuring length different from the specified standards in ISO 13041 and ISO 230-1:1996, it is essential to consider that the minimum permissible tolerance value is 0.005 mm This ensures accuracy and compliance with established measurement guidelines.
Machine classifications
The machines considered in this part of ISO 13041 are divided into the following basic configurations:
⎯ type A: single column machines (Figure 1);
⎯ type B: dual column machines (Figure 2)
Type B machine configurations are further classified into the following types:
Linear motions
All machine examples in Figures 1 and 2 utilize axis designations such as a letter and number (e.g., X, X1, X2), as specified in ISO 841:2001, 6.1 Additionally, the letters U, V, or W can be substituted in these examples, providing flexibility in axis labeling.
Turrets — toolholding components (element)
Cutting tools, whether stationary or power-driven, are typically positioned on the railhead ram, side head ram, or turret, depending on the machine configuration An automatic tool change device may also be incorporated to enhance machining efficiency However, ISO 13041 standards do not specify test methods for automatic tool change operations, highlighting a gap in testing protocols for these systems.
Machine size category
The machines are classified into four size categories, on the basis of the criteria specified in Table 1
Table 1 — Machine size range Criteria Category 1 Category 2 Category 3 Category 4
Diameter of workholding spindle/table
NOTE 1 The choice of criteria is at the manufacturer's discretion
NOTE 2 Nominal diameter of chuck (up to 800 mm) is defined in ISO 3442-1, ISO 3442-2, and ISO 3442-3.
Machine configurations
a) Compound head type b) Shared motion
(moving workholding spindle) type c) Shared motion (moving head/saddle) type d) Compound workholding spindle type
Figure 1 illustrates various machine configurations, including single-column machines (Type A) These configurations comprise fixed column with a moving cross-rail (a), fixed column with a fixed cross-rail (b), gantry-type machines featuring a moving column (c), and portal-type machines with a fixed column and a moving workholding spindle along the Y-axis (d) Understanding these configurations helps in selecting the right CNC machine for specific manufacturing applications, improving efficiency and precision.
Figure 2 — Examples of machine configurations: dual column machines (type B)
Figure 3 — Machine with single column
Table 2 — Terminology corresponding to Figure 3
1 workholding spindle (turntable) Spannfutter broche porte-outils
4 cross-rail Querführung traverse porte-chariot
5 railhead (saddle) Querschlitten chariot de traverse (traợnard)
6 turret slide Revolverschlitten chariot de tourelle
8 workholding spindle head Spindelkasten tête de broche porte-outils
Figure 4 — Machine with dual columns
Table 3 — Terminology corresponding to Figure 4
1 workholding spindle (turntable) Spannfutter broche porte-outils
3 right-hand column rechter Maschinenstọnder montant droit
4 left-hand column linker Maschinenstọnder montant gauche
5 cross-rail Querführung traverse porte-chariot
6 turret slide Revolverschlitten chariot de tourelle
7 railhead (saddle) Querschlitten chariot de traverse (traợnard)
8 railhead ram Traghülse coulisseau du chariot de traverse
10 side head seitlicher Werkzeugtrọger chariot porte-outils latộral
11 side head ram seitliche Traghülse broche porte-outils
Workholding spindle
To check the flatness of the workholding spindle face (workholding table)
Local tolerance 0,01 over any measuring length of 300
NOTE Category 4 machines only — for each further 1 000 increase in diameter, increase the tolerance by 0,01
Spindle face shall not be convex
Straightedge, gauge blocks and linear displacement sensor or optical instruments
For alternative method: Guide bar and support blocks, precision level and an isostatic 3-bearing support
Observations and references to ISO 230-1:1996, 5.322, 5.324
Alternative method (checking with the aid of a precision level): 5.323
1) Circular checking The precision level shall be placed on a support having three bearing points on the workholding table
The isostatic 3-bearing support shall be moved to positions equally spaced along the workholding table
2) Diametrical checking The precision level shall be placed on the workholding table and along a diametrical direction with the aid of a guide bar
The precision level shall be moved at positions equally spaced along the guide bar
The procedure shall be repeated, moving the guide bar according to the successive positions
To check the face run-out of workholding spindle: a) face run-out of the workholding table surface; b) face run-out of the spindle face
NOTE Category 4 machines only — for each further 1 000 increase in diameter, increase the tolerance by 0,01 b) 0,01 0,015 0,02 0,02
The linear displacement sensor must be installed on a fixed part of the machine, positioned as close as possible to the periphery of the workholding table It should be located approximately 180° opposite the position occupied by the tool when the workholding spindle was machined, ensuring accurate measurement and optimal performance according to ISO 230-1:1996, 5.632.
Cross-rail and railhead locked in position, where possible b) Measurements shall be taken on the maximum diameter
NOTE If detaching the workholding table is difficult, this test need not be done
To check run-out of a) the workholding spindle bore; b) the external cylindrical surface of the workholding spindle (in the case of a workholding spindle not having a central bore); c) centring diameter
Category 1 Category 2 Category 3 Category 4 a) and b) 0,01 0,02 0,035 0,05
NOTE Category 4 machines only — for each further 1 000 increase in diameter, increase the tolerance by 0,01 c) 0,01 0,015 0,02 0,02
Observations and references to ISO 230-1:1996, 5.611.4 and 5.612.2 a) The linear displacement sensor shall be placed approximately 180° from the position occupied by the tool when the workholding spindle was machined
Cross-rail, railhead and slide locked in position, where possible
The linear displacement sensor should be mounted on a stable, fixed part of the machine to ensure accurate measurements According to subclauses 5.611.4 and 5.612.2, proper installation is essential for optimal performance When measuring conical surfaces, the sensor's stylus must be positioned perpendicular to the contacting surface to maintain measurement integrity Proper alignment and placement of the sensor are crucial for achieving precise linear displacement readings.
Relationship between workholding spindle and linear axes of motion
To check the parallelism between the Z-axis motion (railhead ram or turret slide) and the workholding spindle axis of rotation: a) in the YZ plane; b) in the XZ plane
NOTE Also applicable for a second railhead ram and turret slides on the column
Tolerance a) 0,015 for the measuring length of 300 b) 0,01 for the measuring length of 300
Test mandrel or cylindrical square and linear displacement sensors and adjustable blocks
Alternative method: Precision test ball and linear displacement sensors
Observations and references to ISO 230-1:1996, 5.412.1 and 5.422.3
To assess spindle run-out and parallelism, first rotate the workholding spindle to identify its mean position Next, move the railhead ram sequentially to the upper (3), mid-travel (2), and lower (1) positions along the Z-axis, recording the maximum difference in readings at each position The largest variation observed indicates the parallelism deviation in the XZ plane This testing process is then repeated for the YZ plane to ensure comprehensive measurement accuracy.
The test ball is positioned along the Z-axis travel, and measurements are repeatedly taken at three different positions (1, 2, and 3) Readings are recorded at both 0° and 180°, with the difference between these two angles noted for each position The position exhibiting the largest change in this difference indicates the parallelism deviation, providing a precise assessment of the component's alignment accuracy.
YZ plane The test is then repeated for the XZ plane
When testing machines with adjustable cross-rails, the procedure must be repeated with the cross-rail set to its lower, mid, and upper positions This comprehensive testing approach ensures all railhead configurations are evaluated for optimal performance and safety.
To check the squareness between the railhead motion (X axis) and the workholding spindle axis of rotation (C axis)
For a measuring length of 300 or full stroke up to 300: categories 1 and 2: 0,020 categories 3 and 4: 0,030 Direction of deviation: αW 90°
Straightedge, adjustable blocks and linear displacement sensor
Observations and references to ISO 230-1:1996, 5.422.22, 5.522.2
A linear displacement sensor is fixed to the turret close to the tool position
Block gauges are used to set the straightedge square to the workholding spindle rotation axis
Checking should be performed by positioning the stylus of the linear displacement sensor on the railhead onto a straightedge aligned perpendicularly to the workholding spindle's axis of rotation This method ensures accurate measurement and proper alignment, crucial for maintaining precision in machining operations Utilizing a properly placed straightedge allows for effective detection of deviations, helping to uphold quality standards and equipment accuracy Regular calibration using this technique contributes to optimal machine performance and minimizes errors during production.
Ensure the straightedge is approximately parallel to the work table surface for accurate measurements Take measurements at multiple positions along the X-axis, then rotate the spindle 180° and repeat the measurements at the same X locations Calculate the squareness deviation as the range of the mean values from both measurement sets The generated surface will typically be concave unless specified otherwise through a special arrangement between the user and the manufacturer or supplier.
To check the parallelism between the side head (Z axis) motion and the workholding spindle axis of rotation (C axis)
Test mandrel or cylindrical square and linear displacement sensor
Observations and references to ISO 230-1:1996, 5.422.3
Turn the workholding spindle to find the mean position of run-out and then move the side head in the
Z direction and take maximum difference of the readings
To ensure accurate measurement, take readings at multiple positions along the Z-axis, then rotate the workholding spindle by 180° and capture a second set of readings at the same Z positions The parallelism deviation is determined by calculating the range between the means of these two measurement sets, providing an precise assessment of spindle alignment This method helps identify any deviations in spindle parallelism, ensuring optimal machine performance and precision in machining operations.
This test applies to all side heads
To check the squareness between the side head ram (X axis) motion and the workholding spindle axis of rotation
Straightedge, gauge blocks, and linear displacement sensor
Observations and references to ISO 230-1:1996, 5.522.2
The side head shall be locked in position
Gauge blocks are used to set the straightedge perpendicular to the workholding spindle rotation axis
Checking should be performed by positioning the stylus of the linear displacement sensor on the side head ram onto a squarely aligned straightedge, ensuring precise calibration relative to the spindle's rotation axis This method guarantees accurate measurement and proper machine alignment, essential for maintaining machining precision Properly executed, this process helps identify any deviations, ensuring optimal performance and quality in machining operations.
Set straightedge approximately parallel to the work table surface Take readings at several positions of the
To measure squareness deviation accurately, start by rotating the C axis by 180° around the X axis and take a second set of readings at the same X positions The squareness deviation is determined by calculating the range between the mean values of these two measurement sets This method ensures precise assessment of the component's squareness, adhering to quality control standards.
This test applies to all side heads
To check the parallelism between the toolholding spindle axis of rotation and the railhead ram motion: a) in the YZ plane; b) in the ZX plane
0,02 for any measuring length of 300
Linear displacement sensor and test mandrel
Observations and references to ISO 230-1:1996, 5.412.1, 5.422.3
A test mandrel is mounted on the live tooling spindle
NOTE If necessary, workholding spindle should be clamped a) Linear displacement sensor is attached to the workholding spindle indicating against the mandrel in the
The mean orientation of the mandrel is established by rotating the live tooling spindle between the two extreme readings of the displacement sensor, which is set to zero at this central position Subsequently, the railhead ram is moved to the opposite end of the measuring stroke, and the displacement sensor reading is recorded to ensure accurate measurement Additionally, a linear displacement sensor is attached to the workholding spindle, indicating against the mandrel to facilitate precise positioning and measurement.
The mean orientation of the mandrel is determined by rotating the live tooling spindle between its two extreme positions as indicated by the displacement sensor The displacement sensor is calibrated to zero at this mean orientation to ensure accurate measurements Subsequently, the railhead ram is moved to the opposite end of the measuring stroke, and the sensor reading is recorded for precise alignment.
To accurately evaluate spindle parallelism, take measurements at multiple positions along the Z axis Then, rotate the toolholding spindle by 180° and repeat the measurements at the same Z positions The parallelism deviation is determined by calculating the range of the averages of these two measurement sets, ensuring precise assessment of spindle alignment.
To check the parallelism between the cross-rail Z-axis motion and the workholding spindle axis of rotation: a) in the YZ plane; b) in the ZX plane
Linear displacement sensor and test mandrel or cylindrical square
Observations and references to ISO 230-1:1996, 5.422.3
Turn the workholding spindle to find the mean position of run-out and then move the cross-rail in the Z direction and take the maximum difference of the readings
To ensure accurate alignment, take readings at multiple positions along the cross-rail Z axis, then rotate the workholding spindle by 180°, and record a second set of measurements at the same Z positions The parallelism deviation is determined by calculating the range of the average values from these two measurement sets This method helps assess and improve machining accuracy by verifying the parallelism of the workpiece.
The test ball is positioned using only the Z-axis travel, with measurements repeated at three different positions (1, 2, and 3) Readings are taken at both 0° and 180°, and the difference between these readings is recorded for each position The maximum variation in these differences indicates the parallelism deviation, providing a precise assessment of the component's alignment This method ensures accurate detection of any misalignment, essential for maintaining high-precision manufacturing standards.
Angular deviations of linear axes of motion
To check the angular deviation of the cross-rail in its Z-axis motion in the vertical ZX plane
For any measuring length up to 1 000: categories 1 and 2: 0,02/1 000 (20 àrad or 4″) categories 3 and 4: 0,04/1 000 (40 àrad or 8″)
Observations and references to ISO 230-1:1996, 5.232.21
Place the measuring level at possibly mid-position of the cross-rail on an appropriate surface and read the indication in the quoted positions
The railhead shall be placed in a central position of the cross-rail
When Z-axis motion causes angular deviation of both the cross-rail and the workholding spindle, differential measurements of the two angular movements shall be taken
When differential measurement is applied, the reference level shall be placed on the workholding spindle Lock the cross-rail at each position, where possible
To accurately assess angular deviations in gantry-type moving columns or portal-type moving workholding spindles, focus on three key planes: pitch is evaluated in the YZ plane (EAY), roll is measured in the ZX plane (EBY), and yaw is checked in the XY plane (ECY) These measurements are essential for ensuring precise alignment and optimal machine performance.
For any measuring length up to 1 000: categories 1 and 2: 0,02/1 000 (20 àrad or 4″) categories 3 and 4: 0,04/1 000 (40 àrad or 8″)
Measuring instruments a) Precision level, or optical angular deviation measuring instrument b) Precision level c) Optical angular deviation measuring instrument
Observations and references to ISO 230-1:1996, 5.231.3, 5.232.2
The measuring instrument must be precisely positioned on the fixed railhead, with placement aligned to specific axes: the EAY (pitch) should be set in the Y-axis direction, the EBY (roll) in the X-axis direction, and the ECY (yaw) in the Z-axis direction Proper alignment of the measuring level ensures accurate measurement results and optimal instrument performance.
When workholding spindle slide motion causes angular deviations of both workholding spindle and column, differential measurements of the two angular deviations shall be made and this shall be stated
To assess the angular deviations of railhead movement on the cross-rail (X axis), measurements are conducted in three planes: the ZX plane (EBX) to determine pitch, the YZ plane (EAX) to evaluate roll, and the XY plane (ECX) to analyze yaw These assessments are essential for ensuring precise rail alignment and optimal operational safety Accurate detection of pitch, roll, and yaw deviations helps maintain rail track stability and improves the overall performance of the railway system.
For any measuring length up to 1 000: categories 1 and 2: 0,02/1 000 (20 àrad or 4″) categories 3 and 4: 0,04/1 000 (40 àrad or 8″)
Measuring instruments a) Precision level, or optical angular deviation measuring instrument b) Precision level c) Optical angular deviation measuring instrument
Observations and references to ISO 230-1:1996, 5.231.3, 5.232.2
The measurement instrument should be securely positioned on the turret or railhead to ensure accurate readings It must be aligned correctly along the three essential axes: the pitch (EBX) in the X-axis direction, set vertically; the roll (EAX) in the Y-axis direction, also set vertically; and the yaw (ECX) in the Z-axis direction, set horizontally Proper placement and alignment of the measuring device are critical for precise calibration and effective performance.
When railhead motion causes an angular deviation of both railhead and workholding spindle, differential measurements of the two angular deviations shall be made and this shall be stated
The reference level shall be placed on the workholding spindle
To check the angular deviations of the turret slide (ram) motion (Z axis); a) in the YZ plane EAZ (tilt around X); b) in the XZ plane EBZ (tilt around Y)
For any measuring length up to 1 000:
Precision level or optical angular deviation measuring instrument
Observations and references to ISO 230-1:1996, 5.231.3, 5.232.2
The measuring level shall be placed on the workholding spindle and the measuring level placed on a special fixture located at the tool location
Measurements shall be carried out at a minimum of five positions equally spaced along the travel in both directions of the movement.
Straightness deviation of linear axes of motion
To check the straightness of the railhead (X axis) motion on the cross-rail: a) in the vertical ZX plane (EZX); b) in the horizontal XY plane (EYX)
NOTE Applicable for turning centres only
Add 0,01 for each additional length of 500
Local tolerance: 0,01 for any measuring length of 500
Measuring instruments a) Straightedge, adjustable block and linear displacement sensor or optical equipment b) Straightedge, adjustable block and linear displacement sensor or optical equipment or taut wire and microscope
Observations and references to ISO 230-1:1996, 5.232.1
To ensure proper alignment, when the column or workholding spindle (table) moves along the Y-axis, it must be positioned so that the railhead ram or turret tool pockets are in line with the workholding spindle's average axis This precise positioning is essential for accurate machining operations Proper alignment of these components helps optimize machine performance and ensures high-precision results.
Position and lock the cross-rail in the middle of its travel range, with the column secured near the workholding spindle if it is movable along the Y-axis and locking is possible Use a straightness reference tool such as a straightedge, straightness reflector, alignment telescope, or taut wire placed on the workholding spindle parallel to the railhead slide movement Ensure that the reference is aligned so that the readings at both ends of the movement are the same; the maximum difference between these readings indicates the straightness deviation.
The linear displacement sensor, interferometer, target, and microscope should be mounted on the railhead close to the tool's position for accurate measurement Proper placement enhances precision by ensuring that measurement devices are near the tool's operational area The cross-rail is positioned at the midpoint of its travel path, optimizing measurement stability and consistency during operation Proper positioning of these components along the rail ensures reliable data collection and improved overall system performance.
To ensure the accurate alignment of gantry-type moving columns or portal-type moving spindles, it is essential to check their straightness of motion along the Y-axis This involves inspecting the movement in two key planes: the vertical YZ plane (EZY) and the horizontal XY plane (EXY) Conducting these checks helps identify any deviations in the straightness of the machine's motion, ensuring optimal precision and performance.
Tolerance a) 0,02 for a measuring length of 500 b) 0,04 for a measuring length of 500
Measuring instruments a) Straightedge, adjustable block and linear displacement sensor or optical equipment b) Straightedge, adjustable block and linear displacement sensor optical equipment or microscope and taut wire
Observations and references to ISO 230-1:1996, 5.212.11
Cross-rail locked in the middle position, railhead locked in the measuring position, where possible
To ensure accurate straightness measurement, the straightness reference (such as a straightedge, straightness reflector, alignment telescope, or taut wire) must be positioned parallel to the workholding spindle Parallel alignment means that the readings at both ends of the movement are identical, and the maximum difference between these readings indicates the straightness deviation Proper placement of the straightness reference is essential for precise alignment and measurement in machining and inspection processes.
For accurate measurements, the linear displacement sensor, interferometer, target, or microscope must be mounted on the railhead near the tool position, ensuring precise alignment The measuring line should be positioned close to the workholding spindle axis of rotation to optimize measurement accuracy and reliability Proper mounting and alignment of these components are essential for effective displacement measurement in machining processes.
To check the straightness of motion of the cross-rail in the Z-axis direction: a) in the YZ plane; b) in the ZX plane
Straightedge, square, adjustable blocks or test mandrel and linear displacement sensor
Observations and references to ISO 230-1:1996, 5.212.11
The square is set on the workholding spindle surface to obtain the same readings at both ends of the measuring length.
Turret and workholding and toolholding spindle(s)
To check the co-axiality deviation between the axes of the turret bore(s) and the workholding spindle axis of rotation
Test mandrel and linear displacement sensor
Observations and references to ISO 230-1:1996, 5.442
A mandrel of sufficient length shall be inserted in one of the turret bores
A linear displacement sensor must be securely mounted on the workholding spindle, ensuring contact with the test mandrel near the turret bore During measurement, the sensor should be positioned at a distance of 100 mm without any vertical movement of the railhead ram or cross-rail, maintaining precise and stable alignment for accurate readings.
Repeat the same operations for each of the turret bores
NOTE The value of permissible deviation is equal to half of the readings of the linear displacement sensor
To check the squareness between the tool-fixing faces of the turret and the workholding spindle axis of rotation
NOTE The test applies to tool-fixing faces of turrets that are square to the workholding spindle axis
L is the diameter of measurement
Linear displacement sensor and reference block
Observations and references to ISO 230-1:1996, 5.512.11
A linear displacement sensor shall be fixed on the workholding spindle and shall touch the reference block located on the face of turret located opposite
The workholding spindle shall be rotated and the linear displacement sensor shall be moved to touch the face of the turret on the largest possible diameter
The test shall be repeated for each of the tool-fixing faces of the turret
To check the run-out of the internal taper of the toolholding spindle(s): a) at the spindle nose; b) at a distance of 300 mm from the spindle nose
NOTE Carry out these tests for each toolholding spindle of the machine
D f > 200 a) 0,015 b) 0,030 where D f is the external diameter of the spindle-nose face
Linear displacement sensor and test mandrel
Observations and references to ISO 230-1:1996, 5.612.3
Attach a linear displacement sensor to the table (workholding spindle) and insert the test mandrel in the live tooling spindle
Place the displacement sensor as close as possible to position a), rotate the toolholding spindle and record the reading
Repeat the same operation at position b)
To check the repeatability of the turret indexing: a) in the X direction; b) in the Z direction
Test mandrel and linear displacement sensor
Observations and references to ISO 230-1:1996, 6.42
Position the sensors at a distance l from the turret face or tool-fixing face, ensuring accurate measurement setup With the turret in mid-stroke, align the linear displacement sensors to contact the test mandrel at 0° and 90° measurement positions Record the turret’s axis position along with the sensor readings to ensure precise assessment of turret alignment and rotation accuracy.
To ensure accurate measurements, first move the turret to a position clear of the linear displacement sensors Next, index the turret a full 360° to verify complete rotation Then, position the turret axis to the pre-recorded point within an automatic cycle Finally, record the readings from the linear displacement sensors to capture precise displacement data.
To ensure accurate measurements, repeat the testing cycle three times, resetting the linear displacement sensor to zero at the beginning of each cycle The deviation is determined by calculating the maximum difference among the three sets of readings Properly resetting the sensor and analyzing the deviation are essential steps for reliable displacement measurement results.
Also, the linear displacement sensor can be mounted on the spindle housing to avoid locking the spindle (preferred method)
The test should be repeated at a minimum of three different turret orientations and, for each orientation, the linear displacement sensor should be set to zero
The repeatability of positioning of the linear axes (used for clearing the linear displacement sensors) may influence the measuring result
To check the accuracy of the turret indexing
Observations and references to ISO 230-1
Position the linear displacement sensor styli a), b), and c) to ensure proper contact with the turret reference holes or grooves Record the turret axis position and the sensor readings at this initial point Withdraw the turret to clear the sensor, then index it to the next orientation and reposition the turret axis accordingly Finally, record the linear displacement sensor readings again to capture the new position data.
If the turret reference face is used, the linear displacement sensor should be used at position f)
To ensure accurate turret indexing, each turret orientation should be tested three times, with readings averaged to reduce variability The overall accuracy is determined by identifying the maximum difference among all averaged linear displacement sensor readings This method helps minimize the impact of turret repeatability, providing a reliable measure of turret positioning precision.
The repeatability of the turret indexing might influence the readings
6 Tests for checking the accuracy of axes of rotation
Rotational accuracy of workholding spindle
The axis of rotation error motion for the workholding spindle (C axis) includes several key components: radial error motion in the X direction (EXC), radial error motion in the Y direction (EYC) specific to turning centers, axial error motion (EZC), tilt error motion around the X axis (EAC) which is applicable to turning centers, and tilt error motion around the Y axis (EBC) These errors can impact machining precision and are essential considerations in high-precision turning and milling operations Proper measurement and compensation of these error motions can significantly enhance the accuracy and surface quality of machined parts Understanding the different axes and error components helps in diagnosing issues and optimizing spindle performance for improved manufacturing outcomes.
NOTE Probes 2 and 5 are for turning centres only
At percentage of maximum speed
The article discusses key error motion values in precision measurement, including the total radial error motion values EXC and EYC, which quantify deviations in radial directions It also covers the total axial error motion value EZC, indicating axial misalignments, along with the total tilt error motion values EAC and EBC, representing angular deviations These parameters are essential for assessing the accuracy of rotational components, with error levels typically expressed as 10%, 50%, and 100% of the specified tolerances, emphasizing the importance of maintaining minimal error motions for optimal performance Proper measurement and control of these error motion values ensure high precision in machinery and instrument calibration.
If the minimum speed is larger than 10 % of the maximum speed, then the spindle should be operated at minimum speed instead
If the supplier/manufacturer decides, by mutual agreement, to include this test in the contractual machine acceptance procedures, then they should also
At percentage of maximum speed
Test mandrel, non-contacting probes and angular measuring device or two precision spheres located slightly eccentric to the spindle average line and non-contacting probes
Observations and references to ISO 230-7
This test is a spindle test with fixed sensitive direction (ISO 230-7:2006, 5.5)
After installing the measuring instrument, the spindle should be warmed up at 50% of its maximum speed for 10 minutes, unless otherwise agreed upon by the manufacturer or user Proper warm-up ensures accurate measurement results and optimal instrument performance.
Total error motion and total error motion value are defined in ISO 230-7:2006, 3.2.4 and 3.5.1, respectively a), b) Total radial error motion values EXC and EYC (using probes 4 and 5)
Radial error motion measurement is described in ISO 230-7:2006, 5.5.3 The radial error motion shall be measured as close as possible to the spindle nose (probes 4 and 5 in the R1 diagram)
For each radial error motion EXC and EYC, a total error motion polar plot should be provided in accordance with ISO 230-7:2006, section 3.3.1, including the least squares circle (LSC) center as specified in ISO 230-7:2006, section 3.4.3 Additionally, the total axial error motion value EZC should be reported, utilizing probe 3 for measurement.
Axial error motion measurement is described in ISO 230-7:2006, 5.5.4
For axial error motion EZC, a comprehensive total error motion polar plot, as specified by ISO 230-7:2006 (section 3.3.1), must be provided, featuring a polar chart centered according to ISO standards (section 3.4.1) Additionally, the total tilt error motion values EAC and EBC should be determined using probes 2 and 5, and probes 1 and 4, respectively, ensuring accurate measurement of tilt deviations.
Tilt error motion measurement is described in ISO 230-7:2006, 5.5.5 Any tilt error motion can also be checked with just one non-contacting probe (see ISO 230-7:2006, 5.5.5.3)
For each tilt error motion EAC and EBC, a total error motion polar plot (ISO 230-7:2006, 3.3.1) with a polar chart (PC) centre (ISO 230-7:2006, 3.4.1) shall be provided
For these tests, the following parameters shall be stated:
1) the radial, axial or face locations at which the measurements are made;
2) identification of all artifacts, targets and fixtures used;
3) the location of the measurement setup;
4) the position of any linear or rotary positioning stages that are connected to the device under test;
5) the direction angle of the sensitive direction, e.g axial, radial or intermediate angles as appropriate;
6) presentation of the measurement result, e.g error motion value, polar plot, time-based plot, frequency- content plot;
7) the rotational frequency of the spindle (zero for static error motion);
8) the time duration in seconds or number of spindle rotations;
9) appropriate warm up or break-in procedure;
The frequency response of the instrumentation, measured in hertz or cycles per revolution, includes the roll-off characteristics of electronic filters, ensuring accurate signal transmission For digital instrumentation, key parameters such as displacement resolution and sampling rate are essential for precise measurements and data quality.
The structural loop encompasses the positioning and orientation of sensors relative to the spindle housing from which error motion is measured It specifies the objects associated with the spindle axes and the reference coordinate axes, detailing their spatial relationships Additionally, it describes the connecting elements that link these objects, ensuring accurate error reporting and calibration of the spindle system.
12) time and date of measurement;
13) type and calibration status of all measurement instrumentation;
Rotational accuracy of toolholding spindle(s)
Axis of rotation error motion for toolholding spindle(s) (live tool) C: a) radial error motion (ERC); b) axial error motion (EZC); c) tilt error motion (ETC)
At percentage of maximum speed
10 % 50 % 100 % a) total radial error motion value ERC1 b) total axial error motion value EZC1 c) total tilt error motion value ETC1
If the minimum speed is larger than 10 % of the maximum speed, then the spindle should be operated at minimum speed instead
When a supplier or manufacturer mutually agrees to incorporate this test into the contractual machine acceptance procedures, they must also establish and agree upon the specific tolerances to be applied during the testing process.
The second edition of ISO 13041 may include specific tolerances for spindle performance testing, provided that validated measurement data from industrial environment assessments are available This update aims to enhance accuracy and reliability in spindle performance evaluations under real-world operating conditions Incorporating confirmed measurement data ensures that the tolerances assigned reflect practical operational standards.
At percentage of maximum speed
Observations and references to ISO 230-7
This test is a spindle test with rotating sensitive direction (ISO 230-7:2006, 5.4)
After setting up the measuring instrument, the spindle should be warmed up at 50% of its maximum speed for 10 minutes, unless otherwise specified by the manufacturer or user.
Total error motion is defined in ISO 230-7:2006, 3.2.4; total error motion value is defined in ISO 230-7:2006, 3.5.1 a) Total radial error motion value ERC1, (using probes 1 and 2)
Radial error motion measurement is detailed in ISO 230-7:2006, section 5.4.2 It specifies that the radial error motion should be measured as close as possible to the spindle nose, utilizing probes 1 and 2 positioned accordingly Accurate measurement near the spindle nose is essential for reliable assessment of radial accuracy in machine tools Following ISO standards ensures standardized and precise evaluation of radial error motion.
The radial error motion ERC1 should be represented using a total error motion polar plot, in accordance with ISO 230-7:2006, section 3.3.1, which visually depicts the error distribution Additionally, the center of the plot must be determined using a least squares circle (LSC) method, as specified in ISO 230-7:2006, section 3.4.3, to accurately quantify the error motion Furthermore, the total axial error motion value EZC1 should be calculated using probe 3 to ensure precise measurement of axial deviations.
Axial error motion measurement is described in ISO 230-7:2006, 5.4.4
For the axial error motion EZC1, a total error motion polar plot (ISO 230-7:2006, 3.3.1) with a polar chart (PC) centre (ISO 230-7:2006, 3.4.1) shall be provided c) Total tilt error motion values ETC1 (using probes 1, 2, 4, 5)
Tilt error motion measurement is described in ISO 230-7:2006, 5.4.3 The tilt error motion can be also be checked with just two non-contacting probes (see ISO 230-7:2006, 5.4.3.2)
For the tilt error motion ETC1, a total error motion polar plot (ISO 230-7:2006, 3.3.1) with a polar chart (PC) centre (ISO 230-7:2006, 3.4.1) shall be provided
For these tests the following parameters shall be stated:
1) the radial, axial or face locations at which the measurements are made;
2) identification of all artifacts, targets and fixtures used;
3) the location of the measurement setup;
4) the position of any linear or rotary positioning stages that are connected to the device under test;
5) the direction angle of the sensitive direction, e.g axial, radial or intermediate angles, as appropriate;
6) presentation of the measurement result, e.g error motion value, polar plot, time-based plot, frequency- content plot;
7) the rotational frequency of the spindle (zero for static error motion);
8) the time duration in seconds or number of spindle rotations;
9) appropriate warm-up or break-in procedure;
The frequency response of instrumentation, measured in hertz or cycles per revolution, includes the roll-off characteristics of electronic filters For digital instrumentation, it also encompasses displacement resolution and sampling rate, ensuring accurate measurement and performance analysis.
The structural loop involves the positioning and orientation of sensors relative to the spindle housing from which error motion is measured It specifies the objects in relation to which the spindle axes and reference coordinate axes are aligned, as well as the elements connecting these objects Proper understanding of this loop is essential for accurate error detection and correction in machine tool calibration.
12) time and date of measurement;
13) type and calibration status of all measurement instrumentation;
14) any other operating conditions which may influence the measurement such as ambient temperature
When tilt measurements are not required, as mutually agreed between the supplier and the user, only three displacement probes (1, 2, and 3) are used during testing In this case, the test mandrel can be replaced by a precision test sphere to ensure accurate measurement results.
1 to 3 sensors θ angle measured from the Y axis τ angle between sensor 1 and sensor 3 φ angle between sensor 1 and sensor 2 a Roundness profile
Figure A.1 — Three point measuring method
The roundness deviation of the artefact significantly affects the accuracy of axis of rotation error measurements To mitigate this influence, a measurement method employing three radially arranged linear displacement sensors against an imperfect artefact has been developed This approach effectively eliminates the impact of artefact roundness deviations, ensuring more precise and reliable axis of rotation measurements.
The article describes the angular relationships between sensors, with the angle between sensor 1 and sensor 2 denoted as φ, and the angle between sensor 1 and sensor 3 as τ, measured from the Y-axis as θ The roundness profile of the reference artifact (test bar) is represented by r(θ), capturing its surface deviations Additionally, x(θ) and y(θ) characterize the radial error motions in the X and Y directions, respectively, providing critical data for assessing the accuracy and surface profile of the artifact.
The output signals of these three sensors are given by Equations (A.1)
After multiplying the output signals of sensor 1, sensor 2 and sensor 3 by the coefficients “1, p, q”, total summation is given as S(θ)
1 cos cos 0 sin sin sin 0 sin sin p p q p q q τ φ τ τ φ φ τ φ τ φ
If p, q, φ, τ are chosen so as to satisfy Expression (A.3), then Equation (A.2) becomes independent of error motion x(θ) and y(θ) The roundness profile of the reference artefact r(θ) is expressed as
( ) 1 cos cos sin sin cos sin sin 1 cos cos sin
Substituting α k , β k from Equations (A.6), the Fourier coefficients of S(θ), i.e F k , G k , are given by
Then, Fourier coefficients of the roundness profile of the reference artefact, A k , B k , are obtained as follows.
Then, the radial error motion in X and Y direction are estimated as follows Here, rˆ represents the estimated roundness profile of the reference artefact
[1] ISO 1708:1989, Acceptance conditions for general purpose parallel lathes — Testing of the accuracy
[2] ISO 2806:1994, Industrial automation systems — Numerical control of machines — Vocabulary
[3] ISO 3442-1:2005, Machine tools — Dimensions and geometric tests for self-centring chucks with two- piece jaws — Part 1: Manually operated chucks with tongue and groove type jaws
[4] ISO 3442-2:2005, Machine tools — Dimensions and geometric tests for self-centring chucks with two- piece jaws — Part 2: Power-operated chucks with tongue and groove type jaws
[5] ISO 3442-3:2007, Machine tools — Dimensions and geometric tests for self-centring chucks with two- piece jaws — Part 3: Power-operated chucks with serrated jaws
[6] ISO 6155:1998, Machine tools — Test conditions for horizontal spindle turret and single spindle automatic lathes — Testing of the accuracy
[7] ISO 13041-1:2004, Test conditions for numerically controlled turning machines and turning centres — Part 1: Geometric tests for machines with a horizontal workholding spindle
[8] ISO 13041-3, Test conditions for numerically controlled turning machines and turning centres — Part 3: Geometric tests for machines with inverted vertical workholding spindle
[9] SHINNO, H., MITSUI, K., TATSUE, Y., TANAKA, N., OMINO, T., TABATA, T., NAKAYAMA, K A new method for evaluating error motion of ultra precision spindle Ann CIRP, 1987, 36, pp 381-384
This article discusses a novel measurement method for assessing spindle rotation accuracy using a three-point technique Developed by K Mitsui, this method offers improved precision in spindle performance evaluation The research was presented at the 23rd International Machine Tool Design and Research Conference held in Manchester in September 1982 The study is documented in the conference proceedings edited by B.J Davies, spanning pages 115 to 121, and published by UMIST in Manchester This innovative approach enhances the reliability of spindle error measurement, benefiting machine tool quality assurance.