A method and device for measuring RTCP parameters of a five-axis CNC machine tool

Abstract

This invention discloses a method and device for measuring RTCP parameters of a five-axis CNC machine tool. It proposes a universal geometrical mathematical model that, by rotating the axis forward and backward by the same angle, changes the relative height of the workpiece pallet surface so that the execution point falls on the workpiece pallet surface. The change in height of the execution point relative to a reference plane during this process is measured, and the distance *r* between the laser / tool ​​tip and the rotation center in the five-axis machine tool is directly calculated using a formula. The core advantage of this model lies in its use of mathematical model analysis to solve for parameters that are difficult to measure directly using directly measurable parameters. Its ingenious symmetrical measurement design cancels out height errors introduced by human judgment in the formula, thereby significantly improving the authenticity and reliability of the measurement results. This achieves micron-level precision in RTCP parameter calibration, significantly improving the accuracy of five-axis machining. The same core mathematical model and process are applicable to two different types of five-axis machine tools: those using cutting tools and those using lasers, demonstrating strong versatility.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of five-axis numerical control machine tools, and particularly relates to a five-axis linkage machine tool RTCP parameter measurement method and device. BACKGROUND

[0002] The RTCP function (Rotated Tool Center Point) of a machine tool, also known as the tool tip point following function, is one of the core technologies of a five-axis numerical control machine tool. It compensates for the offset of the tool center point caused by the movement of the rotating shaft in real time, ensuring machining accuracy and operational convenience. The implementation of the RTCP function relies on accurately obtaining the offset between the end effector, such as the tool tip or laser focal point, and the center of the rotating shaft it depends on. The accuracy of this parameter directly determines the compensation effect of the RTCP function.

[0003] For traditional tool five-axis machine tools, the tool is often fixed on the rotating shaft and needs to be connected by multiple components. The offset between the tool tip and the rotating center is usually calculated theoretically based on the design dimensions of the mechanical components. However, due to mechanical assembly errors, wear and deformation after long-term use, there is often a large deviation between the theoretical test value and the actual value of the offset.

[0004] For laser five-axis machine tools, the laser focal point does not come into contact with the workpiece and therefore does not experience mechanical deformation. However, the laser undergoes multiple reflections during transmission from the laser to the light outlet, making it impossible to directly calculate the offset between the laser focal point and the rotating center through mechanical structure. Instead, it usually relies on complex machine simulation models, which may not be consistent with the actual situation due to optical path adjustment errors.

[0005] Therefore, there is a lack of low-cost, convenient, repeatable, and high-precision RTCP parameter direct measurement methods suitable for different types of five-axis machine tools in the prior art. SUMMARY

[0006] To overcome the deficiencies in the prior art, the present application provides a five-axis linkage machine tool RTCP parameter measurement method and device, which can accurately, cost-effectively, and conveniently measure the distance between the laser or tool tip and the rotating center, thereby improving the machining accuracy of the five-axis machine tool.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] In a first aspect of the present application, a five-axis linkage machine tool RTCP parameter measurement method is provided, wherein the RTCP parameter is the offset r of the end effector from the center of the rotating shaft. The measurement method includes the following steps:

[0009] S1. Determine the zero-angle position of the rotation axis. At this position, the ejection direction of the end effector is perpendicular to the workpiece tray plane.

[0010] S2. Control the rotary axis to the zero-angle position, adjust the machine tool Z-axis to change the relative height of the workpiece pallet surface, place the execution point of the end effector on the first plane Z of the workpiece pallet, and record the first position point A;

[0011] S3, Control the rotation axis to deflect in the positive direction by the first angle. Adjust the Z-axis of the machine tool to change the relative height of the workpiece pallet surface, so that the execution point of the end effector falls on the second plane Z1 of the workpiece pallet, record the second position point B, and obtain the first height change of the machine tool Z-axis relative to the first position point A at this time. ;

[0012] S4. Control the rotating axis to deflect in the opposite direction by the first angle. Adjust the machine tool's Z-axis to change the relative height of the workpiece pallet surface, and place the execution point of the end effector on the third plane Z2 of the workpiece pallet. Record the third position point C, and obtain the second height change of the machine tool's Z-axis relative to the first position point A at this time. ;

[0013] S5, Based on the first height change Second altitude change and the first angle The offset r is calculated using the following formula:

[0014] .

[0015] The first plane Z, the second plane Z1, and the third plane Z2 on the workpiece tray are the same plane. By adjusting the Z-axis of the machine tool, their height position relative to the rotation axis changes. In other words, the first plane Z, the second plane Z1, and the third plane Z2 are raised or lowered relative to each other due to the change of the Z-axis of the machine tool.

[0016] Further, in step S1, the end effector is a laser processing head, the execution point is the laser focus, and determining the zero-angle position of the rotation axis specifically includes the following steps:

[0017] (1) Place the beam quality analyzer parallel to the workpiece tray;

[0018] (2) Control the machine tool Z-axis to move between the maximum height Zmax and the minimum height Zmin, and record the movement trajectory of the centroid of the laser spot on the detector of the beam quality analyzer;

[0019] (3) Based on the moving trajectory of the laser spot centroid, the tilt angle of the trajectory line is obtained by fitting;

[0020] (4) Adjust the angle value of the rotation axis and repeat the above steps until the fitted trajectory line is parallel to the direction of tray movement. Then, determine the angle of the rotation axis at this time as the zero angle position.

[0021] Furthermore, after determining the zero-angle position of the rotation axis, the offset angle of the laser beam emission direction of the laser processing head in the pallet movement direction is calculated based on the offset β of the fitted trajectory straight line in the direction parallel to the pallet movement. ,in And compensate for it in motion control.

[0022] Furthermore, in steps S2, S3, and S4, the indicator light device set on the laser processing head determines whether the laser focus falls within the corresponding workpiece tray plane.

[0023] Furthermore, the indicator light device consists of three indicator laser beams, which are adjusted to converge at the laser focal point and their positions are observed by a coaxially mounted CCD camera.

[0024] Furthermore, in steps S2, S3, and S4, the Z-axis of the machine tool is adjusted up and down to focus the three indicator laser beams onto the photographic paper placed on the workpiece tray, and then the laser processing head is turned on to mark the position points on the photographic paper.

[0025] Furthermore, the end effector is a cutting tool, and the actuation point is the tool tip; in steps S2, S3, and S4, the determination is made by directly contacting the tool tip with the workpiece tray plane. and The value of .

[0026] A second aspect of the present invention provides a measuring apparatus for implementing the above-described measuring method, the measuring apparatus comprising:

[0027] The control unit is used to control the movement of each axis of a five-axis linkage machine tool;

[0028] The measurement unit measures the position of the centroid of the laser spot when the end effector is a laser processing head, or detects the contact between the tip of the tool and the workpiece when the end effector is a cutting tool.

[0029] An indicator unit is used to assist in determining whether the execution point falls on the plane of the workpiece tray;

[0030] The calculation unit is used to execute the formula for calculating the offset r and to calculate the RTCP parameters.

[0031] To implement the above measurement method, the present invention also provides a matching measurement device, including a beam quality analyzer for aligning the perpendicularity of the rotation axis, a three-point indicator light device for assisting in locating the laser focus, and a control and calculation unit for performing calculations.

[0032] A third aspect of the present invention provides a five-axis linkage machine tool, comprising the above-described measuring device.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) This invention proposes a general geometric mathematical model. By rotating the axis in the forward and reverse directions by the same angle and measuring the height change of the execution point relative to the reference plane during this process, the distance r of the laser / tool ​​end point deviating from the rotation center in the five-axis machine tool can be directly calculated using the formula. The core advantage of this model is that it cleverly uses a symmetrical measurement design to cancel out the height error introduced by human judgment in the formula, thereby greatly improving the authenticity and reliability of the measurement results, realizing micron-level precision RTCP parameter calibration, significantly improving the five-axis machining accuracy. Experiments have shown that the five-axis linkage machining accuracy can be improved by about 600μm.

[0035] (2) The same set of core mathematical models and processes are applicable to two different types of five-axis machine tools, namely cutting tools and lasers. Only the specific implementation method of the step of judging "the execution point falls on the pallet plane" needs to be finely adjusted (such as using indicator light for laser machine tools and direct contact for cutting tool machine tools). It has strong universality and solves common problems in the industry. Attached Figure Description

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0037] Figure 1 A schematic diagram of the structure of a BC rotary five-axis linkage machine tool body;

[0038] Figure 2 A schematic diagram showing the laser focus or the tool tip deviating from the center of rotation;

[0039] Figure 3 This is a schematic diagram of the laser five-axis machine tool measuring device in Example 1;

[0040] Figure 4 This is a schematic diagram of the method for measuring the zero-angle position of the rotation axis in Example 1;

[0041] Figure 5 This is a comparison of the laser spot centroid shift curves under different rotation axis angles in Example 1;

[0042] Figure 6 This is the mathematical model for measuring the laser focus offset rotation center in Example 1;

[0043] Figure 7 The machining effect diagram is shown using RTCP parameters measured by a machine tool simulation model;

[0044] Figure 8 This is a processing effect diagram of the RTCP parameters measured using the method in Example 1. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] This invention provides a universal and high-precision method and apparatus for calculating the RTCP parameters (i.e., the offset r of the end effector point from the rotation center) of a five-axis linkage machine tool.

[0047] The following will use laser five-axis linkage machine tools and tool five-axis linkage machine tools as examples to illustrate the specific implementation process of the present invention in detail.

[0048] For laser five-axis CNC machine tools and tool five-axis CNC machine tools, the body structure of the five-axis machining tools is the same (e.g. Figure 1 As shown in the diagram, the laser processing head or tool is mounted on the B-axis rotation axis, which can move along the positive and negative directions of the Z and X axes. The workpiece is mounted on the C-axis, which can move along the positive and negative directions of the Y-axis. The offset r of the laser beam focus emitted by the laser processing head or the tool tip from the center of its rotation axis is as follows: Figure 2 As shown.

[0049] Example 1

[0050] This embodiment uses a typical XYZBC five-axis laser processing machine as an example. To accurately measure the distance of the laser beam deviating from the rotation center of the five-axis laser linkage machine, the device designed in this method is as follows: Figure 3 As shown, a three-point indicator light device is integrated and installed on the laser processing head. This device emits three visible indicator laser beams, which are adjusted to converge at the invisible processing laser focal point. The specific installation and focusing methods of the three-point indicator light device can be found in the applicant's previous patent application, publication number CN120170243B. Simultaneously, a CCD camera is coaxially mounted on the laser processing head to observe the position of the indicator spots formed by the three indicator laser beams on the workpiece surface.

[0051] Using a beam quality analyzer (such as the Gentec-Eo brand), the detector can be placed parallel to the machine tool table (i.e., the workpiece tray).

[0052] Photographic paper (or other materials that can record laser ablation marks) is used to record the laser focal point position;

[0053] The control and calculation unit is used to control the machine tool's movement, record data, and perform calculations.

[0054] The specific measurement steps for the RTCP parameters of the aforementioned laser five-axis CNC machine tool are as follows:

[0055] Step 1: Determine the zero-angle position of the B rotation axis (perpendicularity calibration)

[0056] After setting up the above-mentioned device, in order to measure the offset between the laser focus and the center of rotation, it is first necessary to find the angle between the rotation axis (the rotation axis that carries the tool or laser processing head) and the workpiece tray, and mark it as the zero angle. After the machine tool is set up, the initial laser emission direction is often not perpendicular to the plane of the workpiece tray. Since the laser direction cannot be directly measured, a special method is needed to find the angle of the rotation axis so that the laser emission direction is perpendicular to the workpiece tray.

[0057] This process uses a beam quality analyzer, which can continuously track and record the positional changes of the laser spot centroid on the detector plane.

[0058] The steps for measuring whether the laser emission direction is perpendicular to the workpiece tray are as follows:

[0059] First, place the detector for laser beam quality analysis parallel to the workpiece tray. Then, use NC code to make the machine tool's Z-axis perform a reciprocating motion between two appropriate height values, Zmax and Zmin (e.g., ...). Figure 4 As shown), and record the offset curve of the laser spot centroid (as shown). Figure 5 As shown in the left figure, since the initial laser emission direction is not perpendicular to the workpiece tray plane, the laser spot centroid offset curve will show a slanted straight line, and the slope of the straight line is determined by the initial angle of the laser rotation axis.

[0060] Then, the coordinates of this line are derived, the line is fitted using the least squares method, and the inclination angle of the line is obtained.

[0061] Then, adjust the angle of the laser rotation axis, repeat the above steps to obtain a new set of laser spot centroid offset coordinates, and recalculate the tilt angle until the fitted line of the laser spot centroid offset coordinates is parallel to the workpiece pallet movement direction (Y-axis direction). At this point, the angle of the laser rotation axis is marked as zero. Using this method, the perpendicularity value of the rotation axis angle can be accurate to 0.01°. After repeating the above operations, the laser spot centroid offset curve is as follows: Figure 5 As shown in the right figure, the straight line is parallel to the Y direction, and its offset in the Y direction is β. This offset is caused by the initial offset of the laser beam towards the Y direction of the machine tool coordinate system, using the formula: The offset angle of the laser beam in the direction of movement of the workpiece tray can then be calculated. This value can be compensated for in motion control to eliminate system errors.

[0062] Offset Angle The occurrence of this error is due to minor installation deviations in the laser or optical path components, such as the laser being installed slightly crooked or a minor error in the angle of the reflector. This cannot be corrected by adjusting the B-axis angle; it falls under the category of "optical path collimation" issues. This represents the offset angle between the optical axis of the laser beam and the Z-axis of the ideal machine tool coordinate system along the Y-axis of the machine tool. Offset Angle This describes the overall collimation of the laser beam, specifically whether the laser beam's axis coincides with the machine tool's theoretical Z-axis. This is an error that must be minimized during optical path adjustment. During the machine tool's B-axis yaw, the offset angle... It is also a relatively stable value and does not affect the formula. The calculation results show that the actual coordinates of the execution endpoint after RTCP is enabled have a fixed amount of offset in the Y-axis direction of the machine tool coordinate system.

[0063] Execution end offset angle The compensation is easily implemented in subsequent motion control; it simply involves adding a compensation layer to the B-axis motion in the NC code. The offset angle, or the amount of offset of the end effector point in the Y-axis direction to compensate for it, can be directly input as the end effector offset angle in many motion control systems (such as Beckhoff and Siemens). Compensation will be provided.

[0064] Step 2: Measure the amount r by which the laser focus deviates from the B-axis rotation center.

[0065] For ease of understanding, the mathematical model of the measurement method is simplified to: Figure 6 As shown in the diagram, in this model, the large circle R is the trajectory of the laser focus after the laser rotation axis rotates 360 degrees, and the small circle r is the virtual trajectory formed by the laser deflection rotation center amount r. The value of r is the laser focus deflection rotation center amount that needs to be calculated. The three-point laser focus indicator device and the measurement of the zero angle value of the rotation axis have already been introduced in the above steps. Based on this, a piece of photographic paper is placed on the workpiece tray. The purpose of the photographic paper is to record the laser emission position. The steps for measuring the laser focus deflection rotation center amount r are as follows:

[0066] First, deflect the laser rotation axis to the zero angle value calculated in the above steps, and adjust the machine tool Z-axis up and down so that the three visible indicator laser beams converge on the photographic paper. At this time, the laser focus also falls on the photographic paper. Turn on the laser processing head and print laser mark point A on the photographic paper. The plane where the photographic paper is located is the Z-plane. Record the machine tool coordinates of the machine tool Z-axis at this time.

[0067] Then the laser rotation axis deflects to After adjusting the angle, moving the machine tool's Z-axis up and down causes the three visible indicator laser beams to converge again onto the photographic paper, i.e., at the current position... When the laser focus falls on the photographic paper again at the specified angle, and the laser marker point B is activated, the machine tool coordinates along the Z-axis are recorded at this point. The height of the machine tool's Z-axis relative to point A is calculated and recorded as the first height change. In practice, the human eye needs to use a three-point laser pointer to determine whether the focus is on the photographic paper, which introduces a slight error. Therefore, the theoretical height change should be... + ,in To determine the error, the plane on which the photographic paper is located is the Z1 plane;

[0068] Finally, the laser rotation axis is deflected to - After adjusting the angle, repeat the above operation, move the machine tool's Z-axis to find the laser focus and mark the laser marker point C at this time, record the machine tool's Z-axis coordinates at this time, and calculate the height of the machine tool's Z-axis relative to point A, which is recorded as the first height change. At this time, the theoretical height of the Z-axis relative to point A is , It is an error that uses a three-point indicator light to determine whether the focus falls on the photographic paper. The plane on which the photographic paper is located is the Z2 plane.

[0069] Lines L, L1, and L2 deflect forward and backward through the center of rotation, point B. Three rays at an angle. (Refer to...) Figure 6 The mathematical model shown, due to the existence of the value of the laser focus offset rotation center r, and There is a height difference. The point is The point is the reflection of the point across line L2, and we can know that... From geometric relationships, we can know that point B is... Point is symmetric about the perpendicular line L, and The point is at the intersection of the Z2 plane and the great circle R. Point C is the projection of point C onto the Z2 plane, therefore... ,Depend on Figure 6 According to the mathematical model, It is a chord on the great circle R. That is, L2 is perpendicular So obviously in middle, From the triangular relationship, we can obtain:

[0070]

[0071] There is a judgment error when using a three-point laser pointer to determine whether points B and C fall on the tray surface. and Therefore, the value of the laser focus offset rotation center r can be obtained. Error analysis shows that, however, when the same judgment method is used, and Since they are of the same sign and approximately equal, the judgment error can be effectively eliminated. Therefore, the value of the laser focus offset rotation center r is approximately equal to:

[0072] .

[0073] This formula greatly eliminates human subjective error, making the measurement results very close to the true value.

[0074] Example 2

[0075] This embodiment uses a typical XYZBC five-axis machining center as an example to illustrate how the measurement method of this invention can be applied to a five-axis machining center with a physical tool as the end effector. Its core mathematical model is exactly the same as in Embodiment 1, with the only differences being: 1. the method for determining the zero-angle position of the B-axis rotation, and 2. the method for determining whether the "tool tip falls on the pallet plane".

[0076] Step 1: The method for determining the zero-angle position of the B rotation axis is as follows.

[0077] Compared to the invisible laser at the end point of execution, the tool end is a visible entity, so it can be measured using a laser interferometer. The emitting end of the laser interferometer is placed on the workpiece tray surface, so that the detection laser is emitted vertically upwards, and the receiving end is fixed at the tool end, with the detection surface of the receiving end parallel to the workpiece tray surface.

[0078] Raise the tool to a certain height and adjust the XY axis so that the laser interferometer receiver on the tool can receive the detection laser. At this time, move the Z axis up and down to move the tool up and down. If the tool is vertically downward, the coordinates of the detection light on the receiver remain unchanged. If there is a shift, adjust the B axis angle until the Z axis moves up and down within its inner stroke and the laser point detected by the receiver does not move. At this time, the B axis angle is zero.

[0079] Step 2: Measure the amount r by which the laser focus deviates from the B-axis rotation center.

[0080] At zero angle, move the machine tool's Z-axis so that the tool tip lightly touches the surface of the workpiece tray, and record this position as point A and its Z-axis coordinates.

[0081] Deflect the laser rotation axis in the positive direction Move the machine tool's Z-axis to bring the tool tip lightly touch the same plane as the workpiece tray again, and record the position B and Z-axis coordinates to obtain... .

[0082] Reverse the laser rotation axis Repeat the operation, recording the position C and Z-axis coordinates, to obtain the angle. .

[0083] Calculate: the measured change in height and Substitute into the formula: This allows us to calculate the offset r of the tool tip from the center of its rotation axis.

[0084] Experimental verification

[0085] The method was verified using the XYZBC five-axis laser processing machine tool of Example 1. Since the processing accuracy of the five-axis machine tool is limited by a variety of factors, the processing effect of the verification equipment after enabling the five-axis RTCP function was compared under different RTCP parameters while keeping other factors unchanged.

[0086] Specifically, while keeping other machining parameters unchanged, five-axis linkage machining was performed using the RTCP parameters (laser focus offset rotation center amount) calculated by the original machine tool simulation model and the RTCP parameters (laser focus offset rotation center amount) measured by the method in Embodiment 1 of this invention, respectively. The machining results are shown in the figures below. Figure 7 and Figure 8 .

[0087] like Figure 7 As shown, the RTCP parameters measured using the machine tool simulation model have a large error between the simulation model value and the actual value due to mechanical assembly errors and optical path errors, resulting in obvious deformation of the machined pattern.

[0088] like Figure 8 As shown, after enabling the RTCP function using the parameters measured by this invention, the deformation of the processed pattern is greatly reduced (due to the influence of other factors, there is still an error between the processed pattern model and the actual object), but the processing accuracy is improved by about 600μm.

[0089] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method of measuring RTCP parameters for a five-axis machine tool, characterized by, The RTCP parameter is an offset r of an execution point of the end effector from a center of a rotating shaft where the end effector is located, and the measurement method comprises the following steps: S1, determining a zero angle position of the rotating shaft, at which a shooting direction of the end effector is perpendicular to a plane of the workpiece tray; S2, controlling the rotating shaft to be at the zero angle position, adjusting a machine tool Z axis to change a relative height of the workpiece tray surface, and dropping the execution point of the end effector on a first plane Z of the workpiece tray, and recording as a first position point A; S3, control the rotation axis to deflect the first angle in positive direction , adjust the machine tool Z axis to change the relative height of the workpiece tray surface, drop the execution point of the end effector on the second plane Z1 of the workpiece tray, record as the second position point B, and obtain the first height change amount of the machine tool Z axis relative to the first position point A at this time ; S4, control the rotating shaft to reverse deflect the first angle , adjust the machine tool Z axis to change the relative height of the workpiece tray surface, drop the execution point of the end effector on the third plane Z2 of the workpiece tray, record the third position point C, and obtain the second height change amount of the machine tool Z axis relative to the first position point A at this time ; S5、based on the first height variation , the second height variation , and the first angle , the offset r is calculated by the following equation: 。 2. The five-axis machine tool RTCP parameter measurement method according to claim 1, characterized by, In step S1, the end effector is a laser processing head, and the execution point is a laser focal point, and the determination of the zero angle position of the rotating shaft specifically comprises the following steps: (1) placing a beam quality analyzer parallel to the workpiece tray; (2) controlling the machine tool Z axis to move between a maximum height Zmax and a minimum height Zmin, and recording a moving track of a laser spot centroid on a detector of the beam quality analyzer; (3) fitting an inclination angle of a straight line of the moving track based on the moving track of the laser spot centroid; (4) adjusting an angle value of the rotating shaft, and repeating the above steps until a straight line of the fitting track is parallel to a moving direction of the tray, and determining the angle of the rotating shaft at this time as the zero angle position.

3. The five-axis machine tool RTCP parameter measurement method according to claim 2, characterized by, After the zero angle position of the rotation axis is determined, the offset angle of the laser beam emission direction of the laser processing head in the tray moving direction is calculated according to the offset β of the fitted trajectory straight line in the direction parallel to the tray moving direction wherein and is compensated for in the motion control.

4. The five-axis machine tool RTCP parameter measurement method according to claim 3, characterized by, In steps S2, S3 and S4, whether the laser focal point falls in the corresponding workpiece tray plane is determined by an indicating light device arranged on the laser processing head.

5. The five-axis machine tool RTCP parameter measurement method according to claim 4, characterized by, The indicating light device is three indicating lasers, which are adjusted to converge at the laser focal point, and the position is observed by a coaxially arranged CCD camera.

6. The five-axis machine tool RTCP parameter measurement method according to claim 5, characterized by, In steps S2, S3 and S4, the machine tool Z axis is adjusted up and down, the three indicating lasers are converged on a photo paper placed on the workpiece tray, and then the laser processing head is turned on to mark a position point on the photo paper.

7. The five-axis machine tool RTCP parameter measurement method according to claim 1, characterized by, The end effector is a cutter, and the execution point is a cutter tip; in steps S2, S3 and S4, the cutter tip is directly touched against the workpiece tray plane to determine and .

8. A measuring device for implementing the measuring method according to any one of claims 1 to 7, characterized in that, The measurement device comprises: a control unit for controlling movements of each axis of a five-axis linkage machine tool; a measurement unit for measuring a laser spot centroid position when the end effector is a laser processing head, or detecting a contact between a tool tip of a tool and a workpiece when the end effector is the tool; an indicating unit for assisting in determining whether the execution point falls on the plane of the workpiece tray; a calculation unit for executing a calculation formula of the offset r to calculate the RTCP parameter.

9. A five-axis machine tool, characterized by The measurement device of claim 8 is included.

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