CN102338626A - A method for monitoring the stylus position of a contact coordinate measuring machine for tiny holes - Google Patents

Abstract

The invention discloses a method for monitoring the probe position of a contact type coordinate measuring machine for tiny holes, which includes the following steps: (1) fixing the workpiece to be measured on the tooling, installing a light source on the Z axis of the measuring machine, The camera used for imaging the stylus and the small hole is placed on the workbench of the measuring machine; (2) the Z-axis of the measuring machine is moved above the hole to be measured, and the small hole image of the small hole is taken by the camera, and the small hole is captured by the camera. The image is output to the computer for image processing to obtain the center position and radius of the small hole, and then based on the center coordinates of the small hole, the stylus is moved to the top of the small hole through the control system of the measuring machine; (3) the stylus Before entering the small hole, the image of the ruby end of the stylus is captured by the camera, and the camera outputs the image of the stylus to the computer for image processing of the stylus to obtain the center position of the end of the stylus. The method improves the measurement efficiency and effectively protects the probe.

Description

A method for monitoring the stylus position of a contact coordinate measuring machine for tiny holes

technical field

The invention relates to a method for monitoring the position of a stylus, in particular to a method for monitoring the position of a stylus of a contact coordinate measuring machine for tiny holes.

Background technique

For CMMs using mechanical trigger probes, the stylus must be positioned prior to contact measurement of the feature being measured, and this step is performed by the operator. Taking the inner diameter of a measuring hole as an example, before measuring, the operator must position the stylus directly above the hole to be measured, and then the stylus can be inserted into the hole to be measured. There are two bases for operator positioning: one is human eye observation, and the other is the positioning reference of the tested part. When the measurement object is a tiny hole with a diameter of less than 1 mm, the difference between the diameter of the end of the stylus and the diameter of the tiny hole is less than 1 mm, and it is unreliable to observe with the human eye at this time. When the positioning datum is difficult to obtain accurately, or the manufacturing error of the measured part is out of tolerance, the stylus cannot be accurately positioned directly above the measured hole. When the positioning error of the stylus is too large, the stylus will collide with the measured object when it is inserted into the measured hole. Since the measurement is a tiny hole, the stylus used is also very small, once a collision occurs during the non-measurement process, the stylus will be damaged. At present, domestic enterprises are still unable to produce high-precision contact styli with excellent performance, and the annual cost of purchasing styli from foreign companies is very high, so it is necessary to improve the service life of styli and reduce costs.

The existing stylus anti-collision protection device is mainly designed for the excessive force when the stylus is in contact with the workpiece to be measured in the measurement state, such as the stylus with a zero-contact force protection device produced by the British Renishaw company. However, there is no good solution for the contact between the stylus and the tested part in the non-measurement state. Usually, when the three-dimensional coordinate measuring machine is working, the relevant technical personnel will observe it and stop the equipment in time before the accidental collision occurs. run. This method is time consuming and in most cases the stylus is destroyed when the equipment is out of service.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, to provide a method that can quickly determine the position of the small hole to be measured, automatically position the measuring needle, and can conveniently monitor the position of the measuring needle and the tiny hole, and effectively prevent the measuring needle from being damaged. A contact coordinate measuring machine stylus position monitoring method for tiny holes.

The method for monitoring the position of the stylus of a contact coordinate measuring machine for tiny holes of the present invention comprises the following steps:

(1) Fix the workpiece to be measured on the tooling, and install a light source on the Z-axis of the three-coordinate measuring machine to realize the illumination of the stylus installed on the Z-axis of the three-coordinate measuring machine and the small hole on the workpiece to be measured. The camera used to image the stylus and the small hole is placed on the workbench of the three-coordinate measuring machine inside the tooling. The camera is placed on the adjustment seat for fixing and adjusting the position of the camera. The adjustment seat and the tooling are fixed on the three-coordinate measuring machine. on the workbench;

(2) Move the Z-axis of the three-coordinate measuring machine to the top of the measured hole so that the light source is within the working distance range, and then use the camera to capture the small hole image of the small hole, and the camera outputs the small hole image to the computer for image processing, and obtain The center position and radius of the small hole, and then based on the center coordinates of the small hole, move the stylus directly above the small hole through the control system of the three-coordinate measuring machine;

(3) Before the stylus is inserted into the small hole, the image of the ruby end of the stylus is captured by the camera, and the camera outputs the image of the stylus to the computer for image processing of the stylus to obtain the center position of the end of the stylus and pass through the small hole The center position and radius of the stylus, as well as the center position of the end of the stylus and the preset radius of the end of the stylus can be used to determine whether the stylus will collide with the small hole.

The beneficial effects of the present invention are:

1. It can quickly locate the small hole, and automatically move the stylus to the top of the small hole through the control system to improve the measurement efficiency.

2. The small hole and the stylus are positioned by the system to ensure the accuracy of the stylus positioning, avoiding the collision of the stylus when it is inserted into the small hole, and effectively protecting the stylus.

3. The optical magnification of the tiny hole and the stylus is carried out, which is convenient for the operator to observe.

Description of drawings

Fig. 1 is a schematic diagram of the test structure adopted by the contact type coordinate measuring machine probe position monitoring method for tiny holes of the present invention;

Fig. 2 is the enlarged view of the I place of the structure shown in Fig. 1;

FIG. 3 is a schematic structural diagram of a light source in the structure shown in FIG. 1 .

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

如果d≤r_o-r_o-ε，则说明测针处在安全范围内，其中r_c是测针的半径值，ε是用户设定的安全系数，取值区间为(0，r_o-r_c)The method for monitoring the position of the stylus of a contact coordinate measuring machine for tiny holes of the present invention includes the following steps: (1) fixing the workpiece 103 to be measured on the tooling 104, and installing a light source 102 on the Z axis 101 of the three coordinate measuring machine Realize the illumination of the stylus 201 installed on the Z-axis of the three-coordinate measuring machine and the small hole 202 on the workpiece to be measured. The camera 105 of the hole 202 imaging, the camera 105 is placed on the adjustment seat 106 for fixing and adjusting the position of the camera 105, and the adjustment seat 106 and the tooling 104 are fixed on the workbench 107 of the three-coordinate measuring machine; (2) the three-coordinate measurement The Z-axis 101 of the machine moves to the top of the measured hole 202, so that the light source 102 is within the working distance range, and then the camera 105 is used to shoot the small hole image of the small hole 202, and the camera outputs the small hole image to the computer for image processing to obtain the small hole 202 center position (x _o , y _o ) and radius r _o , and then based on the center coordinates of the small hole 202, move the stylus 201 directly above the small hole 202 through the control system of the three-coordinate measuring machine; (3 ) Before the stylus 201 is inserted into the small hole 202, the image of the ruby end of the stylus 201 is captured by the camera 105, and the camera outputs the image of the stylus to the computer for image processing of the stylus to obtain the center position of the ruby end of the stylus 201 (x _c , y _c ). The distance between the center of the ruby end of the stylus 201 and the center of the small hole 202

If d≤r _o -r _o -ε, it means that the stylus is in the safe range, where r _c is the radius value of the stylus, ε is the safety factor set by the user, and the value range is (0, r _o - r _c )

Preferably, the light source is composed of a housing 301 and an annular LED light-emitting diode array 302, and a frosted glass 303 is installed on one of the rings. In the step (2), the frosted glass 303 part of the light source is aligned with the small hole for backlighting. illumination.

In this method, the focus plane of the camera 105 should be adjusted to the upper surface of the workpiece 103 so that both the small hole 202 and the probe 103 can obtain clearer images.

The camera 105 should be adjusted through the adjustment seat 106 so that the length and width directions of the obtained image are as parallel as possible to the X and Y directions of the three-coordinate measuring machine respectively, so as to facilitate the operator to observe, and make the small hole 202 in the center of the image .

The camera 105 should be calibrated after installation to establish a connection between the camera coordinate system and the machine coordinate system.

By adopting the method, the image can be displayed on the computer screen, which is convenient for operators to observe.

Example 1

r_c是0.15mm，取ε＝0.1mm，则d＜r_o-r_c-ε＝0.09mm，说明测针处在安全范围内。Fix the workpiece 103 to be measured on the tooling 104, install the light source 102 on the Z-axis 101 of the three-coordinate measuring machine to realize the illumination of the stylus 201 installed on the Z-axis of the three-coordinate measuring machine and the small hole 202 on the workpiece to be measured , the camera 105 for imaging the stylus 201 and the small hole 202 is placed on the workbench of the coordinate measuring machine located inside the tooling 104, and the camera 105 is placed on the adjustment seat 106 for fixing and adjusting the position of the camera 105, adjusting The seat 106 and the tooling 104 are fixed on the workbench 107 of the three-coordinate measuring machine; (2) the Z-axis 101 of the three-coordinate measuring machine is moved to the top of the hole 202 to be measured. A frosted glass 303 is installed on one place, so that the light source 102 is within the working distance range, and the frosted glass 303 part of the light source is aligned with the small hole for backlighting, and then the small hole image of the small hole 202 is taken by the camera 105, and the small hole is captured by the camera. The image is output to the computer for image processing to obtain the central position (x _o , y _o )=(325.123, 201.020) and the radius r _o =0.34mm of the small hole 202, and then use the central coordinates (x _o , y _o ) as the basis, the stylus 201 is moved to the top of the small hole 202 through the control system of the coordinate measuring machine; (3) before the stylus 201 is inserted into the small hole 202, the ruby end of the stylus 201 is captured by the camera 105 The camera outputs the stylus image to the computer for stylus image processing to obtain the center position (x _c , y _c )=(325.130, 201.011) of the ruby tip of the stylus 201 . The distance between the center of the ruby end of the stylus 201 and the center of the small hole 202

r _c is 0.15mm, taking ε=0.1mm, then d<r _o -r _c -ε=0.09mm, indicating that the stylus is in the safe range.

By adopting the method, the measurement efficiency is improved, the collision of the measuring needle when it is inserted into the small hole is avoided, and the measuring needle is effectively protected. The optical magnification of the tiny hole and the stylus is convenient for the operator to observe.

Claims (2)

1. to the contact coordinate measuring machine chaining pin position monitoring method of micro hole, it is characterized in that it may further comprise the steps:

(1) workpiece for measurement is fixed on the frock; In that being installed on the Z of the three coordinate measuring machine axle, realizes light source being installed in chaining pin and the illumination of the aperture on the workpiece for measurement on the three coordinate measuring machine Z axle; On the worktable that is positioned at the inner three coordinate measuring machine of frock, place and be used for video camera chaining pin and pinhole imaging system; Video camera is placed on and is used for fixing and adjusts on the adjustment seat of camera position, and adjustment seat and frock are fixed on the worktable of three coordinate measuring machine;

(2) the Z axle with three coordinate measuring machine moves to the measured hole top; Make light source in the operating distance scope; Use video camera to take the aperture image of aperture then, video camera is exported to computing machine with the aperture image and is carried out Flame Image Process, obtains the center and the radius of aperture; Centre coordinate with aperture is a foundation then, the control system through three coordinate measuring machine with chaining pin move to aperture directly over;

(3) before chaining pin puts in aperture; Obtain the image of chaining pin ruby end through the video camera shooting; Video camera is exported to computing machine with the chaining pin image and is carried out the chaining pin Flame Image Process, obtains the center of chaining pin end, through the center and the radius of aperture; And the center of chaining pin end and preset these four information of chaining pin end radii, just can judge chaining pin and whether can bump with aperture.

2. the contact coordinate measuring machine chaining pin position monitoring method to micro hole according to claim 1; It is characterized in that: described light source is to be made up of and a place on annular is equipped with frosted glass the annular LED light emitting diode matrix, and the frosted glass part alignment apertures of light source is carried out back lighting in described step (2).

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