CN108917667B - Three-dimensional scanning-based method for measuring inner surface of narrow deep cavity of casting - Google Patents
Three-dimensional scanning-based method for measuring inner surface of narrow deep cavity of casting Download PDFInfo
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- CN108917667B CN108917667B CN201810698866.2A CN201810698866A CN108917667B CN 108917667 B CN108917667 B CN 108917667B CN 201810698866 A CN201810698866 A CN 201810698866A CN 108917667 B CN108917667 B CN 108917667B
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
- G01B17/02—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations for measuring thickness
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Abstract
A three-dimensional scanning-based method for measuring the inner surface of a narrow deep cavity of a casting comprises the following steps: constructing a theoretical model into a theoretical surface associated with the size of the casting by using three-dimensional scanning measurement equipment; selecting typical points on the inner surface of the casting; arranging a marking ring on the outer surface of the casting, and enabling the circle center of the marking ring to be located on a straight line which is vertically intersected with the rotational symmetry axis of the casting and passes through a typical point; three-dimensional scanning is carried out on the casting; adjusting the contrast color band to enable the marked ring and the intra-ring area of the marked ring to have obvious difference in the three-dimensional scanning point cloud of the outer surface of the casting; calibrating the distance from the circle center of the marking ring to the theoretical surface; measuring the wall thickness of the casting at the position of the circle center of the marking ring; and calculating the distance from the typical point to the theoretical surface by using the distance from the circle center of the marking ring to the theoretical surface and the wall thickness. The invention utilizes the marking ring to accurately combine the typical point of the inner surface and the outer surface of the narrow deep cavity of the casting, thereby realizing the high-efficiency and rapid measurement of the size of the inner surface of the casting.
Description
Technical Field
The invention relates to a three-dimensional scanning-based method for measuring the inner surface of a narrow deep cavity of a casting, and belongs to the technical field of casting detection.
Background
With the continuous popularization and application of the three-dimensional scanning technology, the part size inspection is faster and more comprehensive, and particularly, the method has incomparable advantages for the detection of complex space curved surfaces by other detection methods. However, the method is limited by the principle of the three-dimensional scanning technology, and the scanning blind areas exist at the inner surface parts of the narrow deep cavity, so that the surface size data of the parts cannot be acquired. Three-dimensional scanning has been an obstacle to the measurement of the inner surface of a narrow deep cavity.
The traditional measurement of the inner surface of a narrow deep cavity of a casting is mainly divided into destructive direct measurement and indirect measurement after the whole machining of the outer surface. The direct measurement needs to destroy the casting body, and the measurement is carried out after a narrow deep cavity is converted into an open surface or a small segmented cavity, so that the size condition and the size change rule of other castings cannot be directly reflected; and the indirect measurement is carried out, because the dimensional accuracy of the surface of the casting is small and the irregular smooth surface is used as reference, the measurement is carried out after the whole outer surface is machined, the measurement period is long, the feedback is delayed, and the production of the casting cannot be guided in time.
The rapid measurement method is provided for the scanning blind area of the three-dimensional scanning on the inner surface of the narrow deep cavity, particularly the inner surface of the narrow deep cavity of the casting, and the rapid detection problem of the circumferential dimension of the inner surface of the part of the narrow deep cavity of the casting is solved.
Disclosure of Invention
The technical problem solved by the invention is as follows: the defects of the prior art are overcome, and the method for measuring the inner surface of the narrow deep cavity of the casting based on three-dimensional scanning is provided.
The technical solution of the invention is as follows:
a three-dimensional scanning-based method for measuring the inner surface of a narrow deep cavity of a casting comprises the following steps:
designing a theoretical model for the casting, and constructing the theoretical model into a theoretical surface associated with the size of the casting by using three-dimensional scanning measurement equipment;
secondly, selecting typical points on the inner surface of the casting according to the inner surface structure of the casting;
thirdly, arranging a marking ring on the outer surface of the casting, and enabling the circle center of the marking ring to be located on a straight line which is perpendicularly intersected with the rotational symmetry axis of the casting and passes through the typical point; the thickness of the marking ring is 6-12 mm, the diameter of the inner ring is 8-12 mm, and the radius of the outer ring is 4-6 mm larger than that of the inner ring;
step four, three-dimensional scanning is carried out on the casting by utilizing the three-dimensional scanning measuring equipment, so that a three-dimensional scanning point cloud containing a scannable area of the inner surface of the casting and the outer surface of the casting is obtained;
fifthly, utilizing the scannable area of the inner surface of the casting to carry out alignment analysis, and enabling the three-dimensional scanning point cloud of the scannable area of the inner surface of the casting to be coaxial with the theoretical surface; adjusting a contrast color band of the three-dimensional scanning measuring equipment to enable the marked ring and an intra-ring area of the marked ring to have obvious difference in the three-dimensional scanning point cloud of the outer surface of the casting; calibrating the distance from the circle center of the marking ring to the theoretical surface;
measuring the wall thickness of the casting at the position of the circle center of the marking ring;
and step seven, calculating the distance from the typical point to the theoretical surface by using the distance from the center of the marking ring to the theoretical surface and the wall thickness of the position of the center of the marking ring, and taking the distance from the typical point to the theoretical surface as the size data of the typical point.
Further, in the third step, the marking ring is a flexible marking ring and is attached to the outer surface of the casting.
Further, in the fifth step, the obvious difference is that the mark ring and the intra-ring area of the mark ring can be distinguished from the three-dimensional point cloud of the outer surface of the casting by naked eyes.
Further, in the second step, the inner surface of the casting is cut by adopting a plurality of straight lines extending longitudinally and circumferentially, so that the inner surface of the casting is cut into grids arranged regularly, and all intersection points of the grids are taken as typical points; and in the seventh step, the distance from all the typical points to the theoretical surface is utilized to obtain the size data of the inner surface of the casting.
Further, in the second step, when a typical point is selected on the inner surface of the casting, a typical point is selected from the scanning blind area of the three-dimensional scanning measuring device.
Further, in the fifth step, an ultrasonic thickness gauge is adopted to measure the wall thickness of the casting at the position of the circle center of the marking ring.
Further, in the seventh step, when the radius of the theoretical surface is smaller than the radius of the inner surface of the casting, the distance from the representative point to the theoretical surface is calculated by: subtracting the wall thickness of the position of the circle center of the marking ring from the distance from the circle center of the marking ring to the theoretical surface; when the radius of the theoretical surface is greater than the radius of the outer surface of the casting, the distance from the representative point to the theoretical surface is calculated by: and adding the distance from the circle center of the marking ring to the theoretical surface and the wall thickness of the position of the circle center of the marking ring.
Compared with the prior art, the invention has the advantages that:
(1) the three-dimensional scanning-based measuring method for the inner surface of the narrow deep cavity of the casting utilizes the marking ring to accurately combine the typical point of the inner surface and the outer surface of the narrow deep cavity of the casting, so that the size of the inner surface of the casting can be efficiently and quickly measured, and the size condition of the inner surface of the narrow deep cavity of the casting can be comprehensively reflected.
(2) The invention fully exerts the advantages of three-dimensional scanning and rapid measurement and effectively overcomes the problem that the scanning blind area can not be measured.
(3) The marking ring is simple to manufacture and low in cost.
(4) The method for measuring the inner surface of the narrow deep cavity of the casting based on three-dimensional scanning has the characteristics of high measurement efficiency, comprehensive measurement result and low measurement cost.
Drawings
FIG. 1 is a schematic illustration of measurements taken on a casting using the method of the present invention in one embodiment.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
As shown in FIG. 1, the invention provides a three-dimensional scanning-based method for measuring the inner surface of a narrow deep cavity of a casting, which comprises the following steps:
designing a theoretical model for the casting, and constructing the theoretical model into a theoretical surface associated with the size of the casting by using three-dimensional scanning measurement equipment;
secondly, selecting a typical point 2 on the inner surface of the casting according to the inner surface structure of the casting 1;
thirdly, arranging a marking ring 3 on the outer surface of the casting, and enabling the circle center of the marking ring to be located on a straight line which is perpendicularly intersected with the rotational symmetry axis of the casting and passes through the typical point; the thickness of the marking ring is 6-12 mm, the diameter of the inner ring is 8-12 mm, and the radius of the outer ring is 4-6 mm larger than that of the inner ring;
step four, three-dimensional scanning is carried out on the casting by utilizing the three-dimensional scanning measuring equipment, so that a three-dimensional scanning point cloud containing a scannable area of the inner surface of the casting and the outer surface of the casting is obtained;
fifthly, utilizing the scannable area of the inner surface of the casting to carry out alignment analysis, and enabling the three-dimensional scanning point cloud of the scannable area of the inner surface of the casting to be coaxial with the theoretical surface; adjusting a contrast color band of the three-dimensional scanning measuring equipment to enable the marked ring and an intra-ring area of the marked ring to have obvious difference in the three-dimensional scanning point cloud of the outer surface of the casting; calibrating the distance from the circle center of the marking ring to the theoretical surface;
measuring the wall thickness of the casting at the position of the circle center of the marking ring;
and step seven, calculating the distance from the typical point to the theoretical surface by using the distance from the center of the marking ring to the theoretical surface and the wall thickness of the position of the center of the marking ring, and taking the distance from the typical point to the theoretical surface as the size data of the typical point.
The marking ring is arranged on the outer surface of the casting, so that the circle center of the marking ring is positioned on a straight line which is vertically intersected with the rotational symmetry axis of the casting and passes through a typical point, namely, the marking ring is utilized to mark the point on the outer surface of the casting, which corresponds to the typical point. And carrying out three-dimensional scanning on the casting to obtain a three-dimensional point cloud of a scannable area of the inner surface and the outer surface of the casting. In order to ensure that accurate measurement data can be obtained, the scannable area of the inner surface of the casting needs to be utilized for alignment analysis, so that the three-dimensional scanning point cloud of the scannable area of the inner surface of the casting is coaxial with the pre-constructed theoretical surface. Since the three-dimensional scanning point cloud displays the distance from each scanning point to the theoretical surface visually in color, the distance from each scanning point to the theoretical surface is not directly given, and the contrast color band needs to be adjusted in order to make the marking ring and the inner ring area be visually distinguished. And identifying the mark ring and the ring-in area thereof from the three-dimensional scanning point cloud on the outer surface of the casting, and further calibrating the circle center of the mark ring so as to obtain the distance from the circle center of the mark ring to the theoretical surface. And calculating the distance from the typical point to the theoretical surface by combining the distance from the center of the marking ring to the theoretical surface and the wall thickness of the casting at the position, namely obtaining the size data of the typical point. The dimensional data of the representative points can accurately reflect the dimensional condition of the inner surface of the casting.
The thickness of the marking ring is 6-12 mm, the diameter of the inner ring is 8-12 mm, and the radius of the outer ring is 4-6 mm larger than that of the inner ring. The thickness of the marking ring is matched with the ring diameter. If the thickness is too small, the three-dimensional scanning cannot be analyzed easily. The ring diameter of the marking ring is as small as possible, so that the measurement precision is improved. However, if the diameter of the ring is too small, the center of the ring cannot be analyzed and displayed easily.
The marking ring can be manufactured according to the requirement, and the marking ring is simple in structure, low in cost and easy to realize.
The theoretical model can be a nominal model established by three-dimensional software or a surface data model of a contrast piece acquired by three-dimensional scanning of three-dimensional scanning measurement equipment.
The invention utilizes the marking ring to accurately combine the typical point of the inner surface and the outer surface of the narrow deep cavity of the casting, so that the circumferential dimension of the casting can be efficiently and quickly measured, and the circumferential dimension condition of the inner surface of the narrow deep cavity of the casting is comprehensively reflected. The invention fully exerts the advantages of three-dimensional scanning and rapid measurement and effectively overcomes the problem that the scanning blind area can not be measured. The method for measuring the inner surface of the narrow deep cavity of the casting based on three-dimensional scanning has the characteristics of high measurement efficiency, comprehensive measurement result and low measurement cost.
Preferably, in the method for measuring the inner surface of the narrow deep cavity of the casting based on three-dimensional scanning, in the third step, the marking ring is a flexible marking ring and is attached to the outer surface of the casting. The marking ring is made of a deformable flexible material (such as rubber) and can be better attached to the outer surface of the casting.
Preferably, in the step five, the obvious difference is that the mark ring and the intra-ring area of the mark ring can be distinguished from the three-dimensional point cloud of the outer surface of the casting by naked eyes.
And distinguishing the mark ring and the ring-inside area of the mark ring from the three-dimensional point cloud by naked eyes, thereby accurately positioning the circle center of the mark ring, and further marking the typical comparison size of the circle center of the mark ring from the three-dimensional point cloud, namely the distance from the circle center of the mark ring to the theoretical surface.
In a preferred embodiment, in the three-dimensional scanning-based method for measuring the internal surface of the casting with a narrow and deep cavity, in the second step, the internal surface of the casting is divided by a plurality of straight lines extending longitudinally and circumferentially, so that the internal surface of the casting is divided into regularly arranged grids, and all intersection points of the grids are taken as typical points; and in the seventh step, the distance from all the typical points to the theoretical surface is utilized to obtain the size data of the inner surface of the casting.
When the inner surface of the casting needs to be completely measured, the inner surface of the casting is cut into grids which are regularly arranged, all intersection points of the grids are used as typical points, and the distance from all the typical points to the theoretical surface is utilized, so that the size data of the inner surface of the casting can be obtained. The grid is preferably composed of grids with the length and the width of 5mm, and the size of the grids can be adjusted according to needs.
Preferably, in the three-dimensional scanning-based method for measuring the inner surface of the narrow deep cavity of the casting, in the second step, when a typical point is selected on the inner surface of the casting, a typical point is selected from a scanning blind area of the three-dimensional scanning measuring device.
The interior surface of the casting may be visually inspected and only specific areas or locations within the scanning blind areas may be measured. In this case, the specific region may be divided into grids arranged regularly, and then all intersection points of the grids are selected as typical points, and finally, the size data of the specific region is measured.
Preferably, in the method for measuring the inner surface of the narrow deep cavity of the casting based on three-dimensional scanning, in the fifth step, an ultrasonic thickness gauge is used for measuring the wall thickness of the casting at the position of the circle center of the mark ring. The ultrasonic thickness gauge has high measurement precision and high measurement speed, and a casting cannot be damaged.
Preferably, in the three-dimensional scanning-based method for measuring the inner surface of the narrow deep cavity of the casting, in the seventh step, when the radius of the theoretical surface is smaller than the radius of the inner surface of the casting, the calculation process of the distance from the typical point to the theoretical surface is as follows: subtracting the wall thickness of the position of the circle center of the marking ring from the distance from the circle center of the marking ring to the theoretical surface; when the radius of the theoretical surface is greater than the radius of the outer surface of the casting, the distance from the representative point to the theoretical surface is calculated by: and adding the distance from the circle center of the marking ring to the theoretical surface and the wall thickness of the position of the circle center of the marking ring.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications without departing from the spirit and scope of the present invention.
Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.
Claims (6)
1. A three-dimensional scanning-based method for measuring the inner surface of a narrow deep cavity of a casting is characterized by comprising the following steps:
designing a theoretical model for the casting, and constructing the theoretical model into a theoretical surface associated with the size of the casting by using three-dimensional scanning measurement equipment;
secondly, selecting typical points on the inner surface of the casting according to the inner surface structure of the casting;
thirdly, arranging a marking ring on the outer surface of the casting, and enabling the circle center of the marking ring to be located on a straight line which is perpendicularly intersected with the rotational symmetry axis of the casting and passes through the typical point; the thickness of the marking ring is 6-12 mm, the diameter of the inner ring is 8-12 mm, and the radius of the outer ring is 4-6 mm larger than that of the inner ring;
step four, three-dimensional scanning is carried out on the casting by utilizing the three-dimensional scanning measuring equipment, so that a three-dimensional scanning point cloud containing a scannable area of the inner surface of the casting and the outer surface of the casting is obtained;
fifthly, utilizing the scannable area of the inner surface of the casting to carry out alignment analysis, and enabling the three-dimensional scanning point cloud of the scannable area of the inner surface of the casting to be coaxial with the theoretical surface; adjusting a contrast color band of the three-dimensional scanning measuring equipment to enable the marked ring and an intra-ring area of the marked ring to have obvious difference in the three-dimensional scanning point cloud of the outer surface of the casting; calibrating the distance from the circle center of the marking ring to the theoretical surface;
measuring the wall thickness of the casting at the position of the circle center of the marking ring;
step seven, calculating the distance from the typical point to the theoretical surface by using the distance from the center of the marking ring to the theoretical surface and the wall thickness of the position of the center of the marking ring, and taking the distance from the typical point to the theoretical surface as the size data of the typical point;
in the third step, the marking ring is a flexible marking ring and is attached to the outer surface of the casting.
2. The three-dimensional scanning-based measuring method for the inner surface of the narrow deep cavity of the casting as claimed in claim 1, wherein in the step five, the obvious difference is that the mark ring and the intra-ring area of the mark ring can be distinguished from the three-dimensional point cloud of the outer surface of the casting by naked eyes.
3. The three-dimensional scanning-based measuring method for the inner surface of the narrow deep cavity of the casting according to claim 1 or 2, wherein in the second step, the inner surface of the casting is divided by a plurality of straight lines extending longitudinally and circumferentially, so that the inner surface of the casting is divided into regularly arranged grids, and all intersection points of the grids are taken as typical points; and in the seventh step, the distance from all the typical points to the theoretical surface is utilized to obtain the size data of the inner surface of the casting.
4. The three-dimensional scanning-based measuring method for the inner surface of the narrow deep cavity of the casting as claimed in claim 1 or 2, wherein in the second step, when the representative point is selected on the inner surface of the casting, the representative point is selected from the scanning blind area of the three-dimensional scanning measuring device.
5. The three-dimensional scanning-based measuring method for the inner surface of the narrow deep cavity of the casting according to claim 1, wherein in the fifth step, an ultrasonic thickness gauge is used for measuring the wall thickness of the casting at the position of the circle center of the marking ring.
6. The three-dimensional scanning-based measuring method for the inner surface of the narrow deep cavity of the casting as claimed in claim 1, wherein in the seventh step, when the radius of the theoretical surface is smaller than the radius of the inner surface of the casting, the distance from the typical point to the theoretical surface is calculated by: subtracting the wall thickness of the position of the circle center of the marking ring from the distance from the circle center of the marking ring to the theoretical surface; when the radius of the theoretical surface is greater than the radius of the outer surface of the casting, the distance from the representative point to the theoretical surface is calculated by: and adding the distance from the circle center of the marking ring to the theoretical surface and the wall thickness of the position of the circle center of the marking ring.
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| CN111223067B (en) * | 2020-02-21 | 2023-05-26 | 成都工业学院 | Automatic alignment method for machining bridge anchorage device round hole |
| CN114200891B (en) * | 2021-12-10 | 2023-09-22 | 上海交通大学 | Model-free cylindrical casting inner cavity milling system and track planning method |
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| DE10236756A1 (en) * | 2002-08-10 | 2004-02-19 | Sms Meer Gmbh | Device for measuring the wall thickness of a pipe in a rolling mill has lamp emitting a bundled light and fixed to different sites on a measuring head |
| DE102007043004A1 (en) * | 2007-09-06 | 2009-04-02 | V&M Deutschland Gmbh | Method for complete detection of the geometry of test objects by means of ultrasound |
| AT510554B1 (en) * | 2011-03-18 | 2012-05-15 | A Tron3D Gmbh | DEVICE FOR TAKING PICTURES OF THREE-DIMENSIONAL OBJECTS |
| CN102288123B (en) * | 2011-06-27 | 2013-03-27 | 清华大学 | Method for accurately positioning three-dimensional non-contact measurement of welding deformation |
| DE102013200898A1 (en) * | 2013-01-21 | 2014-07-24 | Siemens Aktiengesellschaft | Endoscope, especially for minimally invasive surgery |
| GB201417162D0 (en) * | 2014-09-29 | 2014-11-12 | Renishaw Plc | Inspection appartus |
| CN107504926B (en) * | 2017-08-15 | 2020-11-24 | 厦门日村环保科技有限公司 | Pipeline scale deposit thickness detection probe and pipeline cleaning method |
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