CN109489581B - Large-pitch conical external thread detection device and method - Google Patents
Large-pitch conical external thread detection device and method Download PDFInfo
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- CN109489581B CN109489581B CN201811533417.9A CN201811533417A CN109489581B CN 109489581 B CN109489581 B CN 109489581B CN 201811533417 A CN201811533417 A CN 201811533417A CN 109489581 B CN109489581 B CN 109489581B
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Abstract
The invention discloses a coarse pitch conical external thread detection device and a method, wherein the device comprises a workpiece fixing component and an image capturing component; the device also comprises a detection assembly and a light source assembly; the light source component is a plane light source and is used for providing a light source for the image capturing component; the detection assembly comprises a display interface, a data storage system, a thread outline extraction module and a thread reverse calculation module and is used for extracting a thread image outline, calculating thread machining parameters and judging results; specifically, the thread profile extraction module and the thread reverse calculation module are used for processing the thread image, measuring the size of the thread image and performing inversion calculation, so that thread machining parameters are obtained, a machining result is judged, and meanwhile, a detection result is recorded in the data storage system. The invention can realize the non-contact online rapid high-precision detection of the large-pitch conical external thread.
Description
Technical Field
The invention belongs to the technical field of thread detection, and particularly relates to a large-pitch conical external thread detection device and method.
Background
At present, the method for detecting the screw thread mainly comprises a contact detection method and a non-contact detection method, wherein the contact detection method mainly comprises a comprehensive measurement method (such as gauge measurement) and a single measurement method (such as three-pin measurement); the non-contact method mainly detects through thread image information, and comprises a tool microscope method and a machine vision detection method. With the development of a thread detection technology, the automation degree of thread detection is higher and higher, and the traditional external thread contact type detection method has the defects that a measuring tool is easy to wear, the working efficiency is low, and the requirements of large-batch and online detection are difficult to meet; the machine vision detection technology has the advantages of non-contact, high speed, high precision, real-time online, high automation degree and the like, the detection of the threads by applying the machine vision technology is the development trend of the current detection technology, and the thread detection is an important application of the machine vision detection.
At present, the visual detection technology is well applied in conventional thread pitch and straight thread detection in China, the method comprises the steps of firstly extracting a thread image outline, then segmenting the outline into conventional geometric shapes such as a straight line, an arc and the like, then fitting, and directly measuring related parameters of the thread through the fitted outline. The thread bottom and the thread top of the conventional thread are mostly in straight line connection, the helix angle is small, the thread projection has small influence on relevant measurement parameters of the thread, and the size of the thread image can be directly used for obtaining the size parameters after thread machining. For common and conventional threads, the detection method is high in detection precision at present and can meet actual requirements. However, compared with the common conventional thread, the large-pitch tapered thread has the advantages that the thread outline size is changed linearly, the thread lead angle is large, the projection area of the thread plane is large, the projection area is changed functionally along with the length and the taper of the thread, the root parts of two adjacent threads and the top part of a single thread tooth are mostly connected in an arc-straight line-arc manner, the large-pitch tapered thread is complex to machine, the detection parameters are many, the accurate machining size cannot be obtained through the conventional thread optical detection method, and no relevant documents or reports exist in the large-pitch tapered thread detection aspect at present.
Disclosure of Invention
Aiming at the defects and shortcomings in the prior art, the invention provides a large-pitch conical external thread detection device and method, which overcome the defect that the size of the large-pitch conical external thread cannot be accurately obtained by the conventional detection method at present.
In order to achieve the purpose, the invention adopts the following technical scheme:
a coarse-pitch conical external thread detection device comprises a workpiece fixing component and an image capturing component; the device also comprises a detection assembly and a light source assembly; the light source assembly is a plane light source and is used for providing a light source for the image capturing assembly; the detection assembly comprises a display interface, a data storage system, a thread profile extraction module and a thread reverse calculation module, and is used for extracting thread image profiles, calculating thread machining parameters and judging results.
The invention also comprises the following technical characteristics:
optionally, the workpiece fixing assembly comprises a gripper and a fixing platform capable of automatically clamping, and is used for clamping, fixing and rotating the workpiece to be measured and adjusting the height of the workpiece to be measured;
the image capturing assembly comprises an industrial camera and a telecentric lens and is used for capturing images of the thread of the workpiece to be detected through the light source assembly and sending the obtained thread image to the detection assembly;
the data storage system is used for supporting the operation of the thread contour extraction module and the thread reverse calculation module and storing a detection result;
the display interface is used for displaying an operation interface, setting model parameters and displaying the calculation results of the thread profile extraction module and the thread reverse calculation module.
The invention also provides a detection method using the coarse-pitch conical external thread detection device, which comprises the following steps:
step S1: inputting the design parameters of the thread of the workpiece to be detected and the parameters of a cutter used for processing the thread in the display interface of the detection assembly; the thread design parameters comprise a thread major diameter, a pitch diameter, a thread pitch, a thread form angle, a thread total length and a thread taper;
step S2: placing a workpiece to be measured in the workpiece fixing assembly, and adjusting the workpiece fixing assembly to enable the light source assembly, the thread of the workpiece to be measured and the image capturing assembly to be on the same horizontal line;
step S3: the image acquisition assembly acquires a thread image of a workpiece to be detected and transmits the thread image to the detection assembly;
step S4: the detection assembly and the thread profile extraction module thereof process a thread image of a workpiece to be detected and extract a thread profile, and the thread projection size of the thread image of the workpiece to be detected is measured, wherein the thread projection size comprises a thread major diameter, a pitch diameter, a thread pitch, a thread form angle, a thread total length and a thread taper;
step S5: the detection assembly and the thread reverse calculation module thereof reversely calculate thread machining parameters according to the thread projection size and the thread profile, wherein the thread machining parameters comprise thread major diameter, pitch diameter, thread pitch, thread form angle, thread total length and thread taper;
step S6: the detection assembly compares the thread machining parameters with the thread design parameters to give a judgment result, stores the detection result in the data storage system, and gives an action instruction to the workpiece sorting mechanism and the thread machining equipment according to the judgment result.
Optionally, the tool parameters in step S1 include tool deviation, rake angle and wear ratio.
Optionally, the step S2 includes the following steps:
step S201: the workpiece sorting mechanism places a workpiece to be detected in the workpiece fixing assembly, and the claw of the workpiece fixing assembly automatically clamps the workpiece to be detected;
step S202: the workpiece fixing assembly lifts the fixing platform according to the length of the threaded section of the workpiece to be detected, so that the light source assembly, the threaded section of the workpiece to be detected and the image capturing assembly are on the same horizontal line.
Optionally, the step S3 includes the following steps:
step S301: the detection assembly is ready, and the image taking assembly is matched with a light source assembly using telecentric parallel backlight to acquire a first thread image;
step S302: the workpiece fixing assembly rotates 360 degrees at a fixed speed, the image capturing assembly collects a plurality of thread images at fixed intervals, and the thread images are transmitted to the detection assembly.
Optionally, the step S4 includes the following steps:
step S401: the detection assembly performs gray processing on the acquired thread image, extracts a thread area, and removes noise points to obtain a preliminary thread image;
step S402: performing first-order sharpening on the preliminary thread image by using a prewitt operator to obtain a first-order gradient, recording a part of the gradient value greater than a set threshold as a contour edge, and performing corrosion expansion treatment on a discontinuous boundary to obtain a pixel-level thread contour;
step S403: determining the precise thread contour boundary of the pixel-level thread contour based on a sub-pixel edge extraction algorithm of the field area;
step S404: measuring the preliminary thread projection dimension L according to the precise thread profile boundarymSaid preliminary thread projection dimension LmThe thread comprises a large diameter of a thread, a thread pitch and a total length of the thread;
step S405: according to the preliminary thread projection dimension LmMachining deviationmDeviation of tooltCalculating the projected dimension L of the threadr。
Lr＝Lm-m-t
Optionally, the step S5 includes the following steps:
step S501: according to the thread projection size and the thread projection relation, a thread reverse calculation model is established, and the model is as follows:
major diameter of thread (L)t，D)：Lt，D＝Lr，D
Total length of thread (L)t，L)：Lt，L＝Lr，L
Thread pitch (L)t，P)：Lt，P＝Lr，P
The lower thread profile on the left side of the thread is symmetrical to the right side along the central line and translates upwards by Lt，PDistance of/2, the thread profile on the right side of the thread is symmetrical to the left side along the central line and translates downwards Lt，PAnd a/2 distance, respectively extending the upper and lower tooth molded lines to obtain a tooth form angle vertex and a tooth form angle bottom point, and calculating a tooth form angle, a taper and a pitch line:
1) tooth form angle α: α ═ 180 ° -arctan (k1) + arctan (k)2)
Wherein k is1Is the slope of the thread profile lower line, k2Is the slope of the thread profile on the line.
2) The taper β is that β is 180-arctan (k)3)-arctan(k4)
Wherein k is3Is the slope of the line connecting the vertices of the right-hand thread profile angle, k4The slope of the line connecting the vertex of the left thread profile angle.
3) Medium diameter line: a straight line parallel to the vertex angle connecting line of the right thread ridge translates leftwards and intersects with two adjacent thread ridges at a1，a2，a3，a4Four points of where | a1a2L is the thread thickness, | a2a3Taking | a as the distance between two adjacent threads1a2|＝|a2a3The straight line parallel to the crest angle connecting line is the rightThe middle diameter line K1 of the side thread is similar to the middle diameter line K2 of the left side thread;
step S502: substituting the projection dimension of the thread into the thread reverse calculation model, calculating thread machining parameters, and calculating the maximum difference of the left and right central lines, the maximum difference of the left and right crest lines and the maximum difference of the left and right base lines according to the thread machining parameters;
step S503: comparing the thread processing parameters with the thread design parameters, and calculating error valuem,nM is a thread parameter type, m ∈ { major diameter, minor diameter, thread pitch, thread form angle, total thread length and taper }, N is the number of the same thread image, and N is 1,2,3,4,5 … N.
Optionally, the step S6 includes the following steps:
step S601: the thread parameter error judgment standard is deltamAnd m is a thread parameter type, m ∈ { thread major diameter, pitch diameter, thread pitch, profile angle, total thread length and taper }, and comparing error values with an error judgment standard:
the number of qualified images with the same parameter is HmThe parameter sets the qualified number as H:
step S602: obtaining all parameter detection results according to the step S601, if all key parameters are qualified, and the non-key parameter qualification rate is greater than a set value, the thread detection is qualified, otherwise, the thread processing is determined to be unqualified; the key parameters are as follows: the thread pitch diameter, the taper, the thread form angle and the thread pitch, wherein the non-critical parameters are as follows: the major diameter and the total length of the thread;
step S603: generating an action command according to the detection result, and transmitting the action command to the workpiece sorting mechanism; meanwhile, transmitting the instruction to a machine tool control system, and if the instruction is qualified, continuing machining; and if the machining speed is not qualified, stopping machining and making a next instruction.
Compared with the prior art, the invention has the beneficial technical effects that:
the large-pitch conical external thread detection device is simple in structure, concise and efficient in contour recognition and size conversion algorithm, and completely meets the requirement of an automatic production line on thread detection.
And (II) the image capturing assembly, the workpiece fixing assembly and the light source assembly are sequentially arranged on the same workbench, the image capturing assembly is connected with the detection assembly, the shooting ratio of the camera is set to be 1:1, and the size is prevented from being converted for multiple times in the detection process. The workpiece fixing assembly can move up and down, and the horizontal positions of the thread of the workpiece to be detected and the image taking and light source assembly are adjusted, so that the detection requirements of workpieces with different sizes can be met; after the horizontal position is adjusted and fixed, the workpiece fixing assembly can rotate along the axis, so that the image capturing assembly can capture images of the workpiece in all directions conveniently.
(III) the detection method of the large-pitch conical external thread is based on a full-automatic detection device and a machine vision contour detection algorithm, the plane projection size of the large-pitch conical external thread is accurately obtained, accurate processing parameters of the large-pitch conical external thread are obtained through an innovative model inversion algorithm, and non-contact online rapid high-precision detection of the large-pitch conical external thread is realized.
(IV) in the coarse pitch conical external thread detection method, the thread size conversion method is to convert the shadow surface of each thread profile and the relevant sizes of the non-shadow surface of each thread profile after the thread profile rotates 180 degrees along the spiral line when the workpiece faces the image capturing component and is back to the light source through the thread machining cutter parameters on the basis of thread machining, and the conversion comprises the steps of thread large diameter, medium diameter, small diameter, thread pitch, thread profile angle, thread bottom arc radius, thread total length, thread height, thread center line taper and the like.
Drawings
FIG. 1 is a schematic view of the external thread detection apparatus of the present invention;
FIG. 2 is a schematic illustration of the shaded and unshaded surfaces of the external thread of the present invention;
FIG. 3 is a schematic view of the thread projection relationship of the present invention;
FIG. 4 is a thread detection flow diagram of the present invention;
FIG. 5 is a flow chart of the thread projection dimension calculation of the present invention.
The reference numerals in the figures denote: 1-a detection assembly, 2-an image capturing assembly, 3-a workpiece fixing assembly, 4-a workpiece to be detected and 5-a light source assembly; 6-thread shadow, 7-symmetrical translation back tooth profile and 8-virtual tooth apex angle.
Detailed Description
The following embodiments of the present invention are provided, and it should be noted that the present invention is not limited to the following embodiments, and all equivalent changes based on the technical solutions of the present invention are within the protection scope of the present invention.
Example 1:
as shown in fig. 1, the present embodiment provides a coarse-pitch tapered external thread inspection apparatus, which includes a workpiece fixing assembly 3 and an image capturing assembly 2; also comprises a detection component 1 and a light source component 5; the light source assembly 5 is a planar light source and is used for providing a light source for the image capturing assembly 2; the detection assembly 1 comprises a display interface, a data storage system, a thread outline extraction module and a thread reverse calculation module, and is used for extracting thread image outlines, calculating thread machining parameters and judging results; specifically, the thread profile extraction module and the thread reverse calculation module are used for processing the thread image, measuring the size of the thread image and performing inversion calculation, so that thread machining parameters are obtained, a machining result is judged, and meanwhile, a detection result is recorded in the data storage system.
Specifically, the workpiece fixing component 3 comprises a paw and a fixing platform which can be automatically clamped, and is used for clamping and fixing the workpiece 4 to be measured and rotating and adjusting the height of the workpiece 4 to be measured; the image capturing component 2 comprises an industrial camera and a telecentric lens and is used for capturing images of the thread of the workpiece 4 to be detected through the light source component 5 and sending the obtained thread image to the detection component 1; the data storage system is used for supporting the operation of the thread contour extraction module and the thread reverse calculation module and storing the detection result; the display interface is used for displaying the operation interface, setting the model parameters and displaying the calculation results of the thread profile extraction module and the thread reverse calculation module.
Example 2:
as shown in fig. 1 to 5, the present embodiment further provides a detection method using the coarse-pitch tapered external thread detection apparatus, including the following steps:
step S1: inputting the design parameters of the thread of the workpiece to be detected and the parameters of a cutter used for processing the thread in a display interface of the detection assembly; the thread design parameters comprise major diameter, intermediate diameter, thread pitch, thread form angle, total thread length, taper and the like;
step S2: placing a workpiece to be measured in the workpiece fixing assembly, and adjusting the workpiece fixing assembly to enable the light source assembly, the thread of the workpiece to be measured and the image capturing assembly to be on the same horizontal line;
step S3: the image acquisition assembly acquires a thread image of a workpiece to be detected and transmits the thread image to the detection assembly;
step S4: the detection assembly and the thread profile extraction module thereof process the thread image of the workpiece to be detected and extract the thread profile, and the thread projection dimension of the thread image of the workpiece to be detected is measured, wherein the thread projection dimension comprises thread major diameter, pitch diameter, thread pitch, thread form angle, total thread length, taper and the like;
step S5: the detection assembly and the thread reverse calculation module thereof reversely calculate thread machining parameters according to the thread projection size and the thread profile, wherein the thread machining parameters comprise thread major diameter, pitch diameter, thread pitch, thread form angle, thread total length, thread taper and the like;
step S6: the detection assembly compares the thread machining parameters with the thread design parameters to give a judgment result, stores the detection result in the data storage system, and gives an action instruction to the workpiece sorting mechanism and the thread machining equipment according to the judgment result.
Specifically, the tool parameters in step S1 include tool offset, rake angle, and wear ratio.
Specifically, step S2 includes the following steps:
step S201: the workpiece sorting mechanism places a workpiece to be detected in the workpiece fixing assembly, and the claw of the workpiece fixing assembly automatically clamps the workpiece to be detected;
step S202: the workpiece fixing assembly lifts the fixing platform according to the length of the threaded section of the workpiece to be detected, so that the light source assembly, the threaded section of the workpiece to be detected and the image capturing assembly are on the same horizontal line.
Specifically, step S3 includes the following steps:
step S301: the detection assembly is ready, and the image taking assembly is matched with a light source assembly using telecentric parallel backlight to acquire a first thread image;
step S302: the workpiece fixing assembly rotates 360 degrees at a fixed speed, the image capturing assembly collects a plurality of thread images at fixed intervals, and the thread images are transmitted to the detection assembly.
Specifically, step S4 includes the following steps:
step S401: the detection assembly performs gray processing on the acquired thread image, extracts a thread area, and removes noise points to obtain a preliminary thread image;
step S402: performing first-order sharpening on the preliminary thread image by using a prewitt operator to obtain a first-order gradient, recording a part of the gradient value greater than a set threshold as a contour edge, and performing corrosion expansion treatment on a discontinuous boundary to obtain a pixel-level thread contour;
step S403: determining the precise thread contour boundary of the pixel-level thread contour based on a sub-pixel edge extraction algorithm of the field area;
step S404: measuring the preliminary thread projection dimension L according to the precise thread profile boundarymSaid preliminary thread projection dimension LmThe thread comprises a large diameter, a thread pitch, a total thread length and the like;
step S405: according to the preliminary thread projection dimension LmMachining deviationmDeviation of tooltCalculating the projected dimension L of the threadr。
Lr＝Lm-m-t
Specifically, step S5 includes the following steps:
step S501: establishing a thread reverse calculation model according to the thread projection size and the thread projection relation; the thread projection relation specifically means: in the thread machining process, two side profile angles of each thread profile are formed by two side cutting edges of a thread machining tool in the machining process, when a workpiece is looked up, a non-shadow surface of a first thread profile on the left side and a shadow surface of the same thread rotated by 180 degrees to the right side are machined by the cutting edge on the same side of the tool, and a non-shadow surface of a first thread profile on the right side and a shadow surface of the same thread rotated by 180 degrees to the left side are machined by the cutting edge on the other side of the tool, so that the size of the shadow surface of the thread on the left side of the workpiece can be converted by the non-shadow surface of the thread on the right side, and the size of the shadow surface of the thread on the right side can; the reverse calculation model of the thread is as follows:
major diameter of thread (L)t，D)：Lt，D＝Lr，D
Total length of thread (L)t，L)：Lt，L＝Lr，L
Thread pitch (L)t，P)：Lt，P＝Lr，P
As shown in the schematic diagram of the thread projection principle in fig. 3, the thread shadow 6, the symmetrically translated back thread profile 7, the virtual thread apex angle 8, the lower thread profile on the left side of the thread symmetrically to the right side along the central line, and the thread is translated upwards by Lt，PDistance of/2, the thread profile on the right side of the thread is symmetrical to the left side along the central line and translates downwards Lt，PAnd a/2 distance, respectively extending the upper and lower tooth molded lines to obtain a tooth form angle vertex and a tooth form angle bottom point, and calculating a tooth form angle, a taper and a pitch line:
1) tooth form angle α: α ═ 180 ° -arctan (k)1)+arctan(k2)
Wherein k is1Is the slope of the thread profile lower line, k2Is the slope of the thread profile on the line.
2) The taper β is that β is 180-arctan (k)3)-arctan(k4)
Wherein k is3Is the slope of the line connecting the vertices of the right-hand thread profile angle, k4The slope of the line connecting the vertex of the left thread profile angle.
3) Medium diameter line: the straight line parallel to the vertex angle connecting line of the right thread ridge translates leftwards and is connected with two adjacent threadsThe teeth intersect at a1，a2，a3，a4Four points of where | a1a2L is the thread thickness, | a2a3Taking | a as the distance between two adjacent threads1a2|＝|a2a3A straight line parallel to the crest angle connecting line in the case of |, is a right thread pitch diameter line K1, and a left thread pitch diameter line K2 is obtained in the same way;
step S502: substituting the projection dimension of the thread into the thread reverse calculation model, calculating thread machining parameters, and calculating the maximum difference of the left and right central lines, the maximum difference of the left and right crest lines and the maximum difference of the left and right base lines according to the thread machining parameters;
step S503: comparing the thread processing parameters with the thread design parameters, and calculating error valuem,nM is a thread parameter type, m ∈ { major diameter, minor diameter, thread pitch, profile angle, total thread length and taper … … }, N is the number of the same thread image, and N is 1,2,3,4,5 … N.
Specifically, step S6 includes the following steps:
step S601: the thread parameter error judgment standard is deltamAnd m is a thread parameter type, m ∈ { thread major diameter, pitch diameter, thread pitch, profile angle, total thread length and taper … … }, and comparing each error value with an error determination standard:
the number of qualified images with the same parameter is HmThe parameter sets the qualified number as H:
step S602: obtaining all parameter detection results according to the step S601, if all key parameters are qualified, and the non-key parameter qualification rate is greater than a set value, the thread detection is qualified, otherwise, the thread processing is determined to be unqualified; wherein, the key parameters are as follows: the thread pitch diameter, the taper, the thread form angle and the thread pitch, wherein the non-critical parameters are as follows: the major diameter and the total length of the thread;
step S603: generating an action command according to the detection result, and transmitting the action command to the workpiece sorting mechanism; meanwhile, transmitting the instruction to a machine tool control system, and if the instruction is qualified, continuing machining; and if the machining speed is not qualified, stopping machining and making a next instruction.
Claims (4)
1. A method for detecting a coarse-pitch conical external thread is characterized in that a detection device comprises a workpiece fixing assembly (3) and an image capturing assembly (2); the device is characterized by further comprising a detection assembly (1) and a light source assembly (5);
the light source assembly (5) is a plane light source and is used for providing a light source for the image capturing assembly (2);
the detection assembly (1) comprises a display interface, a data storage system, a thread profile extraction module and a thread reverse calculation module, and is used for extracting a thread image profile, calculating thread machining parameters and judging results;
the workpiece fixing component (3) comprises a paw and a fixing platform which can be automatically clamped, and is used for clamping, fixing and rotating the workpiece (4) to be measured and adjusting the height of the workpiece (4) to be measured;
the image capturing assembly (2) comprises an industrial camera and a telecentric lens and is used for capturing images of the threads of the workpiece to be detected (4) through the light source assembly (5) and sending the obtained thread images to the detection assembly (1);
the data storage system is used for supporting the operation of the thread contour extraction module and the thread reverse calculation module and storing a detection result;
the display interface is used for displaying an operation interface, setting model parameters and displaying calculation results of the thread contour extraction module and the thread reverse calculation module;
the detection method comprises the following steps:
step S1: inputting the design parameters of the thread of the workpiece to be detected and the parameters of a cutter used for processing the thread in the display interface of the detection assembly; the thread design parameters comprise a thread major diameter, a pitch diameter, a thread pitch, a thread form angle, a thread total length and a thread taper;
step S2: placing a workpiece to be measured in the workpiece fixing assembly, and adjusting the workpiece fixing assembly to enable the light source assembly, the thread of the workpiece to be measured and the image capturing assembly to be on the same horizontal line;
step S3: the image acquisition assembly acquires a thread image of a workpiece to be detected and transmits the thread image to the detection assembly;
the step S3 includes the steps of:
step S301: the detection assembly is ready, and the image taking assembly is matched with a light source assembly using telecentric parallel backlight to acquire a first thread image;
step S302: the workpiece fixing assembly rotates 360 degrees at a fixed speed, the image capturing assembly collects a plurality of thread images at fixed intervals and transmits the thread images to the detection assembly;
step S4: the detection assembly and the thread profile extraction module thereof process a thread image of a workpiece to be detected and extract a thread profile, and the thread projection size of the thread image of the workpiece to be detected is measured, wherein the thread projection size comprises a thread major diameter, a pitch diameter, a thread pitch, a thread form angle, a thread total length and a thread taper;
the step S4 includes the steps of:
step S401: the detection assembly performs gray processing on the acquired thread image, extracts a thread area, and removes noise points to obtain a preliminary thread image;
step S402: performing first-order sharpening on the preliminary thread image by using a prewitt operator to obtain a first-order gradient, recording a part of the gradient value greater than a set threshold as a contour edge, and performing corrosion expansion treatment on a discontinuous boundary to obtain a pixel-level thread contour;
step S403: determining the precise thread contour boundary of the pixel-level thread contour based on a sub-pixel edge extraction algorithm of the field area;
step S404: measuring the preliminary thread projection dimension L according to the precise thread profile boundarymSaid preliminary thread projection dimension LmThe thread comprises a large diameter of a thread, a thread pitch and a total length of the thread;
step S405: according to the preliminary thread projection dimension LmMachining deviationmDeviation of tooltCalculating the projected dimension L of the threadr：
Lr＝Lm-m-t；
Step S5: the detection assembly and the thread reverse calculation module thereof reversely calculate thread machining parameters according to the thread projection size and the thread profile, wherein the thread machining parameters comprise thread major diameter, pitch diameter, thread pitch, thread form angle, thread total length and thread taper;
the step S5 includes the steps of:
step S501: according to the thread projection size and the thread projection relation, a thread reverse calculation model is established, and the model is as follows:
major diameter of thread (L)t，D)：Lt，D＝Lr，D
Total length of thread (L)t，L)：Lt，L＝Lr，L
Thread pitch (L)t，P)：Lt，P＝Lr，P
The lower thread profile on the left side of the thread is symmetrical to the right side along the central line and translates upwards by Lt，PDistance of/2, the thread profile on the right side of the thread is symmetrical to the left side along the central line and translates downwards Lt，PAnd a/2 distance, respectively extending the upper and lower tooth molded lines to obtain a tooth form angle vertex and a tooth form angle bottom point, and calculating a tooth form angle, a taper and a pitch line:
1) tooth form angle α: α ═ 180 ° -arctan (k)1)+arctan(k2)
Wherein k is1Is the slope of the thread profile lower line, k2Is the thread profile on-line slope;
2) crest line taper β: β ═ 180 ° -arctan (k)3)-arctan(k4)
Wherein k is3Is the slope of the line connecting the vertices of the right-hand thread profile angle, k4The slope of the connecting line of the vertex of the left thread form angle;
3) medium diameter line: a straight line parallel to the connecting line of the bottom angles of the right thread teeth translates leftwards and intersects with two adjacent thread teeth at a1，a2，a3，a4Four points of where | a1a2L is the thread thickness, | a2a3Taking | a as the distance between two adjacent threads1a2|＝|a2a3The straight line parallel to the root angle connecting line in the period I is the right thread pitch diameter line K1, and the left thread pitch diameter line K is obtained by the same method2；
Step S502: substituting the projection dimension of the thread into the thread reverse calculation model, calculating thread machining parameters, and calculating the maximum difference of the left and right central lines, the maximum difference of the left and right crest lines and the maximum difference of the left and right base lines according to the thread machining parameters;
step S503: comparing the thread processing parameters with the thread design parameters, and calculating error valuem,nM is a thread parameter type, m ∈ { major diameter, minor diameter, thread pitch, thread form angle, total thread length and taper }, N is the number of the same thread image, and N is 1,2,3,4,5 … N;
step S6: the detection assembly compares the thread machining parameters with the thread design parameters to give a judgment result, stores the detection result in the data storage system, and gives an action instruction to the workpiece sorting mechanism and the thread machining equipment according to the judgment result.
2. The method for testing a coarse tapered external thread according to claim 1, wherein said tool parameters in step S1 include tool runout, rake angle, and wear ratio.
3. The method for detecting a steep tapered external thread as claimed in claim 1, wherein said step S2 includes the steps of:
step S201: the workpiece sorting mechanism places a workpiece to be detected in the workpiece fixing assembly, and the claw of the workpiece fixing assembly automatically clamps the workpiece to be detected;
step S202: the workpiece fixing assembly lifts the fixing platform according to the length of the threaded section of the workpiece to be detected, so that the light source assembly, the threaded section of the workpiece to be detected and the image capturing assembly are on the same horizontal line.
4. The method for detecting a steep tapered external thread as claimed in claim 1, wherein said step S6 includes the steps of:
step S601: the thread parameter error judgment standard is deltamAnd m is a thread parameter type, m ∈ { thread major diameter, pitch diameter, thread pitch, profile angle, total thread length and taper }, and comparing error values with an error judgment standard:
the number of qualified images with the same parameter is HmThe parameter sets the qualified number as H:
step S602: obtaining all parameter detection results according to the step S601, if all key parameters are qualified, and the non-key parameter qualification rate is greater than a set value, the thread detection is qualified, otherwise, the thread processing is determined to be unqualified; the key parameters are as follows: the thread pitch diameter, the taper, the thread form angle and the thread pitch, wherein the non-critical parameters are as follows: the major diameter and the total length of the thread;
step S603: generating an action command according to the detection result, and transmitting the action command to the workpiece sorting mechanism; meanwhile, transmitting the instruction to a machine tool control system, and if the instruction is qualified, continuing machining; and if the machining speed is not qualified, stopping machining and making a next instruction.
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