Cross-flow fan blade detection method
By integrating vision, vibration, and dynamic balance detection devices to perform multi-angle inspections of cross-flow fan blades at the same workstation, the problems of low inspection efficiency and large equipment footprint in existing technologies are solved, achieving efficient and low-cost inspection.
Patent Information
- Application Number
- CN202511201225.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-26
- Publication Date
- 2025-11-04
AI Technical Summary
Existing cross-flow fan blade testing requires multiple transfers between different devices, resulting in low testing efficiency, high labor costs, and large equipment footprint.
An integrated testing method is adopted, which integrates visual inspection, runout inspection and dynamic balance inspection devices into the same inspection station. The cross-flow fan blades rotate on the station for multi-angle inspection, and then move out of the station after the inspection is completed.
It improves testing efficiency, reduces labor costs, and reduces the space occupied by the equipment.
Smart Images
Figure CN120890995A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the production of cross-flow fan blades, in particular to a cross-flow fan blade detection method. BACKGROUND
[0002] Cross-flow fan blades are the core components of air conditioners, household fans and other wind-generating devices. In the production process, cross-flow fan blades need to be detected to ensure quality compliance. Common detection methods include appearance detection, runout detection and dynamic balance detection.
[0003] Currently, appearance detection, runout detection and dynamic balance detection are performed in different detection equipment. Manual handling of fan blades between different equipment is required, resulting in low detection efficiency, high labor costs and large space occupied by multiple equipment. The technical personnel in the field hope to have a detection method that can improve detection efficiency and reduce equipment space. SUMMARY
[0004] The main purpose of the present application is to provide a cross-flow fan blade detection method to solve the technical problem of different detection in different detection equipment in the prior art.
[0005] To achieve the above purpose, the present application provides a cross-flow fan blade detection method, comprising the following steps: loading the cross-flow fan blade to be detected into the detection station and positioning and clamping the cross-flow fan blade, the detection station is provided with a visual detection device, a runout detection device and a dynamic balance detection device; rotating the cross-flow fan blade and detecting the rotation angle, the visual detection device, the runout detection device and the dynamic balance detection device respectively perform visual detection, runout detection and dynamic balance detection on the rotating cross-flow fan blade at different rotation angles; moving the detected cross-flow fan blade out of the detection station.
[0006] Loading the cross-flow fan blade to be detected into the detection station and positioning and clamping, rotating the cross-flow fan blade during detection, the detection station is integrated with a visual detection device, a runout detection device and a dynamic balance detection device, the visual detection device, the runout detection device and the dynamic balance detection device can respectively perform visual detection, runout detection and dynamic balance detection on the cross-flow fan blade, and the cross-flow fan blade is removed after detection. In this way, the cross-flow fan blade does not need to be moved between multiple equipment, integrated detection can improve detection efficiency, reduce labor costs and reduce the space occupied by detection equipment.
[0007] Preferably, the number of detection stations is two, and the two detection stations are a first detection station and a second detection station; First, the cross-flow fan blades are loaded into the first inspection station, and the visual inspection device, the runout inspection device and / or the dynamic balance inspection device inspect the cross-flow fan blades at the first inspection station. After the cross-flow fan blades have been inspected at the first inspection station, they are moved to the second inspection station for visual inspection, runout inspection, and / or dynamic balance inspection, which were not performed at the first inspection station.
[0008] The cross-flow fan blades can be moved from the first inspection station to the second inspection station for different inspections. Different inspections can be performed simultaneously at the first and second inspection stations. If different inspections are performed at one station, the inspection time will be longer. This can shorten the inspection time of each station and improve the inspection efficiency.
[0009] Preferably, the visual inspection device and the agitation detection device are set up corresponding to the first inspection station, and visual inspection and agitation detection are performed synchronously in the first inspection station. The dynamic balance detection device is set up corresponding to the second inspection station, and dynamic balance detection is performed in the second inspection station.
[0010] Visual inspection and runout detection are performed at the first inspection station. Since the rotational speed of the cross-flow fan can be the same during visual inspection and runout detection, performing these two inspections simultaneously improves inspection efficiency. Dynamic balancing detection is performed at the second inspection station, resulting in a more rational layout. Furthermore, image analysis after visual inspection can take a long time. Therefore, performing visual inspection at the first inspection station followed by dynamic balancing detection at the second station allows the time available for image analysis to continue, reducing overall processing time.
[0011] Preferably, if the test result at the first testing station is unqualified after the test is completed at the first testing station, then no test is performed at the second testing station.
[0012] Preferably, the visual inspection device includes an inspection camera, a coaxial light source, and a back-side light source. The second inspection station is located in front of the first inspection station. The inspection camera is located on the upper front side of the first inspection station and is tilted downwards towards the cross-flow fan blades in the first inspection station. The coaxial light source and the back-side light source are respectively located on the upper front side and the upper rear side of the first inspection station. The inspection camera is located in front of the coaxial light source and is arranged parallel to the coaxial light source. Both the coaxial light source and the back-side light source are tilted downwards towards the cross-flow fan blades in the first inspection station. The vibration detection device is located directly above the first inspection station and is located between the coaxial light source and the back-side light source.
[0013] The inspection camera is tilted at the upper front side of the cross-flow fan blades to capture images. A coaxial light source and a backlight source illuminate the upper side of the cross-flow fan blades downwards from the upper front and upper rear sides, respectively, providing a better lighting environment and improving inspection accuracy. Furthermore, the inspection camera, coaxial light source, and backlight source do not need to move upwards to avoid obstructing the flow when the cross-flow fan blades are being loaded. The runout detection device is positioned between the coaxial light source and the backlight source, ensuring that the runout detection device does not interfere with the loading of the cross-flow fan blades and does not interfere with the inspection of the vision inspection device.
[0014] Preferably, the angle between the shooting direction of the detection camera and the illumination direction of the back-side light source is 90-120 degrees. At this angle, the light from the back-side light source and the light from the coaxial light source together create a better lighting effect in the shooting area, which can more effectively highlight defects on the blades and improve detection accuracy. In addition, at this angle, the illumination range can be adapted to the detection of cross-flow fan blades of different diameters.
[0015] Preferably, the runout detection includes radial runout detection and end shaft runout detection; The radial runout detection location is set on the outer periphery of the radial plate of the cross-flow fan blade. The radial runout detection includes detecting the radial runout of the cross-flow fan blade at different rotation angles in multiple radial plates in the length direction. The supported position of the cross-flow fan blade includes the end shaft of the cross-flow fan blade. The detection position of the end shaft runout detection is the end shaft of the cross-flow fan blade. The end shaft runout detection includes detecting the runout amount of the end shaft of the cross-flow fan blade corresponding to different rotation angles.
[0016] Preferably, the visual inspection includes blade defect detection and overall length detection; The blade defect detection includes acquiring images of the cross-flow fan blade at multiple positions along its length corresponding to different rotation angles, and analyzing whether there are defect features in the images; The overall length detection includes acquiring images of the end plates at both ends of the cross-flow fan blade, and determining the distance between the two end plates based on the position of the end plates in the images to obtain the overall length of the cross-flow fan blade.
[0017] Preferably, before loading the cross-flow fan blades to the testing station or before starting the testing, the cross-flow fan blades are rotated and the origin feature position of the cross-flow fan blades is detected at the same time, so as to determine the origin of the rotation angle of the cross-flow fan blades based on the origin feature position of the cross-flow fan blades.
[0018] Preferably, when a defective cross-flow fan blade is detected, a mark indicating the defect is made on the cross-flow fan blade. Marking the cross-flow fan blade when a defective defect is detected facilitates identification. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.
[0020] Figure 1 This is a flowchart of the cross-flow fan blade detection method of the present invention; Figure 2 This is a side view of the detection device of the present invention.
[0021] In the attached diagram: 1-Cross-flow fan blade, 21-First inspection station, 22-Second inspection station, 23-Loading station, 3-Vision inspection device, 31-Inspection camera, 32-Coaxial light source, 33-Backside light source, 4-Runout detection device, 41-Runout sensor, 5-Dynamic balance detection device, 6-Origin detection device.
[0022] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0023] 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 a part of the embodiments of the present invention, and not all of the 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.
[0024] It should be noted that if the embodiments of the present invention involve directional indicators, such as up, down, left, right, front, back, etc., the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.
[0025] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.
[0026] A method for testing cross-flow fan blades includes the following steps: The cross-flow fan blade 1 to be tested is loaded into the testing station, and the cross-flow fan blade 1 is positioned and clamped. The testing station is equipped with a visual inspection device 3, a runout detection device 4 and a dynamic balance detection device 5. The cross-flow fan blade 1 is driven to rotate and the rotation angle is detected. The visual inspection device 3, the runout detection device 4 and the dynamic balance detection device 5 respectively perform visual inspection, runout detection and dynamic balance detection on the rotating cross-flow fan blade 1 at different rotation angles. Remove the inspected cross-flow fan blade 1 from the inspection station.
[0027] The cross-flow fan blade 1 to be inspected is loaded, positioned, and clamped at the inspection station. The cross-flow fan blade 1 to be inspected can be a straight blade, a slanted blade, or a similar type. The clamping method can be set according to the shape of the stepper shaft hole of the cross-flow fan blade 1, such as a round hole or a D-shaped hole. During inspection, the cross-flow fan blade 1 is rotated. The inspection station integrates a vision inspection device 3, a runout inspection device 4, and a dynamic balancing inspection device 5. The vision inspection device 3, the runout inspection device 4, and the dynamic balancing inspection device 5 can perform visual inspection, runout inspection, and dynamic balancing inspection on the cross-flow fan blade 1, respectively. After the inspection is completed, the cross-flow fan blade 1 is removed. In this way, the cross-flow fan blade 1 does not need to be moved between multiple devices. Integrated inspection can improve inspection efficiency, reduce labor costs, and also reduce the space occupied by inspection equipment.
[0028] In some specific embodiments, reference is made to Figure 1 There are two inspection stations, namely the first inspection station 21 and the second inspection station 22. First, the cross-flow fan blade 1 is loaded into the first inspection station 21. The visual inspection device 3, the runout inspection device 4 and / or the dynamic balance inspection device 5 inspect the cross-flow fan blade 1 on the first inspection station 21. After the cross-flow fan blade 1 has been inspected at the first inspection station 21, it is moved to the second inspection station 22, where visual inspection, runout inspection and / or dynamic balance inspection that were not performed at the first inspection station 21 are carried out.
[0029] The cross-flow fan blade 1 can be moved from the first inspection station 21 to the second inspection station 22 for different inspections. Different inspections can be performed simultaneously on both cross-flow fan blades 1 at the first and second inspection stations 21 and 22. If all inspections were performed at one station, the inspection time would be longer. This method shortens the inspection time at each station and improves inspection efficiency. The inspection items at the first and second inspection stations 21 and 22 can be set according to actual needs.
[0030] Furthermore, the visual inspection device 3 and the runout detection device 4 are set up corresponding to the first inspection station 21, and visual inspection and runout detection are performed simultaneously in the first inspection station 21. The dynamic balance detection device 5 is set up corresponding to the second inspection station 22, and dynamic balance detection is performed in the second inspection station 22.
[0031] Visual inspection and runout detection are performed at the first inspection station 21. Since the rotational speed of the cross-flow fan can be the same for both visual inspection and runout detection, while dynamic balancing requires a higher rotational speed, performing visual inspection and runout detection simultaneously improves inspection efficiency. Dynamic balancing detection is then performed at the second inspection station 22, resulting in a more rational layout. Furthermore, image analysis after visual inspection may require a long processing time. Therefore, performing visual inspection first at the first inspection station 21 and then dynamic balancing detection at the second inspection station 22 allows the time available for image analysis to be continued, reducing overall processing time. In other embodiments, dynamic balancing detection can also be performed at the first inspection station 21, while visual inspection and runout detection are performed at the second inspection station 22.
[0032] In some specific embodiments, if the test result at the first testing station 21 is unqualified after the test is completed, no test is performed at the second testing station 22, thus reducing the waste of testing resources. In other embodiments, the test is performed at the second testing station 22 regardless of whether the first testing station 21 is qualified or not, so as to fully understand the condition of the cross-flow fan blade 1. The operator can select and set the parameters according to their needs.
[0033] In some specific embodiments, the visual inspection device 3 includes an inspection camera 31, a coaxial light source 32, and a back-side light source 33. The second inspection station 22 is located in front of the first inspection station 21. The inspection camera 31 is located on the upper front side of the first inspection station 21 and is tilted downward toward the cross-flow fan 1 in the first inspection station 21. The coaxial light source 32 and the back-side light source 33 are respectively located on the upper front side and the upper rear side of the first inspection station 21. The inspection camera 31 is located in front of the coaxial light source 32 and is arranged parallel to the coaxial light source 32. The coaxial light source 32 illuminates the upper front side of the cross-flow fan 1 in the first inspection station 21, and the back-side light source 33 illuminates the upper rear side of the cross-flow fan 1 in the first inspection station 21. The vibration detection device 4 is located directly above the first inspection station 21 and is located between the coaxial light source 32 and the back-side light source 33.
[0034] The inspection camera 31 is tilted at the upper front side of the cross-flow fan 1 to capture images of the cross-flow fan 1. The coaxial light source 32 and the back-side light source 33 illuminate the upper side of the cross-flow fan 1 downwards from the upper front and upper rear sides, respectively, providing a better lighting environment and improving inspection accuracy. Moreover, when the cross-flow fan 1 is being fed, the inspection camera 31, coaxial light source 32, and back-side light source 33 do not need to move upwards to avoid obstruction. The runout detection device 4 is positioned between the coaxial light source 32 and the back-side light source 33, ensuring that the runout detection device 4 does not affect the feeding of the cross-flow fan 1 and does not interfere with the inspection of the vision inspection device 3.
[0035] Furthermore, the angle α between the shooting direction of the detection camera 31 and the illumination direction of the backlight 33 is 90-120 degrees. At this angle, the light from the backlight and the coaxial light source together create a better lighting effect in the shooting area, which can more effectively highlight defects on the blades and improve detection accuracy. In addition, at this angle, the illumination range can be adapted to the detection of cross-flow fan blades of different diameters.
[0036] Furthermore, the detection camera 31 can move in a direction that is close to or away from the cross-flow fan blade 1. After manually adjusting the camera's focus, when it is necessary to switch between different specifications of cross-flow fan blades 1, the distance between the detection camera 31 and the cross-flow fan blade 1 can be adjusted to adjust the image clarity, making it convenient to switch between different products.
[0037] In some specific embodiments, runout detection includes radial runout detection and end shaft runout detection.
[0038] The radial runout detection location is set on the outer periphery of the radial plate of the cross-flow fan blade 1. The radial runout detection includes detecting the radial runout of the cross-flow fan blade 1 at different rotation angles in multiple radial plates along the length direction.
[0039] The supported position of the cross-flow fan blade 1 includes the end shaft of the cross-flow fan blade 1. The detection position of the end shaft runout detection is the end shaft of the cross-flow fan blade 1. The end shaft runout detection includes detecting the runout amount of the end shaft of the cross-flow fan blade 1 corresponding to different rotation angles.
[0040] The runout detection method can be either contact detection or non-contact detection. The runout detection device 4 includes a runout sensor 41, which can be a contact sensor such as a contact probe, and the runout sensor 41 can be driven to move closer to or away from the cross-flow fan blade 1 by a runout lifting drive unit, or a non-contact ranging sensor such as a laser sensor can be used for measurement. Multiple runout sensors 41 are set up to simultaneously detect the outer periphery of multiple radial plates of the cross-flow fan blade 1 to detect the radial runout at different positions. A runout sensor 41 is also set above the end shaft to detect the runout of the end shaft.
[0041] In some specific embodiments, the dynamic balance detection device 5 includes a piezoelectric sensor. The piezoelectric sensor is set in the base that clamps and supports the cross-flow fan blade 1. Using a piezoelectric sensor to detect dynamic balance is an existing technology. When the cross-flow fan blade 1 rotates, if it is unbalanced, a small amount of deformation and vibration will occur in the base. The piezoelectric sensor can detect the deformation and vibration of the base to detect the dynamic balance of the cross-flow fan blade 1.
[0042] In some specific embodiments, visual inspection includes blade defect detection and overall length detection.
[0043] Blade defect detection involves acquiring images of the cross-flow fan blade 1 at multiple positions along its length corresponding to different rotation angles, and analyzing whether there are defect features in the images.
[0044] The overall length detection includes acquiring images of the end plates at both ends of the cross-flow fan blade 1, and determining the distance between the two end plates based on the position of the end plates in the images to obtain the overall length of the cross-flow fan blade 1.
[0045] There are multiple inspection cameras 31 arranged side by side to inspect the entire length range of the cross-flow fan blade 1. On the one hand, visual inspection can detect defects such as dents, scratches or deformations on the blades through image analysis; on the other hand, the cameras located at the left and right ends can detect the ends of the cross-flow fan blade 1 and obtain the distance between the two ends, thereby determining whether the length of the cross-flow fan blade 1 is qualified.
[0046] In some specific embodiments, before the cross-flow fan blade 1 is loaded to the testing station or before testing begins, the cross-flow fan blade 1 is rotated and its origin feature position is detected simultaneously. The origin feature position of the cross-flow fan blade 1 is used to determine the origin of the rotation angle of the cross-flow fan blade 1. Preferably, a loading station 23 is provided behind the first testing station 21, and an origin detection device 6 is set on the loading station 23 to find the origin of the cross-flow fan blade 1.
[0047] The origin feature position of the cross-flow fan blade 1 can be the locking hole on the blade or other feature points. Specifically, the origin detection device 6 can detect the rotating cross-flow fan blade 1 through a laser sensor. When the laser sensor detects the parameter of the origin feature position, the origin feature position of the cross-flow fan blade 1 can be determined. Since the angular position of the cross-flow fan blade 1 is uncertain during material feeding, after finding the origin, this origin feature position can be used as the origin of the rotation angle of the cross-flow fan blade 1 to determine the detection value at different rotation angles during subsequent detection.
[0048] In some specific embodiments, when a defective cross-flow fan blade 1 is detected, a mark indicating the defect is made on the cross-flow fan blade 1. Marking the cross-flow fan blade 1 when a defect is detected facilitates identification. The marking can be done using a marking device, specifically, the marking device may include a marking drive unit and a marking element. The marking drive unit can move the marking element closer to or away from the cross-flow fan blade 1. The marking element can be a marker pen or a stamp. When the marking element contacts the cross-flow fan blade 1, it can leave a mark on the end plate of the cross-flow fan blade 1. Alternatively, the marking device can be an inkjet printer or a laser device, which can spray a mark onto the cross-flow fan blade 1 or apply a mark using a laser.
[0049] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.
Claims
1. A method for detecting cross-flow fan blades, characterized in that, Includes the following steps: The cross-flow fan blade (1) to be tested is loaded into the testing station, and the cross-flow fan blade (1) is positioned and clamped. The testing station is equipped with a visual inspection device (3), a runout detection device (4) and a dynamic balance detection device (5). The cross-flow fan blade (1) is driven to rotate and the rotation angle is detected. The visual detection device (3), the jump detection device (4) and the dynamic balance detection device (5) respectively perform visual detection, jump detection and dynamic balance detection on the rotating cross-flow fan blade (1) at different rotation angles. Remove the tested cross-flow fan blade (1) from the testing station.
2. The cross-flow fan blade detection method as described in claim 1, characterized in that, The number of the testing stations is two, namely the first testing station (21) and the second testing station (22). First, the cross-flow fan blade (1) is loaded into the first inspection station (21), and the visual inspection device (3), the vibration inspection device (4) and / or the dynamic balance inspection device (5) inspect the cross-flow fan blade (1) on the first inspection station (21); After the cross-flow fan blade (1) is inspected at the first inspection station (21), the cross-flow fan blade (1) is moved to the second inspection station (22) and then visual inspection, runout inspection and / or dynamic balance inspection are performed that were not performed at the first inspection station (21).
3. The cross-flow fan blade testing method as described in claim 2, characterized in that, The visual inspection device (3) and the agitation detection device (4) are set up corresponding to the first inspection station (21) and perform visual inspection and agitation detection simultaneously in the first inspection station (21). The dynamic balance detection device (5) is set up corresponding to the second inspection station (22) and performs dynamic balance detection in the second inspection station (22).
4. The cross-flow fan blade testing method as described in claim 2, characterized in that, If the test result at the first testing station (21) is unqualified after the test is completed, then no test will be performed at the second testing station (22).
5. The cross-flow fan blade testing method as described in claim 2, characterized in that, The visual inspection device (3) includes an inspection camera (31), a coaxial light source (32), and a rear-side light source (33). The second inspection station (22) is located in front of the first inspection station (21). The inspection camera (31) is located on the upper front side of the first inspection station (21), tilted downwards towards the cross-flow fan (1) in the first inspection station (21). The coaxial light source (32) and the rear-side light source (33) are respectively located on the upper front and upper rear sides of the first inspection station (21). The camera (31) is located in front of the coaxial light source (32). The detection camera (31) is arranged parallel to the coaxial light source (32). The coaxial light source (32) illuminates the upper front side of the cross-flow fan (1) in the first detection station (21). The back light source (33) illuminates the upper rear side of the cross-flow fan (1) in the first detection station (21). The vibration detection device (4) is located directly above the first detection station (21). The vibration detection device (4) is located between the coaxial light source (32) and the back light source (33).
6. The cross-flow fan blade testing method as described in claim 5, characterized in that, The angle between the shooting direction of the detection camera (31) and the illumination direction of the back light source (33) is 90-120 degrees.
7. The cross-flow fan blade detection method as described in claim 1, characterized in that, The runout detection includes radial runout detection and end shaft runout detection; The detection position for the radial runout detection is located on the outer periphery of the radial plate of the cross-flow fan (1). The radial runout detection includes detecting the radial runout of the cross-flow fan (1) at different rotation angles in multiple radial plates along the length direction. The supported position of the cross-flow fan blade (1) includes the end shaft of the cross-flow fan blade (1). The detection position of the end shaft runout detection is the end shaft of the cross-flow fan blade (1). The end shaft runout detection includes detecting the runout amount of the end shaft of the cross-flow fan blade (1) corresponding to different rotation angles.
8. The cross-flow fan blade testing method as described in claim 1, characterized in that, The visual inspection includes blade defect detection and overall length detection; The blade defect detection includes acquiring images of the cross-flow fan blade (1) at multiple positions along its length corresponding to different rotation angles, and analyzing whether there are defect features in the images; The overall length detection includes acquiring images of the end plates at both ends of the cross-flow fan blade (1) and determining the distance between the two end plates based on the position of the end plates in the images to obtain the overall length of the cross-flow fan blade (1).
9. The cross-flow fan blade testing method as described in claim 1, characterized in that, Before feeding the cross-flow fan blade (1) to the testing station or before starting the testing, rotate the cross-flow fan blade (1) and simultaneously test the origin feature position of the cross-flow fan blade (1) to determine the origin of the rotation angle of the cross-flow fan blade (1) based on the origin feature position of the cross-flow fan blade (1).
10. The cross-flow fan blade testing method as described in claim 1, characterized in that, When a defective cross-flow fan blade (1) is detected, a mark indicating the defect is made on the cross-flow fan blade (1).