Patent Publication Number: US-2019186890-A1

Title: Workpiece measuring machine, measuring method and calibration method of sectional difference of casing of workpiece

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 106144697, filed on Dec. 20, 2017. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a workpiece measuring machine, and a measuring method and a calibration method of sectional difference of casing of workpiece. 
     2. Description of Related Art 
     In general, an external housing of an object is commonly formed by two casings. In an example where the two casings are respectively a main casing and a cover, the main casing may include an appearance surface and an assembly surface, a sectional difference is present between the appearance surface and the assembly surface, and the cover may be disposed to the assembly surface of the main casing. Accordingly, a profile of the assembled cover and appearance surface of the main casing is coherent. However, since the sectional differences between the appearance surface and the assembly surface of the main casing may differ at different regions, when the cover is assembled to the main casing, the surface of the cover may be higher or lower than the appearance surface. Thus, an overall appearance may be affected. 
     SUMMARY OF THE INVENTION 
     One or some exemplary embodiments of the invention provide a workpiece measuring machine capable of measuring a distance between an assembly surface and an adjacent appearance surface of a workpiece under test for subsequent adjustment. 
     One or some exemplary embodiments of the invention provide a measuring method of sectional difference of casing of workpiece capable of measuring a sectional difference between an assembly surface and an adjacent appearance surface of a workpiece under test. 
     One or some exemplary embodiments of the invention provide a calibration method of sectional difference of casing of workpiece capable of adjusting the workpiece under test based on the measuring method of sectional difference of casing of workpiece. 
     A workpiece measuring machine according to an embodiment of the invention is adapted to measure a workpiece under test. The workpiece under test includes an assembly surface and an appearance surface surrounding the assembly surface. A sectional difference is present between the assembly surface and the appearance surface. The workpiece measuring machine includes a bearing base, a height measuring device, and a calculation device. The bearing base is adapted to bear the workpiece under test. The height measuring device is movably disposed at a side of the bearing base. In addition, the height measuring device is adapted to measure heights of the assembly surface and the appearance surface. The calculation device is electrically connected to the height measuring device to calculate a height difference between the assembly surface and the appearance surface. 
     A measuring method of sectional difference of casing of workpiece according to an embodiment of the invention includes: providing a workpiece under test including an assembly surface and an appearance surface surrounding the assembly surface, wherein a sectional difference is present between the assembly surface and the appearance surface; measuring height information of a plurality of first measuring points on the assembly surface and a plurality of second measuring points on the appearance surface, wherein the second measuring points respectively correspond to the first measuring points; and calculating whether a plurality of height differences between the first measuring points and the corresponding second measuring points are respectively within a predetermined range. 
     A calibration method of sectional difference of casing of workpiece according to an embodiment of the invention includes: the measuring method of sectional difference of casing of workpiece; and adjusting a height of the assembly surface near the first measuring point or a height of the appearance surface near the second measuring point when the height difference between each of the first measuring point and the corresponding second measuring point falls out of the predetermined range, such that the height difference between the first measuring point and the corresponding second measuring point after adjustment falls within the predetermined range. 
     Based on the above, in the measuring method of sectional difference of casing of workpiece according to the embodiments of the invention, the height measuring device is adapted to measure the heights of the assembly surface and the appearance surface of the workpiece under test, and the measurement information is transmitted to the calculation device to calculate the sectional differences between the assembly surface and the appearance surface and thereby determine whether the calculated sectional difference falls within the predetermined range. If the sectional differences fall out of the predetermined range, the calibration method of sectional difference of casing of workpiece according to the embodiments may be adopted to adjust the heights of the assembly surface and the appearance surface of the workpiece under test based on the calculated sectional differences and standard values, so as to fit the thickness of the cover. Hence, the workpiece with a desirable appearance quality is manufactured in a simple and convenient way. 
     In order to make the aforementioned and other features and advantages of the invention comprehensible, several exemplary embodiments accompanied with figures are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a schematic top view illustrating a workpiece under test and a cover. 
         FIG. 2  is a schematic perspective view illustrating an A-A cross-section of the workpiece under test of  FIG. 1 . 
         FIG. 3  is a schematic view illustrating a workpiece measuring machine according to an embodiment of the invention. 
         FIG. 4  is a schematic partially enlarged view illustrating the workpiece measuring machine of  FIG. 3 . 
         FIG. 5  is a schematic top view illustrating that the workpiece measuring machine of  FIG. 3  measures a workpiece under test. 
         FIG. 6  is a flowchart illustrating a measuring method of sectional difference of casing of workpiece according to an embodiment of the invention. 
         FIG. 7  is a flowchart illustrating a calibration method of sectional difference of casing of workpiece according to an embodiment of the invention. 
         FIGS. 8 and 9  are schematic perspective views illustrating other workpiece under tests. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
       FIG. 1  is a schematic top view illustrating a workpiece under test and a cover.  FIG. 2  is a schematic perspective view illustrating an A-A cross-section of the workpiece under test of  FIG. 1 . Referring to  FIGS. 1 and 2 , in the embodiment, a workpiece under test  20  is described as a golf club head main casing, for example. However, the type of the workpiece under test is not limited thereto. The workpiece under test  20  and a cover  30  may be assembled to form a workpiece product  10 . In the embodiment, the workpiece product  10  is described as a golf club head, for example. However, the type of the workpiece product  10  is not limited thereto. 
     As shown in  FIGS. 1 and 2 , in the embodiment, the workpiece under test  20  is a hollow casing and has an opening  22 . The workpiece under test  20  is provided with an assembly surface  23  adjacent to the opening  22 . The cover  30  is fixed to the assembly surface  23  and covers the opening  22  to complete manufacture of the workpiece product  10 . In general, the assembly surface  23  of the workpiece under test  20  is lower than the appearance surface  21 , and a sectional difference H (shown in  FIG. 2 ) between the assembly surface  23  and the appearance surface  21  is approximately equivalent to a thickness of the cover  30 . Accordingly, after the cover  30  is assembled to the workpiece under test  20 , a surface of the cover  30  and the appearance surface  21  of the workpiece under test  20  are expected to be at the same height at an interface, so as to keep the overall appearance coherent. 
     However, under some conditions, such as that the appearance of the workpiece under test  20  is in an irregular shape or that a precision level of a manufacturing process imposes a limitation, there may be a greater tolerance at sectional differences H (shown in  FIG. 2 ) between the appearance surface  21  and the assembly surface  23 . In addition, the sectional differences H between the appearance surface  21  and the assembly surface  23  may differ at different regions. Therefore, when the cover  30  is assembled to the workpiece under test  20 , the surface of the cover  30  may be higher or lower than the appearance surface  21  and thus affect the overall appearance of the workpiece product  10 . In such circumstance, the appearance of the workpiece product  10  may exhibit a discontinuous profile at the interface between the workpiece under test  20  and the cover  30 . In the following, a workpiece measuring machine and a measuring method thereof are described. With the machine and the method, the sectional differences between the appearance surface  21  and the assembly surface  23  of the workpiece under test  20  at different regions may be reduced. 
       FIG. 3  is a schematic view illustrating a workpiece measuring machine according to an embodiment of the invention.  FIG. 4  is a schematic partially enlarged view illustrating the workpiece measuring machine of  FIG. 3 .  FIG. 5  is a schematic top view illustrating that the workpiece measuring machine of  FIG. 3  measures a workpiece under test. As shown in  FIG. 5 , a measuring point is further marked at the workpiece under test  20 , so as to schematically show which part of the workpiece under test  20  is measured by a workpiece measuring machine  100  of  FIG. 3 . 
     Referring to  FIGS. 3 to 5 , the workpiece measuring machine  100  of the embodiment is adapted to measure a height at a specific position of the workpiece under test  20 . As shown in  FIG. 5 , the workpiece under test  20  includes the assembly surface  23  and the appearance surface  21 . The assembly surface  23  is a surface contacting the cover  30  when the cover  30  is assembled to the workpiece under test  20 . When the cover  30  is assembled to the workpiece under test  20 , the opening  22  of the workpiece under test  20  may be shielded by the cover  30 , and the workpiece under test  20  and the cover  30  are assembled to form the workpiece product  10  (shown in  FIG. 1 ). The appearance surface  21  is a surface not shielded by the cover  30  but is exposed after the cover  30  is assembled to the workpiece under test  20 . 
     In the embodiment, the workpiece measuring machine  100  may obtain sectional information of the assembly surface  23  and the appearance surface  21  of the workpiece under test  21  before the cover  30  is assembled to the workpiece under test  20  to determine whether the sectional differences H between the assembly surface  23  and the appearance surface  21  at different regions may be excessively great or small. Then, based on values obtained, the manufacturer may adjust the sectional difference H between the assembly surface  23  and the appearance surface  21  through, for example, polishing the assembly surface  23  or the appearance surface  21  of the workpiece under test  20 , so that the adjusted sectional difference may meet the needs. 
     Accordingly, in a subsequent assembling process, after the cover  30  is assembled to the workpiece under test  20 , the surface of the cover  30  and the appearance surface  21  of the workpiece under test may  20  may fit each other well. Thus, in a manufacturing process of the workpiece product  10 , the workpiece measuring machine  100  may automatically carry out measurement to manufacture the workpiece product  10  with a desirable appearance quality in a simple and convenient way. In the following, the workpiece measuring machine  100  is described in detail. 
     As shown in  FIGS. 3 and 4 , the workpiece measuring machine  100  includes a bearing base  110 , a height measuring device  120 , a motion device  130 , and a calculation device  140 . The bearing base  110  is adapted to bear the workpiece under test  20 . Due to the irregular shape of the workpiece under test  20 , in order to stably support the workpiece under test  20 , the bearing base  110  of the embodiment provides a plurality of columns  112 . The workpiece under test  20  is adapted to be disposed on the columns  112  to be maintained at a specific angle. 
     In the embodiment, the columns  112  may have different heights. For example, the columns  112  may be designed to have different heights in correspondence with variations of the profile of the workpiece under test  20 . The columns  112  may be distributed irregularly in correspondence with the profile of the workpiece under test  20 . Of course, the shapes, heights, number, and disposed positions of the columns  112  are not limited to those in the embodiment. Besides, in other embodiments, the bearing case  110  may also be arranged in a different form, and is not limited to the form shown in the embodiment. 
     As shown in  FIG. 3 , the height measuring device  120  is disposed at a side of the bearing base  110 , and is adapted to measure heights of the assembly surface  23  (shown in  FIG. 5 ) and the appearance surface  21  (shown in  FIG. 5 ) of the workpiece under test  20 . In the embodiment, the height measuring device  120  is disposed above the bearing base  110 . However, the position of the height measuring device  120  is not limited thereto. The height measuring device  120  may, for example, optically measure height information of first measuring points  25  on the assembly surface  23  and corresponding second measuring points  27  of the appearance surface  21 . While  FIG. 4  only schematically illustrates a light beam L, the height measuring device  120  may project a light beam or detect a variation of a light beam, and a position irradiated by the light beam L is not limited to the illustration of  FIG. 4 . 
     Of course, in other embodiments, the height measuring device  120  may also obtain the height information by mechanically moving from a reference point to the first measuring points  25  on the assembly surface  23  and the corresponding second measuring points  27  on the appearance surface  21 . How the height measuring device  120  measures height positions of the first measuring points  25  on the assembly surface  23  and the corresponding second measuring points  27  on the appearance surface  21  is not limited to those described above. 
     In the workpiece measuring machine  100  of the embodiment, by connecting the motion device  130  to at least one of the bearing base  110  and the height measuring device  120 , a position of the bearing base  110  relative to the height measuring device  120  may be adjustable. Accordingly, the height measuring device  120  is able to measure the first measuring points  25  on the assembly surface  23  of the workpiece under test  20  on the bearing base  110  and the second measuring points  27  corresponding to the first measuring points  25  on the appearance surface  21 , so as to more thoroughly measure the sectional differences H between the assembly surface  23  and the appearance surface  21  of the workpiece under test  20  at different sections and thereby facilitate a precision level of subsequent calibration. 
     Specifically, in the embodiment, the motion device  130  includes a first movement module  132 , a second movement module  134 , and a third movement module  136  whose movement directions are perpendicular to each other. The bearing base  110  is disposed on the first movement module  132 , the first movement module  132  is disposed on the second movement module  134 , and the height measuring device  120  is disposed at the third movement module  136 . Of course, positions where the first movement module  132 , the second movement module  134 , and the third movement module  136  are disposed are not limited to those described above. 
     In the embodiment, the first movement module  132 , the second movement module  134 , and the third movement module  136  may respectively move along the first direction D 1 , the second direction D 2 , and the third direction D 3 , so that the bearing base  110  may be adjusted to a position suitable for the height measuring device  120  to carry out measurement. Besides, in the embodiment, the motion device  130  further includes a rotating module  138  connected to the bearing base  110 . Accordingly, the bearing base  110  may rotate relative to the height measuring device  120 . As shown in  FIG. 4 , the rotating module  138  is located between the bearing base  110  and the first movement module  132 . However, a position at which the rotating module  138  is arranged is not limited thereto. Through operation of the motion device  130 , the height measuring device  120  may move relative to the bearing base  110 . Accordingly, the height measuring device  120  may measure the five first measuring points  25  and the five second measuring points  27  (shown in  FIG. 5 ) of the workpiece under test  20  and obtain the height information of these positions. 
     Even though the height measuring device  120  of the embodiment is described to measure the five first measuring points  25  and the five second measuring points  27  as an example, the numbers and positions of the first measuring points  25  and the second measuring points  27  on the workpiece under test  20  are not limited thereto. In other words, numbers and positions of the measurement carried out by the height measuring device  120  on the workpiece under test  20  are not limited to those described in the embodiment. In the embodiment, the first measuring points  25  on the assembly surface  23  and the second measuring points  27  on the appearance surface  21  are set at equidistant positions on the assembly surface  23  and the appearance surface  21 , for example. In other words, the height measuring device  120  may measure height values at positions with equal intervals on the assembly surface  23  and the appearance surface  21 . 
     Besides, in the embodiment, the calculation device  140  may store a motion path corresponding to location information of the first measuring points  25  and the second measuring points  27 . After the operator places the workpiece under test  25  on the bearing base  110  and starts the workpiece measuring machine  100 , the calculation device  140  may instruct the motion device  130  to move along the motion path as planned, so that the height measuring device  120  may measure and obtain the height information as desired. Of course, in other embodiments, the height measuring device  120  may also move relative to the workpiece under test  20  manually or by other means. 
     After the calculation device  140  receives the height information of the first measuring points  25  on the assembly surface  23  and the second measuring points  27  on the appearance surface  21 , the calculation device  140  may calculate the sectional differences H (i.e., height differences) between the assembly surface  23  and the appearance surface  21  at the positions of the measuring points. Besides, the calculation device  140  may further make comparison to determine whether the sectional differences H at the different positions are within a predetermined range. 
     Since different sections of the assembly surface  23  and the appearance surface  21  of the workpiece under test  20  may have different sectional differences H, if the whole assembly surface  23  is polished based on sectional difference information at one of the positions, there may be a greater error. In the embodiment, the height measuring device  120  may measure the sectional differences H between the assembly surface  23  and the appearance surface  21  of the workpiece under test  20  at different sections, and polish the assembly surface  23  based on the sectional information, so as to facilitate a precision level of calibrating the sectional difference of the workpiece under test  20 . 
     For example, if the thickness of the cover  30  is in a range from about 0.95 millimeters to 1.05 millimeters, the predetermined sectional difference range of the workpiece under test  20  may correspond to the thickness of the cover  30  and range from about 0.95 millimeters to 1.05 millimeters. If the sectional differences calculated by the calculation device  140  fall out of the range from 0.95 millimeters to 1.05 millimeters, there may be a height difference at the interface between the workpiece under test  20  and the cover  30  after the cover  30  is subsequently assembled to the workpiece under test  20 , and the appearance may be less coherent. Therefore, the calculation device  140  may record such information (e.g., a position where the actual sectional difference is inconsistent with the predetermined sectional difference and a difference therebetween). Accordingly, a manufacturer may modify the workpiece under test  20  based on such information (e.g., polishing the assembly surface  23 , such that the actual sectional difference after polishing falls within the range of the predetermined sectional difference) subsequently. 
     Besides, in the embodiment, the workpiece measuring machine  100  further includes a marking device  150  electrically connected with the calculation device  140 . When the sectional difference between the assembly surface  23  and the appearance surface  21  falls out of the predetermined range, the calculation device  140  may instruct the marking device  150  to leave an identification mark on the assembly surface  23 . The marking device  150  may leave the identification mark at a specific position by laser or printing, so that the manufacturer may easily determine which position of the workpiece under test  20  requires modification afterwards. Besides, based on sizes of the differences between the actual sectional differences and the predetermined sectional difference, the calculation device  140  may instruct the marking device  150  to leave different identification marks on the assembly surface  23 . For example, the identification marks may include sizes, colors, or patterns in different shapes. Alternatively, the identification marks may also be numbers or letters. Accordingly, the manufacturer may determine extents of modification based on the identification marks. 
     In the following, a measuring method  200  and a calibration method  300  of a sectional difference of a workpiece under test (i.e. a golf club head casing) applicable for the workpiece measuring machine  100  are described.  FIG. 6  is a flowchart illustrating a measuring method of sectional difference of casing of workpiece according to an embodiment of the invention. Referring to  FIG. 6 , the measuring method  200  of sectional difference of casing of workpiece includes steps as follows. 
     First of all, referring to  FIGS. 2, 5, and 6 , the workpiece under test  20  is provided at Step  210 . The workpiece under test  20  includes the opening  22  and the assembly surface  23  surrounding the opening  22  and the appearance surface  21  surrounding the assembly surface  23 . In addition, the sectional difference H (shown in  FIG. 2 ) is present between the assembly surface  23  and the appearance surface  21 . 
     Then, at Step  220 , the height information of the first measuring points  25  on the assembly surface  23  and the second measuring points  27  on the appearance surface  21  is obtained. The positions of the second measuring points  27  respectively correspond to the positions of the first measuring points  25 . In the embodiment, Step  220  may further include, for example, moving or rotating the workpiece under test  20  relative to the height measuring device  120  (shown in  FIG. 2 ), so that the height measuring device  120  may measure different positions on the assembly surface  23  and the appearance surface  21 . 
     Then, at Step S 230 , whether a plurality of height differences between the first measuring points  25  and the corresponding second measuring points  27  are respectively within the predetermined range. As an example, the predetermined range may be from 0.95 millimeters to 1.05 millimeters. However, the invention is not limited thereto. It should be noted that the predetermined range may also be obtained from a standard sample of the workpiece under test  20 . The operator may firstly measure the height differences between the first measuring points  25  and the corresponding second measuring points  27  on the standard sample to serve as the predetermined range of the height differences at Step  230 . 
     Accordingly, whether the sectional differences between the assembly surface  23  and the appearance surface  21  of the workpiece under test  20  at different positions meet the needs may be determined. If the sectional differences meet the needs, the profile at the interface between the cover  30  and the workpiece under test  20  is coherent when the cover  30  is subsequently assembled to the workpiece under test  20 , and the overall appearance is desirable. 
     If differences between respective first heights and corresponding second heights are not within the predetermined range, the surface of the cover  30  may be higher or lower than the appearance surface  21  of the workpiece under test  20 , thus resulting an incoherent interface, after the cover  30  is subsequently assembled to the workpiece under test  20 . Under the circumstance, the following calibration method  300  of the sectional differences of the casing of the workpiece may be applied to modify the sectional difference between the assembly surface  23  and the appearance surface  21  of the workpiece under test  20  at a specific position, so that the appearance may be more desirable after the cover  30  is assembled to the workpiece under test  20  subsequently. 
       FIG. 7  is a flowchart illustrating a calibration method of sectional difference of casing of workpiece according to an embodiment of the invention. Referring to  FIG. 7 , in the calibration method  300  of the sectional differences of the casing of the workpiece of  FIG. 7 , details of Steps  210  to  230  may be referred to the descriptions of  FIG. 6  and will not be repeated in the following. After Step  230 , a step may be subsequently carried out to leave the identification mark at where the height difference is not within the predetermined range on the assembly surface  23  or the appearance surface  21 . Leaving the identification mark may include, for example, leaving the identification mark at a specific position by laser or printing. Accordingly, the manufacturer may easily determine which position requires modification subsequently. 
     Besides, leaving the identification mark may further include instructing the marking device  150  to leave different identification marks on the assembly surface  23  or the appearance surface  21  based on the sizes of the differences between the actual sectional differences on the workpiece under test  20  and the predetermined sectional difference. For example, the identification marks may include sizes, colors, or patterns in different shapes. Alternatively, the identification marks may also be numbers or letters. Accordingly, the manufacturer may determine extents of modification based on the identification marks. 
     Then, at Step  350 , the height of the assembly surface  23  near the first measuring point  25  or the height of the appearance surface  21  near the second measuring point  27  is adjusted. Accordingly, the height difference between the first measuring point  25  and the corresponding second measuring point  27  after the adjustment is within the predetermined range. 
     In the embodiment, if the actual sectional difference H is excessively small, a portion of the assembly surface  23  near the first measuring point  25  in a height direction may be removed (by polishing, for example) to increase the height difference between the first measuring point  25  and the corresponding second measuring point  27  at the position and keep the sectional difference H after the adjustment within the predetermined range. In the embodiment, if the actual sectional difference H is excessively great, a portion of the appearance surface  21  near the second measuring point  27  in the height direction may be removed (by polishing, for example), so as to reduce the height difference between the first measuring point  25  and the corresponding second measuring point  27  at the position and keep the sectional difference H after the adjustment within the predetermined range. 
     In the embodiment, the identification mark may be removed after the assembly surface  23  or the appearance surface is polished, so the appearance is not affected. Besides, means adopted to remove the portion of the assembly surface  23  or the appearance surface  21  is not limited to polishing. In other embodiments, the height may be reduced through chemical etching, for example, or other means. 
     Besides, in other embodiments, the sectional difference H may be adjusted by increasing the height. For example, if the actual sectional difference H is excessively great, a padding block (not shown) may be attached to the portion of the assembly surface  23  near the first measuring point  25 , for example, to increase the height. In such case, the height difference between the first measuring point  25  and the corresponding second measuring point  27  at the position is also reduced, and the sectional difference H after the adjustment is kept within the predetermined range. The above only describes some enforceable aspects and has no intention to impose a limitation on this regard. Moreover, in other embodiments, Step  350  may be directly carried out after Step  230 . In other words, the calibration can still be made if the step of the identification mark is omitted. 
     Even though the workpiece under test  20  is described as a golf club head main casing as an example in the above embodiments, the type of the workpiece under test  20  is not limited thereto.  FIGS. 8 and 9  are schematic perspective views illustrating other workpiece under tests.  FIGS. 8 and 9  only schematically illustrate workpiece under tests  20   a  and  20   b,  and parts or elements disposed in the workpiece under tests  20   a  and  20   b  are omitted. 
     Referring to  FIG. 8 , in the embodiment, the workpiece under test  20   a  may also be a main casing of a mobile phone adapted for a mobile phone back cover (not shown) to be fixed onto the main casing. The workpiece measuring machine  100  may similarly measure the sectional differences H between an assembly surface  21   a  and an appearance surface  23   a  at different positions of the workpiece under test  20   a  to ensure the appearance quality. Referring to  FIG. 9 , in the embodiment, the workpiece under test  20   b  may also be a main casing of a tablet computer adapted for a tablet computer back cover (not shown) to be fixed onto the main casing. The workpiece measuring machine  100  may similarly measure the sectional differences H between an assembly surface  21   b  and an appearance surface  23   b  at different positions of the workpiece under test  20   b  to ensure the appearance quality. 
     In view of the foregoing, in the measuring method of sectional difference of casing of workpiece according to the embodiments of the invention, the height measuring device of the workpiece measuring machine is adapted to measure the heights of the assembly surface and the appearance surface of the workpiece under test, and the measurement information is transmitted to the calculation device to calculate the sectional differences between the assembly surface and the appearance surface and thereby determine whether the calculated sectional difference falls within the predetermined range. During the measurement, the height measuring device may adjust a relative position with respect to the bearing base of the workpiece measuring machine to measure the sectional differences between the assembly surface and the appearance surface of the workpiece under test at different regions. When the sectional difference between the assembly surface and the appearance surface falls out of the predetermined range, the calibration method of sectional difference of casing of workpiece according to the embodiments of the invention may be adopted to adjust the heights of the assembly surface and the appearance surface of the workpiece under test based on the difference between the calculated sectional difference and the predetermined sectional difference by, for example, removing an excessive portion through polishing. Accordingly, the appearance profile may be smooth and coherent after the workpiece under test and the cover fit and fixed to each other. Hence, the workpiece with a desirable appearance quality is manufactured in a simple and convenient way. 
     Compared with manually touching the workpiece to inspect whether the profile is normal after the workpiece is assembled, the measuring method of sectional difference of casing of workpiece according to the embodiments of the invention is able to test quickly and accurately. Therefore, the testing efficiency is effectively facilitated. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.