Patent Publication Number: US-9409275-B2

Title: Material removal system for use with articles having variations in form

Description:
BACKGROUND 
     This disclosure relates generally to material removal systems and, in one example described below, more particularly provides an automated material removal system for use with custom manufactured oilfield drill bits. 
     Extensive personal protection equipment can be required for an operator to remove unwanted material from custom molded, cast or forged articles. However, the fact that the articles are custom manufactured prevents the use of typical automated material removal systems for removal of the unwanted material. For example, precise tool paths cannot be programmed into such a system, accounting for all possible variations in the articles. 
     Therefore, it will be appreciated that improvements are needed in the art of constructing material removal systems. Such improvements could be used for removing unwanted material from custom manufactured articles, or from other types of articles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a representative side view of an oilfield drill bit. 
         FIG. 2  is a representative cross-sectional view of the drill bit, taken along line  2 - 2  of  FIG. 1 . 
         FIG. 3  is a representative side view of another example of the oilfield drill bit. 
         FIG. 4  is a representative end view of the  FIG. 3  example. 
         FIG. 5  is a representative top view of a material removal system which can embody principles of this disclosure. 
         FIG. 6  is a representative elevational view of certain components of the material removal system. 
         FIG. 7  is a representative axial scan of the drill bit. 
         FIG. 8  is are representative circumferential scans of the drill bit. 
         FIG. 9  is a representative helical scan of an unwanted web of the drill bit. 
         FIGS. 10  A &amp; B comprise a representative flowchart for a method which can embody principles of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Representatively illustrated in  FIGS. 1 &amp; 2  is a drill bit  10  of the type used to drill wellbores through subterranean formations. The drill bit  10  is an example of an article which can benefit from having unwanted material thereon removed using a material removal system and method described below. 
     However, it should be clearly understood that the drill bit  10  is merely one of a wide variety of different types of articles which can benefit from the principles of this disclosure. Such articles are not necessarily limited to the oilfield. In particular (but not exclusively), articles which are cast, molded or forged, with significant variations in the articles, can most benefit from the principles described here, but the scope of this disclosure is not limited to cast, molded or forged articles. 
     Oilfield articles which can benefit from this disclosure&#39;s principles can comprise fixed cutter bits (such as the drill bit  10  depicted in  FIGS. 1 &amp; 2 ), roller cone bits, coring bits, side picket mandrels, welded-together components (e.g., to remove excess weld material), hard facing, etc. Therefore, it will be appreciated that the scope of this disclosure is not limited to any of the details of the drill bit  10 , or of the material removal system and method described below for use with the drill bit. 
     The drill bit  10  has multiple generally helically formed blades  12 , with recesses  14  (known as “junk slots”) between the blades. Note that, in other examples, the blades  12  may not be helically formed. 
     In an as-molded configuration as depicted in  FIGS. 1 &amp; 2 , the drill bit  10  also has unwanted material  16  between the blades  12 , which unwanted material could interfere with flow of fluids and cuttings through the recesses  14 . Therefore, the unwanted material  16  should be removed. 
     One problem with removing the material  16  using typical conventional automated material removal systems is that, in this example, the drill bit  10  is custom manufactured, with a certain geometry designed to suit a particular use of the drill bit. Thus, it would be impractical and inefficient in a relatively high volume manufacturing operation to produce custom programming for an automated material removal system each time a custom drill bit is manufactured. 
     Another problem with removing the material  16  using typical conventional automated removal systems is that, even if many of the custom designed drill bits  10  are manufactured, the molding process induces variations in the form of the blades  12 , the location of the unwanted material, etc. Thus, even if an automated material removal system were programmed with the geometry of the drill bit  10 , that geometry can change from bit to bit in practice, and so the system would not be able to adequately remove the unwanted material, without removing any wanted material (e.g., the blade  12  material, material of a shank  18  of the bit, etc.). 
     Referring additionally now to  FIGS. 3 &amp; 4 , another example of the drill bit  10  is representatively illustrated, with the unwanted material  16  removed. In this example, it may be seen that the blades  12  of the drill bit  10  have a helical pitch P, a radius R between each recess and sides  20  of adjacent blades, a width W between the blades, a depth D of the recess between the blades, a diameter DB of the blades, a diameter DS of the shank  18  and a bevel  22  between the blades and the shank. 
     It will be appreciated that, in order to determine the location of the unwanted material  16 , the geometry of the drill bit  10  should be determined (including, for example, the number and locations of the blades  12  and recesses  14 , the pitch P, the radius R between each recess and the sides  20  of adjacent blades, the width W between the blades, the depth D of the recess between the blades, the diameter DB of the blades, the diameter DS of the shank  18 , the bevel  22  between the blades and the shank, the location of the unwanted material, etc.). By determining the geometry of the drill bit  10  prior to the cutting operation, appropriate tool paths for displacement of a cutting tool relative to the drill bit can be determined, even though there may be variations in form of the drill bit. 
     Referring additionally now to  FIG. 5 , a plan view of a material removal system  30 , and an associated method, which can embody principles of this disclosure is representatively illustrated. The system  30  in this example is configured for removing the unwanted material  16  from between the blades  12  of the drill bit  10 . However, in other examples, the system  30  could be used to remove unwanted material from other types of articles. 
     As depicted in  FIG. 5 , the system  30  includes an enclosure  24  having a dust collector  26  for removing grinding dust, etc. from within the enclosure. The drill bit  10  is mounted in an axial indexing device  28  in the enclosure  24 . A cutting tool  32  (in this example, a grinding wheel) is displaced by a robot  34  along tool paths determined by a controller  36 . 
     The controller  36  can comprise at least one processor, memory devices and suitable programming for performing various functions. A suitable controller for use in the system  30  is a Model R30iA Controller manufactured by Fanuc Robotics, although other types of controllers may be used, if desired. 
     The system  30  also includes an operator terminal or user interface  38  (such as, an industrial computer with a display and an input device). A spindle chiller  40  draws heat from a spindle carrying the cutting tool  32 . 
     Referring additionally now to  FIG. 6 , an elevational view of certain components of the system  30  is representatively illustrated. In this view, it may be seen that an axis  42  about which the cutting tool  32  rotates is oriented perpendicular to a longitudinal axis  44  of the drill bit  10  when the drill bit is mounted in the rotary indexing device  28 . 
     The robot  34  is of the six-axis type having multiple linear actuators. A suitable robot for use in the system  30  is a Model F-200iB manufactured by Fanuc Robotics of Rochester Hills, Mich. USA. Other robots, and other types of robots, may be used in keeping with the scope of this disclosure. Operation of the robot  34  is controlled by the controller  36 . 
     The rotary indexing device  28  rotates the drill bit  10  as needed to allow a scanning device  48  to appropriately scan an outer surface  46  of the bit (see  FIGS. 1-4 ), and to allow the cutting tool  32  to remove the unwanted material  16  from the bit. A suitable rotary indexing device for use in the system  30  is a Single Axis Positioner manufactured by Fanuc Robotics, although other rotary indexing devices may be used, if desired. 
     The scanning device  48  is used to determine the geometry of the drill bit  10  by scanning the outer surface  46  of the bit using certain techniques described more fully below. A suitable scanning device for use in the system  30  is a laser sensor with a dust tight, positively-pressured laser enclosure, a pneumatic shutter and hard guarding of the laser from collisions. Other types of scanning devices which may be used include radar, an ultrasound sensor, a physical probe and an optical scanning device (e.g., other than a laser), etc. 
     The cutting tool  32  is mounted to a spindle extending from a servo motor  50 . The servo motor  50  is mounted to an adjustable force device or active compliant tool  52 . A suitable active compliant tool for use in the system  30  is the 1000 Series Adjustable Force Device manufactured by PushCorp, Inc. of Dallas, Tex. USA, although use of the tool  52  is not necessary in the system, and other types of active compliant tools may be used in keeping with the scope of this disclosure. 
     A carriage  54  is used to mount the cutting tool  32 , device  48 , motor  50  and tool  52  to the robot  34 . In this manner, the cutting tool  32  and scanning device  48  can be displaced with six degrees of freedom (rotated and displaced along each of three axes) relative to the drill bit  10 . 
     In addition, the drill bit  10  can be rotated as desired relative to the robot  34 , cutting tool  32  and scanning device  48 . Since the robot  34  can manipulate the cutting tool  32  and scanning device  48  with six degrees of freedom, it is not necessary to rotate the drill bit  10  for the cutting tool and scanning device to adequately access the outer surface  46  of the drill bit. However, it is advantageous in the  FIGS. 5 &amp; 6  example to rotate the drill bit  10  for most convenient access to the outer surface  46  by the cutting tool  32  and scanning device  48 . 
     A horizontal plate  56  is provided at a known location for measuring a diameter of the cutting tool  32 . The robot  34  can position the cutting tool  32  above the plate  56 , and then slowly lower the cutting tool until it contacts the plate. The device  52  senses this contact (resulting in a force applied to the cutting tool  32 ), and the controller  36  determines the diameter of the cutting tool, based on the position of the robot  34  when the contact occurs. Alternatively, the device  52  can sense deflection due to the contact in addition to, or instead of, sensing the actual contact to determine the diameter of the cutting tool  32 . 
     The cutting tool  32  in this example is a grinding wheel. The grinding wheel abrasively removes the unwanted material  16  from between the blades  12 . However, in other examples, the cutting tool  32  could comprise a circular mill or another type of cutting device. 
     Referring additionally now to  FIG. 7 , a representative scan  58  produced by the scanning device  48  is illustrated. The scan  58  is produced by the robot  34  displacing the scanning device  48  axially along the outer surface  46  of the drill bit  10 , so that a blade  12  is axially traversed at least partially by the scan. 
     The axial scan  58  as depicted in  FIG. 7  includes a section  58   a  which indicates the diameter DS of the shank  18 , a section  58   b  which indicates the diameter DB of a blade  12 , and a section  58   c  which indicates the bevel  22 . The controller  36  can use the data from the axial scan  58  to determine the bit and shank diameters DB, DS, and the location and angle of the bevel  22 . Of interest in this example is locating a top  60  of the bevel  22  since, in a method described below, the top of the bevel can be used to determine the location of the blades  12  and the unwanted material  16 . 
     Referring additionally now to  FIG. 8 , a representative circumferential scan  62  is illustrated. The scan  62  is produced in this example by the rotary indexing device  28  rotating the drill bit  10 , so that the blades  12  are traversed by the scan. 
     Many geometry characteristics of the drill bit  10  can be determined by the controller  36  from the data in the scan  62 . The number of the blades  12  and recesses  14  is readily determined, based on the circumferential scan  62 . The blade diameters DB and angular positions of the blades  12  are indicated by sections  62   a  of the scan  62 , the positions of the recesses  14  are indicated by sections  62   b , the rakes of the blade sides  20  are indicated by sections  62   c , the widths W between adjacent blades  12  are indicated by the distances between the sections  62   c , the depths D of the recesses  14  are indicated by differences between the sections  62   a  &amp;  b , radii R between the recesses  14  and adjacent sides of the blades are indicated by sections  62   d . In effect, the circumferential scan  62  gives a lateral cross-sectional representation of the drill bit  10  at a certain axial position along the bit. 
     To determine how the geometry of the blades  12  changes along their length, another circumferential scan  64  is performed at another axial position. By determining the change in angular positions of the blades  12  between the two circumferential scans  62  &amp;  64 , the helical pitch P of the blades can be readily calculated. The helical pitch P may be expressed in angular units (e.g., relative to the longitudinal axis  44 , as in  FIG. 3 ), or in any other units. 
     The controller  36  can identify the various sections of the circumferential scans  62 ,  64 , and compare the scans to determine the geometrical characteristics of the drill bit  10 . Data manipulation techniques may be used, e.g., data validation, averaging measurements, etc., to produce accurate geometrical information on the drill bit  10 , from which appropriate tool paths for the cutting tool  32  can be determined. 
     Referring additionally now to  FIG. 9 , another scan  66  is performed by the scanning device  48 . The scan  66  in this example helically traverses the drill bit  10  outer surface  46  between the shank  18  and a recess  14 . In this manner, the scan  66  also traverses the unwanted material  16  between the blades  12 . 
     This scan  66  is performed after the circumferential scans  62 ,  64  so that the helical pitch P and the angular positions of the blades  12  are known prior to the scan  66 . With the positions and pitches P of the blades  12  known, the controller  36  can direct the robot  34  to displace the scanning device  48  axially while the rotary indexing device  28  rotates the drill bit  10 , thereby helically scanning between the shank  18  and a recess  14 . 
     The scan  66  includes a section  66   a  (similar to the section  58   a  in  FIG. 7 ) which indicates the shank diameter DS, a section  66   b  (similar to the sections  62   b ) which indicates the depth of the recess  14 , and a section  66   c  which indicates the unwanted material  16  between the blades  12 . Preferably, a peak of the section  66   c  can be identified as a peak  68  of the corresponding unwanted material  16 . 
     The controller  36  can determine from the scans  58 ,  62 ,  64 ,  66  the various geometrical characteristics of the drill bit  10 , including the location of the unwanted material  16  between the blades  12 . To remove this unwanted material  16 , the controller  36  can determine appropriate tool paths of the cutting tool  32  which will result in removal of the unwanted material, without removing any of the wanted material of the drill bit  10 . 
     Referring additionally now to  FIGS. 10A  &amp; B, a method  70  of removing the unwanted material  16  from the drill bit  10  is representatively illustrated in flowchart form. Although the method  70  is suited for removing the unwanted material  16  from the drill bit  10 , with appropriate modification, the method could be used for removing unwanted material from other types of articles. 
     In one aspect, the method  70  accomplishes a desirable result of removing the unwanted material  16 , even though the precise geometry of the drill bit  10  is unknown before commencement of the method. An operator can input (e.g., via the interface  38 ) an approximate size of the drill bit  10 , as well as other identifying characteristics, so that the controller  36  has a basis for beginning the process of determining the drill bit&#39;s geometry. 
     In step  72 , the drill bit  10  is loaded into the rotary indexing device  28 , so that the longitudinal bit axis  44  is centered in the device&#39;s rotor. 
     In step  74 , the drill bit  10  is painted so that the scanning device  48  can readily detect the outer surface  46  of the bit. This step  74  is optional if the scanning device  48  can accurately detect the outer surface  46  without it being painted. 
     In step  76 , the operator inputs an initial axial position into the interface  38 . The controller  36  uses this information to determine where to start the axial scan  58 . In this example, the initial axial position is on the shank  18 , somewhat toward the indexing device  28  from the bevel  22 . The controller  36  ignores any data for axial positions opposite the blades  12  from the initial axial position. 
     In step  78 , the axial scan  58  is performed. The robot  34  displaces the scanning device  48  so that the scan  58  traverses the drill bit  10  from the shank  18  to a blade  12 . 
     In step  80 , the controller  36  determines the bit diameter DB, the shank diameter DS and an inflection point  110  of the bevel  22  (diameter reductions along the shank  18  can be ignored in determination of the inflection point  110  position). These determinations are, in this example, based on the information obtained from the axial scan  58 , as discussed above in relation to  FIG. 7 . In addition, the operator can input to the interface  38  an angle of the bevel  22  (e.g., 30 or 45 degrees, etc.). 
     In step  82 , the controller  36  determines the location of the bevel top  60 . In this example, the location of the bevel top  60  can be readily calculated, since the location of the inflection point  110  and the angle of the bevel  22  are known. 
     In step  84 , the robot  34  positions the scanning device  48  (a laser in this example) for circumferentially scanning the outer surface  46  of the drill bit  10 . The drill bit  10  can be rotated by the rotary indexing device  28  relative to the scanning device  48 . In other examples, the scanning device  48  could be rotated about the drill bit  10  (e.g., by the robot  34 ). 
     In step  86 , the drill bit  10  is circumferentially scanned by the scanning device  48  at a first axial position along the drill bit. In this example, the axial position is chosen to be in the area of the blades  12 , so that the circumferential scan  62  will allow for geometrically characterizing each of the blades and recesses  14  about the drill bit  10 , as discussed above in relation to  FIG. 8 . 
     For example, the number of the blades  12  and recesses  14 , the blade diameters DB and angular positions of the blades (e.g., as indicated by sections  62   a  of the scan  62 ), the positions of the recesses (e.g., as indicated by sections  62   b ), the rakes r (e.g., see  FIG. 4 ) of the blade sides  20  (e.g., as indicated by sections  62   c ), the widths W between adjacent blades  12  (e.g., as indicated by the distances between the sections  62   c ), the depths D of the recesses  14  (e.g., as indicated by differences between the sections  62   a  &amp;  b ) and radii R (e.g., as indicated by sections  62   d ) can be readily determined from such a circumferential scan  62 . 
     In step  87 , the scanning device  48  is repositioned to a second axial position, offset from the first axial position in step  86 . 
     In step  88 , the drill bit  10  is circumferentially scanned by the scanning device  48  at the second axial position along the drill bit. The second axial position is also in the area of the blades  12  in this example, but is axially offset from the first circumferential scan in step  86 , so that certain changes in geometrical characteristics can be determined. 
     In step  90 , the circumferential scans  62  &amp;  64  are compared. For example, by calculating the change in angular positions of the blades  12  between the two circumferential scans  62  &amp;  64 , the helical pitch P of the blades can be readily determined by the controller  36 , as discussed above in relation to  FIG. 8 . 
     In step  92 , the blade rake r is determined by the controller  36 , based on the circumferential scan  62 . For example, the controller  36  can pick two points on a side  20  of a blade  12  (e.g., as indicated by the corresponding scan section  62   c ), and compare their positions in order to calculate the blade rake r. The locations of the recesses  14  (also known to those skilled in the art as “junk slots”) can be readily determined, as well (e.g., at sections  62   b  of the circumferential scan  62 ). 
     In step  94 , the robot  34  positions the scanning device  48 , and the rotary indexing device  28  rotates the drill bit, so that the scanning device can scan the outer surface  46  of the drill bit helically along one of the recesses  14 . The rotary indexing device  28  then rotates the drill bit  10  while the robot  34  displaces the scanning device  48  axially relative to the drill bit, thereby helically scanning the outer surface of the drill bit. However, the robot  34  could displace the scanning device  48  helically about the drill bit  10  (e.g., so that the drill bit is not rotated during the helical scan), if desired. 
     In this example, the unwanted material  16  comprises a web between the blades  12 , resulting from a molding process. However, in other examples, the unwanted material  16  may be be removed from another type of drill bit, or another type of oilfield equipment, or other type of article. Furthermore, the unwanted material  16  may not comprise a web, the article or drill bit may not be produced by a molding process, etc. Thus, it should be clearly understood that the principles of this disclosure are not limited to the details of the method  70  or the drill bit  10  described herein or depicted in the drawings. 
     In step  96 , the controller  36  determines the start, peak and end of the unwanted material  16  (a web in this example). As described above, a peak of the section  66   c  (see  FIG. 9 ) can be identified as a peak  68  of the corresponding unwanted material  16 . 
     In step  98 , the controller  36  determines where the web intersects the wanted material of the blade  12  sides  20 , recesses  14  and radii R. Tool paths for the cutting tool  32  are then calculated, so that the unwanted material  16  will be removed, up to the intersections between the unwanted material and the blade sides  20 , recesses  14  and radii R. 
     In step  100 , the controller  36  rotates the drill bit (if needed) and aligns the cutting tool  32  with a recess  14  between two blades  12 . For example, the robot  34  could rotate the cutting tool  32  so that it is at a same angle (considering the cutting tool as being normal to the axis  42 ) relative to the longitudinal axis  44  of the drill bit  10  as the helical pitch P of the blades  12  adjacent the selected recess  14 . 
     The robot  34  can also rotate the cutting tool  32  so that it is angled to correspond with the rake r of the adjacent blade sides  20 . In this manner, the cutting tool  32  can be conveniently displaced between the blades  12  for removal of the unwanted material  16 , without removing any of the wanted material of the blade sides  22 , radii R or recesses  14 . 
     In step  102 , the cutting tool  32  rough cuts the unwanted material  16 . In this example, the cutting tool  32  is plunged radially (relative to the bit axis  44 ) into the unwanted material  16  between the blades  12 , and then is displaced axially to remove the axial width of the unwanted material. This process is repeated, with the drill bit  10  being rotated by the rotary indexing device  28  as needed between sets of radial plunges and axial displacements, to remove the unwanted material  16  up to near the intersection between the unwanted material and the blade sides  20 , radii R and recess  14 . 
     In step  104 , the cutting tool  32  diameter is again measured, since abrasive rough cutting can reduce the cutting tool diameter. In this example, the cutting tool  32  is displaced by the robot  34  into contact with the plate  56 , the device  52  senses such contact and/or displacement, and the controller  36  uses this information to compute the diameter of the cutting tool. If an abrasive cutting tool is not used, then step  104  may not be performed in the method  70 . 
     In step  106 , the cutting tool  32  finish cuts the unwanted material  16 . In this example, the cutting tool  32  initially plunge cuts partially into the unwanted material  16  near one of the radii R and at the axial start of the unwanted material, the drill bit  10  rotates to displace the center of the recess  14  toward the cutting tool. This is repeated at both sides  20  adjacent the recess  14 , and at the axial middle and end of the unwanted material  16 . Multiple passes at incrementally decreasing radial distances from the bit axis  44  can be performed, until the cutting tool  32  has removed substantially all of the unwanted material  16 . 
     In step  108 , the preceding steps  94 - 106  are repeated for each successive portion of unwanted material  16  between adjacent blades  12 . Certain determinations made in, for example, steps  80 ,  82 ,  90 ,  92  can also be used by the controller  36  in determining tool paths for the cutting tool  32  in the repeated steps  94 - 106 . Although in this example, certain scans  58 ,  62 ,  64  may not be repeated in the repeated steps  94 - 106 , in other examples any or all of these scans could be repeated, as desired. 
     Note that it is not necessary for substantially all of the unwanted material  16  to be removed from between the blades  12 . For example, in order to protect wanted material of the drill bit  10 , the controller  36  could prevent the cutting tool  32  from removing unwanted material adjacent to the wanted material. Such a situation could arise, for example, if the bit is undercut, a weld groove is present, etc. 
     Furthermore, note that it is not necessary for all of the steps  72 - 108  described above to be performed in keeping with the scope of this disclosure. In other examples, more, fewer or different steps could be performed, and the steps could be performed in different orders. For example, step  92  could be part of step  86 , the second circumferential scan  64  may not be performed if the blade pitch P is known, etc. Thus, it will be appreciated that the scope of this disclosure is not limited at all to the details of the method  70  described here or depicted in the drawings. 
     If the blades  12  do not have a helical pitch P, then the helical scan  66  can instead be an axial scan, since the recesses  14  would not extend helically about the drill bit  10 . In addition, if there is no helical pitch P, the cutting tool  32  may not be rotated to align with the nonexistent helical pitch. Similar considerations apply if the blades  12  have no rake r (e.g., the cutting tool  32  would not be rotated to align with the nonexistent rake). 
     It may now be fully appreciated that the material removal system  30  and method  70  result from significant advancements in the art of material removal. Especially (although not exclusively) useful for custom manufactured articles having variations in form, the system  30  and method  70  allow the unwanted material  16  to be efficiently and safely removed, without removing any of the wanted material of the drill bit  10 . 
     In one example, a method  70  of removing unwanted material  16  from an oilfield drill bit  10  is provided to the art by the above disclosure. The method  70  can include scanning the drill bit  10 ; determining, based on the scanning, a location of the unwanted material  16 ; determining tool paths of a cutting tool  32  which will result in removal of the unwanted material  16 ; and displacing the cutting tool  32  along the tool paths, thereby removing the unwanted material  16 . 
     The unwanted material  16  may be positioned between blades  12  of the drill bit  10 . 
     Determining the location of the unwanted material  16  can include determining radii R between a recess  14  and adjacent sides  20  of the blades  12 . 
     Scanning can comprise scanning helically along a surface  46  of the drill bit  10  between the blades  12 . 
     Determining the location of the unwanted material  16  can include determining a width W between the blades  12 , determining a number of the blades  12 , determining an angular spacing of the blades  12 , determining a helical pitch P of the blades  12 , determining a rake r of the blades  12 , and/or determining a depth D between the blades  12 . 
     Displacing the cutting tool  32  can include displacing the cutting tool  32  to approximately the depth D between the blades  12 , thereby removing the unwanted material  16  positioned outward from the depth D. 
     Displacing the cutting tool  32  can include displacing the cutting tool  32  along the tool paths aligned with the helical pitch P. 
     Determining the helical pitch P can include circumferentially scanning the blades  12  at axially spaced apart positions. 
     Scanning can comprise scanning axially along a surface  46  of the drill bit  10 . Determining the location of the unwanted material  16  can comprise determining at least one of the group comprising a drill bit diameter DB, a shank diameter DS, an inflection point  110  and a bevel top  60 , based on the axial scanning. 
     Scanning can comprise scanning circumferentially about blades  12  of the drill bit  10 . Determining the location of the unwanted material  16  can include determining at least one of the group comprising number of the blades  12 , angular spacing of the blades  12 , widths W between the blades  12 , radii R at sides  20  of the blades  20 , rake r of the blades  12  and helical pitch P of the blades  12 , based on the circumferential scanning. 
     A material removal system  30  is also provided to the art for removing unwanted material  16  from an oilfield drill bit  10 . In one example, the system  30  can include a rotary indexing device  28  which rotates the drill bit  10  about a longitudinal axis  44  of the drill bit  10 , a scanning device  48  which scans an outer surface  46  of the drill bit  10  and a controller  36  which a) determines a geometry of the drill bit  10 , based on at least one scan  58 ,  62 ,  64 ,  66  by the scanning device  48 , b) determines a location of the unwanted material  16 , and c) determines tool paths of a cutting tool  32  for removal of the unwanted material  16 . 
     The scanning device  48  may comprises a laser, radar, an ultrasound sensor, a physical probe and/or an optical scanning device. 
     The location of the unwanted material  16  and/or the geometry of the drill bit  10  may be unknown until determined by the controller  36 . 
     There may be relative rotation between the drill bit  10  and the scanning device  48  while the scanning device  48  scans the outer surface  46  of the drill bit  10 . The rotary indexing device  28  may rotate the drill bit  10  while the cutting tool  32  removes the unwanted material  16 . 
     The drill bit  10  geometry determined by the controller  36  may comprise radii R between a recess  14  and adjacent sides  20  of the blades  12 , a width W between the blades  12 , a number of the blades  12 , an angular spacing of the blades  12 , a depth D between the blades  12 , a helical pitch P of the blades  12 , and/or a rake r of the blades  12 . 
     The controller  36  can displace the cutting tool  32  along the tool paths aligned with the helical pitch P. 
     The controller  36  can determine the helical pitch P based on multiple circumferential scans  62 ,  64  of the blades  12  at axially spaced apart positions. 
     The scanning device  48  can scan axially along the outer surface  46  of the drill bit  10 , whereby an axial scan  58  is produced. The drill bit  10  geometry determined by the controller  36  can comprise a drill bit diameter DB, a shank diameter DS, an inflection point  110 , and/or a bevel top  60 , based on the axial scan  58 . 
     The scanning device  48  can scan circumferentially about blades  12  of the drill bit  10 , whereby one or more circumferential scans  62 ,  64  are produced. The drill bit  10  geometry determined by the controller  36  can comprise a number of the blades  12 , an angular spacing of the blades  12 , widths W between the blades  12 , radii R at sides  20  of the blades  12 , rake r of the blades  12 , and/or helical pitch P of the blades  12 , based on the one or more circumferential scans  62 ,  64 . 
     As mentioned above, the scope of this disclosure is not limited to use only in removing unwanted material from an oilfield drill bit. In a broader aspect, a method  70  of removing unwanted material  16  from an article (e.g., the drill bit  10  or another article) having a variable form is described by this disclosure. In one example, the method  70  can include scanning the article; determining, based on the scanning, a location of the unwanted material  16 ; determining tool paths of a cutting tool  32  which will result in removal of the unwanted material  16 ; and displacing the cutting tool  32  along the tool paths, thereby removing the unwanted material  16 . 
     Scanning can comprise scanning axially helically and/or circumferentially along a surface  46  of the article. 
     The article may be rotated during the scanning. 
     Scanning circumferentially may be performed at multiple axial positions along the article. 
     The article may be rotated while removing the unwanted material  16 . The article may be displaced while displacing the cutting tool  32 . 
     Removing the unwanted material  16  may comprise grinding away the unwanted material  16 . 
     The scanning may be performed by a laser, radar, an ultrasound sensor, a physical probe, and/or an optical scanning device. 
     The location of the unwanted material  16  may be unknown prior to the scanning. The form of the article may be unknown prior to the scanning. 
     Although various examples have been described above, with each example having certain features, it should be understood that it is not necessary for a particular feature of one example to be used exclusively with that example. Instead, any of the features described above and/or depicted in the drawings can be combined with any of the examples, in addition to or in substitution for any of the other features of those examples. One example&#39;s features are not mutually exclusive to another example&#39;s features. Instead, the scope of this disclosure encompasses any combination of any of the features. 
     Although each example described above includes a certain combination of features, it should be understood that it is not necessary for all features of an example to be used. Instead, any of the features described above can be used, without any other particular feature or features also being used. 
     It should be understood that the various embodiments described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of this disclosure. The embodiments are described merely as examples of useful applications of the principles of the disclosure, which is not limited to any specific details of these embodiments. 
     In the above description of the representative examples, directional terms (such as “above,” “below,” “upper,” “lower,” etc.) are used for convenience in referring to the accompanying drawings. However, it should be clearly understood that the scope of this disclosure is not limited to any particular directions described herein. 
     The terms “including,” “includes,” “comprising,” “comprises,” and similar terms are used in a non-limiting sense in this specification. For example, if a system, method, apparatus, device, etc., is described as “including” a certain feature or element, the system, method, apparatus, device, etc., can include that feature or element, and can also include other features or elements. Similarly, the term “comprises” is considered to mean “comprises, but is not limited to.” 
     Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the disclosure, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to the specific embodiments, and such changes are contemplated by the principles of this disclosure. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the invention being limited solely by the appended claims and their equivalents.