WO1994002284A1

WO1994002284A1 - Method and apparatus for tool management

Info

Publication number: WO1994002284A1
Application number: PCT/US1993/007016
Authority: WO
Inventors: Kenneth Easterling
Original assignee: TULON CO
Current assignee: TULON CO
Priority date: 1992-07-28
Filing date: 1993-07-26
Publication date: 1994-02-03
Anticipated expiration: 1995-01-28
Also published as: AU4786393A

Abstract

A tool management system utilizes an optically readable indicia to identify tools. The indicia comprises a pattern (180) having pattern elements which are geometrically similar in shape. The pattern elements, which may comprise rings, are sized and positioned to identify characteristics of a tool (110) to which the pattern is applied. Each pattern element is disposed within a predetermined zone, and in the preferred embodiment, the boundaries of each pattern element are compared to the midpoint of the zone to decode the pattern. While the indicia is preferably used in connection with tools, it has application to other objects, and it is particularly advantageous where a relatively large amount of information must be encoded.

Description

METHOD AMD APPARATUS FOR TOOL MANAGEMENT

Background of the Invention Field of the Invention

The present invention relates generally to optically readable codes, and more specifically to improvements in tool usage in computer numerically controlled machines and to tool management in general. The invention includes a method and apparatus for identifying tools and for monitoring and controlling tool selection in computer numerically controlled machines. Description of the Related Art

Computer numerically controlled (CNC) machines have become the standard in manufacturing technology. These numerically controlled machines automate procedures such as drilling, machining, wire wrapping, and many other functions. Most CNC systems utilize numerous tools of varying geometries. The tools are typically placed in a matrix or cassette by an operator of the machine. Once the tools are positioned within the matrix, the computer controls selection of these tools based on pre-determined positions in the matrix, and automatically performs the pre-programmed functions with the selected tools in response to data transmitted from a CNC tape to the computer memory.

These systems are highly automated except for the positioning of the tool within the tool matrix, which is typically accomplished manually. The CNC machine does not verify that the operator has correctly positioned the tools within the matrix, and thus, if the operator incorrectly positions a tool, the CNC machine will select the incorrect tool, assuming it to be correct, and continue its processing as if the correct tool were selected. If the operator fails to notice an improper tool selection promptly, an entire job or batch of products may be run through the numerically controlled machine, in which case the products will typically be useless and are usually scrapped.

This human error problem is especially acute in CNC printed circuit (PC) board drilling machines. These drilling machines utilize a number of drill bits of varying geometries and configurations to accomplish the drilling necessary on each printed circuit board. Typically, the only indication of the drill bit geometry is the label on the drill bit packaging. The drill bits are sometimes so small that without substantial magnification and a very precise reference book describing the drill bits, the operator cannot distinguish between the drill bit geometries. More¬ over, because of the small drill diameters, these bits break readily when used in an application that is unsuitable for the geometry of the bit.

The lack of sufficient identification labeling on the drill bits to indicate geometry results in wasted drill bits when bits are misplaced or not returned to the proper packaging. Companies involved in CNC manufacturing often have millions of dollars of tool inventory and cannot identify the exact configuration of some tools because the tool was misplaced or not returned to its package.

One method proposed for CNC PC board drilling machines is to provide a parallax laser measuring device for each station of the drilling machine. The laser measures the drill bit diameter once the machine has selected a drill bit, but before it begins to cut. The laser device measures the drill bit while it is spinning, or the laser device may measure the bit while it is not turning. If the drill bit it spinning, sometimes at over 100,000 revolutions per minute, a certain amount of run-out occurs that will increase the apparent diameter of the drill bit to the parallax laser measuring device. If the drill bit is measured while not spinning, the parallax laser may channel through some of the drill bit's flutes and not obtain an accurate reading of the drill bit diameter. A further complication is that the parallax laser may not provide comprehensive information such as the cutting aspect, the web thickness, the helix or the flute length. Currently proposed laser measuring devices are also relatively expensive.

Summary of the Invention Accordingly, a need exists for a system of identifying tools, particularly tools used in CNC machines. The system should be economical, and easy to implement and the system should allow the tools to be identified according to their features, even after they have been removed from their packaging. It is also advantageous to provide a system of identifying tools capable of use with CNC machines to allow the CNC machines to automatically identify tools, thereby minimizing or eliminating the common human introduced errors. Such a system would greatly reduce wasted product and wasted tools currently plaguing the industry.

Accordingly, the preferred embodiment of the present invention provides a system which can identify the features of tools and can thereby prevent damage to products and prevent waste. In general, the identification system of the present invention involves marking a tool to be identified with an optically readable indicia which can be read by an optical image processing system. In the presently preferred embodiment, the optically readable indicia comprises a ring code having a plurality of concentric rings. The rings represent a predefined code which indicates a plurality of predefined features of the tool. An imaging processing system digitizes the ring code and interprets the ring code to provide an alphanumeric code represented by the ring code. The alphanumeric code can be referenced in a database to determine the features of the tool. In one embodiment, the system is a stand-alone unit, and in another embodiment, the identification system is efficiently implemented on CNC machines in existence. In yet another embodiment, the present invention is incorporated into newly designed CNC machines. Finally, the system can be adapted to provide inventory control to both the manufacturers and users of tools.

In accordance with one aspect of the invention, a drill bit having an elongated body compris.es a shank portion configured to fit within a spindle and a flute portion configured to cut material from a workpiece, such as a printed circuit board. An optically readable indicia, preferably disposed on a heel of the shank of the drill bit, comprises an optically readable pattern corresponding to at least one characteristic of the drill bit. This pattern is one of a group of a large number (at least tens) of patterns which together form a code for identifying the characteristics of different drill bits.

In the preferred embodiment, each pattern element is disposed within a predetermined zone on the drill bit. Each zone is annularly shaped, and the zones are concentric with respect to the center of the indicia. The shape of the pattern elements corresponds to the shape of their respective zone. Accordingly, the pattern elements of the preferred embodiment are shaped annularly. Although the annular zones have the same width, the pattern elements may vary in width, and each pattern element may cover an entire zone or only a portion thereof. Information is encoded in the pattern elements by varying the width of the pattern element and by varying the position of the pattern element within the zone. Thus, while the boundaries of the pattern elements are concentric with the boundaries of the zones, the boundaries of the elements may nor may not coincide with the boundaries of their respective zones. The annular pattern elements of the preferred embodiment are sized and positioned to overlap or at least touch the midpoints of their respective annular zones.

The information embodied in the pattern of the disclosed embodiment is preferably decoded by reading the pattern with a CCD camera and digitizing the image produced thereby. Using the digitized image, the location of an imaginary circle concentric with the zone boundaries and passing through the midpoint of the zone. More specifically, the distance between the midpoint of the zone and the two pattern boundaries is determined in a directional radial to the center of the indicia. Additionally, for a given pattern boundary, a determination is made as to whether the pattern boundary is closer to the center than the midpoint is to the center, or whether the pattern boundary is further from the center than the midpoint is to the center. Depending on the result of this determination, the distance measurement is assigned either a positive or a negative value. Using this information, a code representative of the entire pattern is generated and cross-referenced to one or more characteristics defined by the pattern. Such characteristic may include cutting diameter, web thickness, flute length, specialized geometry, cutting aspect, manufacturer, date of manufacture, recommended feed and recommended drill speed.

Another aspect of the invention comprises a method of tool verification for a computer numerically controlled machine, which utilizes a plurality of tools positioned in respective locations in a tool matrix. The method comprises reading a pattern of geometrically similar pattern elements on one of the tools with an optical pattern reader capable of reading information coded in the pattern. The coded information is transmitted to a computer which compares the coded information with stored tool characteristic data corresponding to the location of the tool to verify that the coded information on the tool corresponds to the stored data for that location. These steps are repeated for substantially all of the tools in the tool matrix. In one embodiment, the computer is a driller machine controller unit and the tools are drill bits.

An additional aspect of the invention comprises an object having concentric ring optical indicia comprising a plurality of predefined zones concentrically extending from a center of the indicia. The indicia includes optically discernible concentric rings of varying widths, each disposed within one of the plurality of predefined zones. The width of each ring provides information concerning the object to which said indicia is applied.

Yet another aspect of the invention comprises a tool management control system for use with a computer numerically controlled CNC drilling machine, which automatically changes a plurality of drill bits positioned in a tool changer. The system comprises at least one drill bit which includes a shank having a finished diameter of 0.1248 inches, ±.010 inches, and an overall finished length of 1.500 inches, ±.020 inches. A heel on the drill bit contains optically readable information encoded thereon. Coded information from the heel is read by a pattern recognizer, and supplied to a driller machine controller unit connected thereto. The invention also includes a method of coding a group of objects with indicia. In this method, each of a plurality of objects within the group of objects has at least one characteristic that is different from those of the remaining objects in the plurality of objects. The method includes the step of marking each of the objects with a pattern comprising at least one pattern element having at least one circular boundary. The marking step comprises locating the pattern element within a zone having at least one circular boundary, and utilizing the pattern to define at least one characteristic of the object by performing at least one of the steps of (1) positioning the pattern element at a predetermined location within the predetermined zone. and (2) sizing the pattern element to a predetermined size relative to the size of the zone.

The invention further encompasses a method of identifying characteristics of a group of objects coded with a pattern comprising plural pattern elements disposed within respective plural zones of the pattern. Each of the plurality of objects within the group of objects has at least one characteristic that is different from those of the remaining objects and the plurality of objects. The method includes the step of comparing at least one point on a circular reference line of a pattern element with at least one point on a circular reference line of a zone containing the first pattern element. This step is repeated for other pattern elements and other zones within the pattern. The results of the comparisons are utilized to determine at least one characteristic of an object within the group of objects. The foregoing process is then repeated for another object within the group of objects.

Brief Description of the Drawings Figure 1 is a functional block diagram of a basic tool identification system 100 of the present invention. Figure 2 is a functional block diagram of a tool identification system for a CNC drilling machine according to the present invention.

Figure 3 illustrates an exemplary drill bit with a collet mounted on the shank. Figure 4 illustrates an expanded view of the drill bit cutting portion.

Figure 5 illustrates a drill bit shank with opti¬ cally readable information coded on the heel of the drill bit shank.

Figure 6 illustrates a perspective view of a CNC drilling machine spindle with a corresponding drill bit matrix and drilling table. Figure 7 is an end view of a drill bit with optically readable information on the heel of the bit.

Figure 8 illustrates a configuration of the identifying indicia of the present invention.

Figure 9 illustrates a flow chart for identifying the optically readable indicia of the present invention.

Figure 10 illustrates a flow chart of the drill bit verification software residing in the controller of a CNC drilling machine. Detailed Description of the Preferred Embodiment A tool identification system 100 depicted in Figure 1 comprises an optical pattern recognition system 50 and a standard personal computer 52. The tool identification system automatically identifies the geometry of a tool marked with an appropriate identifying optically readable indicia arranged to form an optically readable pattern corresponding to characteristics of the tool. The pattern on any given tool is selected from a group of tens of potential patterns. Each pattern has at least one pattern element, and each pattern element in the group of patterns has geometric similarity. In the preferred embodiment, the tool is marked with an identifying indicia having pattern elements comprising rings which form a pattern readable by the pattern recognition system 50. The width and position of the rings provide information about the tool. The information encoded in each pattern of rings corresponds to a predefined alphanumeric code which represents the features or characteristics of a particular tool.

The pattern recognition system reads the ring code marked on the tool and analyzes the ring code to determine the alphanumeric code represented by the ring code. The pattern recognition system then references a database which stores features and geometries of tools corresponding to the alphanumeric code represented by the ring codes. The tool identification system 100 comprises a pattern recognition system 50 and a computer 52. The pattern recognition system 50 comprises an optical reader 60 coupled to an image processor 62 with supporting hardware. In one embodiment, the optical reader 60 may comprise a Sony XC-75/75CE CCD Vision Camera Module, and the image processor may comprise a conventional Cognex Model 2000/3000 single-board vision system. The functional control program in the Cognex Model 2000/3000 is modified according to the present system as further described below. The computer 52 comprises a conventional personal computer or workstation with appropriate memory 53 and mass storage media 54. The image processor 62 evaluates the image provided by the optical reader and generates measurement information by identifying the ring code on the tool. The measurement data is provided on a communications link 64 such as RS-232 to the computer 52. The computer 52 then utilizes the measurement information provided by the image processor 62 to further identify the tool.

Although the preferred embodiment is especially adapted to identify tools, it should be understood that the system has application for identification of other items. A preferred tool for use in the tool identification system 100 is a PC-board drill bit. An exemplary drill bit 110 for use in the PC board drilling machine, shown in Figures 3-5, has an elongated body which comprises a shank 160, a neck 162, a chamfer 164, a heel 166, a flute 168 and a cutting edge 169. Drill bits 110 of varying cutting diameters have shanks of the same diameter to fit within the collets of a spindle 104, as illustrated in Figure 6. The diameter of the drill bits 110 is typically .1248 inches +/- .0100 inches, and the length of such drill bits is typically 1.500 inches +/" .020 inches. The bits 110 are commonly formed of tungsten carbide, and often include a collar 167, usually formed of plastic, which is pressed onto the shank 160 and maintains a frictional fit with the shank 160. the cutting edge 169 is angled in two sections 170 and 172 to form an angle 174 (Figure 4) .

The density of electronic circuitry on current printed circuit boards requires very precise drilling methods. Therefore, a drill bit 110 utilized in the fabrication of printed circuit boards may incorporate a number of features commonly referred to as the geometry of the bit. These features include, for example, the cutting aspect, the flute length, the web thickness, the helix and the drill diameter, all well known in the art. Other information is also associated with conventional PC-board drill bits, such as the manufac^-1 rer, the date of manufacture, the recommended speed for the drill in revolutions per minute (RPM) , the recommended feed for the drill and any specialized geometry. Specialized geometry is generally a non- standard combination of the web thickness, the flute length and the cutting aspect.

According to the present invention, all or a selected portion of these descriptive features incorporated in a drill bit 110 — the cutting aspect, the flute length, the web thickness, the helix, the drill diameter, the manufacturer, the date of manufacture, the recommended speeds (in RPM) and feed rates — are encoded (assigned a pre-defined optically readable pattern) , and the pattern representing these descriptive features is placed on the heel 166 of the shank 160. For greatest uniformity, industry standardized patterns representing various geometries are desirable.

The present embodiment utilizes an encoding pattern that will be referred to as a ring code, which has certain similarities to a conventional bar code. However, the ring code utilizes concentric rings of varying thicknesses to represent alphanumeric codes as further described herein. A ring pattern is highly advantageous because of its radial and rotational symmetry. When a drill bit is positioned beneath the optical reader 60 of the pattern recognition system 50, it will be at an unknown rotational orientation. Thus, a non-radially symmetric pattern, such as a conventional bar code, may rotationally align in different directions each time the bit is used. While such bar code may nevertheless be utilized, the processing required to read a conventional bar code pattern is more complex because the orientation should first be determined. Because of the radial symmetry of the ring code, orientation becomes irrelevant.

As shown in figures 5 and 7, optically readable indicia forming an optically readable pattern in the form of a radially symmetric ring pattern 180 is placed upon the heel 166 of the drill bit shank 160. Exemplary ring code 180 comprising three ring-shaped pattern elements 181a, 181b, 181c is shown in Figure 7. These rings 18la, 181b, 181c are disposed within respective annular zones that are concentric about the center of the heel 166 of the drill bit. Figure 8 illustrates these zones in detail and depicts circular boundaries which define the zones. Although only three rings and three zones are depicted in Figure 8, it will be understood that the ring code may comprise more or less rings and zones, and that all zones need not necessarily contain rings. Each zone extends from an inside zone radius (an inner circular boundary for the zone) to an outside zone radius (an outer circular boundary for the zone), and has a center zone radius. The center zone radius is a reference location comprising an imaginary circular reference line disposed midway between the inner boundary and outer boundary of each annular zone. ^•" For instance, the outermost zone depicted in Figure 8 extends from an inside zone radius 300c to an outside zone radius 304c and has a center zone radius depicted as an imaginary circular reference line 302c. This center zone radius defines the midpoint between the inner boundary and outer boundary of the zone, and is measured from the center 298 of the heel 166. According to one embodiment of the present invention for use with PC- board drill bits, the innermost zone has a center zone radius 302a of 0.01 inches and subsequent center zone radii 302b, 302c are incremented by 0.01 inches for each consecutive zone toward the outer boundary of the heel of the drill bit. For each zone, the difference between the outside zone radius and the inside zone radius equals 0.01 inches. As explained below, with center zone radii spaced at 0.01 inches, the heel of a PC board drill bit can be divided into 13 zones.

Each zone may contain a ring which can vary in width from zero (no ring) to a maximum equal to the width of the zone. Thus, a ring of maximum width will extend from the inside zone radius (defining an inside edge for the ring) to the outside zone radius (defining an outside edge for the ring) . For purposes of discussion, the ring will be described as having boundaries defined by an inside edge or data radius and an outside edge or data radius. The inside data radius is defined as a radius measured from the center of the bit to the inner boundary of a ring within a zone, which radius is less than or equal to the center zone radius but greater than or equal to the inside zone radius. The outside data radius is defined as a radius measured radially from the center of the bit to the outer boundary of a ring within a zone, which radius is greater than or equal to the center zone radius and less than or equal to the outside zone radius. For instance, as seen in Figure 8, the outermpst ring depicted extends between boundaries defined by (1) an inside data radius 306c that is less than the center zone radius 302c and greater than the inside zone radius 300c, and (2) an outside data radius 308c that is less than the outside zone radius 304c, so that the ring (shown as cross-hatched in Figure 8) is completely within the boundaries formed by the outside and inside zone radii. The remaining rings are similarly defined. Advantageously, each ring in the ring pattern represents one pattern element having a circular boundary. In the present embodiment, each ring represents one alphanumeric digit. If there are 13 zones in the pattern, an alphanumeric code within 13 digits can represent numerous features and characteristics of a tool. The alphanumeric digit represented by any specific ring is dependent on the locations of the inside data radii (306c in the outermost ring of Figure 8) and the outside data radii (308c in the outermost ring of Figure 8) for the ring in each of the annular zones. For example, the alphanumeric digit represented by the outermost ring in Figure 9 is determined by the combination of (a) the difference between the outside data radius 308c and the center zone radius 302, and (b) the difference between the center zone radius 302 and the inside data radius 306c, as further explained below. In other words, the outside and inside data radii for a ring in an annular zone provide optically discernible circular reference lines which can be compared to the center zone radius which acts as an imaginary circular reference line. The rings are optically discernible because they have a contrast different than the polished heel 166 of the drill bit, the contrast or reflectivity being sufficient for detection by a CCD camera. In the preferred embodiment, the optically readable pattern covers an area no greater than the area of the end (the chamfer 164 and heel 166) of the shank 160. The radii and the differences between the radii described above are determined to the nearest 0.001 inch.

Although application of the ring code may be accomplished with ink on an object or a label, in the CNC machine environment, the code should be rugged enough to withstand constant handling by the CNC machine and by the operators. Moreover, many of these CNC machines use cutting and lubricating oils. A label applied to a tool or screening the tool is not desirable in this environment because the bar codes may wear off or become unreadable by the pattern recognition system 50. Moreover, the diameter of drill bit shanks in CNC PC board drilling machines are as small as .1248 inches +/~ -.0100 inches. With a shank of .1248 inches, and center zone radii incremented by .01 inches for each subsequent zone on the heel of the drill bit, the shank of a PC board drill bit can be divided into 13 zones for a 13-digit code. The ring code is very small and precise. Therefore, if the ring code is not rugged enough to withstand the environment, the very small imperfections could make the ring code non-readable. Using ink, the imperfections could be easily introduced by mishandling or even through normal use. in the present embodiment, the ring patterns are etched or otherwise marked on the heel 166 of the drill bit shank 160. The patterns are relatively permanent absent abuse of the tools and are therefore, rugged enough for use in the tool usage environments. In one embodiment, presently available photochemical imaging techniques which are capable of precisely etching the heel 166 are used to place the pattern on the drill bit heel 166. In general, photochemical imaging techniques are well known in the art of integrated circuit fabrication. To use such imaging techniques to mark the heel 166 of the drill bit 110 with a pattern, the bit 110 is first secured in a chase holder or other mechanism to accurately position the bit 110 so that the heel 166 is accessible. Next, using pilot pins or another guiding apparatus, a rubber mask is placed over the bit 110 to protect parts of the bit 110 other than the heel 166 from etchant. In a manner well known to those skilled in the art of semiconductor circuit fabrication, pho¬ toresist is applied to the heel 166. The heel is then exposed to ultraviolet light through a photomask which is configured to expose the photoresist on the heel 166 of the drill bit so as to prevent etching of the drill bit in locations where the ring pattern elements are not present. The portions of the photoresist on the heel 166 of the drill bit 110 which are not exposed can be easily removed, exposing portions of the heel 166 of the drill bit. Those portions of the photoresist which were exposed to UV light remain on the heel 166 to protect the heel 166 in those areas from subsequent etching. In other words, the photoresist is removed in the areas where the ring pattern elements are desired. After removal of the photoresist from the areas which were not exposed to UV light, the ring pattern 180 is etched into the heel 166 with a sodium based etchant capable of etching tungsten steel, which is also well known to those skilled in the art. Finally, the re- maining photoresist is stripped off of the etched heel, the rubber mask is removed, and the bit 110 can be extracted from the chase holder for use. The areas which are etched have a different reflectivity from the heel of the drill bit 110 where etching is prevented by the photoresist.

In another embodiment, the ring code 180 can be etched with presently available lasers, such as Excimer lasers, which are capable of precisely etching tungsten carbide, diamond, stainless steel or a combination of these components. The rings may also be placed on the heel 166 with great accuracy using conventional photolithography techniques such as provided by Eastman Kodak.

Once the tools are encoded with appropriate patterns uniquely identifying tool configuration, the tool identification system depicted 100 in Figure 1 can easily identify the tools as described below. First, a tool is placed in an appropriate tool holder to position the ring code on the tool in view of the optical reader 60. The user then issues a command (e.g., selects a menu entry) for the computer 52 which indicates to the image processor 62 that a tool has been positioned and is ready for identification. The image processor 62 then digitizes, via the optical reader 60, the ring pattern on the tool. As mentioned above, the digitized image is accurate to at least .001 inches using a Sony XC-75/75CE CCD Vision Camera Module and a Cognex Model 2000/3000 image processing system. The image processor 62 then analyzes the digitized image to locate the outer boundary of the heel 166 of the drill bit. Once the outer boundary is located, the image processor 62 then utilizes the outer boundaries it has located to locate the center 298 (Figure 8) of the ring code, and begins analyzing the code from the center 298.

Figure 9 depicts a flowchart of the analysis in general. The analysis involves measuring the appropriate inside and outside data radii (from the center 298 for each ring, as represented in an action block 220. To measure these radii, the image processor 62 scans the digitized image along imaginary lines extending radially from the center 298. Advantageously, the image processor 62 scans the annular ring pattern along three or more linear paths from the center 298 to the outside zone radius for the 5 outermost zone. The image processor 62 then averages each data radius obtained along the three different paths. This enhances the accuracy. The image processor 62 is programmed with the inside zone radius (inner boundary) , center zone radius and outside zone

10 radius (outer boundary) for each zone defined on the heel of the drill bit. Therefore, in order to measure these zones, the image processor 62, for each zone, examines the surface of the heel 166 between the inside zone radius and the outside zone radius. The image

15 processor determines if a ring is present by the reflectivity of the portion of the pattern being examined. The image processor 62 is therefore programmed to ascertain radii for all of the zones (e.g., 13 total zones) on the heel 166 of the drill bit

20 110. This is so even if the rings for two consecutive zones meet, creating the appearance of one large ring instead of two separate rings. The image processor 62 still measures the two rings (which appear as a single ring) as two rings because it is programmed to stop

25 measuring the radius for any given zone once the outside zone radii (outer boundary) for the given zone is reached.

Once the image processor 62 has measured the inside data radius and outside data radius for the ring

30 pattern element in each zone, in one embodiment, the image processor 62 forwards these radii (two radii for each zone in which a pattern element is present) to the computer 52 for further processing. The computer 52 then utilizes the inside and outside data radii to obtain a correlation to determine the characteristics represented by the ring pattern. In one embodiment, the computer 52 correlates the radii to obtain ulti- digit code. Specifically, the computer 52 calculates the inside^"-data radius to center zone radius difference and the outside data radius to center zone radius difference (±Y₂) for each ring, as represented in an action block 230. In one embodiment, the computer 52 can maintain a database which has alphanumeric digits which are assigned for a number of pre-defined AY₁ and ■*Y₂ pairs. Thus, to identify a digit represented by each ring, represented in an action block 235, the computer 52 searches a data base containing

and *Y₂ pairs for each digit which has been pre-defined. In one embodiment, the computer 52 uses the ^Y^ ±Y₂ pairs to address a Lotus format data base to derive an equivalent alphanumeric digit for the ^Y^, ^2 P^ai^{r for} each zone. For instance, for the outermost ring shown in Figure 8, the computer would calculate the distance from the center zone radius 302c to the inside data radius 306c and store this value as AY₁ for the corresponding ring, and also calculate the distance from the outside data radius 308c to center zone radius 302c and store this value as AY₂ for the corresponding ring. Then, the computer 52 searches the database for this (*Y_lf AY₂) pair. The database has a predefined digit associated with this pair. Using the AY*^ and ±Y values instead of simply the ring width allows for representation of more potential alphanumeric digits per ring because a ring of a certain thickness may be offset to the inside or outside of the center zone radius. For instance, if a ring is .006 inches wide, and the inside data radius to center zone radius difference (^Y*^) is .002 inches, the outside zone radius to center zone radius difference (**.Y₂) would be .004 inches. This combination (AY_1# AY₂) would represent a different digit than the same width ring with a ( *. _{l t} AY₂) pair of (.003, .003). Once the alphanumeric digit for each zone is determined, the computer 52 combines the digital to ascertain a multi-digit code, as represented in an action block 240.

Another data base contains the multi-digit codes in relationship to drill bit configurations and characteristics represented by the multi-digit codes. In other words, each drill bit configuration is assigned a multi-digit code. The multi-digit code is stored in the data base and references a particular drill bit configuration. The computer 52 uses the multi-digit code to search a data base which contains the tool configuration information, as represented in an action block 245. The cool configuration information is then displayed by the computer on a display.

Although certain tasks have been described as being carried out by the image processor 62 and the computer 52, these devices may comprise the same unit. The Cognex 2000/3000 series vision systems can be obtained as a board for use in a computer. Therefore, the image processor 62 and the computer 52 need not be separate units. Furthermore, although the task may be divided between the computer 52 and the image processor 62, further processing may be performed by the image processor 62, such as obtaining the AY₁₇ AY₂ pair from the inside data radii and outside data radii measurements.

This system can also easily be incorporated into any system which utilizes a computer. For instance, in the CNC machine environment, this system could be used in conjunction with the control computer to automatically verify proper tool selection, as further explained below.

A CNC machine for drilling printed circuit boards is the preferred implementation of the present invention. Figure 2 is a functional block diagram of a CNC drilling system 200 incorporating aspects of the present invention. Similar to the pattern recognition system 50 (Figure 1) , a pattern recognition system 51 has at least one lens 64 for an optical reader 65 and an image processor 66. In one embodiment, the lens is desirably connected to the optical reader 65 with a fiber optic cable 61. The fiber optic cable 61 allows the lens to be placed remotely from the optical reader 65. The CNC drilling machine 206 is conventional with a CNC controller 210 and a driller 212, as is well known in the art. In one embodiment, the pattern recognition system 51 interfaces with a CNC drilling machine 206 over an RS-232 line 208. As with the pattern recognition system 50 (Figure 1) , one embodiment of the pattern recognition system 51 com¬ prises a Sony XC-75/75CE CCD Vision Camera Module and a Cognex Model 2000/3000, while the CNC drilling machine 216 comprises an Excellon Mark VII. Figure 6 illustrates a perspective view of an exemplary CNC drilling station 90. Many drilling machines have a plurality of drilling stations. The drilling station comprises in summary, a stationary spindle assembly 104 which receives a drill bit 110, a stationary drill bit matrix 108 which holds the drill bits positioned by an operator (not shown) , a movable drilling table 106 where printed circuit boards are positioned for drilling. Figure 6 also shows a lens 64 and part of a fiber optic cable 61 mounted on the side of the spindle 104. The drill bit matrix 108 is shown with a plurality of drill bits 110 positioned in the matrix for use by the station 90. This configuration for CNC drilling machines is well known in the art.

Many other drilling machines are also well known in the art such as those made by Dyna-Motion, Hitachi, Posalux, and Advanced Control.

The overall operation of the system implemented in a CNC driller machine is illustrated in the flowchart of Figure 10. The driller is programmed to select a drill bit from the drill bit matrix and move the drill bit to a position where the lens 64 is directly above and very close to the tool to be selected. The system then determines if the tool is correct for examining the annular ring pattern on the heel of the tool, and the drilling machine then proceeds to load the tool into the spindle assembly 104, as is well known in the art. In an alternative embodiment, for drilling ma- chines which utilize a tool selector, to select a drill bit from the drill bit matrix, the tool selector with¬ draws the tool bit 110 and places it directly beneath the lens 64 of the pattern recognition system 51. Once the tool identification system 200 has determined that the bit is correct, the tool selector positions the bit in the spindle assembly 104, as is well known in the art.

When the tool is located for identification by the pattern recognition system 51, the lens 64 focuses an image onto one end of the fiber optic cable 61 to communicate the image through the fiber optic cable 61 to the optical reader 65. A digitized image is processed by the image processor 66 as described above, and the image processor 66 generates information (e.g. , the Aγ_χ, AY₂ pairs and possibly the alphanumeric code) about the ring pattern. If an alphanumeric code is utilized, the CNC controller 210 could also interpret the ^Y_]^, ^AY pairs into the alphanumeric code.

Once the information has been obtained from the pattern recognition system 51, the CNC machine controller 210 compares the information to expected information to verify that the drill bit 110 of the expected geometry was located in the selected position in the matrix 108. For instance, if the machine is programmed to select a drill bit 110 of expected geometry from a certain location in the drill bit matrix 108, it will first scan the heel 166 of the drill bit 110 to verify that the drill bit conforms to the expected geometry of the drill bit. If the bit is not correct, the controller 210 can signal the machine 212 to either keep scanning to find an appropriate drill bit 110 regardless of the drill bit position in the tool matrix 108, or it can stop the program and signal the operator for manual replacement of the tool.

The controller 210 can also interpret the ring code 180 for a system operator upon request. It will interpret the code into the various features such as the cutting aspect, the flute length, the web thickness, the helix or the drill diameter of the drill bit 110 and then display these on a display screen. In operation in a CNC drilling machine application, the operation of the present invention is integrated with the ordinary functioning of a CNC drilling machine. In existing CNC drilling machines, the CNC controller sends commands to a drilling station to cause the drilling station to perform certain functions. For example, when a hole is to be drilled, the CNC controller sends a command to cause the drilling station to obtain a drill bit from a specified location in the drill bit matrix followed by a command to cause the drilling station to drill a hole at a specified location on the printed circuit board. The present invention provides a system to verify that a drill bit obtained from a specific location in the drill bit matrix is the correct drill bit. Therefore, the process of drilling a hole in a printed circuit board, according to the present invention, comprises a number of steps. As illustrated in Figure 10, when a bit is to be selected, the CNC controller 210 causes the tool changer to select a tool, as represented in an action block 250, and to position the tool at the lens 64, as represented in an action block 252, so as to allow the pattern recogni¬ tion system 51 to analyze the ring pattern on the heel of the tool. The CNC machine then requests ^Y-^, ±Y₂ pairs or the alphanumeric code (depending on the embod¬ iment) from the recognition system 51, as represented in an action block 254. When the image processor 66 receives the command from the CNC controller 210, it generates an electronic representation of the image from the fiber optic cable 61, samples and digitizes the electronic representation to obtain a discrete digital representation suitable for digital storage and computations, and analyzes the digital representation of the image to identify the ring pattern. Identifying information (e.g., the AY_1# Y₂ pairs or the alphanu¬ meric code) is transmitted to the CNC controller via the RS-232 line 208. The CNC controller receives the information generated by the pattern recognition system 51 and determines whether the appropriate drill bit was selected, as represented in a decision block 256. In one embodiment, this involves comparing the alphanumer¬ ic codes (generated by the pattern recognition unit 51 or by the CNC controller 210) to expected codes. If the correct drill bit was chosen, then the CNC control¬ ler 210 issues commands to complete the drilling proc¬ ess with the selected bit, as represented in an action block 258. Otherwise, in one embodiment, the control routine aborts the drilling process and notifies the user that an incorrect drill bit was placed in the selected location of the drill matrix, as represented in an action block 260.

In an alternative embodiment, the CNC controller verifies the correct placement of all bits in the tool matrix prior to beginning the drilling operations. In this embodiment, the CNC machine need not re-verify a tool during use because verification took place before machining began. This system of encoding tools with information for reading by an optical scanner is not restricted to use in CNC drilling machines but would useful for other numerically controlled tooling systems and can also be used for improved inventory management and identification of tools or other objects.

Claims

WHAT IS CLAIMED IS:

1. An apparatus, comprising: a drill bit having an elongated body comprising (i) a shank portion at one end thereof, said shank portion being configured to fit within a spindle, and (ii) a flute portion at another end thereof, said flute portion being configured to cut material from a workpiece; and (iii) an optically readable indicia on said drill bit, said indicia being arranged to form an optically readable pattern corresponding to at least one characteristic of said drill bit, said pattern being one of a group of at least tens of patterns which together form a code for identifying the characteristics of different drill bits, each pattern within said group of patterns being comprised of at least one pattern element, substantially all of the pattern elements in said group of patterns having geometric similarity.

2. The apparatus of Claim 1, wherein said indicia comprises a pattern element comprising a ring.

3. The apparatus of Claim 2, wherein said ring has a reflectivity different than that of portions of said indicia surrounding said ring.

4. The apparatus of Claim 1, wherein said indicia on said drill bit comprises concentric rings which have a contrast sufficient for detection by a CCD camera.

5. The apparatus of Claim 1, wherein said indicia is disposed on one end of said shank portion, the area covered by said indicia being no greater than the area of the end of said shank portion.

6. The apparatus of Claim 1, additionally comprising an optical reader for detecting the pattern embodied on said indicia.

7. The apparatus of Claim 6, wherein said optical reader comprises a CCD camera.

8. The apparatus of Claim 6, wherein said indicia comprises a pattern element comprising a ring, and wherein said apparatus comprises means for comparing the location of edges of said ring to a reference location within said indicia to decode the pattern embodied in said indicia.

9. The apparatus of Claim 8, wherein said ring is disposed within one of plural concentric predetermined annular zones, and wherein said reference location is disposed midway edges of said one of said annular zones.

10. The apparatus of Claim 9, wherein said apparatus comprises means for determining the center of said indicia and for utilizing said center to identify said predetermined annular zones.

11. The apparatus of Claim 1, wherein said at least one characteristic of said drill bit comprises at least one of a plurality of descriptive features including cutting diameter, web thickness, flute length, specialized geometry, cutting aspect, manufacturer, date of manufacture, recommended feed, and recommended drill speed.

12. The drill bit of Claim 1, wherein said flute portion has a cutting surface configured to cut a printed circuit board.

13. The drill bit of Claim 1, wherein said shank portion has a finished diameter of .1248 inches

+/- .010 inches and has a finished overall length of 1.500 inches +/~ 0.020 inches.

14. A computer controlled drilling machine. comprising: a spindle for retaining a drill bit; a drill bit matrix for holding a plurality of drill bits in respective predetermined locations; means for storing predetermined drill bit information for each of said predetermined locations; means for optically reading information encoded on a drill bit in one of said predetermined locations; and means for comparing the optically scanned information with the stored information for said one of said predetermined locations.

15. A tool management control system for use with a computer numerically controlled CNC drilling machine which automatically changes a plurality of drill bits positioned in a tool changer, said system comprising: at least one drill bit which includes a shank, said shank having a finished diameter of .1248 inches +/- .010 inches and having a heel, and said drill bit having an overall finished length of 1.500 inches +/- .020 inches; said drill bit having optically readable information encoded upon said heel; a pattern recognizer capable of reading said optically readable coded information from said heel; and a driller machine controller unit connected to receive said optically readable coded information from said pattern recognizer, said controller providing control for the system.

16. The system of Claim 15, wherein said coded information includes at least one drill bit descriptive feature comprising cutting diameter, web thickness. flute length, specialized geometry, and cutting aspect.

17. The system of Claim 16, wherein said information further comprises drill bit manufacturer, date of manufacture, recommended feeds, and recommended drill speeds.

18. The system of Claim 15, wherein said drill bit comprises diamond, carbide, stainless steel, or a combination thereof.

19. The system of Claim 15, wherein said controller unit provides said coded information in decoded form for use by a driller machine operator.

20. A method of tool verification for a computer numerically controlled machine, which utilizes a plurality of tools positioned in respective locations in a tool matrix, said method comprising the steps of: (a) reading a pattern of geometrically similar pattern elements on one of said tools with an optical pattern reader capable of reading information coded in said pattern; and (b) transmitting the coded information to a computer;

(c) comparing the coded information with stored tool characteristic data corresponding to the location of said one tool to verify that the coded information on said one tool corresponds to said stored data for said location; and

(d) repeating steps (a) to (c) for substantially all tools in said tool matrix.

21. The method of Claim 20, wherein said computer comprises a driller machine controller unit and said tools comprise drill bits.

22. The method of Claim 21, wherein said coded information comprises at least one drill bit descriptive feature comprising manufacturer of the drill bit, manufacturing date, recommended feed rate, recommended speed, cutting diameter, web thickness, flute length, specialized geometry, and cutting aspect.

23. The method of Claim 21, further comprising the step of providing said coded information in decoded form to a driller machine operator.

24. The method of Claim 20, wherein the step of reading comprises reflecting light off said pattern.

25. An object having a concentric ring optical indicia thereon, said indicia comprising: a plurality of pre-defined zones concentrically extending from a center of said indicia; and optically discernable concentric rings of varying widths, each disposed within one of the plurality of pre-defined zones, the width of each ring providing information concerning an object to which said indicia is applied.

26. A method of coding a group of objects with indicia, each of a plurality of objects within said group of objects having at least one characteristic that is different from those of the remaining objects in said plurality of objects, said method comprising: marking each of said objects with a pattern comprising at least one pattern element having at least one circular boundary, comprising:

(a) locating said pattern element within a zone having at least one circular boundary;

(b) utilizing said pattern to define at least one characteristic of the object by performing one or both of the steps (i) of positioning said pattern element at a predetermined location within said predetermined zone, and (ii) sizing said pattern element to a predetermined size relative to the size of said zone.

27. The method of Claim 26, wherein the pattern element is ring shaped.

28. The method of Claim 26, wherein the circular boundaries of said pattern element and said zone are concentric.

29. A method of identifying characteristics of a group of objects coded with a pattern comprising plural pattern elements disposed within respective plural zones of said pattern, each of a plurality of objects within said group of objects having at least one characteristic that is different from those of the remaining objects in said plurality of objects, said method comprising:

(a) comparing at least one point on a circular reference line of a pattern element with at least one point on a circular reference line of a zone containing said first pattern element;

(b) repeating step (a) for another pattern element and another zone;

(c) utilizing the results of steps (a) and (b) to determine at least one characteristic of an object within the group of objects; and

(d) repeating steps (a) , (b) and (c) for another object within the group of objects.

30. The method of Claim 29, additionally comprising the step of locating the center of the pattern.

31. The method of Claim 29, wherein the circular reference line of the pattern element comprises a boundary of the pattern element and the circular reference line of the zone comprises a line bisecting the zone into two annular subzones, said method additionally comprising the step of determining whether said boundary of said pattern element is closer to the center of the pattern than the line bisecting the zone.

32. The method of Claim 29, wherein step (a) comprises comparing at least three points on the reference line of the pattern element with at least three points on the reference line of the zone.

33. The method of Claim 29, wherein the step of comparing comprises comparing at least one point on an optically discernable circular reference line with at least one point on an imaginary circular reference line.