Abstract:
There is provided an apparatus and method for detecting stuck tools in automated machining operations. When a machining operation on a workpiece is finished, the tools are retracted from the workpiece. Prior to moving the workpiece to another machining operation, a stuck tool detector is moved along a plane of separation between the machine head and the workpiece. If a stuck tool is present, the detector senses the stuck tool and sends an alarm signal of the stuck tool condition so that the operator or controlling microprocessor based system is alerted to the stuck tool. Appropriate actions or repairs can then be carried out.

Description:
This patent application claims the benefit of Provisional U.S. Patent application Ser. No. 60/162,566 filed on Oct. 29, 1999. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to systems for detecting failures in machining processes. More particularly, this invention relates to equipment and methods for detecting stuck tools in automated machining operations. 
     BACKGROUND OF THE INVENTION 
     Manufacturers use various machines to drill, bore, tap, and shape workpieces into final products. A particular machine may perform a single machining operation, such as drilling or tapping, or may perform a combination of machining operations. In a typical manual machining operation, an operator may secure a workpiece in a jig, or locating &amp; clamping device, and then position the workpiece adjacent to the head portion of the machine. A tool—e.g., a drill bit—then engages the workpiece piece and performs its particular machining operation—e.g., drilling. When finished, the tool is retracted from the workpiece and returned to its starting position in the head portion of the machine. Prior to moving or repositioning the workpiece, the operator is able to determine whether the tool is stuck in the workpiece. 
     In an automated machining process, several machining operations are commonly performed in tandem by the same machine or multiple machines. Also, the actual machining of the workpiece may be carried at one or more machining stations that comprise the machining process. Initially an operator, robotic device, or other suitable means secures the workpiece to a travelling pallet (sometimes referred to a jig), or to a locating and clamping device at a machining station. 
     Typically, when the workpiece is secured to a travelling pallet, or jig, both the traveling pallet and workpiece travel together through the machining process. In another commonly used machining process, the workpiece travels by itself through the machining process. In this case, the workpiece cooperatively encounters stationary locating and clamping devices that will secure the workpiece at each machining station in the machining process. When the particular machining operation is complete, the locating and clamping devices, that secured the workpiece, remain at the machining station while the workpiece advances to the next machining station. Those of skill in the art will recognize other ways to secure the workpiece for machining are also available. For example, a combination of the two methods just described may be used to secure the workpiece. 
     A microprocessor-based system then moves the secured workpiece through the automated machining process. The secured workpiece is positioned adjacent to the head of a machine. One or more tools extend from the head towards the workpiece in order to perform work on or to machine the workpiece. 
     When a machining operation is completed, the tools retract from the workpiece and return to their starting position within the head. Depending on the machine used, the tools may be completely or partially within the machine head in their starting positions. The microprocessor-based system then moves the workpiece being worked on to another machining station or repositions it for another machining operation on the same machine or machining station. When the automated machining process is completed, the workpiece is removed from the moving pallet or stationary clamping device. 
     Stuck tools are a major problem in automated machining processes. A stuck tool is a tool that has become imbedded in the workpiece when the machining operation is completed. In this state, the stuck tools are usually broken-i.e., the tool has separated from the head even though part of it may extend into the head. However, a stuck tool does not have to be broken. The tool may remain attached to the head for many reasons. In this case, the head, tool, and workpiece are connected to each other. 
     In addition, broken tools are not always stuck in the workpiece. A broken tool may be retracted or pushed into the head. A broken tool may fall out of the head. Also, some tools break into many pieces and fall to the ground. 
     Typically, a stuck tool extends out of the workpiece and into the head. If the workpiece is then moved, which usually is the next step in an automated machining process, the stuck tool will most likely rip apart the head, the workpiece, and surrounding equipment. The expense of repairing or replacing damaged equipment is significant. The production loss is even more costly in this scenario. 
     The prior art provides many devices for detecting broken tools. Some are acoustic devices for measuring the change in frequency of the tool or measuring the change in vibrations within the workpiece when the tool breaks. Some detectors are fluid based devices; they leak water or air when the tool breaks. Other detectors are electrical and measure changing electrical parameters. Some detectors use clutches or other mechanical devices to measure the speed and other changes when a tool breaks. 
     While these prior art devices may detect a broken tool, they are not well suited for detecting a stuck tool. They do not determine whether a tool is imbedded in the workpiece. It is noted that a tool may be broken but not imbedded in the workpiece. While it is good to know a tool is broken, it is very important to know whether the tool is stuck in the workpiece. Moreover, a broken tool detector does not detect when an unbroken tool is stuck in the workpiece. In this case, a broken tool detector would indicate everything is fine, permitting the workpiece to move and thus wreak havoc on the equipment. 
     Accordingly, there is a need in automated machining processes to be able to detect a stuck tool prior to movement of the workpiece to the next or subsequent machining operation. 
     SUMMARY OF THE INVENTION 
     The present invention provides an apparatus and method for detecting stuck tools in automated machining operations. There is provided a stuck tool detector for use in an automated machining process having an automated machining tool with reciprocating tools for work on a workpiece. The stuck tool detector is comprised of at least one stuck tool sensing member that selectively travels in a plane of separation between the workpiece and the automated machine. There is also at least one stuck tool sensor that is cooperatively connected to a corresponding stuck tool sensing member such that the stuck stool sensing member will actuate a corresponding stuck tool sensor when a stuck tool is encountered resulting in an alarm signal. 
     The stuck stool sensing member travel is controlled by the automated machining tool which uses a microprocessor based controller, and can travel in a vertical, horizontal, radial or angled direction. The stuck tool sensing member can be a trip-wire, a blade, a moveable guide member, an electromagnetic wave, a light beam, or a laser beam. The trip-wire can further be a slat, a wire, or a cord, while the moveable guide member can be made of metal, plastic, composite materials, or an engineered elastomer. 
     In operation, the machining tool is retracted from the workpiece at the completion of a machining operation. Prior to moving the workpiece to a subsequent machining operation, the stuck tool detector is actuated to determine whether there is a stuck tool between the workpiece and the machine head. If a stuck tool is present, the stuck stool detector will generate an alarm signal that will alert the operator of a stuck tool. Alternatively or additionally, the microprocessor based system may receive and sense the stuck tool sensor alarm signal and take the appropriate action to prevent the automated machining process from proceeding to the next machining operation and thereby damaging the workpiece and machining tool. 
     In a first embodiment, the stuck tool detector has a detector arm that has a first end and a second distal end. There is also a trip-wire that is attached between the first end and second distal end of the detector arms. The trip-wire is further attached to a stuck tool sensor. The stuck tool detector rotates about a rotating pivot pin to move the trip-wire along a plane of separation between the workpiece and the head. 
     In a second embodiment, a blade, or moveable guide member, is cooperatively positioned between a first and second guide, or blade guide, for sliding the moveable guide member or blade along a plane of separation between the workpiece and the head. At least one proximity sensor is positioned adjacent to one of the blade guides to determine the position of the blade. Alternatively, a stuck tool sensor may be used to sense when the moveable guide member has stopped moving due to a stuck tool. 
     In a third embodiment, a detector transport, moves a moveable guide member, or blade, along the plane of separation between the workpiece and the machine head. Stuck tool sensors, such as an up-sensor and a down-sensor, determine the position of the detector transport and thereby the position of the moveable guide member. 
     There is also provided a method for detecting a stuck tool. First, a machining operation on a workpiece is completed. Next, the machine tool is retracted from the workpiece toward the machine. The workpiece and head are then held in place. The microprocessor based system then operates a stuck tool detector to determine whether there is a stuck tool in the workpiece. The stuck tool detector then generates a signal. The operator or microprocessor based system then carries out certain actions based on the stuck tool detector signal received. If the signal indicates that there is a stuck tool, the operator is alerted to the stuck tool by an alarm, or the machine may be shutdown. Other means or a combination may be used to alert the operator of the stuck tool. If there is no stuck tool, the workpiece moves to the next machining step. 
     The method and embodiments of the present invention can also detect multiple stuck tools. For example, the moving guide member, or blade, of the second and third embodiments may be configured for different or multiple tools. In addition, multiple moving guide members or trip-wires may be used. A fourth embodiment shows multiple, detector transports and moving guide member configurations. Furthermore, the stuck tool detectors may be positioned to pass the blade or wire through the plane of separation horizontally, vertically, or in some other orientation. 
     The following drawings and description set forth additional advantages and benefits of the invention. Other advantages and benefits will be obvious from the description and may be learned by practice of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be better understood when read in connection with the accompanying drawings, of which: 
     FIG. 1 is a side view of a machine and workpiece according to the prior art; 
     FIG. 2 is a perspective view of a machine with a stuck tool detector according to a first embodiment of the present invention; 
     FIG. 3 is a perspective view of the machine in FIG. 2 showing a first embodiment of the stuck tool detector after it has passed the position of the tools; 
     FIG. 4 is a perspective view of the machine in FIG. 2 showing the stuck tool detector engaging a stuck tool; 
     FIG. 5 is a perspective view of a machine with a stuck tool detector according to a second embodiment of the present invention; 
     FIG. 6 is a perspective view of a machine with a stuck tool detector according to a third embodiment of the present invention; 
     FIG. 7 is a front view of a machine with a stuck tool detector according to a fourth embodiment of the present invention; and 
     FIG. 8 is a flowchart of a method for detecting a stuck tool according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a drilling machine  100  according to the prior art. Several elements such as a transfer mechanism, a moving pallet or stationary clamping device, and machine base are not shown. The drilling machine  100  has a head  120 , which forms a tool cavity  150 . A workpiece  110  is positioned adjacent to the machine head  120 . A “plane” of separation  140 , between the workpiece  110  and the machine head  120  separates the workpiece  110  and head  120 . A tool, or reciprocating tool,  130  is positioned inside the cavity  150 . The tool  130  is can be positioned either entirely inside the head  120 , as shown in FIG. 1, or partially outside the head  120  (not shown). In either case, the plane of separation  140  still separates the workpiece  140  and the machine head  120 . Those of skill in the art will also recognize that the plane of separation could instead be a curved surface or other irregular surface that lies between the workpiece  140  and the machine head  120 . 
     In operation, the tool  130  extends from the heading past the plane of separation  140  to engage the workpiece  110 . Although tool  130  is shown as a drill, it could be any other type of well known machining tool  130 . When the machine  120  finishes drilling the workpiece  110 , tool  130  is retracted from the workpiece  110  towards the head  120 . If tool  130  becomes stuck in the workpiece  110 , the tool  130  bridges the plane of separation  140 . Any subsequent movement would most likely destroy the head  120 , the workpiece  110 , and likely any surrounding equipment. 
     FIGS. 2-4 show a machine  200  having a stuck tool detector  240  according to a first embodiment of the present invention. The automated machine shown  200  has a head or machine head  220  with multiple tool cavities  235 . In these figures, a workpiece  210  is positioned adjacent to the machine head  220 . The workpiece  210  is secured in the moving pallet or stationary clamping device  270 , which is connected to a transfer mechanism  275 . Machine head  220  has tools, or reciprocating tools,  230  which extend from the machine head  220  toward the workpiece  210 . The tools  230  then retract from the workpiece  210 , after the machining operation is completed, toward the machine tool cavities  235  or head  220 . 
     The stuck tool detector  240  has a detector arm  242  and  244  that has a first end  245 A and a second distal end  247 A. The detector arm  240  could be viewed as having two arms  242  and  244  forming a substantially triangular shape. Those of skill in the art will recognize that the detector arm  240  could take on other shapes, for example a substantially semi-circular shape. There is also a trip-wire or trip-wire member  250  that is attached between the first end  245 A and second distal end  247 A of the detector arms. The trip-wire  250  is further attached to a stuck tool sensor  260 . In a preferred embodiment, the stuck tool sensor is a limit switch that is actuated when the trip-wire  250  encounters a stuck tool. The stuck tool detector  240  rotates about a rotating pivot pin  245  to move the trip-wire  250  along a plane of separation (shown in FIG. 1) between the workpiece  210  and the machine  220 . In this embodiment, the rotating pivot pin  245  is mounted to the machine  200  and controlled by the microprocessor based system that also controls the machine  200 . FIG. 2 shows the stuck tool detector  240  in its non-operating position. When operated, the stuck tool detector  240  rotates about the rotating pivot pin  245 . This passes the trip-wire  250  through the plane of separation  140  between the workpiece  210  and the machine head  220 . If no tools  230  are stuck in the workpiece  210 , the trip-wire  250  passes unopposed to the position as shown in FIG.  3 . If one or both of the tools  232  are stuck in the workpiece  210 , the trip-wire  250  encounters or catches the stuck tool  232  as shown in FIG.  4 . In this case, the trip-wire  250  actuates the stuck tool sensor  260  thus indicating a tool is stuck in workpiece  210 . In a preferred embodiment, the trip-wire  250  pulls on a limit sensor  260  to indicate a stuck tool  230 . 
     Actuation of the stuck tool sensor  260  results in an alarm signal. The alarm signal can alert an operator of the presence of a stuck tool  230 . Alternatively, the stuck tool signal can be sensed directly by the microprocessor based system which will take the appropriate action to prevent the automated machining operation from proceeding to the next machining operation until the stuck tool  230  condition is rectified. 
     FIG. 5 shows a machine  500  having a stuck tool detector  540  according to a second embodiment of the present invention. The machine  500  has a head  520  which forms one or more tool cavities  535 . A workpiece  510  is positioned adjacent to the head  520 . As with the previous embodiment, the machine head  520  has reciprocating tools  530  that extend from the machine head  520  toward the workpiece  210 . The tools  530  will retract from the workpiece  510  toward the machine tool cavities  535  or head  520  after the machining operation is complete. 
     The stuck tool detector  540  has a first guide  550  and a second guide  555 . In this embodiment, the first and second guides  550 ,  555  are blade guides that are substantially vertically positioned for sliding a blade, or other moveable guide member,  545  vertically along the plane of separation between the workpiece  510  and machine head  520 . Those of skill in the art will readily recognize that the first and second blade guides  550 ,  555  may also be substantially horizontally positioned such that the sliding blade  545  would move or travel horizontally. The first and second blade guides  550  and  555  can also be position in other orientations with respect to the vertical and horizontal. A stuck tool sensor  560  such as a proximity sensor or similar device determines the location of the moveable blade member  545 . Only one stuck tool sensor or proximity sensor  560  is shown in FIG. 5; however it will be readily apparent that more than one proximity sensor or stuck tool detector  560  may be positioned along the first blade guide  550 . Also, stuck tool detectors or proximity sensors  560  may also be positioned along the second blade guide  555 . 
     The moveable guide member or blade  545  may be made of any suitable material including metal, plastic, composite materials, or an engineered elastomer such as KEVLAR. While many materials may work, some will perform better for longer periods of time. The material should preferably have must have an appropriate balance of rigidity and resilience. The material should be rigid enough for its position to be ascertained accurately by the sensors. The material should preferably be resilient enough not to break or deform drastically when it hits a stuck tool. In addition, the moveable guide member blade  545  may be in the form of a slat, wire, cord, or other suitable shape. 
     If no machine tools  530  are stuck in the workpiece  510 , the moveable guide member blade  545  passes by the machine tool cavities  535  unopposed. The moveable guide member  545  travels along the plane of separation between the workpiece  510  and the machine head  520 . If one of the machine tools  530  is stuck in the workpiece  510 , the moveable guide member  545  stops against the stuck tool  530 . The stuck tool sensor or proximity sensor  560  determines the blade  545  has stopped and generates an signal, i.e., an alarm signal, that indicates that a tool  530  is stuck in workpiece  510 . 
     If the stuck tool sensor  560  generates an alarm signal, the operator will be alerted to the presence of a stuck tool  530 . Attentively, the alarm signal will be sensed directly by the microprocessor based system which will take the appropriate action to prevent the automated machining operation from proceeding to the next machining operation until the stuck tool  530  condition is rectified. 
     FIG. 6 shows a partial cross-sectional view of an automated machine  600  having a stuck tool detector  640  according to a third embodiment of the present invention. The automated machine  600  has a machine head  620  with a machine tool cavity  635 . A workpiece  610  is positioned adjacent to the head  620 . A reciprocating tool  630  is positioned to travel in the machine head  620  cavity  635 . As before, the reciprocating tool  530  extends into and out of the workpiece from the machine head  520 . 
     The stuck tool detector of this embodiment has a detector transport  650  connected to a moveable guide member or blade  665 . The detector transport  650  moves the moveable guide member blade  665  vertically along a plane of separation between the workpiece  610  and the machine head  620 . The detector transport  650  is operatively connected to an up-sensor  655  and a down-sensor  660 . The up-sensor  655  and a down-sensor  660 , determine the position of the detector transport  640  and thereby the position of the moveable guide member  665 . Those of skill in the art will recognize that one or more sensors  655  and  660  may be used to determine the position of the moveable guide member  665  along the plane of separation. When the detector transport  640  is in a down-position, the moveable guide member  665  can, depending on the particular application, can partially or fully cover the tool cavity  635  for the reciprocating tool  630 . For example, a partial cover is desired to permit hydraulic fluid, water, or air to escape from cavity  635 . If the reciprocating tool  630  is stuck in the workpiece  610 , the moveable guide member blade  665  will not be able to reach the down-position. 
     The detector transport  640  may be any suitable device or component that can move the moveable guide member  665  along the plane of separation between the workpiece  610  and the machine head  620 . For example, the detector transport  640  may be comprised of components that are pneumatic, electrical, magnetic, mechanical or hydraulic. The moveable guide member  665  may be made of any suitable material including metal, plastic, a composite material, or an engineered elastomer such as KEVLAR. While many materials may work, some will perform better for longer periods of time. The material should have an appropriate balance of rigidity and resilience. The material should be rigid enough for its position to be ascertained by the sensors. It should be resilient enough not to break or deform drastically when it hits a stuck tool. In addition, the blade may take other suitable shapes. 
     In operation, the detector transport  640  is normally in an up-position while a machining operation is performed on the workpiece. In the up-position, the moveable guide member or blade  665  is clear of interfering with the reciprocating tool  630 . Once the machining operation is completed, the detector transport  640  begins to move the blade  665  along the plane of separation toward a down-position. The up-sensor  655  senses when the detector transport  650  has left the up-position. 
     If reciprocating tool  630  is not stuck in workpiece  610 , the detector transport  640  reaches a down-position where the moveable guide member  665  partially or fully covers the tool cavity  635 . The down-sensor  660  will sense when the detector transport  650  has reached and is in a down-position. The detector transport  640  then returns to the up-position. The workpiece  610  then moves to the next machining operation. 
     If the reciprocating tool  630  is stuck in the workpiece  610 , the moveable guide member  665  will not permit the detector transport  650  to reach the down-position. If the detector transport  650  does not reach the down-position within a predetermined time period, a signal or alarm signal is generated. The predetermined time period starts when the up sensor  655  senses the detector transport  640  is no longer in the up position. The predetermined time period may include a buffer period to reduce the number of “false” determinations. If there is an alarm signal, the operator will be alerted to the presence of a stuck tool  630 . The alarm signal may also or alternatively be sensed by the microprocessor based system which will prevent the automated machining operation from proceeding to the next machining operation until the stuck tool condition is rectified. 
     FIG. 7 shows the front view of an automated machine  700  having a stuck tool detector  710  according to a fourth embodiment of the present invention. The machine  700  has a machine head  705  with a first tool cavity  715  and a second tool cavity  725 . Reciprocating tools (not shown) are positioned inside tool cavities  715 ,  725 . No workpiece is shown in FIG. 7, but it is understood that as in FIGS. 1-6, the workpiece is in front of the machine head  705  and that the reciprocating tools extend from the machine head  520  toward the workpiece  210 . The reciprocating tools will retract from the workpiece toward the machine tool cavities  715  and  725  after the machining operation is complete. 
     The stuck tool detector  710  has a first detector transport  740 , which engages a first connecting member or rod  745  to move a first moveable guide member  750  in a first guide or guide pair  730 . The first detector transport  740  moves the corresponding first moveable guide member  750  along a first plane of separation between the first tool cavity  715  and the workpiece. The first detector transport  740  is operatively connected to corresponding position-sensors (not shown), which determine the position of the first moveable guide member  750 . When fully extended in a first closed-position, the first moveable guide member blade  750  can, depending on the particular application, partially or fully cover the first tool cavity  715 . For example, a partial cover may be desired to permit hydraulic fluid, water, or air to escape from the first tool cavity  715 . Fully covering the first tool cavity  715  may be desired in other applications. If the reciprocating tool is stuck in the workpiece, the moveable guide member blade  750  will not be able to reach the first closed-position. When fully retracted by the first detector transport  740 , the first moveable guide member  750  completely uncovers first tool cavity  715 . 
     In this fourth embodiment, the stuck tool detector  710  has a second detector transport  755 , which engages second connecting member or rod  760  to move a second moveable guide member or blade  765 . The second detector transport  755  moves the corresponding second guide or guides pair  735  along a corresponding plane of separation between the second tool cavity  725  and the workpiece. The second detector transport  755  is operatively connected to corresponding second position-sensors (not shown), which determine the position of the second moveable guide member blade  765 . When fully extended, in a second closed-position, the second moveable guide member blade  765  can, depending on the particular application, partially or fully cover the corresponding second tool cavity  725 . For example, a partial cover is desired to permit hydraulic fluid, water, or air to escape from the second tool cavity  725 . Fully covering the second tool cavity  725  may be desired in some applications. If the reciprocating tool is stuck in the workpiece, the second moveable guide member  765  will not be able to reach the second closed-position. When fully retracted by the second detector transport  755 , the second moveable guide member  765  completely uncovers the second tool cavity  725 . 
     The detector transports  740  and  755  may be any suitable device or component that can move the moveable guide members  750  and  765  along the plane of separation between the workpiece and the machine head  705 . For example, the detector transports  740  and  755  may be comprised of components that are pneumatic, electrical, magnetic, mechanical or hydraulic. The blades  750  and  765  may be made of any suitable material including metal, plastic, composite materials, or an engineered elastomer such as KEVLAR. While many materials may work, some will perform better for longer periods of time. The material should have an appropriate balance of rigidity and resilience. The material should be rigid enough for its position to be ascertained accurately by the sensors. It also should be resilient enough not to break or deform drastically when it hits a stuck tool. In addition, the blades  750 ,  765  may take other suitable shapes. 
     When a machining operation is performed, detector transports  740  and  755  open their respective blades  750  and  755  so the tool cavities  715 ,  725  are completely uncovered and the moveable guide member blades  750  and  765  do not interfere with the reciprocating tools. Once the machining operation is completed, the detector transports  740 ,  755  close the moveable guide members  750  and  765  to cover the respective tool cavities  715  and  725 . If no reciprocating tools are stuck in the workpiece, the moveable guide member blades  750  and  765  will reach their respective first and second closed-positions. The first and second position sensors will sense the closed position of the blades  715  and  725 . The moveable guide member blades  715  and  725  will move away from the tool cavities  715  and  725  along the respective first and second planes of separation and the workpiece will move into position for the next machining operation. 
     As before, If one or more of the machine tools are stuck in the workpiece, the corresponding first or second moveable guide member  750  and  765  will stop against the stuck tool. The first or second position-sensors will determine that the moveable guide members  750  and  765  have not reached a first and/or second closed-position. One or more position-sensors will then generate a signal or alarm signal that indicates that a tool is stuck in the workpiece. If the position-sensors generate an alarm signal, the operator will be alerted to the presence of a stuck tool. Alternatively, the alarm signal will be sensed directly by the microprocessor based system which will prevent the automated machining operation from proceeding to the next machining operation until the stuck tool condition is rectified. Other means may be used to alert the operator, such as completely shutting down the automated machine. 
     FIG. 8 shows a flowchart for a method to detect a stuck tool in an automated machining process according to the present invention. In step  810 , a machining operation on a workpiece is completed. At this point, the tool (e.g.,  230 ,  530 ,  630 ) has retracted or is supposed to have retracted completely from the workpiece and towards the tool cavity (e.g.,  235 ,  535 , 635 ) in the head (e.g.,  220 ,  520 ,  620 ). 
     In step  820 , the workpiece (e.g.,  210 ,  510 ,  610 ) and head (e.g.,  220 ,  520 ,  620 ) are held in place. 
     In step  830 , a stuck tool detector is operated to determine whether a reciprocating tool is stuck in the workpiece. This determination may be made using any of the embodiments described in FIGS. 2-7. Other means to physically determine whether a stuck tool is present may be used, e.g., laser, fluid (water, air, etc.), and acoustic methods may be used to determine whether there is a stuck tool. However, they are not very reliable given the machine environment. Metal chips and other debris may block or deflect the laser or fluid. Acoustic signals may be misread or misinterpreted. 
     In step  840 , the operator or the microprocessor based system receives an alarm signal from the stuck tool detector indicating that a stuck tool is sensed. The alert may be an alarm such as a flashing light or horn. The alarm signal may also be a signal to stop the machine, or the alarm signal may actually stop the machine. Further, the alarm signal may instead stop the machine and the surrounding equipment. Those of skill in the art will recognize that there may be other types or a combination of alerts send to the to the operator or microprocessor based system. For example, in many automated machining processes, it is desirable for the alert to notify the operator and to prevent the workpiece from proceeding to the next machining operation until the stuck tool condition is addressed and rectified. In step  850 , the automated machining process continues to the next or subsequent machining operation since no stuck tool was detected. 
     The method and embodiments of the present invention may detect multiple tools having various configurations on the machine head. For example, the moveable guide members or blades  545 ,  630  may be cut or otherwise configured for multiple tools  530 ,  630  on the machine head  520 ,  620 . In addition, multiple moveable guide members or blades (not shown) may be used. For example, the fourth embodiment of FIG. 7 illustrated an automated machine and workpiece with multiple stuck tool detectors (two detectors shown in this embodiment) that can each sense a stuck tool in an automated machine with multiple reciprocating tools. While the embodiments of FIGS. 2-6 illustrated automated machines and workpieces that have a singular stuck tool detector that can senses stuck tools in automated machines with multiple reciprocating tools or with one reciprocating tool (not shown). Also, those of skill in the art will readily recognize that the multiple tool cavities corresponding to a reciprocating tool may all lie in the same plane or may each lie in different planes between the tool cavity and workpiece. 
     Additionally, it will readily apparent to those skilled in the art, that the stuck tool detector could instead use a non-mechanical sensing mechanism to encounter and detect a stuck tool, e.g., electromagnetic (EM) waves, a light beam or a laser sensor beam. The non-mechanical sensing mechanism could be used instead of the trip-wire, blade, or moveable guide member. In this case, the presence of a stuck tool would interfere or interact with the EM waves, light beam or laser sensor beam and result in an alarm signal, indicating the presence of a stuck tool. 
     The present invention has been described and illustrated by way of certain examples of preferred embodiments relating to automated machining processes only. However, the invention may be used on other processes that involve the machining of workpieces other than engine parts. Additional advantages will be readily apparent to those skilled in the art, who may modify the embodiments without departing from the true spirit and scope of the invention. Therefore, this invention is not limited to the specific details, representative devices, and illustrated examples in this description. The present invention is limited only by the following claims and equivalents.