Abstract:
A control system is provided for a laser-equipped machine tool which is capable of preventing self-burning. The temperature of the workpiece proximate the cut is monitored, and a numerical control compares the actual workpiece temperature to a prestored temperature limit, empirically determined, which is predictive of the onset of self-burning. If the workpiece temperature approaches or reaches the limit, an abort signal is generated. Upon generation of an abort signal the control processor deenergizes the laser to prevent commencement of self-burning. In addition the processor stores the cutting parameters and the coordinate locations of the aborted cut, so that the processor can later return to finish the cut, and sets a cool-down timer. The processor then causes movement to a next available cutting position, tests the temperature at that position, then commences cutting. When cutting in the second location is complete, if a cool-down timer has expired, the cutting head is traversed to the aborted position, and then the processor retrieves stored information and completes the cut.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to machine tools, and more particularly relates to machine tools using lasers for cutting metal and other materials. 
     BACKGROUND OF THE INVENTION 
     Laser-equipped machine tools are often used to cut parts from sheet metal and plate. In such machine tools a laser beam, concentrated by a focusing lens or mirror to a small diameter spot, is directed to position the focal point above, on or below the surface of the material to be cut. The laser beam is directed by the focusing optic through a nozzle disposed immediately above the workpiece, with a pressurized gas being directed through the nozzle, typically coaxially with the laser beam, to assist making the cut. The pressurized gas interacts with the laser beam and material, facilitating the cutting process, and creates a high velocity stream that carries the melted material away from the cut. 
     Laser-equipped machine tools are usually Computer Numerically Controlled, and are manufactured in many configurations and sizes and with lasers of various types and power. The present invention has applicability to all such-types, but will be described in association with one configuration, “flying optics”. In that configuration the cutting head is adapted for movement along one axis, such as the Y-axis which is mounted on a bridge adapted for movement in an orthogonal, X-axis. The work is supported on a stationary pallet or table below the bridge. Movement of the cutting head is coordinated with movement of the bridge to define a precise path on the part. The cutting head and laser are controlled to pierce and cut the metal to form holes and shapes in the material, and then to cut the part from the material. 
     Many same or different parts of common thickness and material type may be cut from a sheet or plate. Such groups of parts are commonly called a nest. Left over material, after the parts have been removed, is called a remnant or a skeleton. A small piece of scrap that falls from a hole cut in a part is called a slug. Remains of material from the cut is called slag. Resolidified material clinging to the part is called dross. The mixture of slugs and slag residue from cutting sheet material is generally called scrap. 
     Parts can be categorized as two classes, those that have one or more holes or shapes cut within the part boundary and those that consist of a boundary only, no holes or shapes within the part. Nests are cut such that holes within a part are cut first, then the boundary is cut. This is to maintain control of the part until all internal features are cut to insure accuracy of the part. If the boundary were cut first the part could shift, or worse tip, on the table making it impossible to accurately cut features within the part without additional setups or intervention. 
     Sometimes parts have internal holes or features that could result in substantial scrap. It is common to reduce the amount of scrap by placing one or more smaller parts in these areas. It is possible to have several sub groups of parts that are within parts that are in turn within parts again, etc. until the most practical and efficient use of the material is made. The cutting process for these part groups is the same, in that the parts are cut from inside out. First the holes and internal features are cut in the smallest or furthest part toward the innermost part of the part group, then the boundary of that part(s) is cut, then the next innermost holes or internal features are cut, then the boundary of that part(s), etc., until the boundary of the top level part is cut. A nest could contain none, one, or several instances of groups with parts placed inside another to make efficient utilization of material. 
     Software programs exist for automatically creating nests of parts. Some automatically evaluate the percent of material utilization in the nest. If targeted utilization has not been achieved the program discards the nest, rearranges the parts and evaluates material utilization until a minimum percentage is achieved. After a satisfactory nest has been created the software will create the program for the laser cutting machine. Some such programming systems also have the ability to determine a cut path such that the cut or machine movement never has to cross the cut line. This is beneficial in reducing risk of the cutting nozzle colliding with parts that tip on the work support and project above the surface of the work being cut. 
     As higher power lasers with beam qualities suitable for cutting are developed, cutting machine technology advances to cut greater thicknesses of material. For example, it is now possible to cut steel plate 1 inch thick at 24 inches per minute with a cutting machine equipped with a 6-kilowatt laser. 
     When cutting thick carbon steel plate, the cut quality can rapidly deteriorate when a phenomenon characterized as “self-burning” occurs. Self-burning is a condition that occurs when control of the cutting process is lost and there is a thermal runaway producing a wide kerf which is still closed at the bottom. 
     The self-burning phenomenon will sometimes clear itself. Sometimes the clearing happens while cutting an edge or arc of the part, but it usually happens at a corner. Cutting velocity decreases when a corner is encountered. Often the program includes a dwell in a corner allowing the lagging tail of the cut to catch up with the leading edge of the cut. 
     Sometimes control of the cut can be regained by the machine operator intervening to reduce cutting speed with manual feedrate override. Often control of the cut cannot be regained without stopping the process. 
     When self-burning clears on its own or is cleared by the operator, it leaves a defect on the cut edge. When not noticed, self-burning can result in the production of unacceptable parts which must be reworked or scrapped. 
     The self-burning phenomenon is troublesome. The machine operator must watch the process and be ready to respond to problems or run the risk of cutting unacceptable parts. In this era of production the operator is often expected to run multiple machines unloading cut parts, loading fresh material, loading the next part program, or even unloading trucks and cleaning the area while the machines cut. 
     The inventor is aware of at least one method of dealing with self-burning on an automatic basis. It is based on the visible light generated at the cut when self-burning commences. The visible light is reflected back through the cutting lens into the beam path. During normal cutting little visible light is reflected. A sensor is placed above the cutting lens to sense the light reflected from self-burning. It sends a signal to the CNC. In response to the signal, the CNC stops the cut, repositions the cutting head a short distance back along the cut path, then restarts the cut and again attempts to cut through the problem area. CNC setup parameters determine the number of attempts made to make the cut. If the number of attempts is made without success, the CNC will stop the program, send an error message to the CNC operator&#39;s screen, and wait for operator intervention. 
     While this method of dealing with self-burning is beneficial, it remains problematic. First, it detects self-burning after its onset, therefore, the best that can be expected is to produce a part with a small defect on the edge. Second, since self-burning has commenced, it reduces the chance of successfully cutting through the area seconds later. 
     SUMMARY OF THE INVENTION 
     The objective of the present invention is to provide a laser-equipped machine tool having ability to avoid self-burning. 
     Observation of the self-burning phenomenon and examination of parts and skeletons have led the inventor to postulate certain theories and to arrive at several conclusions, as follows. 
     When the sidewalls of the cut absorb too much heat from the process they melt and fall into the cut. The sudden rush of molten metal is too much to escape from the narrow kerf and closes the cut. The process then feeds itself. With the kerf closed all the heat produced by the laser beam remains in the kerf instead of being removed with material exiting the cut. Oxygen assist gas continues to feed the thermal runaway. This creates a boiling mass of molten steel some of which, in the form of sparks and globules of molten metal, is blown upward, out of the cut, by the assist gas. This makes the self-burning phenomenon visually very noticeable. There is also a noticeable change in the sound of the process. 
     The inventor has observed that the area in which self-burning occurs is often predictable. Self-burning usually occurs when the cut enters an area which has been recently heated by cutting a nearby feature, wherein the material remains hot. Experiments have shown that it is possible to monitor the temperature of the plate and thereby assess the risk of onset of self-burning when cutting into the area. 
     Tests were conducted in which an infrared thermometer was used to monitor the surface temperature of a plate while it was cut. The infrared thermometer was selected to assure it would not detect the laser beam. Monitoring the temperature directly in front of the cut path while cutting 12 mm thick construction grade carbon steel, it was observed that cut quality started deteriorating above 300° F. Around 400° F. the cut was lost due to onset of self-burning. In a test involving the same type material except 25 mm thick, it was observed that stability of the cutting process started deteriorating around 180° F. Dross started forming on the lower edge above 200° F. At 220° F. there was high risk of onset of self-burning. After onset of self-burning the temperature rose, within two seconds, to 350-400° F. 
     It was concluded that the temperature differences between 12 mm and 25 mm and the onset of cut deterioration and self-burning were due to the thickness of the part and the thermal conductivity of the material. It appears that the material was hotter toward the bottom of the part. Heat must therefore be transferred by conduction to the upper surface. The rate of conduction and thus the temperature measured at the surface is dependent upon the thickness and the thermal conductivity of the material. 
     Based on these observations and conclusions, the objective of this invention is to provide a method and apparatus to assess the risk of the onset of self-burning and to take corrective measures to avoid self-burning. 
     A more detailed object of the invention is to provide a method and apparatus to assess the risk of self-burning and to automatically take action such that onset of self-burning is avoided by aborting the cut, moving to another area of the plate to resume cutting, then after a time lapse sufficient to allow the aborted area to cool, returning to the abort point and resuming cutting the aborted program. 
     An object of the present invention is to provide a laser cutting tool with sensing devices capable of detecting a condition in the workpiece indicative of the risk of self-burning onset, and to control or abort the cut as the sensed conditions predict that self-burning is imminent. 
     It is an object of the present invention to provide a laser-equipped cutting machine having a control system which senses temperature conditions in the workpiece indicative of the risk of onset of self-burning, and a control system which aborts the cut in an ordered, recoverable manner, then repositions the cutting head to begin cutting in a different area of the workpiece. 
     It is a resulting object to produce a high power laser-equipped machine tool capable of producing high quality cuts in thick material with high efficiency. 
     A general but subsidiary object of the present invention is to use a non-contact temperature sensor to measure the plate temperature in the region of the cut to predict the risk of onset of self-burning. 
     A more particular object is to utilize one or more infrared temperature sensors, selected to assure the IR wavelength used will not detect the laser beam, to monitor the temperature of the plate while it is cut to assess the risk of onset of self-burning. 
     It is a feature of the invention that the cutting head is equipped with a temperature sensor that senses the temperature of the workpiece in the area of the cut. The control system has a cutting parameter library which includes material cutting parameters and specifically includes temperature limits for warning or aborting a cut to avoid the onset of self-burning. If the temperature of the workpiece approaches the limit temperature, steps are taken to terminate the cut. In order to enhance machine efficiency, if the cut is aborted, the control system repositions the cutting head to another feature, part or group of parts, and begins to cut at that point. Before repositioning the cutting head, sufficient information is captured that the cutting head can be returned to resume the cut. 
     It is a further feature of a preferred embodiment of the invention to provide a laser-equipped machine tool wherein the control system maintains two temperature limits, a warning temperature limit and an abort temperature limit. If the workpiece reaches the abort temperature limit, the cut is stopped immediately, and the CNC repositions the cutting head to a different feature, part or group of parts identified by program flags. The warning temperature limit is lower than the abort temperature limit. If the warning temperature limit is reached, the CNC allows the machine to finish cutting the feature, then sets a flag at that location, then moves the cutting head to another flagged location to resume cutting. If the abort temperature limit is reached while trying to complete the cut, the cut is immediately aborted, the CNC sets a flag at that location then moves the cutting head to another flagged location to resume. 
     It is another detailed feature that upon jumping to another flagged location or upon return to a previously aborted location, the CNC reads the plate temperature, compares the reading to stored warning and abort values to assure the temperature is within acceptable limits, and if it is not, moves the machine to another flagged location to proceed. 
     These and other objectives, and features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a front elevation of a laser-equipped machine tool incorporating a control system exemplifying the present invention; 
     FIG. 2 is a plan view of the machine tool of FIG. 1; 
     FIGS. 3A-3D are diagrammatic cross-sectional views of a workpiece useful in understanding the self-burning problem; 
     FIGS. 4A and 4B are bottom and elevation views of the cutting nozzle showing an array of temperature sensors; 
     FIG. 4C is a diagram showing the coverage areas of the sensors of FIGS. 4A and 4B; 
     FIG. 5 is a schematic block diagram illustrating certain system aspects of the control system of the present invention; 
     FIG. 6 is a flowchart illustrating the process of the invention in its broad and basic form; 
     FIG. 7 is a block diagram representing aspects of the invention in its broad and basic form; 
     FIG. 8 is a flowchart depicting an exemplary embodiment of the logic employed by the control system of the present invention; and 
     FIGS. 9A-9G are diagrams illustrating a parts layout to be cut from a plate, and are useful for understanding the flagging and restart aspects of the present invention. 
     While the invention is susceptible of various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention as defined by the appended claims. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and with specific reference to FIGS. 1 and 2, a preferred embodiment of the present invention is generally depicted as embodied in machine tool  20 . By way of background machine tool  20  includes a laser source  22  that directs a high power laser beam to a collimator  24 , which in turn directs a collimated laser beam  26  to first bending mirror  27 . Laser beam  26  is then directed to cutting head  30  which includes a second bending mirror  28  and a focusing optic  32  (not shown) which focuses the laser beam onto workpiece  34  which is supported on a pallet  36 . Laser beam  26  is projected through a nozzle  29  at the base of the cutting head along with a supply of oxygen assist gas. The focal point of the laser beam is adjusted so that it is approximately at the surface of the workpiece. The position of the focal point can change under the control of the CNC, for particular machining purposes or functions. The laser beam and assist gas interact with each other and with the metal to cut through the workpiece  34 . 
     A machine base  33  supports the operative elements discussed thus far, including the pallet  36  and a bridge  31  that supports the cutting head  30 , along with additional elements such as the slag collection bed, and a slag removal system. In summary, the cutting head  30  is adapted to traverse the width of the machine (up and down as shown in FIG. 2) by moving along the bridge member  31  and the entire bridge is adapted to translate left to right as shown in FIG. 1, such that the cutting head  30  is capable, under the direction of the computer control, to trace virtually any path along the surface of the workpiece. The laser is controlled during movement of the cutting head to cut the patterns in the workpiece defined by the CNC program. The illustrated machine configuration, while preferred, is representative of various machine configurations capable of relatively traversing a laser beam and a workpiece for cutting patterns as directed by a CNC. 
     Referring to FIG. 3A, there is shown in enlarged scale a diagrammatical representation useful in understanding the mechanism of a laser cut. The workpiece is illustrated at  34 , and is shown to be relatively thick. The nozzle  29  is positioned above the workpiece. The laser beam, illustrated at  60 , projects through the nozzle opening along with a flow of assist gas surrounding the beam and directed into the forming kerf  64 . The laser beam  60  is focused very sharply at about the surface  34   a  of the workpiece. The drawing illustrates the divergence of the beam in somewhat exaggerated fashion to better show the position of the focal point  61 . The highly focused energy almost instantly heats a column  62  through the workpiece immediately below the point of incidence of the laser beam. During normal cutting, the nozzle and thus the heated column traverse a path defining the cut. The column is open at the bottom side and is translated into the work in the direction of the cut. The assist gas serves to cooperate with the laser beam and the workpiece  34  in vaporizing and melting the material within column  62 , the cut zone. The material is intensely melted and the assist gas blows it out of the bottom forming the kerf  64 . Kerf  64  has substantially parallel, relatively smooth sidewalls  64   a  as shown in FIG.  3 B. It is noted in passing that adjusting the position of the laser beam focus with respect to the thickness of the workpiece  34  can alter somewhat the shape of the kerf  64 , by making it, for example, slighly cone shaped at the top or at the bottom. However, when the system is operating correctly, the walls  64   a  will be substantially square and relatively smooth. 
     In accordance with the invention, the temperature of workpiece  34  in the area of the cut is used to predict the onset of self-burning. FIG. 3C illustrates the mechanisms at work. The material, illustrated by the hatched areas  67 , can become too hot and start melting and falling into the kerf, schematically illustrated in FIG.  3 C. As the temperature of the workpiece increases more sidewall material melts and falls into the kerf. When too much material melts the assist gas can no longer blow the material out the bottom of the kerf and a pool, schematically illustrated in FIG. 3C as  66 , forms at the bottom of the kerf. The kerf is closed. Pool  66  then absorbs all the energy from the laser beam and the exothermic reaction of the assist gas and becomes still hotter, to the point of boiling and burning. The sidewalls absorb more energy, melt and collapse into the kerf. The fact that the sidewalls have collapsed is illustrated by the wider kerf  64   a  in FIG. 3C as compared to the kerf  64  of FIGS. 3A and 3B. The process feeds itself and is out of control. With the kerf closed all the heat produced by the laser beam remains in the kerf instead of being removed with material exiting the cut. Oxygen assist gas also feeds the thermal runaway. This creates a boiling mass of molten steel some of which, as sparks and globules  63  of molten metal, is blown upward, out of the cut 
     FIG. 3D diagrammatically illustrates the nature of a cut formed during self-burning, where the sidewalls  69  are neither parallel nor smooth, and dross  70  may form on the top of the sheet or splatter to other areas of the workpiece near the cut. Such a cut is unacceptable. 
     In practicing the invention, a high power laser cutting machine tool, such as that illustrated in FIG. 1, is provided with a control system capable of assessing risk of onset of self-burning before self-burning commences, and further capable of taking action to prevent the onset of self-burning. Digressing briefly to FIG. 5, there is shown an automatic control system  50  exemplifying the present invention in juxtaposition to a diagrammatically illustrated machine tool  20 . The machine tool, as previously described, includes a laser  22 , a cutting head  30  having a nozzle  29  positioned proximate a workpiece  34  carried on a pallet  36 . 
     The conventional components of the control system  50  are illustrated in upper block  51 , and include a laser beam control module  51   a  for controlling the on/off state of the laser, in some cases the laser intensity, and in some cases the laser focus. A second module  51   b,  also conventional, includes a multiple axis beam/workpiece position control. In the illustrated embodiment the position control traverses the cutting head with respect to the workpiece, whereas it is also possible to traverse the workpiece, or some combination of the workpiece and cutting head. The remainder of block  51  is available for other modules which are not of significance in the present description. 
     In practicing the invention, the control system  50  is provided with a further software module  52  which may interact with other modules within the control system  50 , and which serves to avoid the onset of self-burning. The module  52  is shown as including two specifically identified modules. A first risk assessment module  52   a,  is adapted to assess the risk of the onset of self-burning. As will be described in greater detail below, the module  52   a  operates through a sensor adapted to monitor the cutting process to continuously assess the risk of the onset of self-burning. In the preferred embodiment, the sensor comprises a plurality of temperature sensors  71 - 73  adapted to sense the temperature of the workpiece near the cut. The risk assessment module  52   a  contains empirical data, in the form of tables or the like, which store the temperature profiles associated with the approaching onset of self-burning for workpiece materials of various types and thicknesses. 
     Further in practicing the invention, a second module  52   b  is provided within the control system for the purpose of cooperating with and responding to the risk assessment module  52   a.  The responsive module  52   b  can take various forms. In the preferred embodiment, the risk assessment module  52   a  contains two sets of temperature limits, a first warning limit and a second abort limit. When configured with a risk assessment module of that type, the response module  52   b  takes the necessary action to avoid the onset of self-burning without overcomplicating or interfering with the parts program. Thus, in the preferred embodiment, the responsive module will respond to the sensed temperature reaching the warning limit by continuing the cut until a convenient break point is reached (usually at a geometry intersection). At that point, if the temperature remains at or above the warning level, the responsive module  52   b  will cooperate with the modules  51   a  and  51   b  to terminate the cut and to traverse the cutting head/workpiece relationship to resume cutting at a new location. The responsive module  52   b  also responds to the temperature reaching the abort limit by terminating the cut immediately, storing sufficient cutting parameter and position data to be able to resume the cut, then, if desired, traversing to a new location on the workpiece to resume cutting. 
     The module  52  is shown as having additional functional locations for other modules, as needed, to configure a particular implementation of the invention. However, in its broadest sense, the software control represented by the block  51  performs the normal cutting functions, and has associated therewith two primary modules, one a risk assessment module which responds to conditions relating to the cut to determine proximity to the onset of self-burning, and a second, responsive to the first, which takes the necessary action to avoid the onset of self-burning. 
     While FIG. 5 shows the structure of the machine tool and control system constructed in accordance with the invention, FIG. 6 is a flowchart demonstrating the functionality of that system in practicing the invention. The flowchart represents the functionality at a reasonably global level, as will be seen. After initiation, the process proceeds to a first step  56  which involves all of the aspects of the machine tool in controlling the cut. As is conventional, the beam/workpiece position is controlled in order to trace the beam across the workpiece in the desired path. Other parameters controlled are the beam characteristics itself (such as by collimating the laser beam), the nozzle height above the workpiece, the power of the laser, the type and flow of assist gas, and all of the other elements which would be well understood by those of skill in this art. 
     In practicing the invention, a step  57  is continuously performed to monitor the cut, by monitoring a condition of the workpiece. In the preferred embodiment, the monitoring step  57  is performed by continuously monitoring the temperature of the workpiece near the cut. 
     As the monitoring continues, the step of assessing the risk of self-burning  58  is also continuously performed. The assessment is preferably performed on the basis of empirical data in which the variables are material type and temperature near the cut. This data, collected by empirical testing of the type described in an earlier portion of this specification, is stored in memory and accessed during cutting to set specific limits for the actual machining conditions. Stored temperature limits are associated with the step  58  which determines the risk of onset of self-burning. Step  58  performs its assessment by performing the test—is the cut approaching self-burning. If it is not, a negative result of the test branches the program back to the control cut step  56 . Thus, this loop continues to cycle in normal operation while the system continues to monitor and assess the risk of onset of self-burning, but has not yet found a condition in which the self-burning condition might be approached. 
     However, if the test  58  indicates a positive result, the program branches to a step  59  which, in its broadest sense, either alters or terminates the cut prior to the commencement of self-burning. For example, if the assessment indicates that self-burning is imminent, the cut will be terminated immediately, and the program will store sufficient information to resume the cut at a later time. If the assessment indicates that the temperature is rising, but self-burning is not yet imminent, the cut program is altered by preparing to abort the cut, but continuing the cut until a convenient stopping point is reached, then aborting the cut. The stopping point is usually at a geometry intersection (where the parts program switches from one cut to another). This allows the machine to terminate the cut at a location which is least likely to create a defect or discontinuity in the finished part. 
     Having taken a corrective actions in the step  59 , the program proceeds to a step  59   a  to test whether all cuts have been concluded. If they have not, and additional cutting remains to be done, the program returns to the control cut module  56  to continue cutting on the altered path determined by the module  59 . When all cuts are completed, a positive test from the module  59   a  branches the program to its termination routine. 
     In summary, the program steps of FIG. 6 illustrates the association of the normal machining functionality of a high power laser equipped machine tool with the steps of sensing the condition, preferably the temperature of the workpiece, proximate the cut, which condition is predictive of the onset of self-burning, and taking corrective measures prior to the onset in order to prevent self-burning. 
     For monitoring the condition of the workpiece at the cut, it is preferred to utilize temperature sensors, preferably of the non-contact variety, as will now be described. The cutting head  30 , FIG. 1, can move in any direction across the surface of the workpiece. Three infrared temperature-measuring devices,  71 ,  72 , and  73 , shown diagrammatically in FIGS. 4A and 4B, having a temperature sensing range of 100° F. to 500° F., are mounted in a triangular arrangement about the cutting head  30 . The infrared detectors are mounted such that the temperature sensing areas,  72 A,  72 B, and  72 C, FIG. 4C, on workpiece  34  are approximately tangent to and surround nozzle  29  for monitoring the temperature ahead of cutting kerf  64 . The sensing areas overlap such that the temperature can be monitored in the area near the cut regardless of the direction of the cut. 
     Infrared detectors of this temperature range typically respond to infrared light of 7 to 14 micrometer wavelength. CO 2  laser light, wavelength 10.6-micrometer, can interfere with accurate temperature measurements. The selected sensors are preferably filtered to avoid sensing the CO 2  laser beam at 10.6 micrometers. 
     The use of infrared temperature sensors and the positioning illustrated in FIGS. 4A,  4 B and  4 C represents the currently preferred arrangement. However, it will be apparent to those skilled in the art that the invention is not limited to use of infrared detectors or to the positioning of those detectors with respect to the cutting head; the invention most broadly deals with sensing conditions near the cut and taking corrective action before, not after, onset of self-burning. 
     Turning now to FIG. 7, certain elements of the machine tool and the control system are shown in association with a diagrammatically illustrated workpiece  34  juxtaposed to a cutting head  30 . 
     Shown diagrammatically and in simplistic fashion in FIG. 7, workpiece  34  is divided into a plurality of nests  42 . Smaller pieces  44  and  44 A can be cut from the waste material of rectangular opening  46  of larger rectangular part  47  and thereby reduce the amount of waste material  48 . 
     As shown in FIG. 7, servomotor  84  is drivingly connected to cutting head  30  to control the position of cutting head  30  with respect to workpiece  34 . One of ordinary skill in the art will readily recognize that first and second motors are typically employed to control movement of cutting head  30  on the X and Y axes respectively. For simplification, only one motor is shown. The axes of motion of the cutting head over the workpiece are indicated at  38  and  40 . Servo drive  86  is electrically connected to processor  88 , which is part of the overall computer control system  50  of machine tool  20 . Depending on the signals directed by processor  88  to drive  86 , the motion of servomotor  84  and thus position of cutting head  30  can be controlled with respect to workpiece  34 . 
     It is also shown in FIG. 7 that temperature sensors  71 - 73  are connected to processor  88  by input/output module  92 . Processor  88  is continually updated as to the temperature of the workpiece surface near the kerf  64 . Memory locations  94  are provided to, among other things, store the warning and abort temperature limits for avoiding self-burning. Comparator  96  represents the mechanism by which processor  88  can compare the measured temperature to the temperature limits stored in memory locations  94 . FIG. 7 also shows the inclusion a timer  98  for of timing the cool-down period after a cut has been aborted. User interface  100  is provided to allow the operator of machine tool  20  to input information, such as the type and thickness of material to be processed, such that appropriate temperature limits are transferred to the memory locations  94  for comparison. 
     Attention will now be directed to the process flow aspects of the present invention, with further reference to FIG. 8 which shows an exemplary embodiment of a machine tool process flow which functions in accordance with the present invention. Start  102  represents the start of a part program. At  104  the control system causes the cutting head to be positioned to the first flagged start location. At  106  the workpiece temperature is measured by temperature sensors  71 - 73  and compared to the warning limit. The temperature will be less than the warning limit so operation will proceed to  112 . At  112  it will be determined that cutting has not commenced so operation will proceed to  118  which will cause the cut to be started then return to  106  to continue to monitor the process. 
     At  106  the workpiece temperature is measured and compared to the warning limit. If the temperature is less than the warning limit the control determines cutting is in process at  112  and continues the cut,  124 , then checks if it is at the end of the cut at  122 . If the end of the cut has not been reached the control returns to  106  to continue the monitoring process. If the end of the cut has been reached the control moves to  130  and checks for an aborted location. In this case there would be none so the control would move to  136  and check for remaining start flags. Assuming there are flags remaining, the control would proceed to  138  positioning the cutting head at the next flagged starting position then return to  106  to check the temperature. If the temperature is and remains less than the warning limit the control system will continue as described until at  136  there are no flags remaining, the end of the program,  140 , is achieved then will stop  144 . 
     If after moving to a new start location, at  106  the control system determines plate temperature exceeds the warning limit, and at  108  determines cutting has not started, it will not start the cut,  114 , but will start a cool down timer,  132 , then check to see if there are aborted locations available,  130 . Assuming none are available and that there are no start flags remaining,  136 , and that the end of the program has not been reached,  140 , the control system will wait for the timer to time out,  142 , then return to  106 . In such case the control system will remain in this loop until the temperature has cooled sufficiently to allow starting the cut. 
     If after moving to a new start location, at  106  the control system determines plate temperature exceeds the warning limit, and at  108  determines cutting has not started, as in the prior example it will not start the cut,  114 , but will start a cool down timer,  132 , then check to see if there are aborted locations available,  130 . Assuming none are available but there are start flags remaining,  136 , the control will proceed to  138  positioning the cutting head to the next flagged starting position then return to  106  to check the temperature. If the temperature is less than the warning limit the control system will determine it is not cutting,  112 , start the cut,  122 , then return to  106  to continue monitoring the process. 
     While processing a part, if the control system determines at  106  that plate temperature exceeds the warning limit and cutting is in process,  108 , but temperature is less than the abort limit,  110 , it will continue cutting until the next geometrical intersection is reached, typically a “end-of block” in the part program,  116 , then abort the cut,  120 , store parameters to allow a later return,  126 , set a restart flag,  128 , start a cooldown timer,  132 , then check for an aborted location with a timed out cooldown timer at  130 . Assuming there are aborted positions available, the control system will select and move to the location having the longest timed out time,  134 , then return to  106  to continue. If no aborted locations are available at  134 , but there are start flags remaining,  136 , the control system will select and move the cutting head to the next available start flag,  138 , then return to  106  to continue. 
     While processing a part, if the control system determines at step  106  that plate temperature exceeds the warning limit and cutting is in process,  108 , and that the plate temperature is equal to or greater than the abort limit,  110 , it will abort the cut immediately,  120 , store parameters to allow a later return,  126 , set another restart flag,  128 , start a cooldown timer,  132 , then check for an aborted location with a timed out cooldown timer,  130 . Assuming there are aborted positions available, the control system will select and move to the location having the longest timed out time,  134 , then return to step  106  to continue. If no aborted locations are available at step  130 , but there are start flags remaining,  136 , the control system will select and move the cutting head to the next available start flag,  138 , then return to  106  to continue. 
     The control system will process the part in such manner until no aborted locations remain,  130 , no start flags remain,  136 , and the end of the program is reached,  140 , then stop,  144 . 
     The inventor refers to the control system diagrammed in FIGS. 7 and 8 as an Adaptive Temperature Control System. Such a control system is configured to operate with commercially available nesting programming systems, not shown, that assure parts are cut from the inside out, in other words, that the outer boundary of a part or group of parts is not cut until all internal features have been cut. The parts program is modified to associate a plurality of start flags with particular cuts. Those particular cuts are selected to be jump points for initiating a new cut in the event a cutting sequence is terminated or aborted earlier in the program. These start flags associated with preselected cuts in the parts program and other flags created at the time cuts are aborted, all as taught herein are utilized when the control decides which aborted cut and/or start point flag is to be processed next. 
     FIGS. 9A-9G are depictions of a workpiece with multiple nests, showing how flags can be set up to assign cut starting positions and to rank them in some order, and to demonstrate how the system can move from cut starting point to cut starting point in accordance with the invention. In conjunction with these figures, the following terms and definitions will be used. A flag is a marker utilized by the CNC to implement the adaptive temperature control of this invention. In the associated table that appears at the end of this specification, flags are numbered, and each number has a unique position. Flags starting with a “P” are assigned to the predetermined start flags as described above. Flags that have a “C” designator are those that are assigned by the machine control system upon an interrupt of cut in accordance with the adaptive temperature control system of this invention. 
     In the nest, a group number identifies a first level nest part perimeter which may or may not contain holes or parts within its boundary. A level number identifies a level of a boundary within a group. Level  1 , for example, is the perimeter of the group or part. Higher level numbers identify other holes, shapes, or part boundaries contained within a group and within other levels. Thus, for example, a cut at level  6  will be within the boundary of a level  5  cut which in turn is within the boundary of a level  4  cut, etc. A feature number identifies an absolute location in the nest. In the associated chart, each feature number is given a two-digit identifier. Each of the digits is representative of a start coordinate. For example, the feature number  01  would be representative of the starting coordinate of the feature at the coordinates X and Y which may be for example X=1234.56 mm and Y=9876.54 mm. These coordinates define the start cut point for the feature. The part program would define the overall shape of the feature to be cut starting at the specified coordinates. 
     Referring to FIG. 9A, there is shown an overall workpiece  34   b  having a large number of features arranged thereon. The control system of the machine tool is programmed to traverse the cutting head to cut each of the features. Thus, each of the solid lines on the figure represents a cut to be made by the machine tool. As shown in FIG. 9A, the features are arranged in groups, with each group being defined by an outer boundary. For example, the first group G 1  is the group of features in the lower left hand part of the workpiece surrounded by the perimeter  200 . Group GI represents a multiple level cut in which the perimeter  200  will be the lowest level L 1 . Other shapes within the perimeter will be at higher levels, with the center most three shaped cut outs  201 ,  202 , and  203  being at the highest level, L 6  in this example. 
     Group G 3  in the upper left hand portion of the drawing illustrates a large piece with a number of cut outs and having two etched fold lines  205 ,  206  to form three sides of a box. Groups G 4 -G 8  in the lower portion, right of center of the workpiece represent a number of individual groups or parts which are not surrounded by a common boundary. 
     A table representing a program for cutting the nest illustrated in FIG. 9A is reproduced at the end of this specification. Certain liberties have been taken to substantially reduce the length of the program representation. Also it is clearly not the only program that could cut the nest. Assume that a conventional parts nesting program, which has been customized to set the cut starting point flags, has determined the cutting order. Note that the program could be modified, after creation of the nest, assigning starting flags at various points in the part. In this example the flags are intended to identify the “next available cut start point” in case a cut is terminated prematurely. It will be noted that not all cuts are identified with a starting point flag. In the preferred embodiment, only selected cuts are identified, and the cuts are selected on the basis of the overall geometry of the workpiece. For example, the starting point P 02 ,  01 ,  02 ,  02  is identified with cut  21  in the Cutting Table. That cut is selected as an appropriate “next available” starting point in the event a cut is aborted at any of the features prior to cut  21 . Cut  21  is selected on the basis that it is sufficiently distant from any of the cuts which might have caused the abort condition, yet close enough to avoid unwanted lengthy traverses of the cutting head. Other factors which might impact the selection of a flagged starting point will be the crossover of the nozzle of cut parts, and other factors well known to those skilled in this art. Similarly, the juxtaposition of starting flags on each of cuts  21 ,  22 , and  23  recognizes that each of the cuts is very localized, and it is possible to move from one overheated condition (should that occur) to a sufficiently distant but reasonably closely adjacent set of features (say from cut  21  to cut  22 ) in an efficient manner. 
     In short, the program is intended to sequence through the steps in the order specified in the table. If, during the course of cutting, either a warning or an abort temperature limit is reached, the control system will terminate the cut and move the cutting head to the next available cut starting point identified by the next flag in sequence. When cutting is terminated prematurely, a new flag is set within the table in real time at the point of termination. For example, if an abort temperature limit is reached, cutting is immediately terminated, a C flag is set at the point of termination, and parameters are saved, including location coordinates and cutting parameters. Like the P flag, the C flag contains complete information on the cut so the cut can be resumed later. When the cool down timer expires and the program sequences to the next available cutting position, in the form of a previously aborted cut, the C flag will identify the cut start point just as the flag identifies a cut start point for a preprogrammed position. 
     FIGS. 9B-9G are enlarged portions of the workpiece of FIG. 9A, annotated to indicate individual cuts and from which one skilled in the art will perceive the different levels of the cut within a particular group. For example, FIG. 9B represents Group G 1  of FIG.  9 A. The program has selected Group G 1  the first group to be cut. The cut numbers are identified by a numeral preceded by the designator C. The cut numbers are in sequence beginning with C 1  and proceeding through C 127 . The table appended at the end of this specification identifies each of those cuts in sequence. Cut C 1  is at level  6  within Group G 1  and is a shaped hole. As will be seen by concurrent reference to the table and FIG. 9B, cut number  1 , C 1 , is made within group  1  at level  6  to cut the feature identified as  01 , the innermost shaped hole in the upper left of the large rectangular cutout. When that feature is completed, the program traverses the head to cut C 2 , also at level  6 , to cut the feature identified by the coordinates  02 . Cut C 3  makes a similar cut for the feature identified by coordinates  03 . Having completed all of the cuts at level  6 , the program then moves to cut C 4 , which is at level  5  at the coordinates for that level identified feature  01 . It will be seen that performing cut C 4  cuts the small part OD and causes that part to be separated from the workpiece. Cutting proceeds in the order identified in the table. If while cutting cut number C 12 , a warning temperature limit is encountered, the control system will finish cut C 12 , then set a flag C 01  at the identifier ( 01 ,  04 ,  07 ) which is the start point for cut C 13 . The appended chart has the aforementioned flag noted thereon for this example. At the point cut C 12  is completed and flag C 01  set, the program will proceed to the next available cutting position, that identified by flag  02 . It will be seen that that flag identifies the location for cut C 21  which, in referring to FIG. 8B, is seen to be substantially removed from the location at which the temperature limit had been exceeded. The control system would then proceed with the cuts, continuously monitoring the temperature, unless and until another warning or abort temperature limit is reached. The parts within group G 1  are completed with the cut C 28  which cuts the perimeter of the group G 1  part. Having completed that group, the program then sequences to the flag  05  to begin cutting the group identified as G 2  (group  02  in the chart), at level  6  and the feature identified by the coordinates  01  within that group. 
     After the cool down timer triggered by the warning condition encountered in cut C 12  has timed out, flag C 01  then also becomes a next available cutting position, and at some point the program will revert to that flag and complete the cutting of group G 1  parts. 
     Those skilled in the art will be able to compare the FIGS. 9B-9G with the appended chart to understand the manner in which all of the  127  cuts will be made. If no temperature limits are encountered, they will be made in the order listed in the chart. Whenever a temperature limit is encountered, the order will change. If a warning temperature limit is encountered, the actual cut then in progress will be completed, and a C flag set at the location of the next sequential cut, i.e., at the next geometry intersection. The program will then proceed to the next available cutting position identified by the next P flag or an available C flag. If an abort temperature limit is encountered, cutting will terminate immediately, and a C flag will be set exactly at the coordinates where the cut was aborted. As in the prior case, the program will sequence to the next available position identified by a P or an available C flag and will commence cutting there. In either case, the C flags, be they at the start of a feature or at an intermediate position on the cut path, a cut will be resumed some time during the program run, after the cool down timer marks the associated C flag to be available for cutting. 
     It can therefore be seen by one of ordinary skill in the art that the present invention provides a new and improved material cutting machine tool having adaptive temperature control. In other words, the material cutting machine tool of the present invention is able to determine ahead of time whether self-burning is likely to ensue, and if so, the particular cut being made can be aborted, and the cutting head can be moved to another area of the workpiece, at a cooler temperature. The quality of the parts cut on such a machine is assured by avoiding onset of self-burning. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
               
               
                 CUTTING TABLE 
               
             
          
           
               
                   
                 Cut 
                   
                   
               
               
                   
                 Identifier 
                   
                 Adaptive Temp. 
               
               
                 Cutting Order 
                 (Group, 
                   
                 Control Flags 
               
             
          
           
               
                 Cut 
                   
                 Level, 
                   
                 (P or C No, Group, 
               
               
                 No. 
                 FIG. 
                 Feature) 
                 Comment 
                 Level, Feature) 
               
               
                   
               
             
          
           
               
                 1 
                 9b 
                 01, 06, 01 
                 Shaped hole 
                 P01, 01, 06, 01 
               
               
                 2 
                 9b 
                 01, 06, 02 
                 ″ 
               
               
                 3 
                 9b 
                 01, 06, 03 
                 ″ 
               
               
                 4 
                 9b 
                 01, 05, 01 
                 Small part OD 
               
               
                 5 
                 9b 
                 01, 05, 02 
                 ″ 
               
               
                 6 
                 9b 
                 01, 05, 03 
                 ″ 
               
               
                 7 
                 9b 
                 01, 04, 01 
                 All small holes in 
               
               
                   
                   
                   
                 flange 
               
               
                 8 
                 9b 
                 01, 04, 02 
                 All small holes in 
               
               
                   
                   
                   
                 flange 
               
               
                 9 
                 9b 
                 01, 04, 03 
                 All small holes in 
               
               
                   
                   
                   
                 flange 
               
               
                 10 
                 9b 
                 01, 04, 04 
                 Shaped hole 
               
               
                 11 
                 9b 
                 01, 04, 05 
                 ″ 
               
               
                 12 
                 9b 
                 01, 04, 06 
                 Flange ID 
               
               
                 13 
                 9b 
                 01, 04, 07 
                 ″ 
                 C01, 01, 04, 07 
               
               
                 14 
                 9b 
                 01, 04, 08 
                 ″ 
               
               
                 15 
                 9b 
                 01, 03, 01 
                 Small part OD 
               
               
                 16 
                 9b 
                 01, 03, 02 
                 ″ 
               
               
                 17 
                 9b 
                 01, 03, 03 
                 Flange OD 
               
               
                 18 
                 9b 
                 01, 03, 04 
                 ″ 
               
               
                 19 
                 9b 
                 01, 03, 05 
                 ″ 
               
               
                 20 
                 9b 
                 01, 02, 01 
                 All small holes 
               
               
                 21 
                 9b 
                 01, 02, 02 
                 ″ 
                 P02, 01, 02, 02 
               
               
                 22 
                 9b 
                 01, 02, 03 
                 ″ 
                 P03, 01, 02, 03 
               
               
                 23 
                 9b 
                 01, 02, 04 
                 ″ 
                 P04, 01, 02, 04 
               
               
                 24 
                 9b 
                 01, 02, 05 
                 Rectangular cutout 
               
               
                 25 
                 9b 
                 01, 02, 06 
                 Center hole 
               
               
                 26 
                 9b 
                 01, 02, 07 
                 ″ 
               
               
                 27 
                 9b 
                 01, 02, 08 
                 ″ 
               
               
                 28 
                 9b 
                 01, 01, 01 
                 Perimeter of part 
               
               
                 29 
                 9c 
                 02, 06, 01 
                 Shaped hole 
                 P05, 02, 06, 01 
               
               
                 30 
                 9c 
                 02, 06, 02 
                 ″ 
               
               
                 31 
                 9c 
                 02, 06, 03 
                 ″ 
               
               
                 32 
                 9c 
                 02, 05, 01 
                 Small part OD 
               
               
                 33 
                 9c 
                 02, 05, 02 
                 ″ 
               
               
                 34 
                 9c 
                 02, 05, 03 
                 ″ 
               
               
                 35 
                 9c 
                 02, 04, 01 
                 All small holes in 
               
               
                   
                   
                   
                 flange 
               
               
                 36 
                 9c 
                 02, 04, 02 
                 All small holes in 
               
               
                   
                   
                   
                 flange 
               
               
                 37 
                 9c 
                 02, 04, 03 
                 All small holes in 
               
               
                   
                   
                   
                 flange 
               
               
                 38 
                 9c 
                 02, 04, 04 
                 Shaped hole 
               
               
                 39 
                 9c 
                 02, 04, 05 
                 ″ 
               
               
                 40 
                 9c 
                 02, 04, 06 
                 Flange ID 
               
               
                 41 
                 9c 
                 02, 04, 07 
                 ″ 
               
               
                 42 
                 9c 
                 02, 04, 08 
                 ″ 
               
               
                 43 
                 9c 
                 02, 03, 01 
                 Small part OD 
               
               
                 44 
                 9c 
                 02, 03, 02 
                 ″ 
               
               
                 45 
                 9c 
                 02, 03, 03 
                 Flange OD 
               
               
                 46 
                 9c 
                 02, 03, 04 
                 ″ 
               
               
                 47 
                 9c 
                 02, 03, 05 
                 ″ 
               
               
                 48 
                 9c 
                 02, 02, 01 
                 All small holes 
               
               
                 49 
                 9c 
                 02, 02, 02 
                 ″ 
                 P06, 02, 02, 02 
               
               
                 50 
                 9c 
                 02, 02, 03 
                 ″ 
                 P07, 02, 02, 03 
               
               
                 51 
                 9c 
                 02, 02, 04 
                 ″ 
                 P08, 02, 02, 04 
               
               
                 52 
                 9c 
                 02, 02, 05 
                 Rectangular cutout 
               
               
                 53 
                 9c 
                 02, 02, 06 
                 Center hole 
               
               
                 54 
                 9c 
                 02, 02, 07 
                 ″ 
               
               
                 55 
                 9c 
                 02, 02, 08 
                 ″ 
               
               
                 56 
                 9c 
                 02, 01, 01 
                 Perimeter of part 
               
               
                 57 
                 9d 
                 03, 04, 01 
                 All small holes 
                 P09, 03, 04, 01 
               
               
                 58 
                 9d 
                 03, 04, 02 
                 Shaped hole 
               
               
                 59 
                 9d 
                 03, 04, 03 
                 ″ 
               
               
                 60 
                 9d 
                 03, 04, 04 
                 ″ 
               
               
                 61 
                 9d 
                 03, 04, 05 
                 ″ 
               
               
                 62 
                 9d 
                 03, 03, 01 
                 Radiused square cutout 
               
               
                 63 
                 9d 
                 03, 03, 02 
                 Small part perimeter 
               
               
                 64 
                 9d 
                 03, 03, 03 
                 ″ 
               
               
                 65 
                 9d 
                 03, 03, 04 
                 ″ 
               
               
                 66 
                 9d 
                 03, 03, 05 
                 ″ 
               
               
                 67 
                 9d 
                 03, 02, 01 
                 All small holes 
               
               
                 68 
                 9d 
                 03, 02, 02 
                 ″ 
                 P10, 03, 02, 02 
               
               
                 69 
                 9d 
                 03, 02, 03 
                 ″ 
                 P11, 03, 02, 03 
               
               
                 70 
                 9d 
                 03, 02, 04 
                 ″ 
                 P12, 03, 02, 04 
               
               
                 71 
                 9d 
                 03, 02, 05 
                 Etch bend line 
                 P13, 03, 02, 05 
               
               
                 72 
                 9d 
                 03, 02, 06 
                 ″ 
               
               
                 73 
                 9d 
                 03, 02, 07 
                 All small holes 
                 P14, 03, 02, 07 
               
               
                 74 
                 9d 
                 03, 02, 08 
                 ″ 
                 P15, 03, 02, 08 
               
               
                 75 
                 9d 
                 03, 02, 09 
                 ″ 
                 P16, 03, 02, 09 
               
               
                 76 
                 9d 
                 03, 02, 10 
                 Large ID 
               
               
                 77 
                 9d 
                 03, 02, 11 
                 Center hole 
               
               
                 78 
                 9d 
                 03, 02, 12 
                 ″ 
               
               
                 79 
                 9d 
                 03, 02, 13 
                 ″ 
               
               
                 80 
                 9d 
                 03, 02, 14 
                 ″ 
               
               
                 81 
                 9d 
                 03, 02, 15 
                 ″ 
               
               
                 82 
                 9d 
                 03, 02, 16 
                 ″ 
               
               
                 83 
                 9d 
                 03, 01, 01 
                 Perimeter of part 
               
               
                 84 
                 9e 
                 04, 02, 01 
                 Shaped hole 
                 P17, 04, 02, 01 
               
               
                 85 
                 9e 
                 04, 01, 01 
                 Perimeter of part 
               
               
                 86 
                 9e 
                 05, 02, 01 
                 Shaped hole 
                 P18, 05, 02, 01 
               
               
                 87 
                 9e 
                 05, 01, 01 
                 Perimeter of part 
               
               
                 88 
                 9e 
                 06, 04, 01 
                 Shaped hole 
                 P19, 06, 04, 01 
               
               
                 89 
                 9e 
                 06, 04, 02 
                 ″ 
               
               
                 90 
                 9e 
                 06, 04, 03 
                 ″ 
               
               
                 91 
                 9e 
                 06, 04, 04 
                 ″ 
               
               
                 92 
                 9e 
                 06, 04, 05 
                 ″ 
               
               
                 93 
                 9e 
                 06, 03, 01 
                 Perimeter of part 
               
               
                 94 
                 9e 
                 06, 03, 02 
                 ″ 
               
               
                 95 
                 9e 
                 06, 03, 03 
                 ″ 
               
               
                 96 
                 9e 
                 06, 03, 04 
                 ″ 
               
               
                 97 
                 9e 
                 06, 03, 05 
                 ″ 
               
               
                 98 
                 9e 
                 06, 02, 01 
                 All small holes 
               
               
                 99 
                 9e 
                 06, 02, 02 
                 ″ 
               
               
                 100 
                 9e 
                 06, 02, 03 
                 Radiused square cutout 
               
               
                 101 
                 9e 
                 06, 02, 04 
                 OD of part 
               
               
                 102 
                 9e 
                 07, 02, 01 
                 Shaped hole 
                 P20, 07, 02, 01 
               
               
                 103 
                 9e 
                 07, 01, 01 
                 Perimeter of part 
               
               
                 104 
                 9e 
                 08, 02, 01 
                 Shaped hole 
                 P21, 08, 02, 01 
               
               
                 105 
                 9e 
                 08, 01, 01 
                 Perimeter of part 
               
               
                 106 
                 9f 
                 09, 02, 01 
                 All small holes 
                 P22, 09, 02, 01 
               
               
                 107 
                 9f 
                 09, 01, 01 
                 Perimeter of part 
               
               
                 108 
                 9f 
                 10, 02, 01 
                 All small holes 
                 P23, 10, 02, 01 
               
               
                 109 
                 9f 
                 10, 01, 01 
                 Perimeter of part 
               
               
                 110 
                 9f 
                 11, 02, 01 
                 Hole 
                 P24, 11, 02, 01 
               
               
                 111 
                 9f 
                 11, 02, 02 
                 Rectangular hole 
               
               
                 112 
                 9f 
                 11, 02, 03 
                 ″ 
               
               
                 113 
                 9f 
                 11, 02, 04 
                 Hole 
               
               
                 114 
                 9f 
                 11, 01, 01 
                 Perimeter of part 
               
               
                 115 
                 9g 
                 12, 04, 01 
                 All small holes 
                 P25, 12, 04, 01 
               
               
                 116 
                 9g 
                 12, 04, 02 
                 Shaped hole 
               
               
                 117 
                 9g 
                 12, 04, 03 
                 ″ 
               
               
                 118 
                 9g 
                 12, 04, 04 
                 ″ 
               
               
                 119 
                 9g 
                 12, 04, 05 
                 ″ 
               
               
                 120 
                 9g 
                 12, 03, 01 
                 Radiused square cutout 
               
               
                 121 
                 9g 
                 12, 03, 02 
                 Perimeter of part 
               
               
                 123 
                 9g 
                 12, 03, 03 
                 ″ 
               
               
                 124 
                 9g 
                 12, 03, 04 
                 ″ 
               
               
                 125 
                 9g 
                 12, 02, 01 
                 All small holes 
               
               
                 126 
                 9g 
                 12, 02, 02 
                 Large ID 
               
               
                 127 
                 9g 
                 12, 01, 01 
                 Perimeter of part