Abstract:
A machine for machining a volume, in particular an inlay, by automatic duplicating, includes an abrasive disc having a rotatable drive, a support for a blank of the volume, the disc and the blank being rotatable, a rotatable duplicator support a touch-sensing probe capable of being urged into contact with the duplicator outer surface, there being relative displacement between the blank support and the disc and between the duplicator support and the touch-sensing probe so as to enable the disc and the touch-sensing probe to remain permanently in contact with the blank and the duplicator, and a mobile carriage having at least two degrees of freedom on which are mounted the support for the blank and for the duplicator, the carriage commanding and controlling the drive of the rotatable disc and the duplicator support.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the field of machines that allow a machining by the removal of material by reproducing a model, more particularly applied to the medical field, particularly the dental field, for manufacturing ceramic components intended to replace all or part of a dental crown, and relating in particular to machines comprising a machining tool with an axis of symmetry and having at least one degree of freedom in rotation about said axis of symmetry, means for driving the rotation of the said machining tool about its axis of symmetry, means of securing a blank, in which said volume is machined, having at least one degree of freedom in rotation, means for driving the rotation of said blank-securing means, means for securing a template, having at least one degree of freedom in rotation, means for driving the rotation of said template-securing means, a feeler capable of coming into contact with the exterior surface of said template, means for bringing about relative movement between said blank-securing means and said machining tool, on the one hand, and between said template-securing means and said feeler on the other hand, said movement means allowing the machining tool and the feeler to remain in constant contact with, respectively, said blank and said template. 
     A known method and to an apparatus for manufacturing volumes by copying in. dentistry, particularly for inlays, is disclosed in U.S. Pat. No. 5,135,393. The machine is an eight-axis machine in which all movements of the moving parts of the machine are performed manually by the operator, except for the rotating of the tool which is done by a motor. More specifically, the machine comprises a first carriage carrying a feeler and a tool support which are held together, the axes of which are mutually parallel and are perpendicular to an axis of movement and translation of the feeler and of the tool support; furthermore, this first carriage is free to rotate and to translate along axes respectively parallel and perpendicular to the axis of translation of the feeler and of the tool joined together; this first carriage is kept pressing and moved by an operator during machining against a second free-rotation carriage which carries the template and the blank themselves which are free to rotate on this second carriage; so that under the pressure and movements brought-about by the operator, the feeler travels over the surface of the template and the tool machines the blank accordingly; the template and the blank are incidentally linked in rotation so that when the operator with one hand turns the template, the blank follows this rotational movement, whereas with the other hand the operator takes care to cause the feeler to travel over the surface of the template. A machine such as this is complicated and expensive because of the high number of degrees of freedom and is tricky to use because the copying precision depends on the quality of service provided by the operator. 
     The prior art in particular teaches a machine of this type with document WO 96/05 782, comprising a diamond-tipped machine tool actuated by a high-speed turbine, a feeler placed on the same machine body of the tool, the tool and the feeler being able to move in translation and in rotation so as to follow the profile of a model secured in alignment with the blank, such a machine allowing a model to be reproduced precisely but entailing a mechanism which is cumbersome, bulky and expensive, particularly because of the high speeds at which the tool rotates. Furthermore, the small-diameter tool which allows small details to be reproduced, which rotates at high speed, may wear rapidly and therefore cause the machine to be expensive to use. 
     SUMMARY OF THE INVENTION 
     The present invention essentially sets out to alleviate these drawbacks and to provide other advantages. More specifically, it consists in a machine for machining at least one volume, particularly an inlay, automatically by copying, comprising at least: 
     a machining tool with an axis of symmetry and having at least one degree of freedom in rotation about said axis of symmetry, 
     means for driving the rotation of the said machining tool about its axis of symmetry, 
     means for securing a blank, in which said volume is machined, having at least one degree of freedom in rotation, 
     means for driving the rotation of said blank-securing means, 
     means for securing a template, having at least one degree of freedom in rotation, 
     means for driving the rotation of said template-securing means, 
     a feeler capable of coming into contact with the exterior surface of said template, 
     means for bringing about relative movement between said blank-securing means and said machining tool, on the one hand, and between said template-securing means and said feeler on the other hand, said movement means allowing the machining tool and the feeler to remain in constant contact with, respectively, said blank and said template, 
     means for commanding and controlling said means for driving the rotation of the machining tool, said means for driving rotation of the template-securing means and said movement means, said machine being characterized in that said machining tool is an abrasive disk and in that said movement means comprise a moving carriage on which said blank-securing means and said template-securing means are mounted so that they are free to rotate, said moving carriage having at least two degrees of freedom of movement. 
     The abrasive disk which makes it possible to reduce the rotational speed of the machining tool appreciably, and the arrangement of the movement means which allow the blank and the template to be moved rather than the machining tool, lead to a significant reduction in the weight and cost of the machine. 
     According to an advantageous characteristic, said two degrees of freedom of said moving carriage are one degree of freedom in rotation and one degree of freedom in translation, and said movement means comprise means for driving the translation and means for driving the rotation of said moving carriage. 
     According to an advantageous characteristic of the foregoing, the machine according to the invention comprises a rigid support, and said means for driving the translation of said moving carriage comprise a first motor connected completely to said rigid support, in that said means for driving the rotation of said blank-securing means and said means for securing the template comprise a second motor connected to said first motor via a screw-nut connection, and said moving carriage is free in rotation about the output shaft of said second motor, said output shaft being guided in rotation and in translation by said rigid support. 
     According to an advantageous characteristic of the foregoing, said means for driving the rotation of said moving carriage about the output shaft of said second motor comprise the friction forces generated by the rotation of said blank-securing means and of said means of securing the template. 
     According to an advantageous characteristic of the foregoing, said blank-securing means and said means for securing the template are connected completely and have aligned axes of rotation. 
     According to an advantageous characteristic of the foregoing, the axis of rotation of said abrasive disk is parallel to the axes of rotation of said blank-securing means and of said means for securing the template, said rigid support having a flat wall perpendicular to said axis of rotation of the abrasive disk separating a machining compartment from a drive compartment. 
     According to an advantageous characteristic of the foregoing, the axis of rotation of said abrasive disk and the output shaft of said second motor are mounted in identical respective bearing supports. 
     The flat wall perpendicular to the axes of rotation makes the bearing supports easier to mount and the use of identical bearing supports lowers manufacturing costs. 
     According to an advantageous characteristic, said feeler is secured rigidly to said rigid support so as, by its abrasion resulting from the rubbing against the template, to compensate for the wear of said abrasive disk, thus making the precision of the reproduction independent of tool wear. 
     According to another advantageous characteristic, the machine according to the invention comprises means of moving said feeler radially, making it possible to establish a given dimensional ratio at which the inlay is reproduced with respect to the template, in a plane perpendicular to an axis of rotation of said template. 
     This characteristic allows the radial reproduction ratio to be varied without varying the axial reproduction ratio, used particularly the case of the manufacture of inlays, so as to form a cementing space or so as to compensate for errors which may impair the fit, without this detracting from the longitudinal dimension. 
     According to another advantageous characteristic, said feeler has a thickness greater than the thickness of said abrasive disk so as to increase the longitudinal dimension of the inlay with respect to that of said template. 
     Aside from compensating for errors in flatness or due to the vibrations of the disk, this characteristic allows compensation for the removal of material carried out when the finished part is polished. 
     According to another advantageous characteristic, said blank-securing means and said means for securing the template are connected by a screw-nut connection, said blank-securing means being secured rigidly to one of said elements—screw or nut—and said template-securing means being secured rigidly to the complementary other one of said elements—nut or screw. 
     This characteristic allows a more ergonomic machine according to the invention, the blank-securing means being fastened to the template-securing means by a screw-nut connection. Thus, the operator can easily, with two hands, assemble the blank and the template, each held in a respective hand, and, through the reverse movement, disassemble the part obtained from the template, and do so without immobilizing the axis of rotation thereof. This characteristic also makes it possible to eliminate any play there might be between the blank and the template. 
     According to another advantageous characteristic, the machine according to the invention comprises means for automatically stopping operation at the end of machining by detecting that said moving carriage is in a given position. At the end of machining, as the feeler no longer holds the template, the moving carriage moves toward the axis of symmetry of the abrasive disk, it being possible for the automatic stop means to be advantageously actuated during this movement. 
     According to another advantageous characteristic, the machine according to the invention comprises a disk which is abrasive over all or part of its two opposite faces, said two opposite faces converging toward the periphery of the disk. As the disk essentially works on a face in opposition to the movement of the moving carriage, turning over the disk, one face of which is worn, makes it possible to double the life of this disk. 
     According to another advantageous characteristic, the machine according to the invention comprises means for slaving said movement means to the force exerted by the abrasive disk on the blank. A characteristic such as this makes it possible to optimize the machining time. 
     According to another advantageous characteristic, the machine according to the invention comprises means of lubricating said machining disk by splash lubrication. This characteristic makes it possible to avoid the use of a machining lubrication circulation pump. 
     According to another advantageous characteristic, the machine according to the invention comprises means for reversing the direction of rotation of said abrasive disk. It is therefore possible to use the two opposite sides of the abrasive grains of a disk, thus optimizing the cost of using the machine. 
     According to another advantageous characteristic, the machine according to the invention comprises means for automatically clearing said moving carriage at the end of machining. This makes it possible to achieve better ergonomics, automatically clearing the carriage at the end of machining allowing easier access for disassembling the machined part and the template. 
     According to another advantageous characteristic, the machine according to the invention comprises a centering jig allowing the blank to be secured to said blank-securing means, and allowing the template to be secured to said template-securing means in such a way that the inlay to be obtained lies within the volume of the blank. This characteristic makes it possible to avoid the volume which is to be machined being positioned with respect to the template in such a way that the volume would lack material with respect to this template. 
     According to another advantageous characteristic, said blank and said template are secured to their respective securing means via at least one of their respective ends. 
    
    
     Other characteristics and advantages will become apparent upon reading the description which follows of one exemplary embodiment of a machine according to the invention, accompanied by the appended drawings, the example being given by way of illustration and without any restrictive interpretation of the invention being derivable therefrom. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts a schematic partial view from above in section on the line II—II of FIG. 2, of one exemplary embodiment of a machine according to the invention, making it possible to machine at least one volume, particularly an inlay, automatically by copying. 
     FIG. 2 depicts a view in cross section on the line I—I of FIG.  1 . 
     FIG. 3 depicts an enlarged first detail of the machine according to FIG.  1 . 
     FIG. 4 depicts an exemplary embodiment of a centering jig for the machine according to FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The machine  1  depicted in FIG. 1, for machining at least one volume, particularly an inlay; automatically by copying, comprises an abrasive disk  4  with an axis of symmetry  18  and having at least one degree of freedom in rotation about the axis of symmetry  18 , means  5  for driving the rotation of the abrasive disk  4  about its axis of symmetry, means  6  for securing a blank  7  in which the volume is machined and having at least one degree of freedom in rotation, means  12 ,  16 ,  17  for driving the rotation of the blank-securing means  6 , means  8  for securing a template  9  having at least one degree of freedom in rotation, the means  12 ,  16 ,  17  also driving the rotation of the template-securing means  8 , a feeler  10  designed to come into contact with the exterior surface of the template, means  11 ,  13 ,  14 ,  15 ,  16  of relative movement between the blank-securing means  6  and the abrasive disk  4 , on the one hand, and between the template-securing means  8  and the feeler  10  on the other hand, the movement means allowing the abrasive disk  4  and the feeler  10  to remain in constant contact with, respectively, the blank and the template, means for commanding and controlling the means  5  for driving the rotation of the abrasive disk  4 , and the means  12  also driving the rotation of the means for securing the template  9  and the movement means  11 . 
     The movement means comprise a moving carriage  13  on which the means  6  for securing the blank  7  and the means  8  for securing the template  9  are mounted so that they can rotate freely, the moving carriage  13  advantageously having two degrees of freedom of movement, namely one degree of freedom in rotation and one degree of freedom in translation. The movement means further comprise means  11 ,  14 ,  15  for driving the translation and means for driving the rotation of the moving carriage  13 . 
     The machine depicted in FIG. 1 further comprises a rigid support  3 . The means for driving the translation of the moving carriage  13  comprise a first motor  11  connected completely to the rigid support  13 . The means for driving the rotation of the means  6  for securing the blank  7  and of the means  8  for securing the template  9  comprise a second motor  12  connected to the first motor  11  via a screw-nut connection  14  and  15 , the moving carriage  13  being free to rotate about the output shaft  16  of the second motor, the output shaft  16  being guided in rotation and in translation via a bearing support  21  rigidly secured to the rigid support  3  as depicted in FIG.  1  and explained in detail later on. 
     The axis of rotation  18  of the abrasive disk  4  is parallel to the axes of rotation of the means  6  for securing the blank  7  and of the means  8  for securing the template  9 , the rigid support  3  advantageously adopting the form of a flat wall perpendicular to the axis of rotation  18  of the abrasive disk  4 , thus dividing a machining compartment  31  from a drive compartment  32 . The axis of rotation  18  of the abrasive disk  4  is mounted in a bearing support  20 , advantageously identical to the bearing support  21 , guiding the output shaft  16  of the second motor  12 , as depicted in FIG.  1 . The fact that the bearing supports  20  and  21  are identical gives the machine according to the invention a simplicity of design and reduces the costs of manufacture. 
     All of the means that make up the machine according to the invention are advantageously housed in an enveloping casing  30  which protects these constituent means, acts as a container for a machining lubricating fluid, as will be expanded upon later on, and improves the appearance of the machine, as depicted in FIGS. 1 and 2. The rigid support  3  will preferably adopt the form of a flat wall capable rigidly of supporting, on the one hand, the bearing support  20  on which are advantageously mounted, free to rotate, the shaft  34  of the abrasive disk  4 , rigidly, the support  22  of the feeler  10  and the drive motor  50  and, on the other hand, the bearing support  21  on which are advantageously rigidly mounted the motor  11 , and, free to rotate and to translate, the output shaft  16 . 
     The output shaft  33  of the drive motor  5  is coupled in rotation in any known way, fir example via a coupling sleeve  35 , to a shaft  34  on which the abrasive disk  4  is centered and secured, as depicted in FIG.  1 . The shaft  34  is guided in rotation in the bearing support  20  in any appropriate way depending on the rotational speed of the disk, via ball- or needle-bearings  25 , for example, in the case of a disk rotating at a speed of the order of  250  revolutions per second approximately. A sealing ring will be placed around the shaft  34 , as depicted in FIG. 1, so as to hold the lubricant in the machining compartment  31 . The abrasive disk  4  will be secured removably to the shaft  34 , for example via a chuck  36  with a central nut  38 , so that it can be changed, and may advantageously be mounted reversibly for the preferred case in which the disk is abrasive on all or part of its two opposite faces, so as to allow the disk to be turned over. The abrasive disk will preferably be a diamond tipped disk, the two opposite faces of which converge toward the periphery of the disk, a cross section along a radius of the disk preferably forming an isosceles triangle, the tip of which consists of the periphery of the disk. 
     The feeler  10  is advantageously rigidly secured to the rigid support  3 , more specifically to the bearing support  20 , itself connected completely and rigidly to the support  3 , as depicted in FIG.  1 . Mounting the feeler  10 ; so that it is fixed, makes it possible, through its abrasion resulting from the friction against the rotating template  9 , to compensate for the wear of the abrasive disk  4 . As depicted in FIG. 1 for example, the feeler  10  connected to a sleeve  22  is sandwiched in a screw-nut connection  39 , the sleeve  22  being secured rigidly and so that it is adjustable in terms of rotation about the bearing support  21  by virtue of a central bore. A radial set screw (not depicted) may, for example, be used to immobilize the sleeve in the bearing support  20 . 
     The machine depicted in FIG. 1 advantageously comprises means for moving the feeler  10  radially, making it possible to establish a given dimensional ratio with which the inlay is reproduced with respect to the template  9 , in a plane perpendicular to an axis of rotation of the template. The radial movement means advantageously consist of a shoulder  37  formed on the sleeve  22  and off-centered with respect to the bore for centering the latter on the bearing support  20 . Thus, rotating the sleeve  22  about the bearing support  20  allows the feeler  10  to be moved radially by virtue of the eccentricity of the shoulder  37 . 
     If the feeler  10  is fixed, the latter may adopt the form of a sector of a disk, the peripheral part of which reproduces part of the periphery of the abrasive disk  4 . 
     The machine may advantageously comprise a means for axially moving the sleeve  22 , thus possibly allowing the machining of shorter blanks. This means of axial movement may, for example, consist of an intermediate ring (not depicted) between the sleeve  22  and the bearing support  20 ; the intermediate ring will be free to translate on the bearing support, and the sleeve  22  free to rotate on the intermediate ring, or vice-versa. 
     Advantageously, the feeler  10  has a thickness greater than the thickness of the abrasive disk  4  so as to increase the longitudinal dimension of the part to be obtained, for example an inlay, compared with that of the template  9 , and also so as to compensate for errors in flatness or errors due to the vibrations of the disk. The increase in the longitudinal dimension of the copy makes it possible to compensate for the removal of material due to the polishing that the part needs after it has been machined on the machine according to the invention. 
     The output shaft  16  is connected in rotation-at a first  41  of its ends to the rotational drive shaft  40  of the second motor  12  possibly via a coupling sleeve  42 , and is connected in translation but free in terms of rotation at its second end  43  to the moving carriage  13 , preferably via rolling bearings  44 , for example ball bearings, needle bearings or the like, as depicted in FIG.  1 . The output shaft  16  is guided in rotation and in translation in the bearing support  21 , preferably by virtue of plain bearings  26 . A sealing ring  46  is fitted around the shaft  16  so as to seal the drive compartment  32  from the lubricant found in the machining compartment  31 . 
     The body of the first motor  11  is secured rigidly to the bearing support  21 , and its rotational drive shaft  46  is connected in rotation to the screw  14  possibly via a coupling sleeve  47 . The screw  14  is engaged in a nut  15  connected in rotation and in translation to the body of the second motor  12 , as depicted in FIG. 1, so that rotation of the drive shaft  46  of the first motor  11  leads to a translation movement of the body of the second motor  12  without causing the latter to rotate, causing a translational movement of the shaft  16  carrying the moving carriage  13 . 
     The first motor  11  is preferably a stepping motor making it possible to cause a translational movement of the shaft  16  of the order of 1 to 2 mm per minute; the second motor  12  is preferably a stepping motor making it possible to cause a rotation of the shaft  16  of the order of one revolution per second; the abrasive disk drive motor  5  must allow the disk to rotate at a speed of the order of 250 revolutions per second. 
     The moving carriage  13  is in the form of an arm, with the output shaft  16  connected to its first end as described previously, and with the blank-securing means  6  and said means  8  for securing the template  9  mounted so that they can rotate freely at its second end, as depicted in FIG.  1 . Placed inside the carriage is a transmission for transmitting the rotational movement of the output shaft  16  to the blank-securing and template-securing means, for example a belt drive  17  as depicted in FIG.  1 . 
     The means  6  for securing the blank  7  and the means  8  for securing the template  9  are advantageously connected completely and have axes of rotation which are aligned, forming a single axis  59 , by a removable link exerting a mutual pull of one toward the other, preferably a screw-nut connection  48 ,  49  as depicted more particularly in FIG.  3 . The means  6  for securing the blank  7  are secured to one of the elements—screw  48  or nut  49 —of the screw-nut connection, and the means  8  for securing the template  9  are secured to the complementary other one of the element—nut or screw—of the screw-nut connection. The means  8  for securing the template  9  may consist of a head of the nut  49  and the means  6  for securing the blank  7  may consist of the head of the screw  48 , as depicted in FIG.  3 . 
     A tubular element  50  will advantageously be sandwiched between the screw  48  and the nut  49 , thus, via bearing surfaces which are preferably conical at its ends, aligning the blank-securing means  6  and the template-securing means  8 . The tubular element  50  is secured to a wheel  51  which takes the rotational drive belt  17 , as depicted in FIG.  1 . The output shaft  16  is secured to a wheel  53  with which the belt  17  engages to transmit the rotational movement of the tubular element  50 . As depicted in FIG. 1, the belt drive  51 ,  53 ,  17  is preferably mounted inside the moving carriage  13  where the housing  54  is produced for this purpose. In order to access the housing  54 , the moving carriage may adopt a structure in two parts assembled and positioned one on the other removably by means of screws  55  and pegs  56  respectively, for example. The wheels  53  and  51  will preferably be placed between the two bearings  44  supporting the output shaft  16  and the two bearings  52  supporting the tubular element  50 , respectively. As depicted in FIG. 1, sealing rings  57 ,  58  will be mounted around the tubular element  50  and the output shaft  16  so as to protect the belt drive and the bearings placed inside the moving carriage  13  from the lubricating fluid placed in the machining compartment  31 . 
     The screw-nut mounting  48 - 49  allows the user, having secured the blank and the template on the head of the screw and the head of the nut respectively, as will be explained later on, to mount these elements on the machine, each in one hand, in an operation of screwing through the tubular element  50 . By virtue of the screw-nut connection  48 ,  49  in collaboration with the conical bearing surfaces described above, the blank support and template support are mounted without play and are correctly aligned on one and the same axis of rotation. The tubular element  50  is mounted so that it can rotate freely on the carriage  13  via two bearings, preferably rolling bearings  52 , as depicted in FIG.  1 . 
     The machine according to the invention advantageously comprises in full or part of itself, a centering jig  60  which allows the blank  7  to be secured to the blank-securing means  6  and allows the template  9  to be secured to the template-securing means  8  in such a way that the part to be obtained, particularly the inlay, is inscribed inside the initial volume of the blank. 
     One exemplary embodiment of such a jig is depicted in FIG. 4, enlarged and in perspective. The jig  60  comprises a housing  61 , preferably tubular, which represents the exterior shape of the blank and which may be slightly smaller in order to compensate for positioning errors, the housing  61  defining an axis of symmetry  62 , and a housing  63  similar to the housing  61  but open at the top and the axis of symmetry of which is colinear with the axis  62 . Between the housings  61  and  63 , the jig forms a clearance  64  that complements the exterior shape of the moving carriage  13  so that the latter can be inserted in it and positioned in such a way that the axis  62  of the jig is parallel to the axis of rotation  59  of the means for securing the blank  7  and means for securing the template  9 . The jig  60  and/or moving carriage  13  will be equipped with any means allowing the operator easily to position the axes  62  and  59  parallel and keep them in this position with respect to one another for long enough to secure the blank and the template to their respective securing means. The exterior shapes of the jig  60  and of the moving carriage  13  will advantageously be used for this purpose to allow these to nest together in the desired position explained above. The flat walls  67  and  68  may be used to bear against the moving carriage. 
     To facilitate the operation that consists in nesting the jig  60  on the moving carriage  13 , the jig may advantageously be equipped with a hinge means  65  allowing the clearance  64  to be opened up by folding the jig about an axis perpendicular to the axis  62 , as depicted in FIG.  4 . The hinge means will preferably be produced by a thinning  66  of a section perpendicular to the axis  62 , altering the flexibility of a plastic material of which, in this case, the jig  60  is preferably made. 
     The tubular housing  61  of the jig will be of a shape that complements that of the blank covering the volume of the template used. It is thus understood that there may be as many jigs as there are essential shapes of templates possible according to the intended applications. The open housing  63  of the jig will be of a shape that complements that of the blank so as to allow the latter to be guided toward the corresponding securing means in a direction parallel to the tubular housing  61  and parallel to the axis  59 . 
     The template  9  is first of all secured by one of its ends to its securing means  8 , preferably by bonding, and preferably by distributing the material uniformly about the axis of rotation  59  of the securing means. The securing means  8  may comprise a spike  69  formed on the head of the nut  49 , for example, which will penetrate a complementary housing in the template  9  in order to provide better securing, as depicted in FIG.  3 . The spike  69  will be secured via an insulator  71  to the head of the nut  49 . The means  8  for securing the template  9  with the associated template are then mounted on the machine  1  via the screw-nut connection  48 ,  49  as described earlier. Next, the jig  60  is fitted on the moving carriage  13  by inserting the template  9  in the tubular housing  61 . The blank  7  is finally secured, preferably by bonding, by one of its ends to the corresponding securing means  6 , in a position thus given by the jig  60  so that the volume of the template  9  is inscribed inside the volume of the blank  7 . 
     The axis of rotation  59  of the blank  7  and of the template  9  is parallel to the axis of rotation  18  of the abrasive disk and the part of the feeler  10  in contact with the template  9  is aligned with the peripheral working part of the abrasive disk  4  along a straight line parallel to the axis  18  so as to obtain a copy which is identical to the template in a plane perpendicular to the axes  59  and  18 . 
     When the motor  12  drives the rotation of the blank  7  and of the template  9  in a given direction, via the output shaft  16 , the belt drive  17 ,  51 ,  53 , the blank-securing means  6  and the means  8  for securing the template  9 , the friction forces due to the rotational drive give rise to a torque which tends to cause the moving carriage  13  to rotate about the output shaft  16 , and therefore to keep the template  9  and the blank  7  pressed respectively against the feeler  10  and against the abrasive disk  4 . These friction forces may act in concert with the forces of gravity and/or the forces generated by the action of a spring (not depicted), as appropriate. If the motor  12  drives the blank  7  and the template  9  in the opposite direction of rotation to the previous one, it is necessary to use the forces of gravity and/or the forces generated by the action of a spring as explained hereinabove. 
     A The machine advantageously comprises means for reversing the direction of rotation of said abrasive disk  4 , which can thus work in opposition or in a downstream direction depending on whether it is rotating in one direction or the other, this being in order to optimize the wear on the disk before it is replaced as a result of wear. 
     The means (not depicted) of command and control of the means for driving the rotation of the machining tool, of the means for driving the rotation of the means that secure the template and the blank, and of the movement means, comprise an electrical power supply, preferably a low-voltage DC supply arranged outside the casing  30  of the machine  1  and connected to the latter at the drive compartment  32  by a supply lead and an electric plug, both of which are sealed (not depicted), command and control electronics (not depicted) placed in the drive compartment  32 , and software for the automatic control of at least a manufacturing cycle. 
     The machine depicted in FIG. 1 advantageously comprises means for automatically stopping operation at the end of machining by detecting that the moving carriage  13  is in the given position, for example when the feeler  10  is near to or on the axis  59  of rotation of the template. 
     The machine depicted in FIG. 1 furthermore advantageously comprises means for slaving the means for moving the moving carriage  13 , more particularly the motor  11  that drives the translational replacement of the carriage, to the force exerted by the abrasive disks on the blank  7 . 
     The machining compartment  31  will be filled up to a given level with a lubricating fluid, particularly water, so as to provide correct lubrication and correct cooling of the abrasive disk  4  by splash lubrication and will be sealed so that the fluid does not enter the drive compartment  32 . 
     The machine depicted in FIG. 1 furthermore advantageously comprises means for automatically clearing the moving carriage  13  at the end of machining, consisting in raising the latter, particularly by rotating the output shaft  40  of the motor  12 , in the opposite direction to the direction of machining, which, by virtue of the friction forces or of a mechanical antideflection device of the free wheel or viscous type (not depicted), causes the moving carriage  13  to tip away from the axis of rotation  18  of the abrasive disk  4 , thus opening up access to the securing means  6  and  8  for the subsequent operations. 
     The wall  3  is advantageously made of an electrically insulating material so as to allow the detection of the presence of lubricating liquid in the machining compartment  31  by measuring the resistivity by applying a voltage between the bearing supports  20  and  21 . This set-up also advantageously makes it possible to detect electrical contact between the moving carriage  13  and the bearing support  20  so as to inform the control electronics of the end of machining. 
     The machining compartment  31  is advantageously fitted with an articulated cover  70 , as depicted in FIG. 2, allowing access to the interior of the compartment  31  and affording the environment outside the machine protection against splashes of lubricating liquid during the machining operation. The machine also advantageously comprises means (not depicted) for automatically opening the cover  70 , these operating at the end of machining. Furthermore, the machine may comprise a system (not depicted) for automatically locking the cover  70 , preventing inopportune opening therefore during machining. 
     The electronic command and control means consist of at least one electronic input/output board (not depicted) placed in the drive compartment  32 . The inputs may, in particular, be connected to sensors as follows: a lubricating liquid level sensor, an end-of-machining sensor, a machining compartment lid open sensor, a cutting motor  5  current strength sensor and a temperature sensor. The outputs may be connected with the following commands: independent command of each motor, command of a visual interface for the user, command of the locking/unlocking of the cover  70 . 
     One exemplary method of operation of the machine according to the invention will now be described, it being possible for this method of operation advantageously to be implemented by automatic control software in the context of automatic operation of the machine. 
     The following mode of operation is described chronologically from the state of the machine at the end of machining and for the next machining operation: 
     when the cover  70  is opened, the “open” sensor sends a signal to the command and control electronics; the latter responds by actuating the motor  11  which will move the motor  12  in translation, and therefore the shaft  16 , and cause it to perform a series of low-amplitude back and forth movements so as to release the remains of blank resulting from an earlier machining operation from its residual bearing against the cutting disk  4 , then will completely return the carriage against the wall  3 ; 
     at the same time, the motor  12  begins to run in the opposite direction to the direction for machining, driving the shaft  16  which itself, by virtue of the friction forces or a non-deflection device as explained earlier, causes the carriage to tip away from the axis  18  of the machining motor, toward the outside of the machine, to make the next operations easier; 
     the operator may separate by unscrewing the means  6 ,  8  for securing the blank and the template, as explained earlier; the template  9  is replaced by unsticking the old one and sticking in the new one L using the spike that forms part of the support  8  which will be bonded into a bore hole made in the template; the blank is replaced either by unsticking the old one, or by replacing its securing means  6  which may be one-use means; the template, its support, and a fresh blank support are assembled on the tubular element  50 ; 
     in order to optimize the amount of material to be machined, the operator offers up various centering jigs  60  to the template  9 , and chooses the smallest one which can fit over the latter; the centering device is then folded down onto the carriage, pressed against the reference planes  64 ,  68 , for example, and the corresponding blank  7  is coated with an adhesive that makes an instant bond, and slipped onto the housing  63  reserved for it on the centering jig  60 , to be assembled by bonding with the blank-securing means  6 ; 
     the carriage  13  is folded down toward the inside of the machining compartment  31  and possibly moved, by virtue of push-buttons which advantageously command high-speed retreat and advance of the carriage, toward the desired machining start point; the protective cover is closed by the operator; the electronic control means check the water level, for example by analyzing the resistivity between the machining means and the movement means; the electronic control means check that the cover  70  has been closed, using a flexible blade switch placed, for example, in a stationary part of the casing  13  and a magnet placed in the cover which moves closer upon closure; if these two checks are passed, the machine is on standby and, by pressing either one of the two push-buttons described hereinabove, machining is begun; 
     the rotation motor  12  drives the rotation of the shaft  16  which, via the belt  17 , drives the tubular element  50  and therefore the blank  7  and the template  9  in rotation, and the carriage  13  which is pressed toward the disk  4  and the feeler  10  by the internal friction forces; at the same time, the advance motor  11  starts, and, by virtue of the screw-nut system  14 ,  15 , drives the translation of the motor  12 , the shaft  16  and therefore the blank and the template, thus allowing systematic exploration of the exterior surface of the template by the feeler, except for the concave regions; at the same time, the cutting motor  5  starts up, driving the rotation of the abrasive disk  4 ; throughout the machining phase, the inputs of the electronic means check a certain number of sensors, including the closure of the cover, the water level, the internal temperature, the strength of the current drawn by the cutting motor  5 , the manual push-buttons: if either one of the two push-buttons is depressed, it acts as an emergency stop; the end of machining by detection of electrical contact between the carriage  13  or the blank-securing means  6 , on the one hand, and the bearing support  20  or the abrasive disk  4 , or some other element of the machining assembly, on the other hand, the strength of the current drawn by the cutting motor  5  can control the speed of the motors  11  and  12  by virtue of an automatic control slaving means intended to optimize the machining rate to suit the machining forces; 
     when the advance movement of the carriage  13  is such that the template is no longer supported by the feeler, the carriage drops towards the bearing support  20  of the machining subassembly, electrical contact is made and the three motors  5 ,  11 ,  12  stop; the machined part is cut off from the rest of the blanks, and drops into the bottom of the machining compartment  31 ; if droppage were not to take place, machining would continue until the blank had been machined away and the blank-securing means would reach the abrasive disk, itself also metal, and the end-of-machining contact would then cause the three motors to stop; the cycle is finished, and returns to its start when the cover is opened; when the cover is open, it can be removed by extracting its spindle, allowing easy emptying and cleaning of the machining compartment  31 .