WO2002029504A1

WO2002029504A1 - Low-cost and rapid production of molds

Info

Publication number: WO2002029504A1
Application number: PCT/IB2000/001431
Authority: WO
Inventors: Khalil Michel Feghali
Original assignee: Khalil Michel Feghali
Priority date: 2000-10-05
Filing date: 2000-10-05
Publication date: 2002-04-11
Also published as: AU2000275480A1

Abstract

A method for the rapid preparation of patterns, molds, dies or forms, consists of a CAD/CAM system (including a postprocessor) in which is modeled the three-dimensional object for which the imprint is to be prepared, a robot with controller and tool bit or end effector, and one or more matrices each containing an array of slidable pins or rods. By displacing the pin/rod elements along their axis by determined amounts according to the shape of the object for which the imprint is being prepared, a pattern or mold or die or form is obtained for producing the three-dimensional object.

Description

Title Low-Cost and Rapid Production of Molds

DESCRIPTION

Technical Field

This invention relates to a method and apparatus for the rapid and low-cost production of patterns, molds, dies or forms, hereinafter called "imprints", to be used in industries such as metal casting, metal forming, concreting, rubber and plastic industries, etc, in cases where a number of short production runs (each requiring a different imprint) is involved, such as in prototyping

Background Art

In current methods for the preparation of imprints, such as machining (traditional, NC or CNC) or other rapid prototyping methods, the base material used being metal, wood, plastic or resin, etc , is not always recyclable after the imprint produced has been used and no longer required While methods which overcome this limitation by using a plurality of rods or pins to rapidly prepare molds, are generally known, the following two methods have been found to be the most relevant to the problem at hand

One method for the preparation of imprints, named "Quick Mold Prototyping" (ref U S patent No 5,914,081 by Shevchuk) overcomes these limitations by using elongated wire elements of circular cross-sections, stacked next to one another inside a frame

Another method for the preparation of imprints (ref U S patent No 5,546,313 by William E Masters) uses mold modules each containing an array of pin elements with threaded drive elements Disclosure of Invention

The apparatus relating to this invention includes a CAD/CAM system with postprocessor, a three-dimensional positioning system (or robot) with controller and end-effector or tool bit, and one or more "matrices" each consisting of a frame holding an array of parallel pins/rods, the matrix(matrices) acting as the base material for the imprint. The pins/rods are not in contact with one another, can be displaced one at a time along their axis when their holding frame is in the "unlocked" position, and have at least one of their two ends originally lying in a same plane.

Once the three-dimentional object is modelled in the CAD/CAM system, a toolpath is generated for an array of points on the surface of the object model, the (x,y) coordinates of each of these points corresponding either to the (x,y) coordinates of the axis of a pin/rod, or to the (x,y) coordinates of the centroid of the axes of a group of adjacent pins/rods. The said toolpath is then processed through the postprocessor and communicated to the robot controller which then guides the robot tool bit to displace the pins/rods individually or in groups along their axis so as to have their originally coplanar ends move by amounts defined by the object shape (i.e. by the third coordinates or z-coordinates of the points on the surface of the object model). After the displacement of all pins/rods is completed, the pins/rods are locked into position thus defining a surface for the imprint.

The advantages of the holding frame design is that it enables the pins/rods to be kept separate from one another during their displacement, and that it allows the simultaneous locking of all the pins/rods while engaging each of them separately, thus avoiding the following:

(a) developing enough friction between the particular element being displaced and its immediate neighbours, resulting in the displacement of at least one of the neighbours together with the particular element being displaced, and/or resulting in the erosion/scratching of the elements along their lines of contact between one another and with the clamping frame, and/or cause some strain on the displacing plunger or tool bit and its carnage/robot, and

(b) having, in case the stack is horizontal or inclined, lower wire elements be subject to the weight of the elements stacked above them in addition to the clamping force, which would aggravate the problems described in (a) above

Also, enabling the pins/rods to be displaced by mere pushing avoids the slow process associated with moving the pin elements to their final position by engaging the threads of corresponding drive elements, and results in a lower cost for the apparatus The new generation of commercially available positioning systems or robots (cartesian or other types) having high speeds of displacements along their axes, render this method an efficient one for the quick preparation of imprints

Brief Description of Drawings

In drawings which illustrate the embodiments of the invention,

Figure 1 is a diagram showing the different components of the apparatus for the method used,

Figure 2 is a perspective view of a matrix holding frame and one pin/rod,

Figure 3 is a perspective view of the matrix holding frame with side guides,

Figure 4 is a detail of the locking/unlocking mechanism of the matrix,

Figure 5 is a top view of the matrix showing the pins/rods heads, pins/rods, and holes,

Figure 6 is a perspective view of a matrix in which pins/rods are individually locked/unlocked with anchor wedge cones, showing one pin/rod during the course of its displacement and another one after its displacement is completed, Figure 7 is a perspective view showing anchor wedge cones for a matrix in which pins/rods are individually locked/unlocked one anchor wedge cone for a pin/rod after its displacement is completed, and another anchor wedge cone for a pin/rod during the course of its displacement, and

Figure 8 is a partial sectional view of a matrix in which pins/rods are individually locked/unlocked with anchor wedge cones, showing one pin/rod during the course of its displacement and another one after its displacement is completed

Best Mode for Carrying Out the Invention

The different components of the apparatus subject of this invention are shown in the diagram depicted in Fig 1 , and include a CAD/CAM system with postprocessor (1 ), a robot (3) with controller (2) and end-effector or tool bit (4), and a matrix (5) The matrix (5) consists of a frame (6) holding a number of parallel pins or rods (7) of equal length, preferably metallic, in a staggered rectangular array arrangement as shown in Fig 3 and Fig 5

The holding frame (6) is such that the pins/rods (7) are at all times not in contact with one another and that they can be displaced individually along their axis when the holding frame is in the "unlocked" position The frame (6) has a locking feature enabling to lock all pins/rods within the said frame simultaneously into position after the displacement of all pins/rods is completed, as well as to unlock all pins/rods within the said frame simultaneously such that they become again free for movement along their axis after the imprint is no longer needed (Fig 4) The holding frame (6) consists of two parallel sets of parallel metallic sheets or slabs (11 ) held into side guides (10), each sheet or slab perforated with an identical staggered rectangular array of holes (12), with the sheets/slabs within each of the sets being fixed to one another independently from the sheets/slabs of the other set, in a way such as to have the centers of holes (12) being aligned across all sheets/slabs within a same set The said sets are positioned parallel to one another in a way such that the sheets/slabs of the different sets interlock (i e between any two adjacent sheets/slabs of a same set lies one sheet/slab of the other set), and that the sets are free only to sliding parallel to one another by a small distance. While sliding parallel to one another, the sets reach a position relative to one another at which the centers of all corresponding holes will be aligned across both sets (i.e. across all sheets/slabs). Each pin/rod will be located through one group of aligned corresponding holes across the two sets (i.e. across all sheets/slabs) and will ideally have a head (8) at its top end and another head (9) at its bottom end, said heads at the pins/rods top ends resting on the top sheet/slab of the top set of sheets/slabs, thus preventing the pins/rods from sliding through their aligned holes and out of the holding frame due to gravity when in the "unlocked" position (see Fig. 4). The holes diameter exceeds the pins/rods diameter by a certain clearance so as to allow for free displacement of the pins/rods along their axis when holes are aligned across all sheets/slabs (i.e. when holding frame is in the "unlocked" position). The diameter of the virtual cylinder in which each pin/rod head is inscribed (such cylinder having its base parallel to the matrix sheets/slabs) exceeds the holes diameter while still being less than the least center-to-center distance between adjacent holes (Fig. 5) such as the heads fit tightly next to one another in a way to minimize gaps between them while keeping a certain clearance to avoid friction between one another during their displacement.

After the three-dimensional object (for which an imprint is to be prepared) is modelled in the CAD/CAM system, a toolpath is generated for an array of points on the surface of the object model, said points having coordinates (x^y^), (x₂.y₂.Z₂), etc... in the model cartesian coordinate system. The orthogonal projection on the xy plane of this array of points has a staggered rectangular pattern similar to that of the array of holes in the sheets/slabs of the matrix holding frame, the (x,y) coordinates in the model cartesian coordinate system of each of these model surface points, correspond to the (x,y) coordinates in the matrix cartesian coordinate system of the axis of a different pin/rod in the matrix, the pins/rods axes being parallel to the z axis. The matrix being an arrangement of pins/rods the top of the upper heads of which originally (before displacement of the pins/rods) lying in the z₀ plane, and the length of each of which extending parallel to the z-direction, with the (x,y) coordinates in the matrix cartesian coordinate system of the axis of each of these pins/rods corresponding to the (x,,y,) coordinates in the model cartesian coordinate system of a different point within the said array of points on the surface of the model, the number of points in said array of points on the surface of the model not exceeding the total number of pins/rods in the matrix.

The toolpath generated on the CAD/CAM system and relating to these points on the surface of the model (namely (xι, ι,zι), (X₂.y₂.z₂). etc. ), is processed through the postprocessor and communicated to the robot controller such that the end effector of the robot or tool bit tip is instructed to move to the (x,y) location (in the matrix cartesian coordinate system) of the pin/rod axis relating to the (Xι,y coordinates of the first point of the array of points on the surface of the model, such movement to be carried out while having all moving parts staying clear from the pins/rods or matrix to avoid collisions during the movement, and then move one end of this pin/rod along its axis (parallel to the z-axis) so as to have the pin/rod head be displaced from its riginal location by a distance of z - z₀) in the positive direction, z₀ corresponding at most to the lowest among all z, coordinates of said points within the array of points on the model surface, and z^ being the value of the third coordinate of this first (x^ yi, z^ point on the surface of the model. The clear length of the tool bit or end effector is larger than the distance between the tip of the pins/rods lower heads when in their original position (before their displacement) and the bottom face of the lowest sheet/slab in the matrix holding frame. The length of the pins/rods is such that the distance between the tip of the pins/rods lower heads when in their original position (before their displacement) and the bottom face of the lowest sheet/slab in the matrix holding frame, is larger than the value of (z_max - z₀), Zm_ax corresponding to the largest among all z, coordinates of said points within the array of points on the model surface. A controller (for the positioning system or robot) with point-to-point control capability, is generally adequate for this application and less costly than one with continuous control capability. The said toolpath is such that the robot tool bit or end effector would then move back in the opposite direction by a same z^ - z₀) distance before moving to the (x,y) location of the next pin/rod corresponding to the next point on the model surface, and so on

For example, if the tool bit is displacing the pins/rods while touching their upper heads, the path for the tool bit tip when in contact with the pins/rods upper heads would be as follows starting with the first (x^y^) point from (x^y^) to (x^y^), then back to (xι,yι,z₀), then to the location of the next point (x₂,y₂,zn) etc If the tool bit is however displacing the pins/rods while touching their lower heads, and if L is the overall length of the pins/rods, the path for the tool bit tip when in contact with the pins/rods lower heads would be as follows starting with the first (x^y^) point from

- L), then back to

- L), then to the location of the next point (X₂.y₂.z₀ - L) etc In this example, the robot end effector would be moving the pins/rods individually along their axis a distance of (z, - z₀)

Measures are taken for preventing gravity from pulling back the pins/rods to their original position after they have been displaced and before they are locked into their final position, such measures taken before and maintained during the pins/rods displacement process, may be in the form of having the pins/rods immersed partially or totally in a medium having a similar specific qravity to that of the pins/rods, or having the pins/rods extend along a horizontal or inclined direction (in which case the (x,y,z) axis of the robot and matrix are rotated with respect to the world (X,Y,Z) axes as well as with respect to the model coordinate system), or any other mechanical, hydraulic, pneumatic (e g air blowing, suction or vacuum) or magnetic or other measures

Once all pins/rods have been displaced to their final positions (1 e their corresponding z, values), the locking feature of the matrix (Fig 4) enables the locking of all pins/rods simultaneously into position, by sliding the sets of sheets/slabs parallel to one another by a small distance (to a location at which the holes will not be perfectly aligned across all sheets/slabs) and fixing the sets relative to one another so that enough friction would be developed between the pins/rods and the side of the sheets/slabs holes, so as to withstand the force applied during the production of the finished castings, moldings or formed parts Once the imprint thus prepared is no longer required, the pins/rods are unlocked simultaneously in a single operation and are brought back to their original position (before displacement) by gravity or other means unlocking the sets of sheets/slabs and bringing them back to the position at which holes are aligned across all sheets/slabs, would allow the resetting of the heads of the pins/rods in their same original plane These locking/unlocking positions are detailed in Fig 4

The robot end effector is equipped with a vacuum or suction or electro-magnetic feature that is activated during the positive displacement of the pins/rods, in order to prevent the momentum gained by the pin/rod during its displacement from driving the pin/rod further than its intended final position

The imprint prepared as described above and defined by the pins/rods upper heads, is a positive imprint for the object, meaning that the imprint has a shape similar to that of the object The toolpath generated can also be such that the resulting imprint would be a negative imprint for the three-dimensional object in such case, the positioning system end effector or tool bit would move one end of the pins/rods along their axis (parallel to the z-axis) so as to have the top of each of the pins/rods upper heads be displaced from its original location by a distance of (z₀' - z,) in the positive direction, z₀' corresponding at least to the largest among all z, coordinates of the points within the array on the model surface, and z, being the value of the third coordinate of the respectively corresponding points on the surface of the model The length of the pins/rods would in this case be such that the distance between the bottom tip of their lower heads when in their original position (before their displacement) and the bottom face of the lowest sheet/slab in the matrix holding frame, is larger than the value of (z₀' - z_mm), z_mιn corresponding to the smallest among all z, coordinates of said points within the array of points on the model surface; the said toolpath would be such that the robot tool bit or end effector would then move back in the opposite direction by a same (z₀' - Zj) distance before moving to the (x,y) location of the next pin/rod corresponding to the next point on the model surface.

Instead of using a different toolpath as described in the above paragraph, for preparing a negative imprint for the object, such negative imprint is simultaneously defined by the set of lower pins/rods heads: the same toolpath can be used for preparing the positive imprint (defined by the set of heads at one end of the pins/rods) as well as the negative imprint (defined by the set of heads at the other end of the pins/rods).

It is sufficient to have only the array of points modelled in the CAD/CAM system, instead of the entire three-dimentional object. Such array of points can also be imported into the CAD/CAM system from a three-dimentional scan of the object surface.

The CAD/CAM system with postprocessor need not be a relatively robust system, but one that can perform the task at hand; it is therefore adequate and sufficient to use a low-cost CAD/CAM system with a low-end postprocessor, for this invention. A variation would be that for the points within the array on the surface of the object model, said points having coordinates (xi.yi.z , (X₂.y₂. ₂), etc... in the model cartesian coordinate system, the (x,y) coordinates in the model cartesian coordinate system of each of said points correspond to the (x,y) coordinates in the matrix cartesian coordinate system of the centroid of the axes of a group of adjacent pins/rods, the size of the selected tool bit tip or end effector being dependent on the number of pins/rods belonging to a same group of adjacent pins/rods to be displaced simultaneously during each stroke of the positioning system or robot, each point within the array on the surface of the model corresponding to a different group of adjacent pins/rods, each pin/rod belonging to only one such group of adjacent pins/rods, with the (x,y) coordinates in the matrix cartesian coordinate system of the centroid of the axes of each group of adjacent pins/rods, corresponding to the (Xj.yi) coordinates in the model cartesian coordinate system of a different point within the array of points on the surface of the object model, with the number of points constituting the array of points on the surface of the model not exceeding the total number of groups of adjacent pins rods in the matrix.

Alternatively, the arrays of points (on the surface of the model) and of holes (in the matrix sheets/slabs) would be non-rectangular and non-staggered. Regular rectangular arrays and circular arrays are examples of such arrays.

Another variation would be to have the matrix locking feature be one that locks each pin/rod individually after it has been displaced. This can be achieved by means of anchors (17 and 18) or other devices (one for each pin/rod). In this case, all sheets/slabs (13 and 14) are permanently fixed to one another in a way by which the centers of holes are aligned across all sheets/slabs, with the holes in the lower sheet/slab (14) being either straight or tapered to fit the anchors wedge cones (17), as detailed in Fig. 6. For a pin/rod undergoing displacement(15), the wedges of the relating anchor cone (18) move apart and away from the pin/rod. As soon as the displacement of the pin/rod is completed, the wedges of the relating anchor cone (17) lock against the pin/rod (16) again.

Still another variation would be to have the sets of sheets/slabs being adjacent to one another instead of having sheets/slabs of the different sets interlock. In such alternative, only the top sheet/slab of the bottom set would be adjacent to the bottom sheet/slab of the top set.

The matrix holding frame can also be replaced with a series of smaller holding frames placed side-by-side in a same plane in a rectangular array, each having its own independent locking feature. Finally, the positioning system or robot may be replaced with an array of wires made up of shape memory material such as Nickel Titanium (also known as Nitinol), each pin/rod being connected to one such wire. In such case, the controller would be robust enough to actuate each wire separately.

While a preferred embodiment of the invention has been described in this section, it is to be understood that various changes and modifications may be made without departing from the spirit or scope of the following claims.

Claims

The embodiments of the invention in which an exclusive property or pnviledge is claimed, are defined as follows

1 A method for producing a pattern or mold or die or form, hereinafter called

"imprint", for a three-dimentional object modelled on a CAD/CAM system, from a toolpath file generated on said CAD/CAM system for the said model, said toolpath being processed through a postprocessor and transmitted to the controller of a three-dimensional positioning system or robot, said method comprising

providing an imprint for said casting or molding or formed part, said imprint consisting of a matrix made up of a frame holding a number of parallel pins or rods of equal length in a staggered rectangular array arrangement, with the final positions of pins/rods of said matrix being such that their ends define the imprint shape, said holding frame being such that the pins/rods are at all times not in contact with one another and that they can be displaced individually along their axis when the holding frame is in the "unlocked" position during the imprint preparation process, said holding frame having a locking feature enabling to lock all pins/rods within the said frame simultaneously into position after the displacement of all pins/rods is completed, said locking feature enabling also the unlocking of all pins/rods within the said holding frame simultaneously such that they become again free for movement along their axis after the imprint is no longer needed, said holding frame consisting of a number of sets of parallel metallic sheets or slabs, each of said sheets/slabs being perforated with an identical staggered rectangular array of holes, with the sheets/slabs within each of the sets being fixed to one another independently form the sheets/slabs of the other sets, in a way such as to have the centers of holes being aligned across all sheets/slabs within a same set, said sets being positioned parallel to one another in a way such that the sheets/slabs of the different sets interlock (i e between any two adjacent sheets/slabs of a same set lies one sheet/slab of each of the other sets) and such that the sets are free only to sliding parallel to one another by a small distance;

allowing the sets of sheets/slabs of said matrix to slide parallel to one another, so as to reach a position relative to one another at which the centers of their corresponding holes are aligned across all sets (i.e. across all sheets/slabs), each of said pins/rods being located through one group of aligned corresponding holes across all sets (i.e. accross all sheets/slabs), each of said pins/rods having a head at its top end, said heads resting on the top sheet/slab of the top set of sheets/slabs and having a size and shape which prevent the pins/rods from sliding through their aligned holes and out of the holding frame due to gravity when in the "unlocked" position, the holes diameter exceeding the pins/rods diameter by a certain clearance so as to allow for free displacement of the pins/rods along their axis when holes are aligned across all sheets/slabs (i.e. when holding frame is in the "unlocked" position), the pins/rods heads being initially (before their displacement) located in a same plane, and having a size, shape and orientation such that they fit tightly next to one another in a way to minimize gaps between them while keeping a certain clearance to avoid friction between one another during their displacement;

having the said toolpath generated for an array of points on the surface of the object model, said points having coordinates (x^y^), (x₂,y₂,z₂), etc... in the model cartesian coordinate system, the orthogonal projection on the xy plane of said array of points, having a staggered rectangular pattern similar to that of the array of holes in the sheets/slabs of the matrix holding frame, the (x,y) coordinates in the model cartesian coordinate system of each of these model surface points, corresponding to the (x,y) coordinates in the matrix cartesian coordinate system of the axis of a different pin/rod in the matrix, the pins/rods axes being parallel to the z axis;

having said matrix be an arrangement of pins/rods the top of the heads of which originally (before displacement of the pins/rods) lying in the z₀ plane, and the length of each of which extending parallel to the z-direction, with the (x,y) coordinates in the matrix cartesian coordinate system, of the axis of each of these pins/rods, corresponding to the (x_hy,) coordinates in the model cartesian coordinate system, of a different point within the said array of points on the surface of the model, the number of points constituting the array of points on the surface of the model not exceeding the total number of pins/rods in the matrix;

having said toolpath processed through said postprocessor and communicated to said controller of said positioning system or robot, such that the end effector or tool bit tip of said positioning system or robot, is instructed to move to the (x,y) location (in the matrix cartesian coordinate system) of the pin/rod axis relating to the said (xι,yι) coordinates of the first point of the array of points on the surface of the model, such movement to be carried out while having all moving parts staying clear from the pins/rods or matrix to avoid collisions during the movement, and then move one end of this pin/rod along its axis (parallel to the z-axis) so as to have the top of the pin/rod head be displaced from its original location by a distance of {z^ - z₀) in the positive direction, z₀ corresponding at most to the lowest among all z, coordinates of said points within the array of points on the model surface, and Z_\ being the value of the third coordinate of this first (x^ y_{1 :} z^ point on the surface of the model, the clear length of the tool bit or end effector being larger than the distance between the tail of the pins/rods when in their original position (before their displacement) and the bottom face of the lowest sheet/slab in the matrix holding frame, the length of the pins/rods being such that the distance between the tail of the pins/rods when in their original position (before their displacement) and the bottom face of the lowest sheet/slab in the matrix holding frame, is larger than the value of (z_max - z₀), z_max corresponding to the largest among all z, coordinates of said points within the array of points on the model surface;

having the said toolpath being such that the robot tool bit or end effector then moves back in the opposite direction by a same (z^ - z₀) distance before moving to the (x,y) location of the next pin/rod corresponding to the next (x₂,y₂,Z₂) point on the model surface, and displacing this pin/rod to its final position by moving it along its axis by a (z₂ - z₀) distance, and so forth for all remaining pins/rods, providing, once all pins/rods having been displaced to their final position (i e their corresponding z, values), a locking feature in the holding frame, which enables the locking of all pins/rods simultaneously into position by sliding the sets of sheets/slabs parallel to one another by a small distance (to a location at which the centers of holes will not be perfectly aligned across all sheets/slabs) and by fixing the sets of sheets/slabs relative to one another so that enough friction would be developed between the pins/rods and the side of the sheets/slabs holes, so as to withstand the force applied during the production of the finished castings, moldings or formed parts,

allowing, once the imprint thus prepared is no longer required, the pins/rods to be unlocked simultaneously in a single operation and to be brought back to their original position (before displacement) by gravity or other means Unlocking the sets of sheets/slabs and bringing them back to the position at which holes are aligned across all sheets/slabs, would allow the resetting of the heads of the pins/rods in their same original plane (the z₀ plane)

2 The method of claim 1 whereby instead of preparing a positive imprint for the object (meaning that the imprint has a shape similar to that of the object), the toolpath generated is such that the resulting imprint is a negative imprint for the three-dimensional object in such case, the positioning system end effector or tool bit would move one end of the pins/rods along their axis (parallel to the z-axis) so as to have the top of each of the pins/rods heads be displaced from its original location by a distance of (z₀' - z,) in the positive direction, z₀' corresponding at least to the largest among all z, coordinates of the points within the array on the model surface, and z, being the value of the third coordinate of the respectively corresponding points on the surface of the model The length of the pins/rods would in this case be such that the distance between the tail of the pins/rods when in their original position (before their displacement) and the bottom face of the lowest sheet/slab in the matrix holding frame, is larger than the value of (z₀' - z_mιn), z_mιn corresponding to the smallest among all z, coordinates of said points within the array of points on the model surface, the said toolpath would be such that the robot tool bit or end effector would then move back in the opposite direction by a same (z₀' - z,) distance before moving to the (x,y) location of the next pin/rod corresponding to the next point on the model surface

3 The method of claim 1 whereby the pins/rods are equipped with another set of heads at their bottom ends, such heads having the same characteristics as those of the heads at their top ends, thus enabling the simultaneous preparation of the negative imprint (defined by the set of heads at the bottom ends of the pins/rods) at the same time as the positive imprint (defined by the set of heads at the top ends of

4 The method of claim 2 whereby the pins/rods are equipped with another set of heads at their bottom ends, such heads having the same characteristics as those of the heads at their top ends, thus enabling the simultaneous preparation of the positive imprint (defined by the set of heads at the bottom ends of the pins/rods) at the same time as the negative imprint (defined by the set of heads at the top ends of

5 The mehod of claim 1 or claim 2 or claim 3 or claim 4, whereby for the points within the array on the surface of the object model, said points having coordinates (x₂.y₂.Z₂), etc in the model cartesian coordinate system, the (x,y) coordinates in the model cartesian coordinate system of each of such points, correspond to the (x,y) coordinates in the matrix cartesian coordinate system, of the centroid of the axes of a group of adjacent pins/rods, the size of the selected tool bit tip or end effector being dependent on the number of pins/rods belonging to a same group of adjacent pins/rods to be displaced simultaneously during each stroke of the positioning system or robot, each point within the array on the surface of the model, corresponding to a different group of adjacent pins/rods, each pin/rod belonging to only one such group of adjacent pins/rods, with the (x,y) coordinates in the matrix cartesian coordinate system of the centroid of axes of each group of adjacent pins/rods, corresponding to the (x,,y,) coordinates in the model cartesian coordinate system, of a different point within the array of points on the surface of the model, the number of points constituting the array of points on the surface of the model not exceeding the total number of groups of adjacent pins/rods in the matrix

6 The mehod of claim 1 or claim 2 or claim 3 or claim 4, including the provision of measures for preventing gravity from pulling back the pins/rods to their original position after they have been displaced and before they are locked into their final position, such measures taken before and maintained during the displacement of the pins/rods, may be in the form of having the pins/rods immersed partially or totally in a medium having a similar specific qravity as that of the pins/rods, or having the pins/rods extend along a horizontal or inclined direction (in this case, the (x,y,z) axis of the robot and matrix are rotated with respect to the world (X,Y,Z) axes as well as to the model cartesian coordinate system), or any other mechanical, hydraulic, pneumatic (e g air blowing, suction or vacuum) or magnetic or other measures

7 The method of claim 1 or claim 2 or claim 3 or claim 4, whereby the robot end effector is equipped with a vacuum or suction or electro-magnetic feature that is activated during the positive displacement of the pins/rods, in order to prevent the momentum gained by the pin/rod during its displacement from driving the pin/rod further than its intended final position

8 The method of claim 1 or claim 2 or claim 3 or claim 4, whereby the matrix locking feature can be one that locks each pin/rod individually after it has been displaced, this can be achieved by means of anchor wedges located between each of the pins/rods and the edge of its corresponding hole, or other devices (one for each pin/rod) In this case, either all sheets/slabs are permanently fixed to one another in a way by which holes are aligned across sheets/slabs (i e across all sets), or only a single set of sheets/slabs is required. The holes in the lower sheet/slab being either straight or tapered to fit the anchor cone wedges.

9. The method of claim 1 or claim 2 or claim 3 or claim 4, whereby the arrays of points (on the surface of the model) and of holes (in the matrix sheets/slabs), would be a type of array other than staggered rectangular, circular arrays being one example.

10. The method of claim 1 or claim 2 or claim 3 or claim 4, whereby the sets of sheets/slabs are such that sheets/slabs of different sets do not interlock. In such alternative, only the edge sheets/slabs (top and bottom sheet/slab) of a same set would be adjacent to sheets/slabs of another set.

11. The method of claim 1 or claim 2 or claim 3 or claim 4, whereby the holes (in the sheets/slabs) have a non-circular shape.

12. The method of claim 1 or claim 2 or claim 3 or claim 4, whereby the pins/rods have a non-circular cross-section.

13. The method of claim 1 or claim 2 or claim 3 or claim 4, whereby the pins/rods heads are overlaid with a membrane of a viscoelastic material, such membrane to act as a curve-fitting surface that minimizes indentations on the surface of the prepared imprint.

14. The method of claim 13 whereby the pins/rods do not have heads and the said membrane overlay the ends of the pins/rods.

15. The method of claim 1 or claim 2 or claim 3 or claim 4, whereby several matrices are placed side-by-side, all pins/rods acting as if they belong to a single matrix when relating to the array of points on the surface of the object model. A single imprint thus prepared would therefore be made up of several parts, each such part being an individual matrix.

16. The method of claim 1 or claim 2, whereby two matrices are placed one on top of the other with the axes of their pins/rods individually aligned, the top matrix holding frame being a certain distance away from the bottom matrix holding frame in a way that the top matrix pins/rods heads are initially resting on the top sheet/slab of the top matrix holding frame, the tails of the top matrix pins/rods resting on the heads of the bottom matrix pins/rods, the displacement of each of the pins/rods of the bottom matrix from their tails resulting at the same time in the displacement of the corresponding pin/rod in the top matrix by an equal amount, thus obtaining two sides of an imprint (mold or die) for the casting or molding of an object having a symmetrical shape about a plane of symmetry running through its centroid.

17. The method of claim 1 or claim 2, whereby two matrices are placed one on top of the other with the axes of their pins/rods individually aligned and with the top matrix being in the inverted position such that its pins/rods heads resting on the bottom matrix pins/rods heads, the top matrix holding frame being a certain distance away from the bottom matrix holding frame in a way that the top matrix pins/rods are initially extended to the maximum distance possible along their axis (i.e. their heads being the farthest possible away from their holding frame), the displacement of each of the pins/rods of the bottom matrix from their tails resulting at the same time in the displacement of the corresponding pin/rod in the top matrix by an equal amount in the opposite direction, thus obtaining two sides of an imprint (mold or die) for the casting or molding of an object having a more-or-less uniform thickness.

18. The method of claim 3 or claim 4, whereby two matrices are placed one on top of the other with the axes of their pins/rods individually aligned and the bottom heads of the upper matrix resting on the top heads of the lower matrix, the displacement of each of the pins/rods of the lower matrix from their bottom heads resulting at the same time in the displacement of the corresponding pin/rod in the top matrix by an equal amount, thus obtaining two imprints for the object, each of said imprints having a positive face and a negative face.

19. The method of claim 1 or claim 2, whereby the positioning system or robot is replaced with an array of wires made up of shape memory material such as Nickel Titanium (also known as Nitinol), each pin/rod being connected to one such wire. In such case, the controller would be robust enough to actuate each wire separately.

20. The method of claim 1 or claim 2 or claim 3 or claim 4, including having only the array of points modelled in the CAD/CAM system, instead of the entire three- dimentional object. Such array of points can also be imported into the CAD/CAM system from a three-dimentional scan of the object surface, said scan being obtained using any of the known available three-dimensions digitizing technologies (laser triangulation, Talbot-effect imaging, photogrammetry methods, etc.).

21. The method of claim 1 or claim 2 or claim 3 or claim 4, including modifying the z-coordinates of the points on the surface model in the CAD/CAM system before the imprint is prepared, by applying mathematical equations to such coordinates.

22. The method of claim 5 whereby groups of adjacent pins/rods have a different number of pins/rods, and the size of the end-effector or tool bit is changed during the imprint preparation process, to account for this difference.