WO2004062861A1

WO2004062861A1 - Method and apparatus for manufacturing a three dimensional element sculpture

Info

Publication number: WO2004062861A1
Application number: PCT/GB2003/000094
Authority: WO
Inventors: Peter David Hurley
Original assignee: Peter David Hurley
Priority date: 2003-01-13
Filing date: 2003-01-13
Publication date: 2004-07-29
Also published as: AU2003202010A1

Abstract

A three-dimensional bust sculpture (8) of a head is formed by removing material from an oversize blank (9) of a heat sensitive thermoplastics material, e.g. a polystyrene foam plastics, by a sublimation process. The blank is attached to a rotary motion provider (3) for rotation about a longitudinal axis of the bust sculpture to be formed. A heating element (7) is moved two-dimensionally longitudinally and transversely relative to the longitudinal axis to remove the material from the blank by the heat of the element. Rotation of the blank and the movement of the heating element are computer controlled such that the heating element removes the material from the blank to form a series of successive profiles on the blank which define the complete shape of the sculpture bust, the profiles corresponding to profiles of the head determined from surface co-ordinate data scanned from around the head.

Description

METHOD AND APPARATUS FOR MANUFACTURING A THREE DIMENSIONAL ELEMENT

SCULPTURE

This invention relates to three-dimensional element sculpture.

More particularly the invention is concerned with the production of a bust sculpture.

It is known, for example from my patent GB 2 254 712, to machine a bust sculpture from a blank using a rotary cutting action. The machining process is relatively slow and noisy.

An object of the present invention is to enable a bust sculpture to be produced at a faster rate than has been usual using a machining process and with a reduced level of noise during the production process. A further object is to provide a process of production which makes it possible to produce a bust sculpture, if desired, of a different size, including larger, from the actual size of the head which is to be represented.

In accordance with the present invention a bust sculpture is produced from an oversize blank of a heat sensitive thermoplastics material by removing material from the blank by a sublimitation process.

The thermoplastics material may be a foam plastics material, preferably a polystyrene foam. Polystyrene foam in the density range, for example, of 30kg/m³ open cell down to 2kg/m³ closed cell may be used, the higher density being used for smaller size, for example 1/3 actual size, representation of a head and the lower density for the actual and larger size representation of a head. The quality of finish using these foams is related to the density of the foam. It would seem that open cell structured foam is most suitable in the higher density ranges.

A heating element, preferably elongate, may be used to remove the material from the blank. Use of such a heating element enables the bust to be formed appreciably more quickly than is possible using a rotary cutter to shape the blank, and with minimal noise. Furthermore, a heating element can provide more flexibility in selection of size to suit the size of the bust sculpture to be made than a rotary cutter, which is limited by safety of length and rotational speed for use. Preferably the heating element is electrically heated although it may possibly be gas heated. The heating element may be moved relative to the blank to remove material from the blank as required to produce the bust sculpture. The blank may be moved relative to the heating element. Preferably the heating element is moved generally longitudinally of the bust sculpture to be produced to remove the material from the blank. Preferably the material is removed to shape the blank progressively in a series of angularly spaced profiles around the head of which the bust is being formed. The heating element may be moved incrementally around the blank for the forming of each profile but it is preferred that the blank is rotated incrementally relative to the heating element for each profile to be shaped by the heating element. Thus the heating element is conveniently arranged to move two-dimensionally relative to the blank for removing material from the blank, i.e. longitudinally of the bust sculpture to be formed and transversely of the direction of the longitudinal movement, inwardly and outwardly of the body of the material of the blank. Preferably the transverse movement is radial to the rotational axis of the blank.

In a preferred embodiment the heating element produces 256 equi- angularly spaced individual profiles around the blank to define the fully shaped bust sculpture. More or fewer than 256 profiles may be produced.

256 is preferred because of the diameter of heating element, for example 3 0.5mm, that may be used with minimal overlap of the paths along which the heating element moves in removing material from the blank at adjacently formed profiles, and the quality of the shaping of the bust sculpture. The longitudinal movement of the heating element for each profile commences at the bottom of the bust sculpture. Conveniently the heating element commences its shaping of the blank from a position on the bust sculpture to be formed corresponding to the neck at the centre of the back of the head to be represented. The first profile is produced as the heating element moves longitudinally upwards with respect to the bust sculpture to be formed, the second profile is produced as the heating element then moves longitudinally downwards, and the following profiles are successively shaped as the heating element moves reciprocally longitudinally upwards and downwards and the blank is incrementally rotated.

For the forming of the profiles surface co-ordinate data of the head of which the bust sculpture is to be made may be collected from all around the head. The data is used to control the movement of the heating element, and rotation of the blank when the blank is rotated. In the preferred embodiment referred to above, the collected data is arranged to produce the 256 individual profiles around the head. The surface co-ordinate data may be obtained by laser line triangulation scanning of the head. This may be done in several ways, for example by single or double line reflection, rapid oscillation of a mirror reflecting a returning laser line onto a sensor array, thereby increasing the sensor array collection rate, stereoscopic imaging of the laser line where two cameras view one laser line from known angles, or by laser spot triangulation.

The principle of Moire Fringe Triangulation scanning may also be used in which beams of white light are projected onto the head and a camera sensor array looks for the differential at the change of light from white to 4 black from two known angles of the camera sensor array. The principle of stereoscopic imaging may be employed in which two cameras each take a snap shot of the subject at the same time from different angles, and the identification of the same points in 3-dimensional space by the two cameras is used to build the 3-dimensional image with the aid of light reflected from contours of the subject, the lighter the section of the image the closer the section being to the respective sensor array. All of the methods build up a 3-dimensional representation of the subject with 3- dimensional co-ordinates in space. The laser line triangulation meets the need for speed of acquisition and accuracy of the data for the forming of the profiles.

The number of profiles to be formed and the number of reference points per profile can be related to the operational speed of the cameras. There may be provision for variation. Preferably 256 profiles are arranged to be formed, as stated, and preferably there are 512 points of reference for each profile. The data for these preferred requirements may be acquired within as little as 3 seconds.

The surface co-ordinate data may be received by a computer, the data being a representation of the head by way of computer file transfer. The computer, with appropriate software, converts the data to suitable machine code for controlling the movement of the heating element for the forming of each of the profiles, and rotation of the blank when rotated.

Movement of the heating element may be by electro/mechanical means. The heating element may be moved along two linear slideways, one for the longitudinal movement described above and the other for the transverse movement. The movement may be provided, for example, by a linear actuator comprising a lead screw, a ball screw, a rack and pinion system or toothed timing belt, all having a prime mover such as a stepper

5 motor or a servo motor. The movement providing means may be selected according to cost, availability, required incremental positioning, anticipated useful life of the apparatus and/or electro/magnetic interference.

Rotational movement of the blank may also be provided by suitable elctro/mechanical means. For example, the movement may be by means of a worm and worm wheel, a bevel or spur gear, or an epicyclic, gearbox driven by a stepper or servo motor which provides the necessary incremental rotational control according to the number of profiles to be shaped around the bust sculpture.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a simplified perspective view of apparatus used in the process of producing a bust sculpture in accordance with the invention, a completed bust sculpture being shown;

Figure 2 is a front view of the apparatus;

Figure 3 is a fragmentary perspective view of motion providers of a modification of the apparatus;

Figures 4, 4a and 4b are respectively a longitudinal section view through a heating element of the apparatus and enlarged fragmentary sectional views of a base and tip end of the element, and

Figures 5 to 11 are simplified perspective views of the apparatus showing the bust being progressively formed to shape as the 6 heating element is moved up and down the blank to shape profiles of the bust sculpture by progressive removal of material of the blank.

Referring to Figures 1, 2 and 4 to 11 of the drawings, apparatus for use in the process of producing a bust sculpture from a head in accordance with this embodiment comprises a horizontal motion provider 1 , a vertical motion provider 2, a rotary motion provider 3, a base 4 on which the motion providers 1, 2, 3 are located, upright supports 5 fixed to the base 4, an attachment bracket 6 of the vertical motion provider 2 and a heating element 7 carried by the attachment bracket 6. A completed bust sculpture is indicated by reference 8 in Figures 1,2 and 11 and a blank from which the bust sculpture is produced is indicated by reference 9 in Figures 5 to 10 of the drawings.

Horizontal motion provider 1 comprises a pair of vertically spaced rails 10, 10' fixed on the upright supports 5 along which an upright carrier 11 is reciprocally moved horizontally by means of a horizontal lead screw 12 supported between the rails 10, 10' for rotation about its longitudinal axis. The horizontal lead screw 12 is threadedly engaged with a complementary internally threaded component, not shown, on the carrier 11 and is rotated by a reversible electric motor, not shown, through a gearbox, not shown.

Vertical motion provider 2 comprises a pair of horizontally spaced vertical guides 13, 13' , formed as parts of the carrier 11 , which support and guide the attachment bracket 6 for reciprocating vertical movement of the attachment bracket. The attachment bracket 6 is moved along the guides 13, 13' by means of a vertical lead screw 14 supported by the carrier 11 for rotation about its longitudinal axis. The vertical lead screw 14 is threadedly engaged with a complementary internally threaded 7 component, not shown, at the rear of the attachment bracket. This lead screw 14 is also rotated by a reversible electric motor, not shown, through a gearbox, not shown.

The attachment bracket 6 is moved vertically along the carrier to position the heating element vertically relative to the base 4 and the carrier is moved horizontally along the rails 10, 10' to position the attachment bracket, and thereby the heating element, horizontally relative to the base.

Rotary motion provider 3 comprises a turntable 15 supported on the base 4 for rotation about a fixed vertical axis. The turntable 15 is incrementally rotated by means of a second horizontal lead screw, not shown, supported by the base for rotation about its horizontal axis. The second horizontal lead screw is engaged by a gear wheel, not shown, fixed co-axially beneath the turntable 15 to an axle, not shown, of the turntable. An electric stepper motor, not shown, drives the second horizontal lead screw through a gearbox, not shown, such that the turntable is rotated in small angular increments. In this embodiment the turntable is rotated through 360° in 256 equal increments of 1.40625 degrees.

Clamps, not shown, are located on the turntable for fixing the blank 9 in place on the turntable for rotation with the turntable. Other suitable fixing means may be provided for fixing the blank mechanically on the turntable. Alternatively the turntable may possibly be arranged to hold the blank in place by suction.

Operations of all of the motion providers 1, 2, 3 are computer controlled according to surface co-ordinate data collected by laser line triangulation scanning, as referred to earlier in this specification, from the head of 8 which the bust sculpture 8 is to be made. The data is converted into machine code for the forming of 256 profiles from the blank as scanned from the head of which the bust sculpture is to be made. Thus the heating element 7 is precision moved, from an initial datum point relative to the turntable determined by the computer, horizontally and vertically respectively by the horizontal and vertical motion providers 1, 2, for the heating element to define each individual profile in turn, and the blank 9 is rotated by the turntable incrementally relative to the heating element by the rotary motion provider 3 for each successive profile to be formed.

The computer programme allows adjustment to suit the size of the bust sculpture that is required to be produced from the actual head. The bust sculpture may be made of actual size, or larger or smaller, as desired. The speed of production of the bust sculpture may also be adjusted.

The heating element 7, which is of an elongated probe-like form, is electrically heated. It comprises a helical resistance wire 17 extending centrally along a tubular metal sheath 18 from a base end 19 of the sheath, at which electrical connections 20 are made, to a closed tip end 21 to which the resistance wire 17 is anchored, the sheath serving as a return conductor. Typically the voltage is limited to less than 50 volts with a maximum current of 8 amps to generate an operating temperature of up to 500°C. The heating element is switched on and off automatically by the computer in association with the control of the motion providers of the apparatus.

The heating element is fixed by a clamp 22 to the attachment bracket which supports the heating element horizontally, extending radially of, with its tip end 21 towards, the rotational axis of the turntable.

9

A modified arrangement of the motion providers 1, 2, 3 is shown in Figure 3 of the drawings. In this arrangement, the heating element 7 is moved only vertically. The vertical motion provider 2 has a vertical carrier 11 on which the attachment bracket 6 is fixed for holding the heating element horizontally, radially of the vertical rotational axis of the turntable 15 of the rotary motion provider 3. The vertical carrier 11 is moved reciprocally vertically by means of the vertical lead screw 14 of the vertical motion provider 2 supported on the base 4 and threadably engaged with a complementary internally threaded component, not shown, at the vertical carrier. Instead of the heating element's being moved horizontally, the turntable 15 is bodily moved horizontally relative to the heating element. This is achieved by having the turntable 15 supported on, so as to move with, a horizontal carrier 11' , which is moved reciprocally horizontally, parallel to the heating element 7, by means of the first horizontal lead screw 12 of the horizontal motion provider 1 supported on the base 4 and threadably engaged with a complementary internally threaded component, not shown, at the horizontal carrier 11 ' . There is, therefore, relative vertical and horizontal movement between the heating element and a blank supported on the turntable for the production of a bust sculpture. As before, the turntable 15 of the rotary motion provider 3 is incrementally rotated by the second horizontal lead screw 16, which in this case is supported transversely on the horizontal carrier 11' .

In the modified arrangement of Figure 3 the turntable 15 has an upstanding rod 15' fixed co-axially on it by which the blank for the bust sculpture is located on the turntable. The rod 15' extends centrally through the blank, longitudinally of the bust sculpture to be produced, and a wing nut 15" screwed onto the externally screw threaded upper end of the rod secures and clamps the blank on the turntable for rotation with the turntable. As before, the lead screws 12, 14 and 16 are driven by electric stepper motors through gearboxes. Operations of the motion providers 1, 2, 3 are computer controlled in the manner described.

Referring back to Figures 1, 2 and 4 to 11, for the production of the bust sculpture 8, the apparatus is first prepared by establishing the datum point from which the forming process commences. The datum point which is indicated by the position of the tip end 21 of the heating element, is at the 0.00 degrees start position of the rotary motion provider 3, the bottom of the vertical movement of the heating element with the vertical motion provider 2 and the centre of the turntable 15 with the horizontal motion provider 1 which corresponds to the centre of the neck at the back of the head to be represented by the bust sculpture. Having established the datum point, the heating element is retracted by the horizontal motion provider and the blank9 from which the bust sculpture is to be formed is fixed centrally on the turntable 15. The blank 9 is oversize in relation to the head of which the bust sculpture is to be produced. It is made of polystyrene foam of a density suitable for the size of the bust sculpture to be produced, as indicated earlier in this specification. Next the computer control programme operates to switch on the heating element. Then the horizontal and vertical motion providers 1, 2 are activated to move the heating element longitudinally and horizontally, radially of the rotational axis of the turntable, according to the shape of the first profile to be formed from the blank as determined by the computer. The heating element evaporates material of the blank with which it makes contact as it is moved, thereby producing the shape of the profile. When the heating element reaches the top of its vertical movement for the forming of that first profile, the rotary motion provider 3 is activated by the computer to turn the turntable and blank through 1.40625 degrees and the horizontal and vertical motion providers are activated to move the heating element downwardly to define the second profile, alongside the first profile, as 11 determined by the computer from the surface co-ordinate data collected from the head. At the bottom of the vertical movement of the heating element for forming that second profile the rotary motion provider 3 is activated to turn the turntable and blank through a further 1.40625 degrees for the next profile to be formed. The procedure described is repeated for the successive forming of profiles on the blank until the blank has been turned through 360° and all 256 profiles have been formed on the blank to produce the completely shaped bust sculpture. When the last profile as been formed the heating element is switched off and retracted, and the completed bust sculpture is removed from the turntable.

Typically, working at an optimum rate of lOOmm/sec in removing material from the blank for the forming of each profile, the bust sculpture may be completely shaped in 8-10 mins, depending upon the size to which it is made.

It will be understood that the modified arrangement of Figure 3 enables the horizontal and vertical motion providers 1, 2 to supply the necessary relative movement between the heating element and blank for the profiles to be formed on the blank as the turntable is incrementally turned by the rotary motion provider 3.

The bust sculpture may be painted, coated and undergo other finishing treatment after the forming process.

Claims

12Claims

1. A method of manufacturing a three dimensional bust sculpture (8) characterised in that an oversize blank (9) of a heat sensitive thermoplastics material has material removed therefrom by a sublimation process to define the shape of the bust sculpture (8) .

2. A method according to claim 1 characterised in that it comprises the steps of locating the blank (9) on a support(15) , heating a heating element (7) and causing relative movement between the blank(9) and the heating element (7) such that the heat of the heating element removes material from the blank by sublimation to define the shape of the bust sculpture (8) .

3. A method according to claim 2 characterised in that the support (15) on which the blank (9) is located is included in rotary motion provider means (3) which rotate the blank about a longitudinal axis of the bust sculpture to be formed, and the heating element(7) is moved two-dimensionally longitudinally and transversely with respect to the longitudinal axis by two-dimensional motion provider means (1, 2) to remove the material from the blank by sublimation to define the shape of the bust sculpture.

4. A method according to claim 3 characterised in that two-dimensional movement of the heating element (7) by the two-dimensional motion provider means (1 , 2) and the rotational movement of the blank (9) by the rotary motion provider means (3) are co-ordinated such that the heating element (7) removes the material from the blank in a series of successive profiles corresponding to profiles determined from the head of which the 13 bust sculpture (8) is being made, which profiles in combination define the complete shape of the bust sculpture.

A method according to Claim 4 characterised in that the heating element (7) is moved reciprocally longitudinally with respect to the longitudinal axis of the bust sculpture to be formed, whereby in the forming of adjacent profiles in the series the heating element moves in one longitudinal direction for the one profile and in the opposite longitudinal direction for the other profile.

6. A method according to claim 4 or claim 5 characterised in that 256 of the profiles are formed on the blank (9) to define the complete shape of the bust sculpture (8) .

7. A method according to any of claims 4 to 6 characterised in that for the forming of the profiles on the blank (9) , surface co-ordinate data of the head of which the bust sculpture (8) is being made is obtained by laser line triangulation scanning of the head, and the data is converted by computer means to machine code for controlling the two-dimensional movement of the heating element (7) and rotational movement of the blank (9) for forming the profiles.

8. A method according to any preceding claim characterised in that the blank (9) is made of a polystyrene foam plastics material.

9. A method according to claim 8 characterised in that the polystyrene is of a density in the range of 30kg/m³ open cell to 2kg/m³ closed cell. 14

10. A method according to any preceding claim characterised in that the heating element (7) is electrically heated.

11. Apparatus for performing the method of manufacturing a three dimensional bust sculpture (8) according to claim 1, characterised in that the apparatus comprises a base (4) , rotary motion provider means (3) on the base by which a blank (9) of heat sensitive thermoplastics material is supported and rotated about a longitudinal axis of the bust sculpture to be formed, two-dimensional motion provider means (1, 2) supported by the base (4) , a heating element (7) carried by the two-dimensional motion provider means (1, 2) and movable by said means two-dimensionally longitudinally and transversely relative to said longitudinal axis to remove the material from the blank (8) by sublimation to define the shape of the bust sculpture (9) , scanning means whereby surface co-ordinate data is obtained from the head of which the bust sculpture is made, to determine a series of successive profiles around the head, and computer means which receives the surface co-ordinate data from the scanning means and converts the data to machine code by which the two-dimensional motion provider means (1 , 2) and the rotary motion provider means (3) are operated and controlled to cause the heating element (7) to remove the material from the blank (8) so as to define a series of successive profiles on the blank corresponding to the profiles determined around the head from the surface co-ordinate data.