WO1999059812A1

WO1999059812A1 - Apparatus and method for manufacturing three-dimensional objects

Info

Publication number: WO1999059812A1
Application number: PCT/US1999/011210
Authority: WO
Inventors: James Ogg
Original assignee: Helisys, Inc.
Priority date: 1998-05-20
Filing date: 1999-05-20
Publication date: 1999-11-25
Also published as: AU4194599A

Abstract

An apparatus for converting sheet material into a three-dimensional object comprised of layers of the material is disclosed. One embodiment of the apparatus comprises a work station (44) adapted to receive the sheet material (41) and a bonding tool (76) mounted to move relative to the work station (44) to bond layers of sheet material (41) to each other to form the three-dimensional object. The bonding tool (76) heats at least a portion of the sheet material (41) to its cohesion melding temperature. The apparatus additionally comprises a material dispensing assembly (30) mounted to supply the sheet material (41) to the work station (44). The dispensing assembly (30) supplies a release sheet (43) adjacent to the sheet material (41) such that the release sheet (43) is interposed between the bonding tool (76) and the sheet material (41) during bonding to prevent heated sheet material (41) from adhering to the bonding tool (76).

Description

APPARATUS AND METHOD FOR MANUFACTURING THREE-DIMENSIONAL OBJECTS

Background of the Invention The present invention relates to an apparatus and method for converting sheet material into three-dimensional objects comprised of a plurality of layers of the sheet material, and more particularly to an apparatus and method for improving the quality and strength of the manufactured three-dimensional object.

In response to the problems of conventional prototype manufacture, many design firms now utilize computer driven, automated production machines. In these machines, a computer assisted design system provides an input three- dimensional shape to a forming machine to create the three-dimensional object for prototyping. Many of these systems involve the bonding together of a number of shaped laminations or layers to form the three-dimensional object. These laminated object manufacturing systems typically use a laser as a tool for forming each lamination, the laser being controlled by an x-y plotter device upon commands from a computer with input from the computer assisted design system

In several of these prior systems, sheets of plastic, paper or other such substrates are bonded together using an adhesive which is pre-applied to the sheet or is applied by a separate device within the laminated object manufacturing system. The adhesive may be either a pressure sensitive or a heat sensitive type. A roller may be used to facilitate bonding the laminations together.

One problem with present laminated object manufacturing systems is that structural discontinuities are created in the three-dimensional object in the z-axis (i.e., perpendicular to the laminated sheets). Such discontinuities are due to the adhesive bonding of the laminations and may cause the object to crack or separate along laminations if the object is subjected to harsh environmental conditions. In addition to separating, the laminations may warp or exhibit other unwarranted dimensional variations.

Accordingly, there is a need for an improved apparatus and method which provides three dimensional objects of higher quality and strength.

Summary of the Invention In one aspect of the invention, an apparatus for converting sheet material into a three-dimensional object comprised of layers of the material comprises a work station adapted to receive the sheet material and a bonding tool mounted to move relative to the work station to bond layers of sheet material to each other to form the three dimensional object. The bonding tool heats at least a portion of the sheet material to its cohesion melding temperature (defined hereinafter). The apparatus additionally comprises a material dispensing assembly mounted to supply the sheet material to the work station. The dispensing assembly additionally supplies a release sheet adjacent to the sheet material such that the release sheet is interposed between the bonding tool and the sheet material during bonding to prevent heated sheet material from adhering to the bonding tool.

In another aspect of the invention, an apparatus for converting sheet material having a cohesion melding temperature into a three-dimensional object comprised of layers of the sheet material comprises a work station adapted to receive the sheet material and a bonding tool mounted to move relative to the work station to bond layers of sheet material to each other to form the three dimensional object. The bonding tool comprises a heating member and a pressure member. The bonding tool is configured such that the heating member applies heat from one side of the sheet material and the pressure member applies pressure from the other side of the sheet material, such that the heated side of the material is pressed into direct contact with an adjacent layer of the material to bond adjacent layers together. The bonding tool heats the sheet material so that at least a portion of the sheet material is at the cohesion melding temperature during bonding.

In yet another aspect of the invention, a three dimensional object comprises multiple layers of sheet material, each of the layers of sheet material being substantially homogenous in a direction perpendicular to the planar surface of the sheet material. Each of the layers are united to an adjacent layer without adhesive therebetween by cohesion melding.

Yet another aspect of the invention relates to method of forming a three-dimensional object, comprising providing sheet material which is substantially homogenous in a direction perpendicular to the plane of the sheet material; bonding layers of the sheet material together; and applying sufficient heat to the sheet material to cause cohesion melding of the layers.

In a further aspect of the invention, a method of converting sheet material into a three-dimensional object comprised of a plurality of layers comprises bonding one layer of sheet material to an adjacent layer of sheet material by heating one side of the one layer and applying pressure to the other side of the one layer.

In another aspect of the invention, a method of converting sheet material into a three-dimensional object comprised of a plurality of layers comprises bonding one layer of sheet material to an adjacent layer of sheet material by heating one side of the one layer until the other side of the one layer reaches a cohesion melding temperature. The bonding additionally comprises applying pressure to the one side using a pressure member, and positioning a release sheet between the one side and the pressure member.

Brief Description of the Drawings Figure 1 is a schematic perspective view of an improved LOM system of the present invention; Figure 2 is a top plan view of the system of Figure 1; Figure 3a is a side elevatioπal view of a sheet feed system used in the present invention showing a sheet feed stage;

Figure 3b is a side elevational view of a sheet feed system used in the present invention showing a bonding stage;

Figure 3c is an enlarged view of the portion of the sheet feed system within line 3c-3c of Figure 3a; Figure 4 is a side elevational view of an alternative sheet feed system used in the present invention; Figure 5 is a side elevational view of another alternative sheet feed system used in the present invention;

Figure 6 is a side elevational view of another alternative sheet feed system used in the present invention; Figure 7a is a side elevational view of the LOM system incorporating an alternative embodiment of a bonding tool;

Figure 7b is an enlarged view of the portion of the sheet feed system within line 7b-7b of Figure 7a; and Figure 3 is a side elevational view of the LOM system incorporating an another alternative embodiment of a bonding tool.

Detailed Description of the Preferred Embodiments As seen in the drawings, the preferred embodiment of the present invention provides a laminated object manufacturing (LOM) system 20 for forming a plurality of layers into a three-dimensional object. A preferred embodiment utilizes a continuous multi-ply sheet 35 fed from a roll to provide layers for forming the three-dimensional object. It will be understood that certain features described herein may be applicable to other types of LOM systems. By way of example (and not limitation), many features of the preferred embodiment may be useful in LOM embodiments disclosed in U.S. Patent Nos.4,752,352 and 5,354,414, 5,730,817 which are expressly incorporated herein by reference With reference to Figure 1 , which schematically illustrates the LOM system 20, a base frame 22 comprises a large, generally rectangular structure on or in which a majority of the components of the system are mounted. The base frame 22 is conventionally formed by rigid metal bracing desirably encompassed by sheet panel siding, and normally is firmly mounted to the floor, but may also be constructed to a smaller scale and be only temporarily held with respect to a table or other foundation. The system is controlled by a computer 24 which may be mounted on the base frame 22, but is typically provided as a stand-alone item and is designed and connected to provide input to and receive and process feedback from the system. The base frame 22 has an elongated front side 26 and a generally horizontal top surface 28.

The LOM system includes a sheet material feed system for feeding the multi-ply sheet 35 across the top surface 28. The multi-ply sheet feed system includes a material dispensing assembly or feed station 30 for dispensing the sheet 35 and main and secondary wind-up stations 34 and 37 for receiving respective plies of the sheet 35 after it travels over the top surface 38. The feed station 30 is shown positioned within a right end of the frame 22, although it may also be positioned outside the frame 22. The feed station 30 comprises a supply or feed roll 32 rotatably mounted within the base frame 22. The feed roll 32 dispenses the continuous multi-ply sheet 35 across the top surface 28 of the base frame 22 to the main wind-up station 34 positioned near a left end of the frame 22 and the secondary wind-up station 37 positioned near a right end of the frame 22. In the illustrated embodiment, the main wind-up station 34 comprises a main wind-up roll 36 that is rotatably mounted on a stand 38 having a tensioπiπg bar 40 pivotally mounted thereto. The tensiomng bar 40 falls by gravity onto the top surface of the sheet and provides a smoothing tension across the sheet to facilitate flatness across the top surface 28 of the system. The secondary wind-up station 37 comprises a secondary wind-up roll 29 that is rotatably mounted on a stand 33 that extends above the top surface 28 of the base frame 22. The secondary wind-up roll 29 is preferably spring mounted on the stand 33 so as to be biased in a predetermined rotational direction, as described more fully below.

The multi-ply sheet 35 preferably comprises a two-ply material. The first ply is a main sheet 41 and the second ply is a release sheet 43 that is disposed on top of the main sheet 41. The main sheet 41 and the release sheet 43 may be adhered together, such as with a light adhesive, or they may be interleaved without adhesive. If an adhesive is used, the main sheet 41 and the release sheet 43 are configured to be separated in a peeling fashion. The main sheet 41 preferably comprises sheet material that is substantially homogeneous in a direction perpendicular to the planar surface of the sheet material. The material 41 preferably bonds to similar sheets of material 41 through cohesion melding. As used herein, the term cohesion melding means the joining of two sheets of material without adhesive by cohesively merging juxtaposed surfaces of the sheets such that structural discontinuities at the boundary between the juxtaposed surfaces are at least substantially reduced or eliminated. By eliminating or substantially reducing structural discontinuities the sheets become unified, thereby resulting in a stronger, more durable, three dimensional object.

In some materials, cohesion melding may be achieved by sufficient heating of the surfaces to be bonded so as to cause diffusion of the material across the boundary upon application of bonding pressure to the heated surfaces. Acrylonitrile-butadiene-stγrene (ABS) and polyvinylchloride (PVC) are examples of such a material. In other materials, such as nylon, cohesion melding may be achieved by sufficient heating to cause a phase change (i.e., solid to liquid) at the surface of the sheet materials during application of bonding pressure to the heated surfaces Additionally, in pre impregnated composites having a resin with fibers imbedded therein, cohesion melding may be achieved by curing the material at an elevated temperature to cause diffusion or phase change after the sheets of material have been cohered by the application of pressure thereto. In general, cohesion melding is achieved by elevating the material to a cohesion melding temperature, which varies as a function of the type of material, and the pressure (if any) applied thereto during temperature elevation. The term "cohesion melding temperature," as used herein, means a temperature to which the cohered material must be elevated to achieve cohesion melding.

The release sheet 43 preferably comprises a material which is resistant to melting at the cohesion melding temperature of the sheet material 41, and which can be peeled away from the material 41 after bonding to an adjacent layer of material 41. Silicon-coated paper is a suitable material for the release sheet 43. A metallic foil may also be used as the release sheet 43.

As indicated previously, in the embodiment shown in Figure 1, the mam sheet 41 and the release sheet 43 are wound in parallel, or in an interleaved fashion, around the feed roll 32. The material 35 is dispensed from the feed roll 32 such that the release sheet 43 is positioned above the mam sheet 41 with respect to the top surface 28. As described more fully below, the main sheet 41 and the release sheet 43 are separated at a predetermined location on the top surface 28 and follow distinct exit paths therefrom. After such separation, the mam wind-up station 34 pulls the main sheet 41 of the material 35 across the top surface 28 of the base frame 22. The secondary wind-up station 37 pulls the release sheet 43 of the material 35 upwardly from the top surface 22. The feed roll 32 and/or the main wind-up roll 36 are preferably dπvinglγ coupled to a drive assembly (not shown), such as a motor, for rotatably driving the rolls 32 and 26.

With reference to Figure 1, a pinch roller 42 is positioned at a left end of the top surface 28 and extends in the Y direction across the width of the sheet. The pinch roller 42 includes the upper roller shown, and a lower roller recessed within the top surface 28. The upper and lower pinch rollers combine to help propel the sheet across the top surface 28. That is, both the upper and lower pinch rollers are motor driven and come into close contact to pinch the mam sheet 41 therebetween. Although the pinch rollers are shown positioned on a left end of the top surface 28 to pull the main sheet 41, they may also be positioned on a right end to push the material 35 across the top surface 28. As shown in Figure 1, at least the main sheet 41 of the material 35 extends across a work station 44, generally defined in the center of the top surface 28 of the base frame 22. A reference frame 46 is mounted adjacent the work station 44. The reference frame 46 defines a reference frame coordinate system 52, indicated on Figure 1, and preferably comprises a pair of elongated reference frame members 54a,b mounted over the top surface 28 of the base frame 22 on a plurality of legs 56. The reference frame members 54a,b comprise rigid beams which support and provide linear guide rails for both a forming tool 48 and a bonding assembly 50, as described in more detail below.

The LOM system 20 may also include a cover (not shown) adapted to enclose the feed, forming and bonding components on the top surface 28. Preferably, the cover is a hollow rectangular housing pivotablγ mounted along a horizontal axis at a rear corner of the top surface 28. The cover further includes windows for viewing the forming and bonding operations within. The cover protects the system components and helps to contain smoke and other particulates generated by the forming tool.

In the embodiment shown, the forming tool 48 and the bonding assembly 50 are movably coupled to the reference frame 46 over the work station 44. As will be described in greater detail below, the forming tool 48 and the bonding assembly 50 work in cooperation to create a plurality of layers 58 to form a stack 60 of layers from the mam sheet 41, which are used to form the three-dimensional object. In the presently illustrated embodiment, both the forming tool 48 and bonding assembly 50 are mounted at each respective end to one of two common reference frame members 54a,b, but it will be appreciated by one of skill in the art that the forming tool 48 and bonding assembly 50 may be mounted to a single frame member suitably designed to provide proper tool support.

In the illustrated embodiment, the forming tool 48 comprises an X-Y positioner, or plotter, 62 having a focusing lens 64 positioned on a Y-axis carnage 66. The carriage 66 is adapted to translate in the Y-axis along one or more lateral supports 70 mounted at each end on X-axis carriages 72. The X-axis carriages 72 are, in turn, adapted to translate linearly along the X-axis on the reference frame members 54a,b. In this manner, the focusing lens 64 may be positioned in the X Y plane above the work station 44. The forming tool 48 further comprises a laser 74 (Figure 2) mounted on the reference frame 46 at the right end thereof. The laser 74 is capable of generating a beam of laser light out of one end, in this case the lower end, which is reflected toward the work station 44 using a movable system of mirrors. The specific system of mirrors may be configured based on geometric or other considerations, and variations in the configuration are within the skill of one knowledgeable in optic systems.

The type of forming tool 48 used in the LOM system 20 preferably comprises a CW carbon dioxide laser with an output of between about 25 and 400 W, and desirably about 50 W, at a wavelength of 10.6 microns. Lasers of different wavelength with continuous wave or pulse characteristics, beams of high energy particles, microwave energy, and heat generated by electrical current, are contemplated. These energy sources will usually be concentrated on the surface of the sheet material 35 by a device, such as the focusing lens 64, mounted on the Y-axis carnage 66 of the X-Y plotter 62. Indeed, the present embodiment discloses the use of a laser 74 in conjunction with a series of mirrors and the lens 64, the laser beam being suitable focused on the sheet material 41 so as to cut lines through the material to a depth of at least one thickness of the sheet. Various other types of forming tools may not require the separately mounted laser and system of mirrors, but may be incorporated completely within the Y-axis carriage 66. For example, a mechanical cutting knife may be provided on the Y-axis carriage 66.

With reference to Figure 1, the bonding assembly 50 comprises a bonding tool 76 that is rotatably mounted onto a pair of carriages 80a,b which are configured to be linearly translated along a lower rail portion of the associated reference frame members 54a,b. A first roller 82 is rotatably mounted to the carriages 80a,b above the material 35 so that the first roller compresses the material 35 against the top surface 28. The first roller 82 is desirably positioned downstream (with respect to the direction of travel of the material 35) from the bonding tool 76. A second roller 84 is rotatably mounted to the carriages 80a,b and is disposed generally above the first roller 82. The bonding tool 76, the first roller 82, and the second roller 84 are mounted for collective translation along the reference frame members 54a,b via the carriages 80a,b.

In the embodiment shown in Figure 1, the bonding tool 76 comprises a roller or fuser 86 mounted on both ends for rotation in carriages 80a,b. A pair of linear bearings (not shown) is provided on each carnage 80a,b for linear translation along the lower rail portion of the associated reference frame members 54a,b. The tool 76 is thus adapted to move in the X-direction underneath the X-Y plotter 62. As mentioned, the mam sheet 41 and the release sheet 43 are separated from one another at a predetermined location which is located at a point downstream of the bonding tool 76 so that the release sheet 41 is continually interposed between the bonding tool 76 and the mam sheet 41. Desirably, the mam sheet 41 and the release sheet 43 are peeled from one another immediately downstream of the first roller 82 so that the release sheet 43 extends upwards around the first roller 82 and around the second roller 84 toward the secondary wind-up roll 39. The main sheet 41 continues across the work station 44 toward the mam wind-up roll 36.

With reference to Figure 1, the stack 60 of layers 58 is positioned on a work table 96 vertically movable in the Z axis using an elevator mechanism 98 driven by a motor 100. More specifically, the motor 100 may rotate a threaded shaft 102 which extends through a threaded coupling (not shown) fixed with respect to the work table 96. Alternately, the motor 100 may be fixed with respect to the table 96, and have a female threaded coupling as an output which rides a fixed threaded shaft. In a preferred embodiment, there is a single motor and threaded shaft, rather than multiple motors and shafts to ensure proper Z axis alignment of the work table.

The work table 96 is supported by a relatively sturdy angle bracket support frame (not shown) under one end thereof. The support frame is sturdy enough, and the work table 96 is thick enough, so that the upper surface of the work table 96 remains horizontal at all times. The stack 60 is, thus, positioπable in parallel with respect to the top surface 28 of the base frame 22. In this respect, a large rectangular aperture (not shown) is provided in the center of the top surface 28 through which the work table 96 may be accessed by the forming tool 48 and the bonding tool 76. The work table 96 provides a support surface for the various layers 58 formed by the forming tool 48 and, thus defines the work station 44.

Figure 2 illustrates a particular layer 58 having been cut from the main sheet 41 of the material 35 in a forming sequence. In this generalized example, a rectangular cut line 90 defines the layer 58. A particular contour line 92 is created by the forming tool 48, upon manipulation of the lens 64 by the X-Y plotter 62 under commands from the controlling computer 24. The material inside of the contour line 92 is intended to form a single layer of the three dimensional object. The material outside of the contour line 92 is typically scrap, and is removed in various methods. Alternatively, of course, the material inside the contour line 92 may be scrap and the material outside is then the desired layer of the final 3-D object. In one method of removing unwanted material, as indicated in the corner of the layer 58 from mam sheet 41, cross-hatching 94 is cut in the mam sheet 41 so that the resulting three-dimensional object will have a volume of loosely bound material around its exterior created by layers of cross-hatched material. The loosely bound material can then be knocked or scraped off, leaving the desired contour layer within. Of course, other methods of removing the unwanted material outside of the cut line are possible, such as those described in U.S. Patent Nos. 4,752,352 and 5,354,414, which are hereby incorporated herein by reference. In a bonding sequence, the bonding assembly 50 translates across the work station 44 so that the bonding tool

76 presses the layer 58 into contact with the uppermost layer of material in the stack 60. During such translation, the bonding tool 76 applies sufficient heat and pressure to the layer 58 to achieve the cohesion melding temperature and thereby cause the layer 58 to bond to the stack 60 by cohesion melding. Advantageously, the release sheet 43 is continually interposed between the bonding tool 76 and the mam sheet 41 to prevent material from the heated main sheet 41 from adhering to the bonding tool 76 during translation across the work station.

In an alternative bonding sequence, the main sheet 41 comprises a material, such as a composite, that is sufficiently tacky to bond to an adjacent sheet of similar material upon the application of pressure without the application of heat. If such a material is used, the bonding tool applies sufficient pressure to the layer 58 so that it bonds with the stack 60 at room temperature. Cohesion melding of the layers in the stack 60 is then achieved in a subsequent curing process during which the stack 60 is cured in an oven at elevated temperatures sufficient to result in cohesion melding of the layers of material.

The forming sequence is further described with reference to Figures 3a, 3b, and 3c which schematically show side views of the LOM system 20. Figure 3a illustrates a stage of operation in which the material 35 is fed across the top surface 28 to expose a new uncut layer over the stack 60. As the mam wind-up roll 36 pulls the mam sheet 41, the secondary wind-up roll 39 also pulls the release sheet 43 so that the sheets are separated at the first roller 82. This is illustrated more clearly in Figure 3c which shows the mam sheet 41 continuing across the top surface 28 to the work station 44 and the release sheet 43 exiting upward from the top surface 28 around the first roller 82. The gaps between the sheets 41, 43, the first roller 82, and the top surface 28 are shown only for clarity of illustration. During this step, the stack 60 has been lowered slightly by the motor 100 and shaft 102. The pinch rollers 42 are shown rotating to pull the main sheet 41 across the top surface 28.

After a new uncut layer is positioned over the stack 60, the table 96 is raised to position the stack 60 directly underneath the main sheet 41. The bonding assembly 50 translates across the top of the work station from right to left to the position shown in Figure 3b so that the bonding tool 76 bonds the newly-formed layer of sheet material 43 to the stack 60. The second wind-up roller is spring-biased to exert a substantially constant tension on the release sheet 43 so that the release sheet 43 can unwind onto the top of the mam sheet 41 during such translation of the bonding assembly 50 along the work station 44. Again, the release sheet 43, which is between the main sheet 41 and the bonding assembly 50, advantageously prevents material from the main sheet 41 from adhering to the bonding tool 76 during the bonding process. The bonding assembly 48 then returns to the position shown in Figure 3a and the forming tool 48 (Figures 1 and 2) translates across the work station 44 and forms a contoured layer 58, as described above with respect to Figure 2. The process is then repeated with a new layer.

The bonding sequence may alternatively be performed after the forming sequence. If the forming sequence is performed prior to the bonding sequence, the release sheet preferably comprises a metallic foil.

Figure 4 illustrates a second embodiment of the material feed system. In this embodiment, the material dispensing assembly or feed station 30 comprises a first feed roll 32a and a second feed roll 32b wherein the main sheet 41 is wound around the first feed roll 32a and the release sheet 43 is wound around the second feed roll 32b The main sheet 41 and the release sheet 43 both extend from their respective feed rolls 32a,b across the top surface 28 of the base frame 22 to collectively form the material 35. The sheets 41 and 43 are separated at the first roller 82 in the manner described above with respect to Figures 3.

Figure 5 illustrates a third embodiment of the material feed system in which the mam wind-up station 34 is eliminated. The material feed system includes a feed station 30 comprising a feed roll 32 around which the mam sheet 41 and the release sheet 43 are both wound. In this embodiment, the mam sheet 41 is comprised of a plurality of discrete sub-sheets 41a that are wound in series around the feed roll 32 and interleaved with the release sheet 43. Each sub-sheet 41a is preferably sized to fit over the work station 44. The sub-sheets 41a are preferably lightly adhered to the release sheet 43 so that the release sheet 43 successively guides the sub-sheets 41 a onto the work station 44 as the release sheet 43 moves over the top surface 28. After each sub-sheet 41a is positioned over the work station 44, the LOM performs the forming and bonding sequences described above. The secondary wind-up roll 39 collects the release sheet 43 This embodiment may also be adapted to work with a continuous main sheet 41 by including a cutter at the right side of the work station. After bonding, the release sheet 43 is peeled off the main sheet by the tension on the roll 39 as the bonding tool moves left to right, and the cutter can cut the main sheet without cutting the release sheet Figure 6 illustrates yet another embodiment of the material feed system. In this embodiment, the feed station 30 comprises a first feed roll 32a and a second feed roll 32b. The first feed roll 32a dispenses the mam sheet 41 and the second feed roll 32b dispenses the release sheet 43. The forming tool 48 cuts the mam sheet 41 at a location upstream of the work station 44 after each bonding and forming sequences so that the mam sheet has a cut edge 104. The feed rolls 32a and 32b are then rotated to advance the sheets 41 and 43 until the cut edge 104 of the main sheet 41 is positioned downstream of the work station 44. The forming and bonding sequences are then performed on the main sheet 41. This embodiment minimizes the amount of waste material that is generated by the LOM system 20.

Figure 7a shows the LOM system 20 which utilizes an alternative embodiment of the bonding tool 76. In this embodiment, the bonding tool 76 comprises a radiating heat source 108, such as a heat lamp that is configured to radiate heat onto the material 41. The bonding assembly 50 additionally comprises a third roller 110 that is mounted upstream of the heat source 108. The heat source 108 is coupled to the first, second and third rollers 82, 84, and 110, so that these components collectively translate across the work station 44.

As best shown in Figure 7b, the sheet material 41 winds upward around the third roller 110 and over the heat source 108 so as to define a nip point 112 where the material 35 contacts the first roller 82. After positioning the bonding assembly 50 at the left side of the stack (from the perspective of Figure 7), the heat lamp 108 is activated. The bottom surface of the main sheet 41 and the top surface of the uppermost layer of the stack 60 are thereby exposed to heat from the heat source 108 at the nip point 112, as the bonding assembly moves from left to right. During the bonding sequence, the heat source 108 radiates sufficient heat onto the top surface of the uppermost layer in the stack 60 and also onto the bottom surface of the main sheet 41 to cohesively meld the adjacent surfaces of material 41 upon the application of pressure by the first roller 82 onto the top surface of the release sheet 43. As shown in Figure 8, the heat source 108 may also be positioned downstream of the first roller 82 so that the heat source 108 radiates heat onto the bottom surface of the main sheet 41 and the top surface of the stack as the roller moves across the work station 44 from right to left.

A cover (not shown) may be included to provide a chamber that encloses the work station. The chamber may be equipped with sources of heat that maintain the chamber at an elevated temperature that is beneath the cohesion melding temperature of the mam sheet 41. Such a heated chamber reduces the likelihood the stack 60 will draw heat from the layers being bonded.

Although this invention has been described in terms of certain preferred embodiments, other embodiments that will be apparent to those of ordinary skill in the art are intended to be within the scope of this invention. Accordingly, the scope of the invention is intended to be defined by the claims that follow.

Claims

WHAT IS CLAIMED IS:

I An apparatus for converting sheet material into a three-dimensional object comprised of layers of said material, comprising: a work station adapted to receive said sheet material; a bonding tool mounted to move relative to said work station to bond layers of sheet material to each other to form said three dimensional object, said bonding tool heating at least a portion of the sheet material to its cohesion melding temperature; a material dispensing assembly mounted to supply said sheet material to said work station, said dispensing assembly additionally supplying a release sheet adjacent to said sheet material such that said release sheet is interposed between said bonding tool and said sheet material during bonding to prevent heated sheet material from adhering to said bonding tool.

2. The apparatus of Claim 1, wherein said sheet material is on one supply roll and said release sheet is on another supply roll.

3. The apparatus of Claim 1 wherein said sheet material and said release sheet are interleaved on a supply roll with said sheet material and release sheet lightly adhered together.

4. The apparatus of Claim 2, additionally comprising a cutting tool adjacent to said work station, said cutting tool positioned to cut said sheet material after being bonded by said bonding tool.

5. The apparatus of Claim 4, wherein said cutting tool cuts said sheet material without cutting said release sheet.

6. The apparatus of Claim 1, wherein said bonding tool comprises a heated roller which heats at least a portion of said sheet material to bond each layer to an adjacent layer.

7. The apparatus of Claim 6, wherein said heated roller applies pressure to at least a portion of said sheet material to bond each layer to an adjacent layer

8. The apparatus of Claim 1, wherein the sheet material comprises ABS.

9. The apparatus of Claim 1, wherein the sheet material comprises nylon.

10. The apparatus of Claim 1 , wherein the sheet material comprises polyvinylchlonde.

I I The apparatus of Claim 1 , wherein the release sheet comprises silicon coated paper

12. The apparatus of Claim 1 , additionally comprising a forming tool mounted to move relative to said work station to form said layers from the sheet material.

13. An apparatus for converting sheet material having a cohesion melding temperature into a three- dimensional object comprised of layers of said sheet material, comprising: a work station adapted to receive said sheet material; a bonding tool mounted to move relative to said work station to bond layers of sheet material to each other to form said three dimensional object; wherein said bonding tool comprises a heating member and a pressure member, said bonding tool configured such that said heating member applies heat from one side of said sheet material and said pressure member applies pressure from the other side of said sheet material, such that the heated side of the material is pressed into direct contact with an adjacent layer of said material to bond adjacent layers together, said bonding tool heating said sheet material so that at least a portion of the sheet material is at said cohesion melding temperature during bonding.

14. The apparatus of Claim 13, wherein the heating member comprises a heat lamp.

15. The apparatus of Claim 13, where the pressure member comprises a roller.

16 The apparatus of Claim 13, wherein said heating member additionally heats said adjacent layer during said heating of said one side of said sheet material.

17. A three dimensional object, comprising: multiple layers of sheet material, each of said layers of sheet material substantially homogenous in a direction perpendicular to the planar surface of the sheet material, each of said layers being united to an adjacent layer without adhesive therebetween by cohesion melding.

18. The three-dimensional object of Claim 17, wherein said substantially homogenous layers are formed from a composite material.

19. The three-dimensional object of Claim 18, wherein said composite material is sufficiently tacky to cause said layers to bond to each other at room temperature upon application of pressure.

20. The three-dimensional object of Claim 19, wherein the composite exhibits cohesion melding in response to curing the bonded layers of composite material at an elevated temperature.

21. The apparatus of Claim 17, wherein the sheet material comprises ABS.

22. The apparatus of Claim 17, wherein the sheet material comprises nylon.

23. A method of forming a three-dimensional object, comprising: providing sheet material which is substantially homogenous in a direction perpendicular to the plane of the sheet material; bonding layers of said sheet material together; applying sufficient heat to said sheet material to cause cohesion melding of said layers.

24. The method of Claim 23, wherein said layers are bonded together prior to application of said heat.

25. The method of Claim 24, wherein said layers are bonded together at room temperature.

26. The method of Claim 24, wherein said sheet material comprises resin having fibers therein, said resin being sufficiently tacky at room temperature to bond said layers together upon application of pressure without heat, said method further comprising curing said bonded layers to cause said cohesion melding.

27. The method of Claim 23 wherein said heat is applied during the bonding of said layers.

28. The method of Claim 23, wherein the application of heat diffuses material from one layer into an adjacent layer to achieve said cohesion melding.

29. The method of Claim 23, wherein the application of heat causes at least a portion of each of two adjacent layers to undergo a phase transition from solid to liquid to achieve said cohesion melding.

30. The method of Claim 23, wherein each of the layers is comprised of sheet material identical to the other layers.

31. The method of Claim 23, wherein the sheet material comprises a pre-impregnated composite.

32. A method of converting sheet material into a three-dimensional object comprised of a plurality of layers, comprising: bonding one layer of sheet material to an adjacent layer of sheet material by heating one side of said one layer and applying pressure to the other side of said one layer.

33. A method of converting sheet material into a three-dimensional object composed of a plurality of layers, comprising: bonding one layer of sheet material to an adjacent layer of sheet material by heating one side of said one layer until the other side of the one layer reaches a cohesion melding temperature, said bonding additionally comprising applying pressure to said one side using a pressure member, said applying comprising positioning a release sheet between said one side and said pressure member.