AU2006202154B2

AU2006202154B2 - A method and system for producing a cast object

Info

Publication number: AU2006202154B2
Application number: AU2006202154A
Authority: AU
Inventors: Stan Nowak
Original assignee: Veem Engineering Group Pty Ltd
Current assignee: Veem Engineering Group Pty Ltd
Priority date: 2006-05-22
Filing date: 2006-05-22
Publication date: 2012-01-19
Anticipated expiration: 2026-05-22
Also published as: AU2006202154A1

Abstract

A method and system 10 as described for producing a mould component such as a propeller. The system 10 comprises a 5 robot 12 and a manipulator 14. The manipulator 14 supports a volume of machinable materials 16 such as a block of cured or hardened sand. The manipulator is provided with at least 3 but preferably more degrees of freedom of motion. Similarly, the robot 12 is provided 10 with at least 3 but preferably more such as 6' of freedom. A computer controls both the manipulator 14 and the robot 12 to cut a cavity in the machinable materials 16 that compensates for shrinkage of the material to be poured in the cavity so that the final cast product is produced 15 without a machining margin. H:\mcamp\keep\speci\COMPLETE\P60934 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT - COMP.doc 22/05/06 'Awl ZzEWuv

Description

AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant: VEEM Engineering Group Invention Title: A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT The following statement is a full description of this invention, including the best method of performing it known to us: - 2 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT FIELD OF THE INVENTION 5 The present invention relates to a method and system for producing a cast object, and in particular, but not exclusively, a cast marine propeller. BACKGROUND OF THE INVENTION 10 It is well known to machine a sand mould for the production of a cast object. In one known technique, a sand core, a cope, a drag or 15 other moulding element is machined from a sand block typically with a diamond or carbide cutting bit of a computer numerical controlled (CNC) machine tool. The machine tool may typically be a mill, lathe or drill press. The sand block is clamped in a variety of 20 positions, and reference points are used to locate the sand block during subsequent clamping and re-clamping of the sand block to various machine tools. Other known methods are directed to a method for directly 25 producing a lost mould by machining a sand mould made with curable binders (for example phenol-formaldehyde). The motivation behind these methods is to decrease tool wear and to increase dimensional accuracy and exactness in the reproduction of the mould. A pattern is set in a fixed or 30 variable moulding box and includes in its volume the desired contours of the casting mould and a machine allowance for the milling of the mould material. After filling the mould box with a curable material, curing and removal from the mould the moulding box is transformed 35 into the casting mould by removal of the machining allowance by appropriate machine tools. H:\mcamp\keep\speci\COMPLETE\P60934 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT - COMP.doc 22/05/06 -3 SUMMARY OF THE INVENTION According to a first aspect of the present invention there 5 is provided a method for producing a mould comprising: providing a volume of a machinable material; supporting the material on a manipulator provided with at least three degrees of freedom of motion; providing a robot supporting and driving a cutting 10 tool with at least three degrees of freedom of motion; cutting a cavity in the material by operating the robot to drive the cutting tool and operating the manipulator and robot to move the material and cutting tool relative to each other. 15 In one embodiment the manipulator is provided with four degrees of freedom of motion. In other further embodiments the manipulator may be provided with five or six degrees of freedom of motion. The degrees of freedom 20 of motion comprise linear freedom of motion along respective axes and/or rotational freedom of motion about the or further axes. Similarly, in further embodiments the robot may be provided with four, five or six degrees of freedom of motion. 25 The method may further comprise providing a programmable computer to operate the manipulator and the robot, and providing the computer with a cutting program that operates the manipulator and robot to cut the cavity in a 30 manner that compensates for shrinkage of a component cast in the mould to the extent that the cast component is provided without a machining margin. Accordingly in this embodiment the cast component meets 35 final working tolerance or at most may require minimal surface finishing such as polishing and/or buffing. H:\mcamp\keep\speci\COMPLETE\P60934 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT - COMP.doc 22/05/06 - 4 In a further embodiment the method may comprise providing a second robot supporting and driving a second cutting tool with at least three degrees of freedom. In this embodiment the cutting of the cavity may be performed by 5 operating both robots to drive their respective cutting tools simultaneously or sequentially. According to a further aspect of the present invention there is provided a system for producing a mould 10 comprising: a volume of machinable material; a manipulator provided with at least three degrees of freedom of motion on which the volume of machinable material is supported; 15 a robot supporting and driving a cutting tool in a manner whereby the cutting tool can move with at least three degrees of freedom; and cutting a cavity in the material to form a mould for casting an object by driving the cutting tool and 20 operating the manipulator and robot to move the material and cutting tool relative to each other. The system may further comprise a programmable computer that is coupled with and operates with the manipulator and 25 the robot, wherein the computer is further provided with a cutting program enabling the computer to operate the manipulator and robot to cut the cavity in a manner that compensates for shrinkage of a component cast in the mould to the extent that the cast component if formed without a 30 machining margin. The system may further comprise a second robot supporting and driving a second cutting tool in a manner wherein the cutting tool can move with at least three degrees of 35 freedom. In this system the computer controls both robots to cut the cavity. The robots may be controlled to simultaneously or sequentially cut the machinable material H:\mcamp\keep\speci\COMPLETE\P60934 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT - COMP.doc 22/05/06 - 5 and to hold and drive identical or different cutting tools. For example one robot may operate a cutting tool that produces a rough cut in the material and the second robot may operate a tool that follows the first tool and 5 smoothes the cut of the first tool. In this example either the first robot can complete the rough cut then the second robot can follow, or the first robot may initiate the rough cut and after a short period of time the second robot is operated to follow the first so that as the first 10 robot is being advanced the second robot smoothes the just cut material. According to a further aspect of the present invention there is provided a method for producing a propeller 15 comprising: providing a volume of a machinable material; supporting the material on a manipulator provided with at least three degrees of freedom of motion; providing a robot supporting and driving a cutting 20 tool with at least three degrees of freedom of motion; operating the robot and manipulator to cut a cavity in the machinable material of a shape and configuration corresponding to the shape and configuration of a propeller to be cast. 25 The method further comprises cutting the cavity in a shape and configuration that compensates for shrinkage of a castable material poured into the cavity to the extent that a propeller cast in the mould is formed without a 30 machining margin. In one embodiment, the method further comprises producing the cavity with a shape and configuration such that in the cast propeller, a minimum radius exists at a root of each 35 blade of the propeller. H:\mcamp\keep\speci\COMPLETE\P60934 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT - COMP.doc 22/05/06 - 6 BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the present invention will now be described by way of example only with reference to the 5 accompanying drawings in which: Figure 1 is a perspective view from the side of a system for performing a method for producing a mould in accordance with the present invention; and Figure 2 is a perspective view from the top of the 10 system shown in Figure 1. DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Figures 1 and 2 illustrate schematically a system 10 that 15 may be used to deploy embodiments of the present method for producing a mould component such as a propeller. In broad terms, the system 10 comprises a robot 12 and a manipulator 14. The manipulator 14 supports a volume of machinable material 16 such as a block of cured or 20 hardened sand. However, the material 16 may comprise any other material that can be machined and is able to receive, without distortion, a molten casting material such as molten bronze or aluminum. 25 The manipulator 14 is provided with at least three but preferably more, such as, but not limited to four, five or six degrees of freedom of motion. In one embodiment the degrees of motion comprise three orthogonal linear degrees of motion such as along three Cartesian axes X, Y and Z 30 together with corresponding rotational degrees of freedom about these or alternate axes to provide for example roll, yaw and pitch motion. Similarly, the robot 12 is provided with at least three 35 but most advantageously six or more degrees of freedom. The degrees of freedom provided by the robot 12 may comprise three linear degrees of freedom of motion along H.\mcamp\keep\speci\COMPLETE\P60934 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT - COMP.doc 22/05/06 - 7 orthogonal Cartesian axes together with rotational degrees of freedom about those or alternate axes. In addition, the robot 12 may be provided with one or more ball joints allowing multiple and/or additional degrees of freedom of 5 motion. The robot 12 is further provided with a chuck 18 to allow the coupling of a cutting tool. Internal motors (not shown) within the robot 12 drive the chuck imparting rotational motion to the coupled tool. The robot 12 may also be provided with a magazine of different tools that 10 can be automatically coupled and decoupled to the chuck 18 as required to vary the cutting rate, fineness of cut, and cut radius in the material 16. Both the robot 12 and the manipulator 14 are typically 15 under the control of a computer (not shown). The computer is provided with a program to operate the robot 12 and manipulator 14 to move relative to each other so that a cutting tool held in the chuck of the robot 12 can cut a cavity of a desired shape and configuration for the 20 product to be cast. The cast product may be any castable product although a product of particular interest is a propeller for a marine vessel. The program provided by the computer makes allowances for the shrinkage of the material poured into the cavity with the ultimate aim that 25 upon removal of the cast product from the material 16 meets final working tolerances and therefore requires no or at most minimal machining to meet final working tolerances. Thus the cast component is produced with substantially no machining margin. The minimal machining 30 is at most commensurate with the tolerance and/or surface finish required. For example, it is envisaged that applications of this method will result in the cast product requiring at most polishing and/or buffing. 35 When the cast component is a propeller for a marine vessel the method and system 10 may be advantageously deployed to H:\mcamp\keep\speci\COMPLETE\P60934 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT - COMP.doc 22/05/06 - 8 ensure that the root of each blade of the propeller is formed with a minimum radius approaching an ideal square. By provision of at least three and advantageously six 5 degrees of freedom for each of the manipulator 14 and the robot 12, the system 10 is able to machine a cavity in the material 16 of complex three dimensional configuration such as required for the casting of a propeller and in a manner that provides three dimensional and geometrical 10 tolerances required so that the cast propeller either meets final working tolerances or requires only minimal machining such as polishing or buffing to meet these requirements. That is the cast product can be produced without a machining margin. Additionally, by use of the 15 robot 12, a magazine containing a number of different cutting tools of different shape and configuration can be incorporated. The system 10 is able to automatically select different tools from the magazine having the necessary shape, dimension or surface characteristics that 20 allow the cavity to be cut in the material 16 to have the dimensional and geometrical tolerances required to ensure that the cast component requires no or minimal machining. In a further embodiment the system 10 may comprise a 25 second robot or otherwise controlled cutting tool. This may enable cutting of the cavity by two cutting tools simultaneously and assist in the production of cavity shapes and configuration of greater complexity that may otherwise be achievable with a single robot or cutting 30 tool. The second robot or cutting tool is also under the control of a computer and typically the same computer used to control the robot 12 and manipulator 14. Modifications and variations of the above described 35 embodiments that would be obvious to a person of ordinary skill in the art are deemed to be within the scope of the H.\mcamp\keep\speci\COMPLETE\P60934 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT - COMP.doc 22/05/06 - 9 present invention the nature of which is to be determined from the above description. H.\mcamp\keep\speci\COMPLETE\P60934 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT - COMP.doc 22/05/06

Claims

1. A method for producing a mould comprising: providing a volume of a machinable material; s supporting the material on a manipulator provided with at least three degrees of freedom of motion; providing a robot supporting and driving a cutting tool with at least three degrees of freedom of motion; cutting a cavity in the material by operating the 1o robot to drive the cutting tool and operating the manipulator and robot to move the material and cutting tool relative to each other.

2. The method according to claim 1 wherein the 15 manipulator is provided with four degrees of freedom of motion.

3. The method according to claim 1 wherein the manipulator is provided with five or six degrees of 20 freedom of motion.

4. The method according to any one of claims 1 - 3 wherein the degrees of freedom of motion comprise linear freedom of motion along respective axes and/or 25 rotational freedom of motion about the or further axes.

5. The method according to any one of claims 1 - 4 wherein the robot is provided with four, five or six 30 degrees of freedom of motion.

6. The method according to any one of claims 1 - 5 further comprising a programmable computer to operate the manipulator and the robot, and providing the 35 computer with a cutting program that operates the manipulator and robot to cut the cavity in a manner that compensates for shrinkage of a component cast in 298B71_1 (GHManum) P60934.AU 25111/11 -11 the mould to the extent that the cast component is provided without a machining margin.

7. The method according to claim 6 wherein the cast 5 component meets final working tolerance or at most may require minimal surface finishing such as polishing and/or buffing.

8. The method according to any one of claims 1 - 7 10 further comprising providing a second robot supporting and driving a second cutting tool with at least three degrees of freedom.

9. A system for producing a mould comprising: 15 a volume of machinable material; a manipulator provided with at least three degrees of freedom of motion on which the volume of machinable material is supported; a robot supporting and driving a cutting tool in a 20 manner whereby the cutting tool can move with at least three degrees of freedom; and cutting a cavity in the material to form a mould for casting an object by driving the cutting tool and operating the manipulator and robot to move the 25 material and cutting tool relative to each other.

10. The system according to claim 9 further comprising a programmable computer that is coupled with and operates with the manipulator and the robot, wherein 30 the computer is further provided with a cutting program enabling the computer to operate the manipulator and robot to cut the cavity in a manner that compensates for shrinkage of a component cast in the mould to the extent that the cast component if 35 formed without a machining margin. 2981871_1 (CHManers) P60934 AU 25111111 - 12

11. The system according to claim 10 further comprising a second robot supporting and driving a second cutting tool in a manner wherein the cutting tool can move 5 with at least three degrees of freedom.

12. The system according to claim 11 wherein the computer controls both robots to cut the cavity. 10

13. The system according to claim 12 wherein the robots are controlled to simultaneously or sequentially cut the machinable material and to hold and drive identical or different cutting tools. 15

14. A method for producing a propeller comprising: providing a volume of a machinable material; supporting the material on a manipulator provided with at least three degrees of freedom of motion; providing a robot supporting and driving a cutting 20 tool with at least three degrees of freedom of motion; operating the robot and manipulator to cut a cavity in the machinable material of a shape and configuration corresponding to the shape and configuration of a propeller to be cast. 25

15. The method according to claim 14 further comprising cutting the cavity in a shape and configuration that compensates for shrinkage of a castable material poured into the cavity to the extent that a propeller 30 cast in the mould is formed without a machining margin.

16. The method according to claim 14 or 15 further comprising producing the cavity with a shape and 35 configuration such that in the cast propeller, a minimum radius exists at a root of each blade of the propeller. H:\mcamp\keep\speci\COMPLETE\P60934 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT - COMP.doc 22/05/06 - 13

17. The method according to any one of claims 14 - 16 wherein the manipulator is provided with four degrees of freedom of motion. 5

18. The method according to any one of claims 14 - 16 wherein the manipulator is provided with five or six degrees of freedom of motion. 10

19. The method according to any one of claims 14 - 18 wherein the degrees of freedom of motion comprise linear freedom of motion along respective axes and/or rotational freedom of motion about the or further axes. 15

20. The method according to any one of claims 14 - 19 wherein the robot is provided with four, five or six degrees of freedom of motion. 20

21. The method according to any one of claims 14 - 20 further comprising a programmable computer to operate the manipulator and the robot, and providing the computer with a cutting program that operates the manipulator and robot to cut the cavity in a manner 25 that compensates for shrinkage of a component cast in the mould to the extent that the cast component is provided without a machining margin.

22. A method for producing a mould substantially as herein 30 described with reference to and as illustrated by the accompanying drawings.

23. A system for producing a mould substantially as herein described with reference to and as illustrated by the 35 accompanying drawings. Ht\mcamp\keep\speci\COMPLETE\P60934 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT - COMP.doc 22/05/06 - 14

24. A system for producing a propeller substantially as herein described with reference to and as illustrated by the accompanying drawings. 5 Dated this 22nd day of May 2006 VEEM ENGINEERING GROUP By their Patent Attorneys GRIFFITH HACK 10 Fellows Institute of Patent and Trade Mark Attorneys of Australia H.\mcamp\keep\speci\COMPLETE\P60934 A METHOD AND SYSTEM FOR PRODUCING A CAST OBJECT - COMP.doc 22/05/06