Method for manufacturing physical objects using precision stereolithography

• US 6,207,097 B1
• Filed: 02/17/1999
• Issued: 03/27/2001
• Est. Priority Date: 02/18/1998
• Status: Expired due to Fees

• Current Assignee: Norma Jean Iverson
• Original Assignee: Norma Jean Iverson
• Inventors: Iverson, Norma Jean
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US09/251,699
• Time in Patent Office: 769 Days
• Field of Search: 264/401
• US Class Current: 264/401
• CPC Class Codes: B29C 37/005 Compensating volume or shape change during moulding, in general
• CPC Class Codes: B29C 41/12 Spreading-out the material on a substrate , e.g. on the surface of a liquid
• CPC Class Codes: B29C 64/135 the energy source being concentrated, e.g. scanning lasers or focused light sources
• CPC Class Codes: B29C 64/40 Structures for supporting 3D objects during manufacture and intended to be sacrificed after completion thereof
• CPC Class Codes: B33Y 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B33Y 50/02 for controlling or regulating additive manufacturing processes
• CPC Class Codes: G05B 2219/36253 Generate machining program from previous test run
• CPC Class Codes: G05B 2219/49013 Deposit layers, cured by scanning laser, stereo lithography SLA, prototyping

Abstract

An improved method for stereolithographic fabrication of structures provides a stereolithography system with a laser light source that is substantially smaller than previously known light sources, and produces a beam that is focused to a smaller spot size, preferably a He—Cd laser operating at approximately 30 mw in the pure TEM00 mode. The method utilizes this system to fabricate smaller structures with substantially higher precision than previously obtained with the stereolithographic technique. The method includes the steps of leveling the stereolithographic apparatus, measuring the actual focused beam spot size to determine the beam width compensation value, building a test structure to determine shrink compensation factors, and entering these data into software data files that are used by a computer to control the fabrication process. The method includes further modifications to the software data files, including modifications of the recoating, overcure, and build parameters, and the configuration files. With these modifications, the method is capable of stereolithographic fabrication of structures using slice layer thicknesses of 3 mils or less, and the fabricated structures have dimensional tolerances substantially smaller than the tolerances in previously fabricated structures. The method also reduces production time even using small slice thicknesses.

Claims

1. In a system for fabricating a three-dimensional structure by means of stereolithography, said system including:

a controllable source of light for generating a focused light beam at a selectable and variable location;

a vat containing liquid photocurable material, said liquid having an upper surface on which said beam is brought to a focus;

a horizontal platform immersed in said liquid photocurable material, said platform further being attached to a support member and the elevation of said platform being controllably movable in the vertical direction by means of said support member;

platform control means attached to said support member, for controlling and varying the elevation of said platform; and

a computer connected to said platform control means and said controllable source of light, said computer having a memory containing control software and data files for controlling said platform control means and said controllable source of light, said computer further containing design software for designing said three-dimensional structure;

an improved method for fabricating a three-dimensional structure by means of stereolithography, comprising the steps of;

providing a source of light as said light source that is substantially smaller and lower in power, and that generates a smaller focused spot, than light sources conventionally used in stereolithographic fabrication processes;

modifying the parameters and variables in said data files to fabricate a structure in said system with said light source that is substantially smaller and lower in power and generates a smaller focused spot, with substantially higher precision than 10 mils; and

carrying out the stereolithographic fabrication process utilizing said light source that is substantially smaller and lower in power and generates a smaller focused spot, and said modified parameters and variables to fabricate said three-dimensional structure.

2. The method recited in claim 1, wherein said light source comprises a laser generating power not exceeding 30 mw.

3. The method recited in claim 2, wherein said laser is operated in the pure TEM00 mode.

4. The method recited in claim 2, wherein said laser is a He—

Cd laser operating at a wavelength of substantially 325 nm.

5. The method recited in claim 4, wherein said laser is operated in the pure TEM00 mode.

6. The method recited in claim 1, wherein said liquid photocurable material comprises epoxy-based resin material.

7. The method recited in claim 1, wherein said step of modifying the parameters and variables in said data files comprises modification of recoating parameters, overcure parameters, build parameters, and configuration files.

8. The method recited in claim 1, further comprising the steps, prior to the step of carrying out the stereolithographic fabrication process, of:

measuring the actual diameter of said focused light beam produced by said light source; and

modifying the parameters and variables in said data files to represent said actual diameter.

9. The method recited in claim 1, further comprising the steps, prior to the step of carrying out the stereolithographic fabrication process, of:

fabricating a test structure by means of said stereolithographic process;

measuring the actual dimensions of said test structure;

comparing said measured dimensions with the nominal dimensions for said test structure to determine shrink compensation factors for the stereolithographic process; and

modifying the parameters and variables in said data files to represent said shrink compensation factors.

10. The method recited in claim 9, further comprising the step, prior to the step of carrying out the stereolithographic fabrication process for said test structure, of leveling said system.

11. The method recited in claim 1, further comprising the step, prior to the step of carrying out the stereolithographic fabrication process, of leveling said system.