Ceramic mold finishing techniques for removing powder

• US 5,814,161 A
• Filed: 02/12/1996
• Issued: 09/29/1998
• Est. Priority Date: 11/30/1992
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Khanuja, Satbir, Yu, Richard Li-chao, Bredt, James F., Cima, Michael J., Sachs, Emanuel M.
• Primary Examiner(s): Warden, Jill
• Assistant Examiner(s): CHAUDHRY, SAEED T
• Application Number:
  US08/600,215
• Time in Patent Office: 960 Days
• Field of Search: 134/22.1, 134/22.18, 134/21, 134/35, 134/37
• US Class Current: 134/21
• CPC Class Codes: B08B 3/10 with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
• CPC Class Codes: B08B 3/12 by sonic or ultrasonic vibrations washing or rinsing machines for crockery or tableware using sonic or ultrasonic waves A47L15/13; of natural teeth, of prostheses using ultrasonic techniques similar to those used for natural teeth A61C17/20; application of ultrasonic vibrations to chemical, physical or physico-chemical processes in general B01J19/10
• CPC Class Codes: B08B 5/04 Cleaning by suction, with or without auxiliary action B08B9/035 takes precedence; suction cleaners A47L
• CPC Class Codes: B08B 7/00 Cleaning by methods not provided for in a single other subclass or a single group in this subclass
• CPC Class Codes: B08B 9/00 Cleaning hollow articles by methods or apparatus specially adapted thereto B08B6/00 takes precedence
• CPC Class Codes: B22C 9/065 Cooling or heating equipment for moulds
• CPC Class Codes: B22C 9/18 Finishing
• CPC Class Codes: B22D 17/22 Dies manufacture, see the appropriate class, e.g. B23P15/24; Die plates; Die supports; Cooling equipment for dies; Accessories for loosening and ejecting castings from dies
• CPC Class Codes: B22D 17/2218 Cooling or heating equipment for dies for permanent moulds B22C9/065; for plastics B29C45/73
• CPC Class Codes: B22D 25/06 by its physical properties B22D27/00 takes precedence
• CPC Class Codes: B22F 5/007 of moulds
• CPC Class Codes: B24B 1/04 subjecting the grinding or polishing tools, the abrading or polishing medium or work to vibration, e.g. grinding with ultrasonic frequency polishing or abrading surfaces on work by means of tumbling apparatus B24B31/00, involving oscillating or vibrating containers B24B31/06; superfinishing surfaces on work, e.g. by means of abrading blocks reciprocating with high frequency, B24B35/00
• CPC Class Codes: B29C 33/04 using liquids, gas or steam tyre moulds with incorporated heating or cooling means using liquids, gas or steam B29D30/0601
• CPC Class Codes: B29C 33/3828 Moulds made of at least two different materials having different thermal conductivities
• CPC Class Codes: B29C 33/56 Coatings , e.g. enameled or galvanised; Releasing, lubricating or separating agents in-mould coating B29C37/0028; using or applying separating agents B29C37/0067
• CPC Class Codes: B29C 64/165 using a combination of solid and fluid materials, e.g. a powder selectively bound by a liquid binder, catalyst, inhibitor or energy absorber
• CPC Class Codes: B29C 64/35 Cleaning
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 40/20 Post-treatment, e.g. curing, coating or polishing
• CPC Class Codes: B33Y 80/00 Products made by additive manufacturing
• CPC Class Codes: Y02P 10/25 : Process efficiency

Abstract

A technique for removing loose powder from the interior surfaces of ceramic molds made using layer manufacturing processes, such as three dimensional printing processes. The interior of a mold is filled with water which is boiled and the particles are entrained in the flow caused by the boiling liquid. In another technique, the mold is immersed in water charged with CO₂ and the pressure rapidly dropped to cause the CO₂ to come out of solution as bubbles which eject the particles. Alternatively, fine particles are introduced into the mold and the mold is agitated to dislodge the particles and the powder so that they can be poured out of the mold. Such technique tends also to remove the surface finish of the mold. Any of the particles which remain can be dissolved in a liquid and removed in the liquid from the mold. Further, the surface finish of the mold can be improved by casting a slip of fine particles on to the surface to form a generally level, and preferably non-conformal, coating on the surfaces.

Claims

1. A process for removing loose powder from interior passages of a body made by layer manufacturing techniques comprising the steps of:

placing the body within a bath of water charged with CO₂ within a vessel;

rapidly lowering the pressure in the vessel so as to cause the CO₂ to come out of solution as bubbles, including within the interior passages of the body, the bubbles of CO₂ thereby causing the expulsion of loose powder.

2. A process for removing loose powder from interior passages of a body made by layer manufacturing techniques comprising the steps of:

placing the body within a liquid bath within a vessel;

rapidly lowering the pressure in the vessel so as to cause gas to evolve from said liquid, including the evolving of gases within the interior passages of the body, the evolving of gases thereby causing the expulsion of loose powder.

3. A process for removing loose powder from interior passages of a body made by layer manufacturing techniques comprising the steps of:

placing the body within a liquid bath within a vessel;

subjecting the body and bath to elevated pressure;

raising the temperature of the body and bath to, or near to, the boiling point of said liquid at the elevated pressure;

rapidly lowering the pressure in the vessel so as to cause the liquid to boil, including boiling within the interior passages of the body, said boiling thereby causing the expulsion of loose powder.