Plastic article or earthenware shaping or treating: apparatus – Means applying electrical or wave energy directly to work – Radiated energy
Patent
1990-01-24
1992-04-21
Housel, James C.
Plastic article or earthenware shaping or treating: apparatus
Means applying electrical or wave energy directly to work
Radiated energy
118620, 156 58, 1562728, 1562733, 1563796, 264 22, 264255, 264308, 365120, 425162, 427 541, B29C 3508
Patent
active
051062887
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a system for producing precision plastic products via the polymerisation of liquid plastics using focussed ulta-violet laser beams whose computer controlled positioning relative to the face of a computer controlled adjustable piston immersed in the said liquid plastic allows for the hardened plastic product being produced to rest on the said end face of said piston as the computer controlled laser beam product profiling processes take place within the liquid plastic.
The system is particularly suitable for the transformation of a computer software product design into a three dimensional, hard plastic copy. The system has application in the production of all-plastic credit and identification cards, plastic models of buildings, toys, letters, numbers, tools, moulds and dies.
DESCRIPTION OF THE PRIOR ART
Prior art laser beam induced plastic model production systems used commercially available two mirror scanners which deflected a single laser beam in two mutually perpendicular directions and projected it into the liquid plastic to be polymerised. The third dimension polymerisation process was accomplished by using a zoom lens to adjust the focal length of the scanned laser beam. The major problem with these prior art laser systems was the fact that the scanner mirrors were of necessity relatively small to minimise inertial effects which would adversely affect the response time of the scanning system if larger mirrors were used. The fact that mirror scanning systems used in prior art systems had of necessity small aperture mirrors led to severe restrictions being placed on the power of the laser beam and its focal length, the smaller the scanner mirror, the larger the focal length and the more extended the focus region. The longer the focal length of the scanned laser beam, the greater is the leverage effect which in turn amplifies any jitter that the movement of the scanning mirror could exhibit, which in turn would degrade the quality of the polymerisation process, seriously limiting the image resolution achievable.
Prior art systems also utilized other techniques than scanning mirrors to profile the plastic models in three dimensions, namely, the projection of photographic images. These fixed stencil images had to be projected into open tanks of liquid plastics or onto a base coated with a thin layer of the said plastic. The problem with such fixed stencil image generation is well known in product marking applications where only the same level of information can be transmitted to each different product with a given fixed stencil. Prior art systems suffered from the fact that they used open tanks of liquid plastics implying that the ratio of the volume of liquid plastic to the volume of the product was large. Such large expensive volumes of liquid plastic proved difficult to keep clean during the polymerisation process, due to the difficulties associated with recirculating and filtering such large amounts of liquid plastics.
Prior art systems also suffered from the fact that they could not achieve coarse and fine polymerisation processes simultaneously during the manufacture of the three dimensional plastic models. It is often the case that a given model can be rapidly produced over its volume where its dimensions are not critical whilst it is always a relatively slower process to achieve the highest precision during any manufacturing process.
My invention overcomes the defects of prior art systems by confining the polymerisation process to within a narrow layer of liquid plastic defined by the space separating an optical window at one end of said liquid plastic tank and the end face of a computer controlled piston within said liquid tank through which said liquid plastic is circulated, having been filtered external to the tank during the recirculating process. The flow of liquid plastic between the inner surface of the optical window of said tank and the face of the movable piston can be separated from said surfaces via either a flow of transparent fluid
REFERENCES:
patent: 2775758 (1956-12-01), Munz
patent: 4078229 (1978-03-01), Swainson et al.
patent: 4575330 (1986-03-01), Hull
patent: 4752498 (1988-06-01), Fudim
patent: 4942060 (1990-07-01), Grossa
Kodoma, Hideo, "Automatic Method for Fabricating a Three-Dimensional Plastic Model with Photo-Hardening Polymer", Rev. Sci. Instrum., vol. 52, No. 11, Nov. 1981, pp. 1770-1773.
Lindsay, Karen, "Desktop Product Prototyping: Services and Systems Proliferate", Modern Plastics, Jul. 1989, p. 90.
Austral Asian Lasers Pty Ltd.
Housel James C.
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