Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2002-09-03
2004-12-14
Mayes, Melvin C (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S247000, C156S284000, C156S289000, C156S305000, C156S307300, C156S308200, C156S356000, C156S563000, C118S697000, C118S045000, C118S046000, C118S056000, C118S308000, C427S099300, C427S069000, C427S113000, C427S125000, C427S126400, C427S128000, C427S131000, C427S207100, C427S334000
Reexamination Certificate
active
06830643
ABSTRACT:
The invention relates to a method of manufacturing an item and an apparatus for manufacturing an item.
Known methods of manufacturing include injection moulding and die-casting. The manufacture of tooling for injection moulding or die-casting is a highly restrictive burden on industry, because of it's high cost and lead times. Similar things are true of the cost of tooling for punch pressing, while the time taken by processes such as photo-chemical machining, electro and electroless plating and the environmental issues that surround these processes limit their use. The cost and the time taken to post-assemble products substantially reduces the flexibility and competitiveness of manufacturing industry.
So-called “Solid Free Form” (SFF) manufacture systems have been used in Rapid Prototyping (RP) applications starting in 1988 with 3D Systems's introduction of their Stereolithography systems. The growth in the RP market has stimulated an accelerating rate of technological development in the field., and firms have developed different types of commercial systems for specific RP applications.
Solid Free Form (SFF) manufacture is essentially the computer controlled additive manufacture of three-dimensional physical forms. All of the commercial SFF systems employ the same basic principle. CAD data of the desired component is sliced into a number of horizontal layers. Each of these layers is built in turn on top of the preceding layer, by the precise addition of material, until the object has been completed. SFF manufacture also encompasses the computer-controlled manufacture of objects comprised of a single layer plus any other additive method of manufacture.
All of the commercial systems use direct computer control of their additive manufacturing processes. Consequently, the main advantages that these systems have over machining and moulding processes is that they can produce a one-off object with complex geometry far more flexibly and quickly than machining and moulding can. The main problem with all of these systems is that they cannot manufacture large batches of duplicate objects as fast as machining and moulding can. These systems have extremely limited capabilities for producing SFF objects with surface or internal colour, tone or doping. Furthermore, none of them can produce objects that are comprised of parts that are made of entirely different materials to the other parts.
Stereolithography RP systems work by using an UV laser to selectively expose the surface of liquid Ultra Violet (UV) reactive polymer to UV radiation (typically from a laser source). This causes the polymer to cure into a solid in the exposed area. The polymer that has been solidified is a physical realisation of a slice of a CAD model. The solidified material is supported on a platform. A new flat area of liquid UV reactive polymer is then laid over this layer by lowering of the platform into the liquid, and the exposure process is repeated to form another layer that bonds to the previous one. This process is repeated until the entire part has been completed.
Another UV polymer curing system is Cubital Ltd's Solid Ground Curing (SGC) RP system. Here a thin layer of UV reactive polymer resin is spread over a platform and then exposed to UV radiation shone through a patterned mask. The transparent areas of the mask correspond to the required cross sections of a CAD model, and the UV radiation that passes through these areas cures part of the polymer layer into the pattern of the required cross section. Ionography technology is used to produce the masks that represent the required cross sections, and once a mask has been used it is erased and then re-imaged and inked with a new mask. A residual polymer cleaner removes the uncured polymer and then a spreader coats the cured polymer in wax. A cooling plate is used to accelerate the solidification of the wax, and once this has solidified it is milled flat by a milling head. The above processes are repeated until the entire model has been built. The wax is removed from the finished products by melting it away with hot (60° C.) water.
By their nature all of the commercial polymer curing systems are limited to manufacturing objects out of UV reactive polymer. Consequently, the physical properties of these objects are not suitable for many functional applications.
Selective sintering systems have enabled objects to be made out of a wide range of powdered materials. As an example, one selective sintering method works by spreading a heat fusible powder on top of a moveable platform that can be lowered within a cylinder that defines the maximum part volume. The layer of powder is then selectively fused by a laser that defines the layer of the CAD model. The platform is lowered and a new layer of powder is deposited and subsequently selectively fused to the preceding layer. This process is repeated until the object is completed.
By combining materials and coating the powders with various binders, it is possible to make specialised powders, tailored to particular functional applications.
Another rapid prototyping technique is “laminated object manufacture” (LOM). In this technique, objects are built by sticking sheets of material together. An uncut sheet is laid down and a heated roller is passed over it, which causes a coating of heat sensitive glue on the sheet to adhere it to the underlying sheet. A laser is then used to cut the sheet to the desired shape. Another layer is then added to the stack and the process is repeated. Most of the LOM RP systems are limited to manufacturing objects out of paper and polymers. Consequently, the physical properties of these objects are not suitable for many functional applications.
The “Fused Deposit Modelling” (FDM) process uses low diameter thermo polymer wire-like filaments, which are extruded in a hot semi-molten form from a delivery head. The motion of the delivery head is computer-controlled. This allows the filament to be extruded in a pattern that depicts a layer of the required object and the object is built up in a layer-wise fashion out of the extruded layers that bond together when they cool. The cost of converting the thermo polymer to a filament can be extremely high and so objects that contain a large volume of the extruded filament can be extremely costly in comparison to injection moulded objects.
The use of hot melt jet printing technology in rapid prototyping is quite a new development. The principle is relatively straightforward. Solid ink is loaded into an ink reservoir and then heated so that the molten ink runs off and is channeled into a piezo-electric jet printer head. The printer then ejects the ink in molten droplet form onto a substrate upon which the droplets cool and thus solidify and adhere. Some systems, such as Sanders Prototyping's Model Maker II use continuous-flow jet printers and others such as 3D Systems Actua 2100 use drop-on-demand (DOD) impulse jet printers. At present, these systems are limited to manufacturing objects out of waxes and thermo polymers. Consequently, the physical properties of these objects are not suitable for many functional applications.
MITs 3DP system and the Soligen Inc DSPC and Extrude Hone Corp.'s Prometal licensed versions use a different method from the previously mentioned selective sintering, but objects are still built by putting down a layer of powder. The difference is that the powder layers are bound together using a continuous jet printer to deposit a binder or solvent selectively onto the powder, and repeating the process consecutively until the required three dimensional object is constructed. Finally the object is removed from the loose powder and any unbound powder left on the object or trapped in inclusions is cleaned away.
Topographic Shell Fabrication (TSF) is a proprietary RP technology developed by Formus, USA. The TSF system is designed for manufacturing ultra large objects that can be the size of cars or even larger. The TSF system is comprised of a chamber, a layering device that deposits consecutive horizontal layers o
Chan Sing Po
Mayes Melvin C
Wood Phillips Katz Clark & Mortimer
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