Expandable methyl methacrylate resin particles having a narrow particle size distribution, a good yield, and excellent expandability and formability are provided. The expandable methyl methacrylate resin particles include a base resin containing, as constitutional units, a certain amount of a methyl methacrylate unit and a certain amount of acrylic ester unit, and a blowing agent. The expandable methyl methacrylate resin particles have an average particle diameter of 0.6 mm to 1.0 mm and a particle diameter variation coefficient of not more than 20%.

The invention relates to a method for producing a helical metal body (Γ), in which initially a preformed, helical metal body is produced in a mould by a casting method and is subsequently compressed along its longitudinal axis by deformation.

A mold assembly for use in forming a component having an outer wall of a predetermined thickness includes a mold and a jacketed core. The jacketed core includes a jacket that includes a first jacket outer wall coupled against an interior wall of the mold, a second jacket outer wall positioned interiorly from the first jacket outer wall, and at least one jacketed cavity defined therebetween. The at least one jacketed cavity is configured to receive a molten component material therein. The jacketed core also includes a core positioned interiorly from the second jacket outer wall. The core includes a perimeter coupled against the second jacket outer wall. The jacket separates the perimeter from the interior wall by the predetermined thickness, such that the outer wall is formable between the perimeter and the interior wall.

A method for producing a helical casting pattern. The method including: providing a pattern body having a longitudinal axis, a cavity extending in the direction of the longitudinal axis, and a pattern body wall that surrounds the cavity; providing a processing tool for creating a recess; arranging the pattern body and the processing tool such that the processing tool extends at least partially through the pattern body wall in the radial direction with respect to the longitudinal axis; and rotatably driving at least one of the processing tool and the pattern body about one of the longitudinal axis of the pattern body and an axis parallel thereto, relative to one another, with a relative movement between the pattern body and the processing tool in a direction parallel to the longitudinal axis being produced one of continuously or at least intermittently during or in alternation with the relative rotational movement.

The invention discloses an expandable copolymer resin used for manufacturing a lost foam casting model and a preparation method thereof, wherein the molecular weight of the expandable copolymer resin is 150000-300000, and the expandable copolymer resin comprises mixed monomers, deionized water, a cellulose ether dispersant, sodium salt, an initiator, a foaming agent and a molecular weight regulator; the mixed monomers comprise MMA and ST, wherein MMA accounts for 70-95% wt of the mixed monomers, and ST accounts for 5-30% wt of the mixed monomers. The model formed by the expandable copolymer resin has the advantage of reducing or eliminating carbon defects of castings when casting cast iron and cast steel.

The invention is directed to a casting process to make a metal 3D product by performing the following steps, (a) providing a form negative mould of the 3D product comprising of a plastic sheet which sheet defines at its inner side a hollow space corresponding with at least the shape of one or more of the 3D products by thermoforming using a master mould, (b) applying a layer of refractory material on the exterior of the plastic sheet of the mould to obtain a ceramic mould having a hollow space, (c) pouring molten metal into the hollow space of the ceramic mould and allowing the metal to solidify, and. (d) removing the layer of refractory material to obtain the metal 3D product.

An expandable poly methyl methacrylate particle including a polymer, which is obtained by a process including polymerizing monomers including 100 parts by weight of an acrylic monomer and from 0.05 to 0.15 parts by weight of a polyfunctional monomer. The acrylic monomer includes 90% to 98% by weight of methyl methacrylate and 2% to 10% by weight of an C.sub.2-8 alkyl acrylate, relative to a total weight of the methyl methacrylate and the C.sub.2-8 alkyl acrylate.

A mold wash is used in a casting method using a lost foam to make a casting having a hole with a diameter of 12 mm or less. The casting method includes determining a thermal decomposition amount C(,t) [wt %] of a resin binder when the mold wash is exposed at a temperature [ C.] for a time t [sec], and determining a room temperature transverse rupture strength .sub.b(,t) [MPa] of the mold wash after receiving thermal loads, and performing casting with the mold wash having the room temperature transverse rupture strength .sub.b(,t) after receiving thermal loads being equal to or larger than a threshold value .sub.cr [MPa].

The invention is directed to a casting process to make a metal 3D product by performing the following steps, (a) providing a form negative mould of the 3D product comprising of a plastic sheet which sheet defines at its inner side a hollow space corresponding with at least the shape of one or more of the 3D products by thermoforming using a master mould, (b) applying a layer of refractory material on the exterior of the plastic sheet of the mould to obtain a ceramic mould having a hollow space, (c) pouring molten metal into the hollow space of the ceramic mould and allowing the metal to solidify, and. (d) removing the layer of refractory material to obtain the metal 3D product.

A mold wash is used in a casting method using a lost foam to make a casting having a hole with a diameter of 12 mm or less. The casting method includes determining a thermal decomposition amount C(,t) [wt %] of a resin binder when the mold wash is exposed at a temperature [ C.] for a time t [sec], and determining a room temperature transverse rupture strength .sub.b(,t) [MPa] of the mold wash after receiving thermal loads, and performing casting with the mold wash having the room temperature transverse rupture strength .sub.b(,t) after receiving thermal loads being equal to or larger than a threshold value .sub.cr [MPa].