A ceramic core includes sintered ceramic powder and a hole opening on a surface of the ceramic core and having an opening portion with a maximum size of 100 μm or less. A manufacturing method for a ceramic core includes: preparing an injection molding composition by mixing ceramic powder and a binder; manufacturing a ceramic compact by performing the injection molding of the injection molding composition; and manufacturing a ceramic core by sintering the ceramic compact, wherein cumulative percentage of coarse powder with a particle diameter of more than 50 μm included in the ceramic powder is 30% or less on an integrated volume particle size distribution curve of the ceramic powder.

An opening is provided in a foam pattern, and a coating agent is applied to the opening. The coating agent applied to the opening is taken as a beam having a sectional secondary moment I, a vertical plate thickness h, and a length L. It is assumed that a volume of a cavity part in the foam pattern is V (mm.sup.3), a bulk density of the casting sand filling the cavity part is ρs (kg/mm.sup.3), a density of the melt is ρm (kg/mm.sup.3), an angle of the opening with respect to a vertical direction is θ, and a transverse strength of the coating agent at the highest temperature during pouring of the melt is σb (MPa). A sectional shape of the opening, the angle θ of the opening, and the transverse strength σb of the coating agent are selected to satisfy the expression:

σbI>V(ρm−ρs){(hL/2)sin θ−cos θ}.

In the following expression, it is assumed that a thickness of a coating agent applied to a foam pattern [2] is t (mm), a diameter of a hole part [3] is D (mm), and a normal-temperature transverse strength of the dried coating agent is σc (MPa). At the time of producing a casting provided with a hole having a diameter of 18 mm or smaller and a length of 1 (mm), a coating agent that satisfies the following expression is used when a solidification end time te (sec) at which solidification of a melt ends on a periphery of the hole part [3] is within a time t0 (sec) at which thermal decomposition of the coating agent ends.

σc≧{t0/(t0−te)}×(1.5×10.sup.−4×1.sup.2/t.sup.2+160/D.sup.2)

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 mold assembly for use in forming a component having an outer wall of a predetermined thickness is provided. The mold assembly includes a mold that includes an interior wall that defines a mold cavity within the mold. The mold assembly also includes a jacketed core positioned with respect to the mold. The jacketed core includes a jacket that includes an outer wall. The jacketed core also includes a core positioned interiorly of the jacket outer wall. The jacket separates a perimeter of the core from the mold interior wall by the predetermined thickness, such that the outer wall is formable between the perimeter and the interior wall.

A method to manufacture reticulated metal foam via a dual investment solid mold, includes pre-investment of a precursor with a diluted pre-investment ceramic plaster then investing the encapsulated precursor with a ceramic plaster.

A method to manufacture reticulated metal foam includes coating a precursor in a molten wax to increase ligament thickness; and investment coating the molten wax coated precursor with a ceramic plaster.

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.

Provided is a casting method using lost foam capable of forming a small highly-finished hole with a diameter of 18 mm or less and a length of 50 mm or more by casting. A casting method using lost foam of the present embodiment includes the steps of embedding, in foundry sand, a casting pattern formed by applying a mold wash with a thickness of 1 mm or more to a surface of the foam pattern, the foam pattern having a hole with a diameter of D (mm); replacing the foam pattern with molten metal by pouring the molten metal into the casting pattern and losing the foam pattern; and forming a casting having a small hole with a diameter of 18 mm or less and a length of 50 mm or more by cooling the molten metal, and the method satisfies the following formulas (0) and (1):

2<D≦19.7   Formula (0)

σc≧−0.36+140/D.sup.2   Formula (1) where σc (MPa) is transverse rupture strength (bending strength) of the mold wash that is heated to decompose resin constituting the mold wash and then returned to room temperature.

A method to manufacture reticulated metal foam via a dual investment, includes pre-investment of a precursor with a diluted pre-investment ceramic plaster then applying an outer mold to the encapsulated precursor as a shell-mold.