Skin passageway trip strips

1 . A method for manufacturing a casting core, the casting core having:

a leg having a first face, the first face having a plurality of grooves,

the method comprising:

molding the core in a die having a first piece and a second piece, the first piece having ridges that mold the grooves;

separating the first piece from the second piece; and

releasing the core from the die,

wherein:

the plurality of grooves are not molded by the second piece;

the ridges are shaped with a rim tapering in height but having a fillet transitioning to project toward a local parting line between the first piece and the second piece.

2 . The method of claim 1 , wherein:

a maximum height of the ridge rim is between 80% and 100% of a height of the parting line.

3 . The method of claim 1 , wherein:

a difference between a maximum height of the ridge rim and a height of the parting line is not more than 200 micrometers.

4 . A method for manufacturing a casting, the method including manufacturing according to claim 1 a casting core, the method comprising:

said manufacturing the casting core;

overmolding the casting core with a pattern material;

shelling the overmolded casting core to form a shell;

casting alloy in the casting shell; and

deshelling and decoring.

5 . The method of claim 4 , wherein:

a maximum height of the ridge rim is between 80% and 100% of a height of the parting line.

6 . The method of claim 4 , wherein:

a difference between a maximum height of the ridge rim and a height of the parting line is not more than 200 micrometers.

7 . The method of claim 4 , wherein the manufactured casting is turbine engine airfoil element comprising:

an airfoil having:

an exterior surface; and

a plurality of spanwise passageways including:

a plurality of main body passageways along a camber line; and

a plurality of skin passageways between the main body passageways and the exterior surface,

wherein:

the plurality of grooves cast a longitudinally spaced plurality of protrusions from skin sides of the plurality of skin passageways.

8 . A die for molding a casting core, the die having a closed condition and an open condition and comprising:

a chamber formed by surfaces of a first piece and a second piece in the closed condition having a plurality of sections for molding respective legs of the casting core; and

a pull direction for separating the first and second pieces from each other to release a molded casting core,

wherein:

for each chamber section, a parting line extends across the section between junctions of the first and second pieces;

for each chamber section:

a face of the first piece has a longitudinally spaced plurality of protrusions;

a pair of lateral rounded transitions extend from the first face toward the second piece;

the protrusions have a height profile having:

at least a first tapering portion;

first and second inwardly concave terminal transitions to or past the lateral rounded transitions;

a minimum difference (D) between a height of the protrusions and a height of the parting line away from the first and second inwardly concave transitions being not more than 200 micrometers;

a difference (D) between a terminal height of the concave transitions and a height of the parting line is not more than 200 micrometers.

9 . A method for using the die of claim 8 , the method comprising:

molding the casting core in the die;

separating the first piece from the second piece; and

releasing the core from the die.

10 . The method of claim 9 further comprising:

overmolding the casting core with a pattern material;

shelling the overmolded casting core to form a shell;

casting alloy in the casting shell; and

deshelling and decoring.

11 . The method of claim 10 , wherein the cast alloy forms turbine engine airfoil element comprising:

an airfoil having:

an exterior surface; and

a plurality of spanwise passageways including:

a plurality of main body passageways along a camber line; and

a plurality of skin passageways between the main body passageways and the exterior surface,

wherein:

the plurality of grooves cast a longitudinally spaced plurality of protrusions from skin sides of the plurality of skin passageways.

12 . A die for molding a casting core, the die having a closed condition and an open condition and comprising:

a chamber formed by surfaces of a first piece and a second piece in the closed condition having a plurality of sections for molding respective legs of the casting core; and

a pull direction for separating the first and second pieces from each other to release a molded casting core,

wherein:

for each chamber section, a parting line extends across the section between junctions of the first and second pieces;

for each chamber section:

a face of the first piece has a longitudinally spaced plurality of protrusions;

a pair of lateral rounded transitions extend from the first face into the second piece;

the protrusions have a height profile having:

first and second tapering portions tapering from a maximum height;

first and second inwardly concave transitions to the lateral rounded transitions;

a difference (D) between a maximum height of the protrusions and a height of the parting line being not more than 200 micrometers;

a difference (D) between a terminal height of the concave transitions and a height of the parting line is not more than 200 micrometers.

13 . A method for using the die of claim 12 , the method comprising:

molding the casting core in the die;

separating the first piece from the second piece; and

releasing the core from the die.

14 . The method of claim 13 further comprising:

overmolding the casting core with a pattern material;

shelling the overmolded casting core to form a shell;

casting alloy in the casting shell; and

deshelling and decoring.

15 . The method of claim 14 , wherein the cast alloy forms turbine engine airfoil element comprising:

an airfoil having:

an exterior surface; and

a plurality of spanwise passageways including:

a plurality of main body passageways along a camber line; and

a plurality of skin passageways between the main body passageways and the exterior surface,

wherein:

the plurality of grooves cast a longitudinally spaced plurality of protrusions from skin sides of the plurality of skin passageways.