Abstract: A motor-driven welding gun has a servomotor for displacing a movable electrode tip toward and away from a fixed electrode tip. The servomotor has a motor housing with a copper pipe which is inserted therein when the motor housing is cast. The copper pipe provides a coolant passage in the motor housing for supplying a coolant therethrough. When the coolant passage is supplied with the coolant, the motor housing is forcibly cooled, reducing the amount of heat generated by the servomotor.

Abstract: A motor-driven welding gun has a servomotor (34) for displacing a movable electrode tip (30) toward and away from a fixed electrode (32). The servomotor (34) has a motor housing (38) with a copper pipe (72) which is inserted therein when the motor housing (38) is cast. The copper pipe (72) provides a coolant passage (70) in the motor housing (38) for supplying a coolant therethrough. When the coolant passage (70) is supplied with the coolant, the motor housing (38) is forcibly cooled, reducing the amount of heat generated by the servomotor (34).

Abstract: A metallic mold for casting a vehicle wheel having openings in a periphery of a disk portion of the wheel comprises a first mold for forming that external side of the wheel which faces an outside of a vehicle when mounted thereon and a second mold for forming an internal side of the wheel. The first mold has those projections for forming the openings which abut the second mold. A high-hardness coating material is coated by electric discharge coating on at least those base portions of the projections which extend diametrically inwards of the wheel, among outer surfaces of the projections. A coating of a mold coating agent is formed on portions of sharp draft in the projections. The coating has a three-layer construction comprising an under coat coated with a mold coating agent consisting essentially of ceramics, a middle coat coated with a mold coating agent consisting essentially of a mixture of boron nitride with ceramics, and a top coat coated with a mold coating agent consisting essentially of titania.

Abstract: The lower mold which forms the external side of the vehicle wheel is water-cooled by water-cooling pipes. The rib-forming portions of the upper mold which forms the internal side of the vehicle wheel are forcibly air-cooled by the air passages provided along the rib-forming portions. Since water-cooling has better cooling capacity than air-cooling, the molten material inside the cavity between the lower mold and the upper mold is solidified from the external side thereof, and no defects such as shrinkage cavities occur on the external side thereof. When the internal side is solidified, the rib portions are solidified not much later than the other portion of the internal side, thereby shortening the casting cycle time. The split molds which form the cavity for forming therein the rim portion of the vehicle wheel are opened earlier than the upper mold, at the time when the surface layer portion of the molten material in the cavity has been solidified.

Abstract: The temperature of a casting die is controlled in a low-pressure casting process for pressurizing the surface of molten metal stored in a closed container to fill the molten metal in a die cavity defined in the casting die. The temperature of the casting die is detected by a temperature sensor, and compared with a preset reference die temperature range. The amount of cooling water to be supplied to the casting die is controlled based on the result of the comparison. When the detected temperature of the casting die falls in the preset reference die temperature range, the molten metal starts to be filled in the die cavity.

Abstract: A light metal alloy such as an aluminum alloy is cast into a casting such as an automobile engine cylinder head under low pressure. A fluid pressure is applied to the surface of a light metal alloy stored in a closed container to introduce the light metal alloy from the closed container through a transfer tube and a sprue into a mold cavity defined in a mold assembly. The introduced molten metal alloy is brought into contact with molds of the mold assembly which have different thermal conductivities, respectively. The time in which the molten metal alloy is solidified is controlled by the molds of different thermal conductivities. The molds may forcibly be cooled by a cooling medium passing therethrough or cooling blocks mounted thereon.