A method for manufacturing interdental cleaning tools, each interdental cleaning tool comprising:
- a base part made of a synthetic resin, the base part having a handle base and an elongated shaft-like core base connected to a leading end of the handle base;
- and a flexible part made of an elastomer and covering at least a portion of the base part, the flexible part having at least a cleaning flexible part covering the core base, the handle base constituting a handle part, and the core base and the cleaning flexible part constituting an interdental cleaning part, wherein the method comprises:
- a core base part molding step of:
- providing a first metal mold for molding the base parts with a plurality of first molding spaces aligned in parallel and including core base molding sections and handle base molding sections;
- providing the first metal mold with connection part molding sections to communicate with adjacent handle base molding sections;
- supplying a synthetic resin material with a fiber material at a time to the plurality of first molding spaces from gates opened to the first molding spaces at base end sides of the first molding spaces opposite to the core base molding sections;
- and forming a plurality of core base parts at a time such that the base parts are connected to each other in parallel by connection parts molded at the connection part molding sections, and
- a flexible part molding step of:
- transferring the connected core base parts molded and connected to each other in the base part molding step to a second metal mold for molding the flexible parts;
- setting at least portions of the core bases of the connected base parts into a plurality of second molding spaces in the second metal mold for molding the flexible parts;
- holding the core bases at two or more longitudinal portions including at leading ends and base ends of the core bases, at approximately centers of cleaning flexible part molding sections of the second mold and by at least two pairs of hold pins of the second mold, each pair of the hold pins including two pins that are opposed to each other and that protrude within the cleaning flexible part molding sections so as to be approximately perpendicular to matching surfaces of the second metal mold from which the pins protrude;
- and charging an elastomer material into the second molding spaces over the held core bases such that the elastomer material is supplied from leading end sides to base end sides of the cleaning flexible part molding sections, wherein:
- a first pair of hold pins of the at least two pairs of hold pins holds the leading end of the connected core base parts with each pin of the first pair of hold pins having a cross sectional area in contact with each core base part of 0.03 to 0.3 mm2,
- the first pair of hold pins is arranged at positions where leading ends of the first pair of pins hold the core base parts within 3 mm from the leading end sides to the base end sides of the cleaning flexible part molding sections,
- a second pair of hold pins of the at least two pairs of hold pins holds the base end of the connected core base parts with each pin of the second pair of hold pins having a cross sectional area in contact with each core base part of 0.1 to 1.1 mm2,
- the second pair of hold pins is arranged at positions where leading ends of the second pair of pins hold the core base parts within 6 mm from the base end sides to leading end sides of the cleaning flexible part molding sections, and
- the positioning and cross sectional areas of the first and second pair of hold pins contributes to centering the core base parts stably in the flexible part molding sections while minimizing a flow resistance to the elastomer material around at least the first and second pairs of holding pins.