Die capable of being opened, manufacturing method thereof, and mold

A method for manufacturing a die, which is configured of a polyhedron having multiple planes (11 through 16) of a similar shape and which can be opened into a continuous polygon area on a plane, each of the multiple planes having inclined boundary portions on one side (Rb1, Rb), the continuous polygon area being contiguous to one another through bridge portions (Br) connected between two adjacent ones of the multiple planes, the method comprising the steps of:

• preparing a mold (31, 32) having a first side and a second side opposite said first side, and a cavity therebetween in the form of said opened polyhedron and comprising inclined portions (34) which are formed on the one side and which correspond to the inclined boundary portions of the die, gate portions (35) connected to the inclined portions (34) on the one side, and raised portions (33) extended from an
• opposite side of the one side to define the bridge portions between the gate and the raised portions (35 and 33), the raised portions (33) forming linear grooves on the opposite side between the two adjacent ones of the multiple planes, said inclined boundary portions including a narrow inclined boundary portion (RB1) that is narrower in width than the remaining inclined boundary portions (Rb);
• and
• injecting a predetermined resin into said mold (31, 32) to obtain said die.