Roll stamping apparatus and method
A roll stamping apparatus includes sets of rollers that rotate while facing each other so as to press opposite surfaces of a material which is continuously supplied to move between the rollers. The sets of rollers have molding portions with a stamping structure applied to outer surfaces so as to mold the material, wherein a plurality of sets of rollers are disposed along a movement direction of the material, the respective molding portions of the sets of rollers are formed to sequentially change a cross section of the material along the movement of the material, and the molding portion of at least one set of rollers before a final set of rollers through which the material finally passes is a set of over-molding rollers having a length in a circumferential direction longer than the molding portions of the final set of rollers.
1. A roll stamping method for changing a material from a first shape into a second shape which is different from the first shape, comprising:
forming the material into the first shape that has a first molding portion length and first transition portions lengths on opposite ends of the first molding portion length in a longitudinal direction of the material by passing the material through a first set of rollers which face each other and have, on outer surfaces thereof, a first molding portion that includes first transition portions on opposite ends of the first molding portion in a circumferential direction of the first set of rollers; wherein the longitudinal direction of the material is defined by the circumferential direction of the first set of rollers; and
changing the first shape into the second shape that has a second molding portion length and second transition portions lengths on opposite ends of the second molding portion length in the longitudinal direction by passing the material through a second set of rollers which face each other and have, on outer surfaces thereof, a second molding portion that includes second transition portions at opposite ends of the second molding portion in a circumferential direction of the second set of rollers which rotate in the circumferential direction of the first set of rollers;
wherein a sum of the first molding portion length and first transition portions lengths is larger than a sum of the second molding portion length and second transition portions lengths in the longitudinal direction.
2. The roll stamping method of claim 1 , further comprising forming the material into a shape before forming the first shape.
3. The roll stamping method of claim 2 , sequentially changing the shape to the first shape.
4. The roll stamping method of claim 1 , wherein the first molding portion length of the first shape is greater than the second molding portion length of the second shape in the longitudinal direction.
5. The roll stamping method of claim 1 , wherein the first transition portions lengths are the same as the second transition portions lengths in the longitudinal direction.
6. The roll stamping method of claim 1 , wherein the first molding portion length of the first shape is the same as the second molding portion length of the second shape and the first transition portions lengths are greater than the second transition portions lengths in the longitudinal direction.
7. The roll stamping method of claim 1 , wherein after changing the first shape into the second shape, the direction of residual stress in the second transition portions lengths and the direction of residual stress in the second molding portion length are formed to be different from each other.
8. The roll stamping method of claim 1 , wherein, prior to the first shape, forming the material into a prior shape that has a prior molding portion length and prior transition portions lengths on opposite ends of the prior molding portion length in the longitudinal direction of the material by passing the material through a prior set of rollers which face each other and have, on outer surfaces thereof, a prior molding portion that includes prior transition portions on opposite ends of the prior molding portion in a circumferential direction of the prior set of rollers which rotate in the circumferential direction of the first set of rollers;
wherein a sum of the prior molding portion length and prior transition portions lengths is smaller than a sum of the first molding portion length and first transition portions lengths in the longitudinal direction.