Abstract: In a crimping process in a crimping machine therefor, a compression force on an extended length of a transiting fiber bundle is exerted by and between means for maintaining a continuous and forced contact. The means for maintaining a continuous and forced contact comprise two closed belts, each of which runs around two motorized rollers travelling at a same velocity as the fiber bundle. Pressurized air or steam is injected into the crimping machine in a same direction as an advancement direction of the fiber bundles, but in an opposite sense thereto.