Investigation of flexible perforation of thin materials using a continuous-wave CO2 laser

Abstract

Thin material laser perforation improves the flexibility and quality of materials such as tipping paper, medicated sticking plaster and breathable plastic film for storage. Perforation processing requires reliable, high speed, robust and adaptable optoelectronic systems to provide controllable permeability and flexibility in thin materials. This article provides descriptions on the design and performance of a new laser perforation system developed to meet such stringent requirements. This system is applicable for on-line thin material perforation. The optoelectronics include a continuous wave CO2 laser whose beam can be modulated into sequences of pulsed laser beams by a mechanical chopper. The focusing characteristics of a real laser beam in the perforation system have been investigated. This allowed laser beams to be focused on the moving thin material to be perforated and adaptable software control to provide the desired pattern distribution of the circular holes perforated on this material. A galvanometer scanner system allows sequential scanning of pulsed laser beams. This unique optoelectronic, mechanical and dedicated embedded control system has been designed and implemented to synchronize the actions of mechanical choppers, galvanometer scanners and the movement characteristics of the thin material. A practical implementation of the sticking plaster and tipping paper laser perforation system has been completed and successfully tested. Results show for example that circular holes with two geometrical distribution patterns are achievable, and unique patterns of perforation can be designed to discourage counterfeiting.