Study of curing characteristicsof photopolymer used in solid laser diode plotter rapid prototyping system

Abstract

For most rapid prototyping (RP) systems, stereolithography processes employ UV or diode pumped, solid state lasers to cure the associated photopolymer to build three-dimensional parts. However, such types of lasers are relatively expensive. Therefore a semiconductor laser has been used in the solid laser diode plotter RP system to cure a specific photopolymer DF2000.The DF2000 photopolymer is formulated from a base resin, hardening agent, and powder. The wavelength of the semiconductor laser used in the solid laser diode system is 680 nm and is in the red light range. In this research, the curing level of most of the visible wavelength spectrum generated by a lamp on the DF2000 photopolymer is investigated, using differential scanning photocalorimetry (DSPC). The DSPC results indicate that the curing effect of the photopolymer using blue light is better than that using red light. The results also show that the shorter the wavelength, the better the curing effect of the photopolymer. Hence, a blue semiconductor laser (405 nm) or a shorter wavelength laser, can be used instead of a red laser to increase the curing level of the photopolymer used in the SLP system. The quantitative effect of the SLP processing parameters on the curing level of the DF2000 photopolymer and the mechanical properties of the SLP test specimen were studied using the Taguchi method. The results show that the mechanical properties of a fabricated part are proportional to the degree of cure of the photopolymer. The results also indicate that the scanning pitch of the processing parameters is the most sensitive parameter of the SLP system to affect the curing level. Hence the curing characteristics of the photopolymer used in the SLP system can be used as an index of the mechanical properties of the fabricated part. In addition, using a shorter wavelength laser rather than a red laser can further improve the mechanical properties and fabrication speed of the part.