Glass molding press (GMP) was applied to the fabrication of glass aspherical Fresnel lens for high-efficiency mass production. A pair of molds for the Fresnel lens was precisely fabricated on the Nickel Phosphorous (Ni-P) plating layer by the single diamond cutting with multi-axis machining center. A kind of low transition temperature (T-g) glass was heated to several tens degree centigrade above its T-g and compressed between the two molds. In this way, the shape of the mold was replicated to the glass lens surface. The molding process was simulated by finite element method (FEM), and the molding condition was optimized to minimize the residual stress.

In a glass moulding press (GMP) for refractive/diffractive hybrid lenses, to improve the service life of nickel–phosphorus (Ni–P) plated moulds, it is necessary to control the diffusion of constituent elements from the mould into the release agent coating. In this study, diffusion phenomena of constituents of Ni–P plating are investigated for two types of release agent coatings, iridium–platinum (Ir–Pt) and iridium–rhenium (Ir–Re), by cross-sectional observation, compositional analysis and stress measurements. The results show that Ni atoms in the plating layer flow from regions of compressive stress to regions of tensile stress. In the case of the Ir–Pt coated mould, the diffusion of Ni is promoted from the grain boundaries between the Ni and Ni3P phases in the plating towards the surface of the Ir–Pt coating. However, in the Ir–Re coated mould, the diffusion of Ni is suppressed because the diffusion coefficient of Ni in the Ir–Re alloy is smaller than that in the Ir–Pt alloy, although the stress state is similar in both cases. By controlling the diffusion of Ni atoms, the use of Ir–Re alloy as a release agent coating for Ni–P plated moulds is expected to lead to a high degree of durability.

Glass molding press (GMP) has been applied to produce the microgrooves on glass plates by using electroless-plated nickel phosphorus (Ni–P) molds. The GMP process for microgrooves was analyzed by finite element method (FEM) simulation. The effects of various pressing conditions, such as the molding temperature, the pressing velocity and the friction in glass deformation, were studied. Then, based on the simulation results, optimal pressing conditions were determined and used in the GMP experiments. By comparing the shape of the molded microgrooves with that of the corresponding microgrooves on the Ni–P mold, the shape transferability was evaluated and the reasons for form error were analyzed. The results show that the GMP process is an effective way to fabricate precision microgrooves on glass.

Glass molding press is an efficient manufacturing technology for ultraprecision optical elements with complex shapes. In glass molding, viscoelastic property of glass is an essential aspect that determines the glass deformation behavior around the molding temperature. In this paper, viscoelasticity of glass has been measured experimentally by uniaxially compressing cylindrical glass preforms above the glass transition temperature using an ultraprecision glass molding machine. The elastic modulus and viscosity of glass were obtained by curve fitting techniques using the Burgers model and the Maxwell model for creep and stress relaxation, respectively. Based on the thermo mechanical and viscoelastic parameters obtained from experiments, finite element model simulations of the glass molding process were performed, which can be used to visualize the stress/strain distribution and to predict the residual stress in glass.

The changes in microstructure and topography of nickel-phosphorus (Ni-P) plated steel moulds in a glass lens moulding process were investigated by heating tests. The results show that, at a high temperature, Ni atoms diffuse from the inner Ni-P plating layer into the outer release agent coating consisting of precious metals. The atomic diffusion leads to partial surface swelling, which makes the mould surface rough and cloudy. The diffusion is influenced by the temperature, interface structure and stress state of the moulds. These findings provide references for developing new mould materials and for improving the service life of the moulds.

Glass molding is as an effective approach to produce precision micro optical elements with complex shapes at high production efficiency. Since glass is deformed at a high temperature where the mechanical and optical properties depend strongly on temperature, modeling the heat transfer and high-temperature deformation behavior of glass is an important issue. In this paper, a two-step pressing process is proposed according to the non-linear thermal expansion characteristics of glass. Heat transfer phenomenon was modeled by considering the temperature dependence of specific heat and thermal conductivity of glass. Viscosity of glass near the softening point was measured by uniaxially pressing cylindrical glass preforms between a pair of flat molds using an ultraprecision glass molding machine. Based on the numerical models and experimentally measured glass property, thermo-mechanical finite element method simulation of temperature rise during heating and material flow during pressing was carried out. The minimum heating time and pressing load changes were successfully predicted.

Optical and optoelectronic product such as digital cameras, mobile phone, and high-density optical disc systems use many optical lenses. Another attention-attracting trend is the development of compound glass lenses, namely, lenses that combine the refractive and diffractive functions of light. Compound lenses can consolidate the functions of two lenses into one. We developed the special Ni-alloy plated mold. This mold can be easily fabricated into diffractive patterns by cutting with a single-crystal diamond tool. In the present work, special Ni-alloy plated molds are applied to mold glass lenses. It is possible to mold a diffractive optical element (DOE) made of glass with special Ni-alloy plated molds. These molds have high-temperature strength sufficient to mold at 500℃ and can be applied to molds for high refractive index glass lenses.