Thermoforming is a process of forming a plexiglass shee […]
Thermoforming is a process of forming a plexiglass sheet or sheet into articles of various sizes and shapes. The blank cut into the required size is clamped on the mold frame, heated to soften it, and then pressed to make it close to the mold surface. The shape is the same as that of the profile, and the product is finished by trimming the edge after cooling and setting. The pressurization may be by vacuum drawing or by direct pressing of a punch having a profile. The thermoforming temperature can be referred to the temperature range recommended in Table 3. When adopting a rapid vacuum low draft forming product, it is preferable to adopt a near-lower limit temperature and a deep drawing product having a complicated forming shape, and it is preferable to adopt a near upper limit temperature, and a normal temperature is generally used.
Engraving and cutting is mainly for hollowing and engraving of already formed acrylic or colored acrylic materials. Ordinary laser engraving and cutting machines can meet the engraving and hollowing requirements of most acrylic products.
1. Polymethyl methacrylate contains a polar side methyl group, which has obvious hygroscopicity, and the water absorption rate is generally 0.3%-0.4%. It must be dried before molding, and the drying condition is drying at 80°C-85°C for 4-5h. .
2. Polymethyl methacrylate has obvious non-Newtonian fluid properties in the temperature range of molding processing. The melt viscosity decreases with the increase of shear rate, and the melt viscosity is also sensitive to temperature changes. Therefore, for the molding process of polymethyl methacrylate, increasing the molding pressure and temperature can significantly reduce the melt viscosity and achieve better fluidity.
3. The temperature at which polymethyl methacrylate starts to flow is about 160 ° C, and the temperature at which decomposition begins is higher than 270 ° C, and has a wide processing temperature interval.
4. Polymethyl methacrylate has a high melt viscosity and a fast cooling rate, and the product is prone to internal stress. Therefore, the control of the process conditions is strict during molding, and post-treatment is also required after the product is formed.
5. polymethyl methacrylate is an amorphous polymer, the shrinkage rate and its range of variation are small, generally about 0.5% -0.8%, which is conducive to the formation of plastic parts with higher dimensional accuracy.
6. Polymethyl methacrylate has excellent cutting performance, and its profiles can be easily machined to various required sizes.