EPS insulation sheet manufacturing process comprises the following stages:
1. Raw material preexpansion.
This is one of the most important stages of the whole process and it influences the quality of the end product tremendously. The preexpander is filled with the necessary amount of raw material and then forced steam is fed to the preexpander. As the result raw beads increase manifold in diameter (they get “expanded”). As the expanded granules reach the volume of 1 m3 steam supply is cut, the preexpander gets unloaded and the expanded granules are fed to silo bunkers by suction. Depending on the desired EPS density brand raw material is fed to the preexpander at the respective rates. Raw material brand is also of great importance as the brands differ in sizes (fractions). Double expansion is used to manufacture light EPS brands (8-9 kg/m3).
2. Beads aging in silo bunkers.
There internal stresses of the beads are stabilized and the preexpanded material is dried after steam treatment. The aging time is between 12 and 24 hours depending on the raw material brand.
3. EPS block molding.
Once the beads have aged they are fed to the blockmold by suction. There they are treated by heat and as the result beads get expanded once again and thus are molded into an EPS block. The molded block is then cooled by means of vacuum exhaustion (created by vacuum system) in the blockmold processing chamber. The block is knocked out of the blockmold with the help of either a pneumocylinder-driven pusher or a pneumocushion, depending on the blockmold design. Our company supplies open — and close-type blockmolds. An open-type blockmold enables you to manufacture blocks and sheets of an infinite length, whereas a close-type blockmold has greater output.
4. Block aging.
The molded block is aged in normal condition for 12-24 hours in order to stabilize internal stresses and to reduce its moisture content.
5. Cutting into sheets.
The blocks are cut into sheets by means of a horizontal or vertical cutter.
6. Waste grinding.
Waste is ground in the grinding machine and is then fed to a separate storage bunker by suction. Ground EPS can be reused to manufacture EPS sheets, they should be added to the new beads in the ratio of around 1:10.