1. Eliminate the air in the slab to prevent a large amount of air from escaping through the slab during hot pressing.

2. The slab has a certain density to improve its own supporting strength, so as not to be scattered or broken due to vibration during transportation.

3. Reducing the thickness of the fluffy slab can reduce the opening of the press.

The pre-pressed slab is 2 / 3-3 / 4 less than the original (including the rebound after off-machine), or 8-10 times the thickness of the product. However, after pre-compression, the width of the slab should be stretched by 5 to 7%.