Question about vacuum laminator silica gel plate

The common laminating machine is a vacuum laminating machine, that is, a negative pressure laminating machine. 

The working principle is to use a vacuum pump to extract air to form a negative pressure, so that the surface material to be attached is combined with the substrate under heating. The substrate is generally pre-sprayed. If the face material is a pvc membrane, do not use a silica gel plate. Place the pvc membrane directly on the workpiece, then press the membrane with the pressure frame, and fasten the clamp to blister. If the surface material you are covering is solid wood or paper, and the surface material itself cannot be sealed, it is necessary to use a silica gel plate to seal the air to form a negative pressure. 

The membrane press machine with positive and negative pressure also uses a silica gel plate to seal the air to form a negative pressure. That is to say, vacuum membrane press machine does not need to use silica gel plate to cover pvc, solid wood skin, paper, etc. must use silica gel plate, positive and negative pressure machine must also use silica gel plate.