in an upper mold part such as a middle plate 2 and a lower mold channel located in a lower plate 3 the upper mold channel extends from top to bottom so as to be connected to the lower mold channel and at least a part of the lower mold channel extends to a position below the product cavity and further extends from bottom to top so as to be in communication with the waterproof structure cavity as shown in fig3 preferably a silicone inlet insert 8 is further provided between the upper mold part and the lower plate 3 and the upper mold channel is connected to the lower mold channel through a channel formed on the silicone inlet insert 8 more preferably the upper mold channel substantially extends vertically to a position below a horizontal position of the product cavity and the channel formed on the silicone inlet insert 8 and a part of the lower mold channel that is in communication with the channel formed on the silicone inlet insert 8 substantially extend horizontally as shown in fig4 to fig6 in some preferred embodiments a manufacturing device further includes an ejection mechanism provided in a lower plate 3 and the ejection mechanism is configured to eject.