If a book block does not have a compact compaction to brush gummed, repaired, when presiding at the cutter press paper for powerful punch, backs will occur as a result of compression wrinkle.

• 若书芯没有压紧压实就刷背胶，修裁时在切纸机压纸器的强力冲压下，书背就会因压缩变形而出现起皱情况。