In order to compensate for the thickness, some factories mass-produce plywood with concave lens shape.为了弥补厚度，一些工厂批量生产凹透镜形状的胶合板
为了竞争价格的工厂，他们制造的胶合板中间一般都很薄， +/-0.8mm到+/-1.0mm， 甚至+/-1.2mm 厚些都有可能。
In order to compete for prices in factories, the plywood they make is usually thin in the middle, +/-0.8mm to +/-1.0mm, or even a little thicker than +/-1.2mm.
For example: 18MMX1220X2440MM is 11 layers, customers require a thickness tolerance of +/-0.5MM, but due to cost control, general factories will consider making 11 layers of edge enough, and then 10 layers of middle.
此类胶合板中间都是轻微凹进去的，这种质量的 胶合板制作为了兼顾外围厚度， 中间尽量做薄。 但到底可以做多薄， 主要看材料的强度， 硬度强度高的， 中间可以薄一些， 反之厚一些。
This kind of plywood is slightly concave in the middle. This quality of plywood is made to take into account the thickness of the periphery and try to be thin in the middle. But how thin it can be depends mainly on the strength and hardness of the material. It can be thinner in the middle and thicker in the opposite direction.
目前一般普通级别的胶合板 由于厚度薄，边缘已经很厚， 为了强度，边缘也不能太厚.
At present, ordinary plywood has very thick edges because of its thin thickness. For strength, the edges can not be too thick.
很多工厂这样做的道理，就不必说了吧，好像胶合板是一片凹透镜， 中间和边缘的差别越大， 为了照顾边缘尽量厚， 那就只能尽可能将边缘做厚，便于客户和质检检验， 中间有多薄关键看材料了。
Many factories do this, needn’t say, as if plywood is a concave lens, the greater the difference between the middle and the edge, in order to take care of the edge as thick as possible, it can only make the edge as thick as possible for customers and quality inspection, and how thin the key material is in the middle.