核心的瓶颈首先在于精度问题。目前技术虽然在不断进步，但在打印精细结构或大尺寸零件时，依然难以达到高精度装配所需的公差要求及优秀的表面质量要求，这直接导致了打印件难以直接作为最终功能部件使用。
Objects typically burn up in the earth's atmosphere before they reach the ground.
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