原因是编组的对象分组错误导致的。
以CAD2010操作为例：
1、首先打开需要出来的CAD文件，按快捷键g跳出对象编组，然后在“组ID-组名”中填写名称。
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2、编辑名称后，单击中间的“创建组-新建”以创建新组。创建新组时，直接选择需要合并在一起的所有线段，如图所示。
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3、最后，新分组完成后，返回页面单击“确定”完成对象分组，这样操作就可以解决问题了，再解除编组就可以了。
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