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计算机磁盘基片,直径为130毫米的,按一般国际标准,加工表面粗糙度Ra<0.015μm,加工平面度要小于6.32微米。在建南机器厂实际生产制造中,使用美国制造的MVP—ST200超精密磁盘车床,采用真空吸盘装夹,用硬质合金车刀进行粗加工和半精加工。用天然单晶金刚石车刀进行精加工。磁盘基片是圆薄板形零件,刚性很差。且在车削加工时,已加工表面将产生残留应力,其残留应力随切削条件的改变而变化。因此,当一个磁盘基片两面的切削条件不一致时,就会造成磁盘基片两面的残留应力的大小和分布不一致,从而使磁盘基片产生变形。磁盘基片两面的残留应力相差越大,产生的变形就越严重。根据测试,在实际生产中,粗加工和半精加工之后产生的磁盘基片变形,一般达数十微米。另外,磁盘基片的厚度只有1.88毫米,所以其刚性极差,虽用真空吸盘装夹,也会变形,所以磁盘基片在半精加工之后的变形在精加工之后仍将被大部分继承下来。正由于上述两个原因,在实际生产中,磁盘基片的平面度公差要满足要求,必须采取两个措施。即:
Computer disk substrate, a diameter of 130 mm, according to the general international standards, the processing surface roughness Ra <0.015μm, processing flatness less than 6.32 microns. In Jiannan Machine Factory actual manufacturing, the use of the United States made MVP-ST200 ultra-precision disk lathe, the use of vacuum chuck clamping, with carbide turning rough machining and semi-finishing. Finishing with natural single crystal diamond turning tools. Disk substrate is a thin sheet-shaped parts, poor rigidity. And in the turning process, the surface will have a residual stress residual stress, cutting stress changes with the change of conditions. Therefore, when the cutting conditions on both sides of a disk substrate are different, the size and distribution of the residual stress on both surfaces of the disk substrate will not be uniform, and the disk substrate will deform. The greater the difference between the residual stress on both sides of the disk substrate, the more serious the deformation is. According to the test, in actual production, the disk substrates produced after roughing and semi-finishing deform, typically by tens of micrometers. In addition, the thickness of the disk substrate is only 1.88 mm, so its rigidity is extremely poor. Even if it is chucked by a vacuum chuck, it will deform. Therefore, the deformation of the disk substrate after semi-finishing will be mostly inherited after finishing . Precisely because of the above two reasons, in actual production, the flatness tolerance of the disk substrate to meet the requirements, we must take two measures. which is: