Blank mainly refers to the raw materials that have not been milled, such as forging and casting, and also refers to the part before the finished product is completed. Due to the under-pressure and allowable wrong modulus during die forging, the allowance will change, and during casting, the allowance will also change due to sand mold error, shrinkage and poor fluidity of molten metal. Therefore, we should also combine the characteristics of CNC milling to analyze the process of blank use. What problems should be paid attention to in the process of blank milling?

I. Blank allowance after milling

In general milling, the final allowance of the workpiece will be determined by secondary positioning, but it is difficult for automatic milling machine to take care of the problem of insufficient allowance. Therefore, whether it is sheet metal, forgings, castings or profiles, as long as it is prepared for CNC milling, sufficient allowance must be reserved. Experience shows that the most difficult thing to ensure in NC milling is the size between workpieces, which should be paid special attention to. In this case, if NC milling has been determined or prepared, the design of the blank should be changed in advance or fully considered in the design, that is, an appropriate allowance should be added at the non-technical surface indicated in the part drawing.

Second, the reliability of the blank in the clamping process

This paper mainly considers the reliability and convenience of the blank in installation and positioning, so as to give full play to the multi-process of NC milling in one installation. The main consideration is whether to increase the clamping allowance or position and clamp the process boss, where to make the process hole or specially prepare the process lug to make the process hole. Some workpieces that seem to be difficult to locate and install or lack locating reference holes and locating surfaces can be fixed with lifting lugs, and can be removed by repairing after completing the locating and installing tasks.

Third, the size and uniformity of the blank margin

The main consideration is whether to divide layers and cut several layers, and also analyze the degree of deformation, and consider whether to take preventive and remedial measures. For example, the hot-rolled plate is easy to deform after quenching and aging, and the quenched slab after pre-stretching treatment is usually used.

Fourthly, the machining speed and accuracy of the blank.

The blank process usually adopts high-speed rough machining, and after reaching the requirements of the specified shape, it is finished and made into finished products. However, whether it is Seiko or Seiko, if there is a problem in the process, it will have a direct impact on the final finished workpiece. Common problems include workpiece fracture, chip accumulation and tool wear, so it is necessary to fully verify the process, and the use of blanks, tools and cutting oil that meet the process can effectively avoid the problems.

The above are the matters needing attention when milling the workpiece blank. Reasonable arrangement of blank technology can effectively improve the quality of finished products.