Cause Analysis and Improvement Measures of Perforated Metal Wavy Patterns

Brief description of the processing of numerical control small hole punch

60t numerical control small punch is a special equipment which is exclusively used in processing mesh roller holes in textile drying equipment. Round mesh drum which is processed evenly distributes more than 3000 round holes whose diameters are 3 mm, with spacing of 3.5mm × 4mm. It adopts 0Cr18Ni9 stainless steel plate whose thickness is 1.5–2.5 mm. Two rows of punches for each row of 18 holes are punching into small mesh holes, then rolled and welded. By calculation, during the punching process, the punching shear force required for each punching is about 30t and the pullout force is about 10t. In the past 30 years of the traditional product processing, it has been playing an active role. But in recent years, because of constant breaking formed punches, the rate of spoiled increases. At the same time, the punching part of the mesh plate has elongated deformation, which produces a sinusoidal raised grain around 150 mm and can not be flattened after processing. It seriously affects the quality of products and becomes a major difficult problem in production. On the basis of arranging the overhaul of the machine tools, the geometric precision and the die precision of the machine tool have been restored. However, the workpiece still has raised grain and its specific fault phenomenon is manifested as:

  • The stripping in the return of the punch is not smooth and the phenomenon in which the punch has not left the workpiece yet when the pressure plate starts to return is serious.
  • The deformation of the pressure plate is serious, and the maximum deformation is 3.5 mm.
  • The deformation of platen supporting foot is serious, and the error reaches 5 mm.
This is the mesh punching process of thin steel sheet.
RGT-01: The action of the press plate and the punch action are synchronous and well-matched.

Analysis of failure cause

Through mechanism analysis, fault analysis and process analysis of pressure plate deformation, after eliminating the influence of machine tool geometric precision and die precision on punching process, the cause of the fault is attributed to the serious deformation of the stripper plate and the loss of accuracy resulting therefrom. Other factors include:

  • The horizontal difference between the left and right pressure plate forms a bevel press material, making it easy to create a distance with the workpiece.
  • The left and right press plate movements are not coordinated, there are fast and slow.
  • The rigidity of the press plate is poor and it is easy to cause deformation. For 5 mm thick pressure pallet location, 120 mm is too wide and it can be reduced to 35 mm.

Improvement measures

  • Repair the pressure foot, eliminate the deformation amount of 5 mm and control the perpendicularity error between its underside and the axis of compression bar within 0.2 mm.
  • Re-make pressure plate and increase the rigidity of the press plate itself. Change the width of the 5 mm thick pressure pallet from 120 mm to 35 mm and increase the thickness of the foot plate from the original 12 mm to 25 mm.
  • During the installation of the press plate mechanism, proper adjustment shall be made to ensure the synchronism between the action of the press plate and the punch action.
  • Adjust the levelness of the dead center under the left and right press plate feet and control the error within 0.2 mm.
  • Adjust the spring strength of the pressure foot and keep the movement speed of the two press plate the same.
  • Change the cam remote angle of repose, change the original 85 acting angle of pressing material to 100, change the drawing distance of the pressure plate from 6.6 mm to 9 mm, increase the pullout space and stroke and reduce the probability of material taking.
The original 85 acting angle of pressing material is changed to 100.
RGT-02: The change diagram of cam remote angle of repose.

Improved effect

  • The action of the press plate and the punch action are synchronous. The action of the press plate and the punch action are synchronous and well-matched. It meets the requirements of processing technology.
  • The material taking phenomenon in disappears.
  • The raised grains caused by punching on the steel plate disappear, and the punching quality of the net plate reaches the requirement of the processing technology.

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