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Common automotive stamping par...

DATE:2019-08-31 17:13:14 FROM:

I. Analysis of common defects and causes of punching parts
 
Blanking is a stamping process in which a mold is used to separate sheets.
 
Common defects in punching parts are: burrs, warpage of the surface of the part, and poor size.
 
1, burr
 
   In the blanking of sheets, different degrees of burrs are generated, which is generally difficult to avoid, but the burr can be reduced by improving the workability of the parts and improving the stamping conditions.
 
 The main reasons for the occurrence of burrs are as follows:
 
1.1 Clearance
 
A burr can be generated if the punching gap is too large, too small or uneven. The following factors affect the excessively large, too small or uneven gap:
 
a Automobile mold manufacturing error - the processing of die parts does not conform to the drawings, the parallelism of the bottom plate is not good, etc.;
 
b mold assembly error - large gap in the guiding part, assembly of the convex and concave molds, etc.;
 
c The accuracy of the press is poor—if the gap of the press guide is too large, the parallelism between the bottom of the slider and the surface of the table is not good, or the perpendicularity of the stroke of the slider and the surface of the press is not good, the rigidity of the table is poor, and the punching is poor. Deflection occurs when both can cause a change in the gap;
 
d Installation error—if the upper and lower surfaces of the die are not wiped clean during installation or the fastening method of the upper die is improper, the upper and lower die of the die are installed with different hearts (especially without a guide die) and the working part is inclined;
 
e The die structure is unreasonable - the die and the working part are not rigid enough, and the punching force is not balanced;
 
d The steel plate has a large buckling curvature - the steel plate is not flat.
 
1.2 Knife blunt
 
The edges are blunt or bruised and can produce burrs. Factors affecting the blunt edge are:
 
a The material of the convex and concave molds of the automobile mold and its surface treatment state are poor, and the wear resistance is poor;
 
b The die structure is poor, the rigidity is poor, causing bruises;
 
c It is not lubricated in time and is worn quickly;
 
d Did not sharpen the cutting edge in time.
 
1.3 Improper punching status
 
If the blank (including the intermediate part) is not in good contact with the punch or the die, when the trimming is performed at a relatively high level of trimming, the part height will be lower than the relative height of the positioning, and the shape of the part during the blanking process. A burr is produced by not conforming to the shape of the cutting edge.
 
1.4 improper mold structure
 
1.5 Materials do not conform to the process regulations
 
If the thickness of the material is seriously out of tolerance or the wrong material is used (such as the wrong steel grade), the relative gap is unreasonable and the workpiece is burred.
 
1.6 The craftsmanship of the parts is poor - the shape is complicated. The sharp corners that are convex or concave are easy to produce burrs due to excessive wear.
 
Automotive stampings summary:
 
    The occurrence of burrs not only makes the deformation process after punching easy to crack due to stress concentration, but also makes it difficult to layer the subsequent process blank. Large burrs are easy to scratch the handle; when welding, the two steel plates are not well joined, easy to weld, and the welding is not strong; when riveting, it is easy to produce riveting gap or cause riveting.
 
    Therefore, burrs outside the allowable range are extremely harmful. The burrs that have been generated can be eliminated by methods such as boring, rolling, electrolysis, and chemical treatment.