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Stamping services - stamping FAQ

December 1, 2023

Rust, mixed parts, burrs.
Wrinkling, folding.
Deformation (protrusions, depressions, hole deformation, etc), roughening (drawing marks).
Indentation (scratches, bumps, embossing, ribbing).
Missing sequence (few holes, holes not punched through, not shaped, not polished, etc).
Thinning (necking, thinning), dark wounds.
Cracking (cracking, cracking).
Missing edge, more/less material.
Hole deviation, gap deviation, pressure package deviation.
The engraving mark is not clear.

 

Glitch:
In sheet metal blanking, burrs are produced to varying degrees, which is generally difficult to avoid. However, burrs can be reduced by improving the workmanship of the parts and improving the stamping conditions.

 

The generation of burrs not only makes the deformation process after blanking easy to crack due to stress concentration, but also brings difficulties to the delamination of the blank in subsequent processes. Large burrs are easy to scratch the handle; when welding, the two steel plates are not well joined, the welding is easy to penetrate, and the welding is not strong; when riveting, it is easy to produce riveting gaps or cause riveting cracks.

 

Therefore, the occurrence of burrs outside the allowed range is extremely harmful. The existing burrs can be eliminated by filing, rolling, electrolysis, chemical treatment and other methods.

 

The main reasons for burrs are as follows: gap between convex and concave molds, blunt knife edge, improper blanking state, improper mold structure, materials that do not comply with process regulations, and poor workmanship of parts.

 

1. Gap
Burrs can occur if the punching gap is too large, too small or uneven. Factors that affect whether the gap is too large, too small or uneven include the following factors:

 

(1) Mold manufacturing errors-the processing of die parts does not conform to the drawings, the parallelism of the bottom plate is not good, etc.

(2) Mold assembly errors - large gaps in the guide parts, non-concentric assembly of the male and female molds, etc.

(3) The accuracy of the press is poor, such as the gap between the press guide rails is too large, the parallelism between the bottom surface of the slider and the surface of the workbench is not good, or the perpendicularity between the slider stroke and the press table is not good, and the rigidity of the workbench is poor. Deflection during cutting can cause changes in the gap.

(4) Installation error - For example, the surface of the upper and lower base plates of the punch die is not wiped clean during installation or the fastening method of the upper mold of a large punch die is improper. The upper and lower molds of the punch mold are not installed concentrically (especially the mold without guide pillars), causing the working part to tilt.

(5) The die structure is unreasonable - the die and working parts are not rigid enough, the punching force is unbalanced, etc.

(6) The steel plate has a large curvature - the steel plate is uneven.

 

2. The blade is dull

Burrs can occur if the cutting edge is worn, dulled or chewed. Factors affecting edge dulling include:

 

(1) The material and surface treatment of the convex and concave molds are poor and have poor wear resistance.

(2) The die structure is poor and the rigidity is poor, causing gnawing injuries.

(3) If it is not lubricated in time during operation, it will wear out quickly.

(4) The cutting edge was not sharpened in time.

 

3. Improper punching state

If the blank (including intermediate parts) is not in good contact with the punch or die, when trimming and punching with improper positioning height, the shape of the part may change during the punching process because the height of the part is lower than the positioning height. It does not conform to the shape of the cutting edge and produces burrs.

 

4. Improper mold structure

 

5. Materials don't comply with process requirements

The material thickness is seriously out of tolerance or the wrong material (such as the wrong steel grade) is used, causing the relative gap to be unreasonable and causing burrs on the product.

 

6. The workmanship of the parts is poor

Complex shapes with protruding or concave sharp corners are prone to burrs due to rapid wear.

 

The generation of burrs not only makes the deformation process after blanking easy to crack due to stress concentration, but also brings difficulties to the delamination of the blank in subsequent processes. Large burrs are easy to scratch the handle. When welding, the two steel plates are not well joined, the welding is easy to penetrate, and the welding is not strong. When riveting, it is easy to produce riveting gaps or cause riveting cracks.


Therefore, the occurrence of burrs outside the allowed range is extremely harmful. The existing burrs can be eliminated by filing, rolling, electrolysis, chemical treatment and other methods.