Stamping parts common bad and countermeasures
About various defects of stamping parts produced by stamping factories, we have analyzed several points in the first two articles. Today, we will take a look at the causes and preventive measures of the last few bad stamping parts.
9. The position of the blank hole changes when bending
1) Reasons
The hole position size is wrong, (bending and tension thinning);
Hole different heart (bending height is not enough, blank sliding, rebound, bending plane fluctuation phenomenon);
When the bending line and the center line of the two holes are not parallel, the bending height is less than the minimum bending height.
Holes close to the bending line are prone to deformation.
2) Countermeasures
Measures of different heart causes:
Make sure the left and right bending height is correct;
Correcting worn dowel pins and dowel plates;
Reduce springback to ensure the parallelism and flatness of the two curved surfaces;
Change the process route, first bending correction and then punching.
It presents an outward-opening game
Ensure the minimum bending height H(H≥R+2t t material thickness R bending radius);
Change the shape of the machined part to drop the part less than the minimum bending height without affecting the use.
The hole near the bending line is easy to produce deformation measures:
In the design of bending parts to ensure that from the bending part to the hole edge distance X greater than a certain value X≥(1.5-2.0)t t bending plate thickness;
An auxiliary hole is designed at the bending part to absorb the bending deformation stress, which can prevent the deformation of the hole near the bending line. Generally, the scheme of bending before punching is adopted.
10. After the parts are bent, the bending part is obviously thinner
1) Countermeasures
The bending radius is too small relative to the plate thickness (r/t> 3 right Angle bending) generally increase the bending radius;
Multi-angle bending makes the bending part thinner and bigger. In order to reduce thinning, single Angle and multi-process bending method is adopted as far as possible.
When the sharp Angle punch is used, the punch enters the die too deeply and the thickness of the bending part is obviously reduced.
11. Flanges of drawing parts wrinkle in the process of drawing
1) Reasons
Flange holding force is too small to resist excessive tangential compressive stress; And cause tangential deformation, thus losing stability after the formation of wrinkles. Thinner material is also easier to form wrinkles.
2) Countermeasures
Increase the holding force of the holder and increase the thickness of the material appropriately.
12. Causes and prevention of wall cracking of deep drawing parts
1) Reasons
The radial tensile stress of the material during deep drawing is too large.
Die fillet radius is too small;
Poor deep drawing lubrication;
The raw material has poor plasticity.
2) Countermeasures
Reduce holding force;
Increase the radius of die fillet;
Proper use of lubricants;
Choose the material with better plain line or increase the annealing process in the workshop.
13. The bottom of the deep drawing piece is torn
1) Reasons
Die fillet radius is too small, so that the material is in the cut state.
2) Countermeasures
(generally occurs in the initial stage of deep drawing) increase the radius of the die fillet and make it smooth. 0.2µm.
14. The edge of the deep drawing parts is uneven and wrinkled
1) Reasons
The blank is inconsistent with the center of the die or the material thickness is uneven, as well as the radius of the die fillet and the gap between the die and the die are uneven (the radius of the die fillet is too large, and it breaks away from the blank holder in the final stage of deep drawing, so that the material blank holder which has not crossed the fillet can not be pressed into the die and then is pulled into the die to form the edge fold.
2) Countermeasures
Reposition the die, correct the radius of die fillet and the gap between the die and the die to make the size even before putting into production (reduce the radius of die fillet or use the curved blank holder device to eliminate the fold).
15. Tapered parts or hemispherical parts wrinkle at the waist during deep drawing
1) Reasons
At the beginning of deep drawing, most of the material is in a suspended state, plus the holding force is too small, the die fillet radius is too large or too much lubricant is used. The radial tensile stress decreases and the material becomes unstable and wrinkled under the action of tangential compressive stress.
2) Countermeasures
Increase the blank holding force or use the calendering bar structure, reduce the radius of the die fillet or make the material slightly thicker.
