Summary of common problems and solutions of sheet metal bending
1. Folding machine processing content
1. L fold
According to the angle, it is divided into 90˚ fold and non-90˚ fold.
According to the processing, it is divided into general processing (L>V/2) and special processing (L<V/2).
>The mold is selected according to the material, the thickness of the plate, and the forming angle.
>Principle of Reliance
①Based on the principle of two post-fixed positioning, and positioning according to the shape of the workpiece.
②Pay attention to the deflection when a back rule is positioned, and it is required to be on the same center line with the bending dimension of the workpiece.
③ In the case of small bends, reverse positioning is better.
④ It is better to set the rule backward and lower in the middle. (When leaning back, the rules are not easy to tilt)
⑤ It is better to stay close to the back rule.
⑥ The long side is better.
⑦ Use jigs to assist the positioning (irregular positioning of the hypotenuse).
>Precautions
① Pay attention to the positioning method during processing and the movement mode of the post-regulation in various positioning processing methods.
② The mold is bent when it is being installed, and it must be pulled back to prevent the workpiece from deforming when it is bent.
③ When the large workpiece is internally bent, due to the larger shape of the workpiece and the smaller bending area, it is difficult for the tool and the bending area to overlap, resulting in difficult positioning of the workpiece or damage to the bent workpiece. In order to avoid the above situation, you can add a positioning point in the longitudinal direction of the processing, so that the processing is positioned in two directions, which makes the processing positioning convenient, and improves the processing safety, avoids the damage of the workpiece, and improves the production efficiency.
2. N fold
N-folds need different processing methods according to different shapes. When bending, the inner size of the material should be greater than 4MM, and the size of the X size is limited by the shape of the mold. If the inner size of the material is less than 4MM, use a special method for processing.
>Choose the mold according to the material thickness, size, material and bending angle.
>Principle of Reliance
① Ensure that the workpiece does not interfere with the mold
② Ensure that the position angle is slightly less than 90 degrees.
③ It is best to use two post-determining rules, except for special circumstances.
>Precautions
① After bending L-folding, the expected angle should be at 90 degrees or slightly less than 90 degrees to facilitate processing and positioning.
② During the second fold processing, the positioning position is required to be centered on the processing surface.
3. Z fold
It is also called the step difference, that is, one positive and the other reverse bending. According to the angle, the difference between the hypotenuse and the straight edge is divided.
The minimum size of bending processing is limited by the processing mold, and the maximum processing size is determined by the shape of the processing machine. Under normal circumstances, when the inner dimension of the Z-folded material is less than 3.5T, the segmental differential mode processing is used. When it is greater than 3.5T, the normal processing method is adopted.
>Principle of Reliance
① Convenient positioning and good stability.
② The general position is the same as the L fold.
③ The secondary positioning requires that the processed workpiece and the lower die are flush.
>Precautions
① The processing angle of the L-fold must be in place, generally 89.5—90 degrees.
② Pay attention to the deformation of the workpiece when pulling back after the rule.
③ The order of processing must be correct.
④ For special processing, the following methods can be used for processing:
——- Center line separation method (eccentric processing)
——-Small V processing (need to increase the bending coefficient)
——-Easy mold forming
——-Reshaping the lower die
4. Reverse fold and flatten
Reverse fold flattening is also called dead edge.
The processing steps of the dead edge:
① First bend and insert to about 35 degrees.
② Use a flattening die to flatten until it is flat and tight.
>Mode selection
According to 5-6 times the material thickness, select the V-groove width of the lower mold with a depth of 30 degrees, and select the upper mold according to the specific conditions of the machining dead edge.
>Precautions
Pay attention to the parallelism of the two sides of the dead side. When the processing size of the dead side is longer, the flattened side can be folded first and then flattened. For shorter dead edges, padding can be used for processing.
5. Press hardware
Use a folding machine to press and mate the hardware, generally using a cavity, a fixture and other auxiliary mold processing.
Under normal circumstances there are: compression nuts, compression studs, compression screws and other hardware.
>Precautions
① When the shape of the workpiece needs to be avoided for processing, the position should be avoided.
② After processing, check the torque, whether the thrust reaches the standard, and whether the hardware and the workpiece are flush and tight.
③ After bending, when pressing next to the machine tool, pay attention to the processing position and the parallelism of the mold.
④ If it is a bulge, please pay attention that there should be no cracks on the bulge, and the bulge must not be higher than the surface of the workpiece.
6. Simple mold forming
The general processing content of easy mold forming includes: small section difference, hook, draw bridge, draw bag, press shrapnel and some irregular shapes.
The design principle of easy mold refers to “Laser cutting easy mold design principle”
Easy molds are generally positioned or self-positioned after use.
The most important thing for the processing of the above content with easy mold processing is that its function and assembly requirements are not affected, and the appearance is normal.
2. Common problems in folding machine processing and solutions
1. The phenomenon of slipping during processing
>Cause Analysis:
① Generally, the V groove width of (4-6)T is selected when selecting the bending mold. When the bending size is less than half of the selected V-groove width, slipping will occur.
② The selected V groove is too large
③ Process treatment
>Solution;
① Centerline deviation method (eccentric processing). If the inner dimension of the bent material is smaller than (4-6)T/2, make up as much as possible
② Lining material processing.
③ Use a small V groove to bend and a large V groove to pressurize.
④ Choose a smaller V groove.
2. The internal bending width is narrower than the standard mold width
>Cause Analysis:
Since the minimum standard width of the lower mold of the folding bed is 10MM, the bending part is less than 10MM. If it is a 90-degree bend, its length shall not be less than √2(L+V/2)+T. For this kind of bending, the mold must be fixed on the mold base (except for the freedom of the upward direction is not restricted) to avoid the displacement of the mold and cause the workpiece to be scrapped or cause a safety accident.
>Solution:
① increase the size (to be agreed with the customer), that is, increase the width of the inner fold.
② easy mold processing
③ grinding tools (this will lead to an increase in processing costs)
3. The hole is too close to the bending line, the bending will cause the hole to pull the material and turn the material
>Cause Analysis:
Assuming that the distance between the hole and the bending line is L, when L<(4–6)T/2, the hole will pull the material. The main reason is that during the bending process, the material is deformed due to the tensile force, which leads to the phenomenon of material pulling and turning.
For different plate thicknesses, according to the groove width of the existing standard mold, the minimum L value is as follows:
>Solution:
① increase the size, and trim the folded edge after forming.
② expand the hole to the bending line (must have no effect on the appearance and function, and the customer agrees).
③ secant processing or crimping processing
④ mold eccentric processing
⑤ modify the hole size
4. The distance between the drawing edge and the bending line is small, and the drawing part is deformed after bending
>Cause Analysis:
When L<(4–6)T/2, because the drawing is in contact with the lower die, the drawing is deformed by force during the bending process.
>Solution:
① secant processing or crimping processing.
② modify the drawing size.
③ using special mold processing
④ mold eccentric processing
5. The long dead edge is warped after being flattened
>Cause Analysis:
Due to the long dead edge, it is not tightly attached when flattened, which causes the end to be warped after flattening. ﹔This situation has a lot to do with the flattening position, so pay attention to the flattening position when flattening
>Solution:
① Fold the warped corners (see diagram) before folding the dead edges, and then flatten them.
② Flatten in multiple steps:
——Press the end first to make the dead edge bend downward.
—— Flatten the roots.
Note: The flattening effect is related to the operating skills of the operator, so please pay attention to the actual situation when flattening.
6. Large height draw bridge is easy to break
>Cause Analysis:
① Because the height of the draw bridge is too high, the material is stretched seriously and it breaks.
② The corners of the easy mold have not been ground or the grinding is not enough.
③ The toughness of the material is too poor or the bridge body is too narrow.
>Solution:
① lengthen the craft hole on the fractured side.
② Increase the width of the pumping bridge.
③ grinding the easy mold R angle to increase the arc transition.
④ add lubricating oil to the draw bridge. (Therefore, this method will make the surface of the workpiece dirty, so it cannot be used for AL parts, etc.)
7. During easy mold processing, the processing size will move
>Cause Analysis:
Due to the forward squeezing force of the workpiece during the machining process, the workpiece is displaced forward, resulting in an increase in the front small tilt angle size L.
>Solution:
① wear off the shaded part in the picture. Generally make up as much as the difference is.
② grind off all the self-positioning parts of the easy mold, and set the position after changing to use.
8. The total size of the blanking (referring to unfolding) is too small or too large, which does not match the round surface.
>Cause Analysis:
① the project is expanded incorrectly.
② the blanking size is wrong.
>Solution:
According to the total amount of deviation in the deviation direction and the number of bending knives, the deviation allocated for each fold is calculated.
If the calculated distribution tolerance is within the tolerance range, the workpiece is acceptable.
—–If the size is too large, it can be processed with a small V groove.
—–If the size is too small, it can be processed with a large V groove.
9. After the hole is closed, it will burst, or the joint will not be tight, and it will be deformed.
>Cause Analysis:
① The bursting is due to the R angle of the punching punch is too small or the burr of the flanging is too large.
② The lack of tightness is due to the inadequate expansion of the pumping hole.
③ The deformation is caused by hole dislocation or wrong joint method.
>Solution:
① Use a punch with a big R angle instead.
Note: The burrs around the hole when the hole is flanged.
② Increase the pressure, the salad hole will increase and deepen, use a big R-angle punch instead.
③ Change the method of jointing and the reason of hole dislocation.
10. The stud is skewed or deformed after pressing
>Cause Analysis:
① There is no flat workpiece when processing the product.
② The pressure on the lower surface of the workpiece is uneven or the pressure is too large.
>Solution:
① When pressing the stud, the workpiece must be flattened.
② Make the support frame.
③ readjust the pressure.
④ Increase the force range of the lower surface and reduce the force range of the upper surface.
11. The two sides are not parallel after the level difference
>Cause Analysis:
① the mold is not calibrated.
② The upper and lower die gaskets are not adjusted properly.
③ the upper and lower mold faces have different choices.
>Solution:
① Re-check the mold.
② Increase or decrease the gasket. (For specific adjustment methods, see “Segment Processing Technology”)
③ The mold is eccentric.
④ Change the surface to take, so that the upper and lower mold surfaces are the same.
12. The crease on the surface of the product is too deep
>Cause Analysis:
① the lower mold V groove is small
② the R angle of the lower mold V groove is small
③ the material is too soft.
>Solution:
① using large V groove processing
② use large R angle mold processing
③ bedding material bending (steel pad or Ugliad)
13. The near bend is deformed after bending
>Cause Analysis:
The machine runs fast during the bending process, and the upward bending speed of the workpiece during the deformation process is greater than the movement speed of the operator’s hand holding the workpiece.
>Solution:
① reduce the operating speed of the machine
② Increase the speed of the operator’s hand support.
14. AL parts are prone to cracks when bent
>Cause Analysis:
Because the AL material has a special crystal structure, it is easy to break when the parallel lines are bent.
>Solution:
① When blanking, consider cutting the AL material in the direction perpendicular to the bending direction (even if the bending direction of the material is perpendicular to the line).
② increase the upper mold R angle