Function of sheet metal fabrication hole
The sheet metal fabrication hole is to avoid drawing during sheet metal bending.
When the sheet metal bending line crosses at one point, or the sheet metal bending line is close to the sheet metal edge and less than twice the plate thickness, it is necessary to increase the sheet metal bending fabrication hole to avoid bending and drawing.
The bending fabrication hole is generally used on the sheet metal parts with edge wrapping and bending, which is not edge wrapping and bending, so the starting fabrication hole can be avoided.
Disadvantages of not opening fabrication holes:
In that case, the material thickness of edges and corners will be less, filler is required for welding, and it is easy to cause welding deformation.
Advantages of opening fabrication hole:
In the case of edge wrapping, the bending fabrication hole can make the edge wrapped bend smoothly in place without bending and drawing.
Hole opening skills of sheet metal bending process
How to determine the size of fabrication hole?
The size of the sheet metal fabrication hole depends on the position of the fabrication hole. If the fabrication hole is on the intersection of two lines, the fabrication hole is twice the plate thickness.
The minimum thickness shall not be less than 1.5 times of the sheet metal thickness.
When bending thick sheet metal plate, the fabrication hole shall be appropriately enlarged in consideration of bending fillet.
Disadvantages of this fabrication hole:
After bending, especially for thick plate, the material loss of bending angle is very serious, unsightly and difficult to weld.
At this time, it is necessary to improve the manufacturing method of fabrication hole.
Optimization method of fabrication hole
The sheet metal fabrication hole can be determined according to the bending edge wrapping, considering the avoidance of plate thickness and bending fillet.
Look at the example in the figure below.
The above figure shows that the thickness of sheet metal material is 3mm, the bending height of four sides is 15mm, and a square sheet metal box.
Fabrication hole improvement scheme
Improvement of blanking method:
There are two methods for sheet metal blanking, punch blanking and laser cutting blanking.
Punch blanking and bending fabrication holes are generally round holes, and square holes or long holes are limited by molds, which is difficult to realize.
The figure above shows 3mm sheet metal, so laser cutting is used for blanking.
Fabrication hole shape improvement:
If the bending fabrication hole adopts long strip shape, the problem of beauty after bending can be avoided.
How to determine the size of long strip fabrication hole:
Generally, I set the width to 1mm, which will not affect the beauty or the release of sheet metal bending deformation.
Depth dimension calculation method:
10 mm is equal to the bending height minus 3 mm bending factor 5;
4 mm is equal to the thickness of sheet metal material plus 1.
Improvement effect of fabrication hole
In this way, the sheet metal part after bending has only a 1mm narrow gap. Look at the three-dimensional rendering:
After the fabrication hole made in this way is bent, the bending angle is well handled. Basically, it can be welded without filling solder.
Why should bending and drawing be avoided?
Harm of bending and pulling:
- It affects the bending size.
During the drawing process, it requires a lot of force to forcibly tear off the thickness of the sheet metal. The uncertain direction of the force will cause the workpiece to move, resulting in dimensional displacement.
- The bending die is easy to be damaged.
As mentioned earlier, there will be a great force at the sharp corner, which will exceed the bearing capacity of the die, resulting in angle collapse and damage.
Application standard of bending positioning fabrication hole
Size and form of fabrication hole:
- Thin plate bending positioning fabrication hole, opening size is 1mmx0.2mm, root R 0.1mm, applicable to plate thickness ≤ 3mm.
- Thick plate bending positioning fabrication hole, opening size is 1mmx0.4mm, root R 0.2mm, suitable for plate thickness of 3mm-6mm.
Scope of use:
- Angle type:
The bending angle is not 90 degrees, and positioning holes are opened at all bending positions, including overlapping bending.
- Docking type:
For appearance parts or butt joint parts with high accuracy requirements, positioning holes shall be opened at the bending position.
- Large size type:
If the bending size is greater than 200mm, all positioning holes shall be opened at the bending position.
- Continuous bending multiple complex types:
For continuous bending of complex parts, add positioning holes from the third bending edge.
- Bend order type:
For parts that cannot be processed according to the normal bending sequence, positioning holes shall be opened at the bending position.
- Repeat bend type:
Due to the limitation of bending equipment, positioning holes shall be opened at all bending positions for parts that need to be bent repeatedly.
- Do not lean against the stop ruler:
Positioning holes shall be opened at all bending positions for parts that cannot be butted against the stop ruler type.
- Guide rail type:
Positioning holes shall be opened at the bending position of parts of guide rail type.
- Circular positioning hole:
Positioning holes are opened at the arc starting points at both ends of the arc.
- Pull plate type:
Positioning holes shall be opened at the bending position of pull plate parts.
- Overlap type:
Positioning holes shall be opened at the overlapping position of overlapping parts; The positioning hole shall be opened at the dimension position of continuous bending depending on the overlapping edge.