The press brake is used to bend and form various metal sheets such as iron, stainless steel, copper and aluminum. It can also be used as a press to complete molding, riveting, leveling and other processes.
The workpieces are cut and fed by LASER or NCT, and other non-bendable shape elements are made by machining, and then bending and forming are done using the folding machine's knife or the die of the folding machine.
In addition, drawing convex and concave shapes, pressing corner pads, and line pressing are also commonly done on press brakes.
With the use of the press brake machine's knife and die, the press brake machine can complete the bending of many types of products, but its processing speed is slower than that of a punch press.
It is suitable for bending and forming in sample production and certain mass production.
1. Working principle of folding machine
The upper and lower dies are fixed on the upper and lower working tables of the press brake respectively. The relative movement of the work tables is driven by hydraulic transmission, combined with the shape of the upper and lower dies, to achieve sheet metal bending and forming.
2. Folding machine structure
The folding machine consists of four parts: 1. Mechanical part 2. Electrical part 3. Hydraulic part 4. NC electrical control part.
3. Two types of movement for the folding machine
(1) Upper movement: The lower worktable does not move and pressure is applied by the upper downward slider.
(2) Lower movement: The upper machine is fixed and pressure is applied by the lower upward working table.
4. Push-up Sequence Basics
Folding from the inside out.
Folding from small to large.
Fold the special shapes first and then the general shapes.
The previous process does not affect or interfere with the subsequent process.
5. Uses of folding machine
Convex and concave shape drawing, corner pressing, self-tapping wire forming, line pressing, printing, riveting, electrostatic conductive rail riveting, grounding symbol pressing, punching, riveting, flattening and triangle reinforcement.
6. Basic knowledge of upper and lower dies in press brake
1. Upper Matrix:
Also known as a folding knife.
The classification of folding machine upper dies and existing tool types are shown in the figure below:
The upper mold of the press brake is divided into integral and segmented type.
The integral upper mold has two sizes: 835mm and 415mm.
The segmented upper mold is divided into type A and type B.
The length of type A segments includes 10mm, 15mm, 20mm, 40mm, 50mm, 100mm (right horn), 100mm (left horn), 200mm and 300mm.
The length of type B segments includes 10mm, 15mm, 20mm, 40mm, 50mm, 100mm (right horn), 100mm (left horn), 165mm and 300mm.
The following figure shows the 107# folding mold with type A segments.
2. Lower the matrix
Also known as “V groove”.
The lower die of the press brake is divided into two types: integral and segmented.
The integral bottom die is divided into L and S types (L: 835mm, S: 415mm), while the segmented bottom die is divided into sizes 10, 15, 20, 40, 50, 100, 200 and 400.
The bottom die is classified into single V and double V based on the V groove.
V-groove is generally referred to as “groove width value + V”. For example, when the width of the V-groove is 5mm, the V-groove is called “5V”.
The width of the V-groove of the lower die used in the press brake is generally 5 times the material thickness (5T).
If 5T-1V is used, the bending coefficient should be increased accordingly. If 5T+1V is used, the bending coefficient should be reduced accordingly.
7. Folding machine back gauge
1) Normal back gauge:
Surface alignment is used for workpiece end face alignment and left-right positioning.
Point alignment is used for two-point or multi-point alignment of the workpiece and can also be used for single-point alignment (with auxiliary features).
2) Double Point Long Back Gauge:
Used for alignment bending of small width parts. Even if the normal rear gauges are joined together, there is still a 70mm gap between the front and rear gauges.
This back gauge can reduce clearance to 10mm: avoiding burr alignment.
It has the same function as a single-point back gauge, but its scope of application is mainly for small-width alignment parts: the base has both functions of the back gauge.
3) Dual Point Short Back Gauge:
The basic function is the same as the double point long back gauge, but it is suitable for a different range of workpieces.
It can be used for the alignment of shorter parts and is suitable for cutting parts of NCT material to avoid burr points and ensure bending accuracy.
4) Extended Back Gauge:
Using the extended feature for indirect alignment of small or negative sized parts.
This back gauge is long and can extend out of the machine by 59.5 to achieve an alignment size of -59.5.
It can be used for some small bends with high alignment difficulty and for left-right positioning of workpieces.
Because it is longer than the normal back gauge, it can be used as left-right positioning of workpieces when the normal back gauge is used for alignment.
5) Rear shim gauge:
Used for small size bending alignment. Generally, alignment of small size bends requires a shim to prevent the upper die from damaging the back gauge, but when adding a shim, the shim tends to move and affect safe operation.
The protruding part of this back gauge serves as a shim.
Use: Install with the protruding part facing down; support workpiece alignment for large size or reverse alignment.
When bending large-sized parts, two people generally need to enter the machine and grasp the alignment of the part, which is extremely unsafe and the size is unstable.
This back gauge can support workpiece alignment and can be operated by one person.
Its base is equivalent to the normal back gauge, so it has the function of a normal back gauge.
6) Single Point Back Gauge:
Used for long side alignment of products with multiple burr points, generally for cutting NCT material or edge cutting products with burr points on the edges.
This back gauge can avoid or pass burr points to improve bending accuracy. It is also used for left-right positioning of workpieces.
Since its base plane is the same as the normal back gauge, this back gauge can be mixed with the normal back gauge on both sides.
Its protruding part can be used for left-right positioning of workpieces, accurately avoiding between the workpiece and the mold. The base serves the function of a normal back gauge.
7) Material Inner Point Alignment Back Gauge:
As the protruding point of this back gauge extends into another plane from the back gauge, it can be used for aligning small square holes within the workpiece.
8) Material Inner Surface Alignment Back Gauge:
Because it has a protruding structure at the top, the protruding plane is level with the base plane and the width is only 1/3 of the base.
It can be used for alignment of narrow gaps with a width smaller than the normal back gauge width.
When the protruding part is fixed downwards, it can be used for direct alignment of the inner fold of the material.
Its best adapting range is inner bend width greater than 20mm but less than 150mm, and it can also be used for aligning small surfaces with irregular outer edges.
Note: The general size of its back gauge is 60*9mm.
During bending, positioning is firmly against the back gauge (parallel to the back gauge).
If the positioning surface of the workpiece is inclined, positioning devices should be designed based on the size of the workpiece (the positioning stability).
Generally, when L≦10mm, it is necessary to consider using positioning fixtures (often designed as easy molds) to assist with positioning, unless it is a particularly small part.
Of course, the positioning stability of a part with 10mm positioning is also poor. Look the following picture:
8. Processing Techniques and Precautions for Folding Beds
1) Bending processing range:
The distance from the fold line to the edge must be greater than half of the V-groove.
For example, when using a 4V lower die for a 1.0mm material, the minimum distance is 2mm.
The table below shows the minimum bending edges for different material thicknesses.
| Material thickness | 90 degree bending angle | 30 degree bending angle | ||
| minimum bending edge | V-groove specifications | minimum bending edge | V-groove specifications | |
| 0.1~0.4 | 1.0 | 2V | ||
| 0.4~0.6 | 1.5 | 3V | 2.2 | 3V |
| 0.7~0.9 | 2.0 | 4V | 2.5 | 4V |
| 0.9~1.0 | 2.5 | 5V | 3.4 | 6V |
| 1.1~1.2 | 3.0 | 6V | ||
| 1.3~1.4 | 3.5 | 7V | 5.0 | 8V |
| 1.5~1.6 | 4.0 | 8V | ||
| 1.7~2.0 | 5.0 | 10V | ||
| 2.1~2.5 | 6.0 | 12V | ||
| 2.6~3.2 | 8.0 | 16V | ||
| 3.3~5.0 | 12.5 | 25V | ||
| 5.1~6.4 | 16.0 | 32V | ||
Note: If the inner dimension of the folded material is smaller than the minimum folded edge size in the table above, the folding base cannot be processed normally.
In this case, the folded edge can be lengthened to the minimum folded edge size, and the edge can be trimmed after folding or mold processing can be considered.
2) When the folding base is folded, proper processing must be carried out due to the small size from the hole edge to the fold line:
(1) LASER processing is carried out on the corresponding cutting line of the bending line.
(2) NCT processing is carried out on the corresponding pressing line of the bending line (this method takes priority).
(3) Enlarge the hole to the bend line (this method must be confirmed with the customer).
Note: When the distance between the hole near the bend line and the bend line is less than the minimum distance listed in the table, deformation will occur after bending.
| sheet metal thickness | 0.6~0.8 | 0.9~1.0 | 1.1~1.2 | 1.3~1.4 | 1.5 | 1.6~2.0 | 2.2~2.4 |
| minimum distance | 2.0 | 2.5 | 3.0 | 3.5 | 4.0 | 5.0 | 5.5 |
3) Reverse folding and flattening:
When the convex bulge is in the opposite direction to the reverse direction of bending and flattening, and the distance from the bending line is L ≤ 2.5t, the flattening will deform the convex bulge.
Processing method: Before flattening, a fixture is placed under the workpiece, and the thickness of the fixture is slightly greater than or equal to the height of the convex bulge. Then use a flattening die to flatten.
4）When the hole is very close to the bending line (≦3T+R), it should be processed with a pressing line or cutting line at the bending line to avoid deformation of the hole during bending.
5）Galvanized part:
When bending galvanized parts, pay attention to pressure marks and peeling of the coating (they must be specially indicated in the engineering drawing).
6）Displacement
The interference processing range caused by displacements can be seen in the figure.
The interference machining range with section deviation can be seen in the diagram.
Based on the forming angle, it can be divided into straight edge deviation and oblique edge deviation, and the processing method depends on the height of the deviation.
For straight edge deviation: when the height of the deviation “h” is less than 3.5 times the thickness of the material, a deviation mold or easy molding is used.
When it is greater than 3.5 times the thickness of the material, the normal fold is used with one forward and one backward.
For deviation of oblique edge: when the length of oblique edge “l” is less than 3.5 times the thickness of the material, deviation mold or easy molding is used.
When it is greater than 3.5 times the thickness of the material, the normal fold is used with one forward and one backward.
7) Electrostatic riveting guide rail
The spacing between the electrostatic guide rails riveted on the press brake is 25.15mm, and 15 points can be riveted at one time (each riveted punch can be removed, so that single-spaced riveting can be performed).
When the distance between the edge of the electrostatic guide rail and the bending line L≧1+V/2mm (where V is the width of the V-groove of the bottom mold of the folding machine), the electrostatic guide rail can be riveted before to fold. If it is less than 1+V/2mm, the electrostatic guide rail must be riveted after bending.
For 1.2mm material, it can be bent with 5V slot as shown in the diagram.
Note: The width of the electrostatic guide rail is 7.12mm, model: 700-02776-01.
8) Thin and highly elastic materials
When bend angles are extremely important for thin, highly elastic materials, it is recommended to consider using pressure line treatment at the bend line or adding process holes or reinforcements at the bend line to prevent springback and dimensional errors after bending. fold.
If using easy molding, the amount of springback must be considered when designing the easy mold.
9）Convex Molding Pressure
When pressing convex molds, if high precision is required for the height of the convex part, it is recommended to consider using a counterpressure method to ensure its accuracy.
10）Folding machine pressing triangular reinforcement
Specifications of the mold for triangular reinforcement:
| Knife model number | 117 | 107 | 202 | |||
| Forming width (mm) | 3.0 | 5.0 | 3.0 | 5.0 | 3.0 | 5.0 |
| Tool width (mm) | 10 20 | 10 20 | 10 20 | 10 20 | 10 20 | 10 20 |
| Number of molds | Two each | Two each | Two each | Two each | Four each | Four each |
There are two types of shaping for triangular reinforcement:
1. Simultaneously with the bending tool, that is, the bend and the triangular reinforcement are processed at the same time.
2. Pressing the triangular reinforcement after bending the part.
Note: The number of triangular reinforcements formed depends on the number of molds.
From the table above, it can be seen that currently the maximum number of triangular reinforcements that can be formed for the same specification is four. If the number exceeds this value, it must be resolved through consultation with relevant personnel.
