220.127.116.11 bending radius
While bending process of sheet metal, there is bending radius, bending radius can’t be too big or too small, should choose bending radius properly. If bending radius is too small, bent part sheet metal will cracked; if bending radius is too big, bending rebound will happen.
18.104.22.168 Bending rebound
Rebound angle Δα=b-a
b-actual angle after rebound of bent sheet metal;
a-angle of die.
22.214.171.124 Interference phenomenon while bending
For twice or above twice bending, there is always interference phenomenon between bent sheet metal and bending tools, as shown in figure 1-6, the black position is interfered part, bending process can’t be done for this case, or sheet metal will deform due to interference.
Figure 1-6 interference phenomenon of bending
For such kind case, we can choose different shape bending tools to avoid interference phenomenon. Check figure 1-7 for various bending tools available.
Figure 1-7 various bending tools
126.96.36.199 Once die edge bending
Method of die edge bending process: check figure 1-8, first use 30° die to form sheet metal to 30°, and then press to flat.
Figure 1-8, die edge bending method
188.8.131.52 180° bending
Method of 180° bending: check figure 1-9, first use 30° die to form sheet metal to 30°, and then press to flat, and take out base pad.
Figure 1-9 180° bending
H is the thickness of plate, such as 0.5mm, 0.8mm, 1.0mm, 1.2mm.1.5mm, and 2.0mm. Normally, thickness of plate can’t be too big.
184.108.40.206 Tripartite folds die edge forming
See figure 1-10, first shape forming, and then die edge forming.
Bending process of sheet metal refers to forming process of changing angle of sheet metal. For instance, bend sheet metal, to V shape, U shape and etc. Regularly, there are two bending method: one is moulds bending for complicated structure forming with small size and large quantity process; the other one is press brake bending for large dimension bending production. Mostly, press brakes are widely used in sheet metal bending.
Different bending method, different bending principle, they are chosen according to different production purpose.
1.1.1 Moulds bending
For annual production quantity is more than 5000pcs, and size of parts is not too big of bending (usually 300×300mm), normally, it is better to think about build special punch moulds for processing.
220.127.116.11 frequently-used bending moulds
Frequently-used bending moulds, as figure 1-1 show: in order prolong lift of moulds, it is better to adopt fillet when design moulds.
1.1.2 Press brake for bending process
Press brakes include conventional press brake and CNC press brake. CNC press brake is chosen to bend irregular shape and high accurate works. Its principle is to utilize bending tools (upper die) and V groove (down die), to do forming of sheet metal.
Advantage: convenient to clamp, accurate locating and fast bending speed
Disadvantage: lower pressure, only for bending simple shape, lower forming efficiency, but with advanced CNC press brake, complicated shape can be formed with continuous bending process.
18.104.22.168 basic principle of forming process
For basic principle of press brake, refer to figure 1-2.
1) bending tool(upper die)
shape of bending tools refer to figure 1-3, shapes of bending tools are determined according to actual needed shape of sheet metal.
Figure 1-3 shapes bending tools
2) down die V=6t(t is thickness of sheet metal)
There are many factors to affect bending process, mostly, radius of circular arc of upper die, material, thickness of sheet metal, strength of down die, mouth dimension of down die and etc. Check figure 1-3, left three ones are upper die, and right two are down die.
Basic principle of bending sequence:
1) Bend from inside to outside
2) Bend from small to large
2) Bend special and complicated shape first and then be bend common shape
3) Former bending doesn’t affect latter bending.
Please check figure 1-4 of two common bending formations
There are three kind different press brakes: manual press brake, hydraulic press brake and CNC press brake. Hydraulic press brakes could be classified according to different method of synchronization; they are twisted shaft synchronization, mechanical-hydraulic synchronization and electro-hydraulic synchronization.
Before maintain hydraulic press bake, it needs to low up die to down die and then shut down machine until maintenance works done, if have to start up machine to make some operation, it should choose manual mode to ensure safety.
Maintenance of hydraulic bending machine includes:
- Check hydraulic circuit
(1) Check oil lever of oil tank, it also has to check it after repair hydraulic system, once oil level of lower than oil indicator, add hydraulic pressure oil to make sure there is enough pressure;
(2) Recommended hydraulic oil could be ISO HM46 or MOBIL DTE25;
(3) Change new oil after 2000 hours continuous working of new press brake, and after that, change new oil every 4000-6000 hours of machining, clean oil tank each time when replace used oil;
(4) Regular temperature of oil should be 35℃-60℃, can’t exceed 70℃, if temperature of oil is too high, it will affect oil quality and damaged relative accessories;
- Filter of hydraulic press brake
(1) Clean completely or replace present filter while change new oil each time;
(2) Change new filter if there is alarm relative to filter or oil is not clean;
(3) There is air filter on the oil tank, check and clean it every 3 months, it’s better to change new one after one year use;
- Hydraulic components
(1) Clean every hydraulic components of press brake every month(base plate, valve, motor, pump, oil pipes and etc.), to avoid dirt get in to recycling system; do not use any detergent;
(2) After one month use of new hydraulic bending machine, check if there is deformation of each bent position of pipes, if there is something abnormal , change with new ones, after two months of use, must tighten every connecting part of whole system, it needs to shut machine when do this job to release pressure of machine.