| Deep drawing process is a technique that widely used in sheet forming process.The key of forming process is the way of blank pressing and the parameters of blank holder force.The control method of electro-permanent magnet blank holder force is based on of loading requirement of blank holder force.Using electro-permanent magnet technology regard magnetic attraction force as the blank holder force to realize the blank holding process.The new blank holder force control method has a positive significance in simplifying the die structure,improving the control effect,energy saving and environmental protection,and innovating the existing deep drawing technology.Using the BHF Control Method of electro-permanent magnet in deep drawing cylindrical parts forming,that the related section bas been studied,including: 1)Based on the theoretical analysis of the static magnetic field,the effects of parameters of magnetic materials for magnetic induction magnet is studied;2)Under the permanent magnet electric control technology which is used for loading of blank holder force.Design blank holder force device of eletro-permanent magnet and die for deep drawing initially;3)Using the FEM,The magnetic induction intensity of the blank holder is simulated under the condition of integral magnetization and demagnetization.Based on the simulation results to improve the design of the die;4)Measure the magnetic induction intensity of the electro-permanent magnet blank holder device.As an example,the experiment of deep drawing with magnetic blank holder force is conducted for cylinder.The static magnetic field is briefly analyzed.Permanent magnet has the magnetic leakage phenomenon on the surface.Changing the shape of permanent magnet can be adjusted to make it produce more uniform magnetic induction intensity.Static magnetic circuit and the magnetic conductance of permanent magnet are derived under the free state.The article gives the calculation formula of magnetic force.The dynamic magnetic circuit is briefly analyzed.An electro-permanent magnet device with four magnetic pole unit is constructed.The magnetic induction intensity of AlNiCo and NdFeB which in the chuck is calculated.The results are 0.97 T and 1.095 T,respectively.Based on the electro-permanent magnet chuck of four magnetic pole unit,an electro-permanent magnet magnetic blank holder and drawing die are designed preliminary.The theoretical calculation shows that the magnetic induction intensity is 2.23 T and the maximum magnetic attraction force of the electro-permanent magnet magnetic blank holder is 227660.63 N.The finite element simulation method is used to simulate the permanent magnet of the four pole unit electro-permanent magnet chuck under different chamfering length.The results show that: With the increase of the chamfering length of the permanent magnet in the direction of magnetization,the magnetic attraction gradually decreases.When the chamfering length is 0 mm,the magnetic induction intensity of AlNiCo and NdFeB in the original state is 0.74 T and 1.11 T,respectively.The simulation results are in agreement with the theoretical calculation.The simulation results of the edge pressing device show that the magnetic induction intensity is between 1.797 T and 2.397 T when magnetization state.The virtual force and Maxwell are 188580 N and 184400 N,respectively.The simulated results of magnetic induction and magnetic attraction are not very different from those of theoretical calculation.The magnetic induction intensity of the device is measured in experiment.The calculated magnetic attraction is 15674.96 N.But the force obtained after calculation is deviate from theoretical calculation and FEM simulation.The reasons for the deviation are analyzed in this paper.The galvanized steel sheet with thickness of 0.5 mm and a diameter of 170 mm was chosed to test the deep drawing that uses electro-permanent magnet blank holder method.When the current is adjusted to 13 levels,it can generate enough blank holder force.When the current is 16,the cracks appear on the galvanized steel plate due to the excessive blank holder force.In addition,during the experiment of the copper plate,The device also produces sufficient blank holder force.The deep drawing experiments of two kinds of plates show that useing electro-permanent magnetic blank holder pressing method can meet the blank holder force that loading requirement of deep drawing process,The feasibility of the method in deep drawing process is further verified. |
PDF Full Text Request