Process characteristics
Because the structure of the part has many steps and convex teeth on the opposite side, the forming position is more, and it is difficult to ensure the stamping size in multiple times. Therefore, the conventional three force sources are obviously not enough, and the fourth, fifth and sixth force sources of the fine blanking machine are needed. The fourth force source is responsible for forming the half punching step, the fifth force source is responsible for forming the belt tooth boss and belt tooth center hole, and the sixth force source is responsible for forming the φ 149.3 mm step.
(1) forming process.
The punch is fixed and the female is floating. During the stamping process, the concave die plate uses the upper auxiliary oil pressure (the fourth force source), the concave template V-ring holds the material, the main cylinder is formed from bottom to top, at the same time, the fourth force source releases the force and moves backward, and the punching hole is pushed out by the counter pressure of the machine. The fifth force source is used to punch the center hole of belt teeth and the six belt teeth boss. The height of the front step is synchronously protected to ensure no deformation. The profile blanking can form a step of 149.3mm at the same time. The sixth force source and counter pressure support are used to ensure the flatness and size. Finally, the strip is ejected and the fine blanking process is finished.
(2) application of the fourth to sixth force source in semi punching and blanking.
In the process of fine blanking, the three-dimensional forces cooperate with each other to complete blanking and punching, and at the same time, the fourth to sixth force source of auxiliary oil pressure is used to complete single or multiple semi punching; the traditional process needs at least six working positions to achieve, and can not guarantee the size, this process only needs one working position to complete multiple semi punching at the same time, and can ensure the product position, roundness and dimensional accuracy.
Fig. 6 force transmission diagram of multi force source
As shown in Figure 6, the hydraulic oil of fine blanking machine is transmitted to the oil pressure piston cylinder through the oil circuit, and the force is transmitted to the die for pressure ejection and material pressing. The oil cylinder needs to be installed with a safety valve to prevent personal injury due to excessive oil pressure or unstable oil pressure; check whether the screw is firmly installed and add protective measures to prevent accidental loosening; keep the inner cavity of the oil cylinder clean, otherwise the installed sensor may be damaged due to piston sticking.
As shown in Fig. 7, during the stamping process, the supporting plate 4 and the lower template 5 hold the raw materials, the main cylinder realizes the shape blanking from the bottom to the top, and the semi punching hole 3 is formed from the top to the bottom, and the semi punching ejection 7 is protected by the protruding steps supported by the auxiliary hydraulic cylinder force source, which is responsible for the pressing and ejecting function of the product. The shape punch adopts the combined structure of bolt and equal height sleeve to realize the floating of punch, which can meet the effect of material clamping required by punch, and is responsible for the shape of punch to realize two functions of one punch.
There is a height difference between the semi punching and the shape stamping, that is, the countersunk depth, i.e. X in Figure 7. Therefore, when designing the length of dowel bar, the height difference between ejector pin x and lower ejector s-x should be considered. Additional protection is added in the design of die structure. The formed boss and hole, with strict requirements, need to be protected from the side force of the die. Especially, the uncontrollable factors of material flow in the shearing process need to be protected, and then the forming and shearing can be completed in the first order by means of auxiliary oil pressure of equipment.
(3) mold details processing.
Fig. 7 synchronous forming of semi punching and lower profile
1) If the half punch clearance is too small, the forming force will be greatly increased, and the punch is easy to crack; if the clearance is too large, the step collapse angle will be too large. Therefore, the design of variable clearance is adopted in the six semi piercing parts of tooth profile. The one-sided clearance between the tooth top and the tooth tip is 0.3 mm, and the unilateral clearance of other parts is 0.2 mm, which can avoid the phenomenon of die edge chipping.
2) The hydraulic cylinder mode of the fourth to sixth force source mold needs to match the appropriate sealing ring, and the special tools are used for installation. The machining accuracy needs to be controlled to prevent the possibility of oil leakage. S390 can be used for punch and die material. All punches and dies are polished with fluid polishing equipment, and the roughness is less than Ra0.2 μ M. coating and assembly can be carried out after confirming that there is no problem.
Conclusion
The semi punching process of fine blanking is a convex pressing process, which is the linear displacement of the local area of the part relative to its surrounding area, so that the material will not be damaged in the shear zone. In this paper, the balance plate adds two semi punching holes on the semi punched base plate. Considering the limitations of the fine blanking die structure and fine blanking equipment, the die has only three working positions, and 1 Multiple complex processes are completed in each station to ensure dimensional stability and consistency.
Multiple force sources play a key role in the fine blanking machine, in which each independent forming part should have its own adjustable pressure, which is used to assist die pressing, ejection, protect die size and meet the processing requirements of balance plate.