Common problems and solutions in the process of aluminum profile stretch bending

There are many problems in the process of stretch bending aluminum profiles, and these problems will seriously affect the qualification rate and production efficiency of the product, and then increase the production cost and have a great impact on the normal operation and production of the enterprise.

In view of the needs of the industrialization of aluminum profile stretch bending, combined with the current situation of aluminum profile stretch bending, this paper analyzes the common problems of aluminum profile stretch bending, and puts forward relevant improvement measures, hoping to provide effective support for aluminum profile stretch bending. reference.

1. Existing problems

(1) Contour deviation

Contour degree refers to the degree of coincidence between the shape profile of the profile after stretching and bending, and the shape model or inspection mold tire. The main factors that cause the deviation of the shape profile are: ②The curvature rebound change of the stretch bending die; ②The material of each batch of metallurgical extrusion profiles is unstable, and the hardness of each material is not uniform in the local area; ③The bending radius of curvature changes too much ; ④ profile blank cross-sectional area is not uniform.

(2) surface defects

Surface defects include cracks, shrinkage wrinkles, concaves on the curved surface and side sags after the profile is stretched and bent.

(3) Twist after bending

The reason for the twisting after stretch bending is that the cross-sectional area of the profile is asymmetrical, and the stress of the edge of the profile is unbalanced with that of the edge.

(4) Perpendicularity out of tolerance

Perpendicularity refers to the angular deviation between the vertical reference of the cross-sectional area of the profile (perpendicular to the radius of curvature of the mold) and the inspection platform after bending.

(5) Profile process length

The length of the profile stretch bending process refers to the length of the process material required by the stretch bending mold, fixture and equipment beyond the actual length of the part.

(6) Safe production

Safety is the most important issue in the process of industrial production. When the profile is stretched and bent, it may suddenly break due to accidental factors and bounce outward, causing equipment damage and personnel casualties, which in turn has a serious impact on the development of the enterprise.

2. Solutions

(1) Adjust the curvature of the mold contour

According to the theoretical analysis and calculation, the amount of springback is calculated, and the correction approximate value is obtained through the tensile test to correct the mold, so that the shape of the profile after stretching the part is consistent with the shape model or the inspection mold as much as possible. Considering the unstable factors of the profile, according to the later stage Correction needs can be pulled over a bit.

Since the change of the bending radius of curvature is too large, it will cause a certain deviation. Therefore, the cylinder can be added at the front end of the mold, perpendicular to the mold direction, so that the bending section needs to match the mold, and there should be no gap between the stretch bending mold and the stretched section. This method can solve the tension bending on the opposite side of the center of curvature.

In the design process, the form of the cross-sectional area of the profile and the thickness of each part should be considered. In view of the asymmetry of the cross-sectional area of the profile, the deviation caused by the unbalanced stress between the edge of the profile and the edge of the profile can be properly increased during pre-stretching.

(2) Surface defect treatment

The cracks after the profile is stretched and bent are caused by the large tensile force and the unsatisfactory edge stress. If the edge of the profile is not in place, it will cause shrinkage and wrinkling, commonly known as the edge with wood ear. This can be solved by improving the cross-sectional area of the profile or adjusting the tension.

Depression of curved surfaces mainly occurs on cavity profiles. This type of material needs to be filled with fillers before bending the cavity. The open cavity can be stacked with spring steel plates or filled with polytetrafluoroethylene, while the closed cavity is usually filled with sand.

Properly adjust the mold gap according to the position of the side drape, and improve the mold material can effectively prevent the profile from being scratched.

(3) Twisting treatment after bending

After stretch bending, the main reason for twisting is that the cross-sectional area is asymmetrical, and the stress between the edge of the profile and the edge of the profile is unbalanced. In view of this, industrial aluminum profiles can improve this problem by increasing the tensile force of the profile, that is, adding a vertical push-up cylinder before the bending die, and at the same time, it will be better to keep the pressure for a period of time after bending. In addition, the slight deformation caused by the instability of the extruded profile needs to be corrected in the later stage.

(4) Verticality out-of-tolerance processing

After stretching and bending, the excessive verticality is also caused by the asymmetry of the cross-sectional area and the uneven stress between the edge of the profile and the edge of the profile. In view of this situation, it can be improved by adjusting the curvature change of the stretch bending die. According to the needs of post-correction, it can be pulled a little bit, and the slight deformation caused by the instability of the extruded profile needs to be completed through post-correction.

(5) Determination of the length of the profile process

The blank length of the stretch-bending profile is composed of the length of the part, the extension part of the mold curvature (the length of the part, the extension part, and the fillet at the end of the mold are collectively called the effective length of the mold), the clamping part of the equipment chuck and the rotation clearance of the equipment chuck along the mold . In addition to the part length, it is collectively referred to as the process length. The length of the mass production process directly determines the cost of the part. Therefore, it is recommended to reduce the effective length of the mold as much as possible to satisfy the forming state of the curved parts. If necessary, a gap can be opened at the rear of both ends of the mold, so that the working chuck of the machine tool can freely enter the rear of the mold, thereby reducing the two ends of the wool. end of the process margin.

(6) Safe production

Safety is the primary concern in industrial production processes. Therefore, in the production process, it is necessary to add protective devices in front of the profile operation table, formulate corresponding rules and regulations, and train comprehensive technical operators. In addition, during the stretching process of the profile, it is strictly forbidden for the operator to stand at the front of the equipment.

3. Conclusion

To sum up, the extension force of each section part should be calculated when designing the cross-sectional area of the profile that needs to be stretched and bent. When designing stretch bending dies, industrial aluminum profiles should consider the change of curvature rebound and the pre-deformation of post-correction, so as to reduce the workload of the correction process as much as possible. While batch production reduces the workload of the calibration process and reduces the process length of stretch-bending materials, safe production is the primary concern of production cost reduction. When the extruded profile is unstable, there will be a small amount of defects such as deviation of the profile of the stretch-bent profile, out-of-tolerance twist, out-of-tolerance verticality, etc., and these can be corrected and remedied in the later stage.