How to use aluminum profile section design skills to solve extrusion production problems?

1 Introduction

    The reason why aluminum alloy profiles are widely used in life and production is that everyone fully recognizes its advantages such as low density, corrosion resistance, excellent electrical conductivity, non-ferromagnetic properties, formability, and recyclability. my country's aluminum profile industry started from scratch, grew from small to large, and developed into a major aluminum profile production country, with output ranking first in the world. However, as the market's requirements for aluminum profile products continue to increase, the production of aluminum profiles has developed in the direction of complexity, high precision, and large-scale production, which has brought about a series of production problems.

    Aluminum profiles are mostly produced by extrusion. During production, in addition to considering the performance of the extruder, the design of the mold, the composition of the aluminum rod, heat treatment and other process factors, the cross-sectional design of the profile must also be considered. The best profile cross-section design can not only reduce the process difficulty from the source, but also improve the quality and use effect of the product, reduce costs and shorten the delivery time. This article summarizes several commonly used techniques in aluminum profile cross-section design through actual cases in production.

2 Aluminum profile section design principles

    Aluminum profile extrusion is a processing method in which a heated aluminum rod is loaded into an extrusion barrel, and pressure is applied through an extruder to extrude it from a die hole of a given shape and size, causing plastic deformation to obtain the required product. Since the metal is affected by various factors such as aluminum rod temperature, extrusion speed, deformation amount, and mold during the deformation process, the uniformity of metal flow is difficult to control, which brings certain difficulties to mold design.

    In order to ensure the strength of the mold and avoid cracks, collapse, chipping, etc., the following should be avoided in the profile section design: large cantilevers, small openings, small holes, porous, asymmetrical, thin-walled, uneven wall thickness, etc. shape. When designing, we must first satisfy its performance in terms of use, decoration, etc. The resulting cross-section is usable, but not the best solution. Because when designers lack knowledge of the extrusion process and do not understand the relevant process equipment, the production process requirements will be too high and too strict, resulting in a reduction in the pass rate, an increase in costs, and even the inability to produce with the existing process. Therefore, the principle of aluminum profile section design is to use the simplest process as possible while satisfying its functional design.

3 Tips on aluminum profile interface design

    3.1 Error compensation

    Sealing is one of the common defects in profile production. The main reasons are as follows:

    (1) Profiles with deep cross-section openings will often close up when extruded.

    (2) Stretching and straightening of profiles will intensify the closing.

    (3) Glue-injected profiles with certain structures will also have shrinkage due to the shrinkage of the colloid after the glue is injected.

    If the above-mentioned closing is not serious, the flow rate can be controlled by mold design to avoid closing; but if several factors are superimposed and the mold design and related processes cannot solve the closing, pre-compensation can be provided in the cross-section design, that is, pre-opening. The amount of opening compensation required should be selected based on its specific structure and previous closing experience. At this time, the design of the mold opening drawing (pre-opening) and the finished drawing are different (Figure 1).

    3.2 Divide the size into smaller sizes

    With the development of large-scale aluminum profiles, the cross-sectional designs of many profiles are getting larger and larger, which means that a series of equipment such as large extruders, large molds, large aluminum rods, etc. are needed to support them, and production costs rise sharply. For some large-size sections that can be achieved by splicing, they should be split into several small profiles during design. This can not only reduce costs, but also make it easier to ensure flatness, curvature, and accuracy (Figure 2).

    3.3 Set stiffeners to maintain flatness

    Flatness requirements are often encountered when designing profile sections. Small-span profiles are easy to ensure flatness due to their high structural strength. For long-span profiles, just after extrusion, the profile will sag due to its own gravity, and the bending stress in the middle will be the largest and the most serious concavity. Also, the long wall panel section will easily generate waves, causing the plane to deteriorate intermittently. Therefore, large-sized flat plate structures should be avoided in cross-section design. If necessary, reinforcing ribs can be installed in the middle to improve its flatness. (image 3)

    3.4 Secondary processing

    In the profile production process, some sections are difficult to complete by extrusion processing. Even if they can be processed, the production cost will be too high. At this time, other processing methods can be considered.

    Case 1: Holes with a diameter less than 4mm on the profile section will make the mold insufficient in strength, easily damaged, and difficult to process. It is recommended to remove the small holes and use drilling instead.

    Case 2: The production of ordinary U-shaped grooves is not difficult, but if the groove depth and groove width exceed 100mm, or the ratio of groove width to groove depth is unreasonable, problems such as insufficient mold strength and difficulty in ensuring the opening will also be encountered during production. When designing the profile section, you can consider closing the opening, so that the original solid mold with insufficient strength can be turned into a stable split mold, and there will be no problem of opening deformation during extrusion, making the shape easier to maintain. In addition, some details can be done at the connection between the two ends of the opening during design.

    For example: set V-shaped marks, small grooves, etc. to facilitate easy removal during final machining (Figure 4).

    3.5 Traditional on the outside and simple on the inside

    Aluminum profile extrusion molds can be divided into solid molds and shunt molds according to whether the cross-section has a cavity. The processing of solid molds is relatively simple, while the processing of shunt molds involving cavities, cores, etc. is relatively complex, so the profile cross-section design is also Full consideration must be given, that is, the outer contour of the cross-section can be designed to be more complex, try to place grooves, screw holes, etc. on the periphery, while the interior should be as simple as possible, and the accuracy requirements cannot be too high. In this way, both mold processing and maintenance will be much simpler, and the yield rate will also be improved.

    3.6 Reserved margin

    After extrusion, aluminum profiles have different surface treatment methods according to customer needs. Among them, anodizing and electrophoresis methods have little impact on the size due to the thin film layer. If the surface treatment method of powder coating is used, powder will easily accumulate in corners and grooves, and the thickness of a single layer can reach 100 μm. If this is an assembly position, such as a slider, it will mean that there are 4 layers of spray coating. Thickness up to 400 μm will make assembly impossible and affect use.

    In addition, as the number of extrusions increases and the mold wears, the size of the profile slots will become smaller and smaller, while the size of the slider will become larger and larger, making assembly more difficult. Based on the above reasons, appropriate margins must be reserved according to specific conditions during design to ensure assembly.

    3.7 Tolerance marking

    For cross-section design, the assembly drawing is produced first and then the profile product drawing is produced. The correct assembly drawing does not mean that the profile product drawing is perfect. Some designers ignore the importance of dimension and tolerance marking. The location of the dimensioning is generally the dimensions that need to be guaranteed, such as: assembly position, opening, groove depth, groove width, etc., and it is easy to measure and inspect. For general dimensional tolerances, the corresponding accuracy level can be selected according to the national standard. Some important assembly dimensions need to be marked with specific tolerance values in the drawing. Too large a tolerance will increase the difficulty of assembly, and too small a tolerance will increase production costs. A reasonable tolerance range is required. Designers’ daily accumulation of experience.

    3.8 Detailed adjustments

    Details determine success or failure, and this is also true for profile cross-section design. Small changes can not only protect the mold and control the flow rate, but also improve the surface quality and increase the yield rate. One of the commonly used techniques is to round the corners. Extruded profiles cannot have absolutely sharp corners because the thin copper wires used in wire cutting also have diameters. However, the flow speed at the corners is slow, the friction is large, and the stress is concentrated, often causing obvious extrusion marks. , Dimensions are difficult to control, molds are prone to chipping, etc. Therefore, the rounding radius should be increased as much as possible without affecting its use.

    Even if a small extrusion machine is used for production, the wall thickness of the profile should not be less than 0.8mm, and the wall thickness of each part of the section should not differ too much, and the difference should not be greater than 4 times. During design, diagonal lines or arc transitions can be used at the sudden changes in wall thickness to ensure regular discharge shape and easy mold repair. In addition, thin-walled profiles have better elasticity, and the wall thickness of some gussets, battens, etc. can be about 1mm. There are many applications for adjusting details in design, such as adjusting angles, changing directions, shortening cantilevers, increasing gaps, improving symmetry, adjusting tolerances, etc. The specific methods will not be listed one by one. In short, profile cross-section design requires continuous summary and innovation, and fully considers the relationship with mold design, manufacturing, and production processes.

4 Conclusion

    As a designer, in order to obtain the best economic benefits from profile production, all factors of the entire life cycle of the product must be considered during design, including user needs, design, manufacturing, quality, cost, etc., and strive to achieve product development in one go. Be successful. These require daily tracking of product production and the collection and accumulation of first-hand information in order to predict the design results and correct them in advance.