The key to improve the yield of aluminum alloy profiles is to reduce and eliminate waste products. Although geometric waste is inevitable, we can try to minimize it. Therefore, effective control and improvement of the yield of extruded products can be adopted.

Measures to reduce geometric waste

Correct selection of ingot length is the main measure to reduce process waste. The ingot length is not calculated after extrusion, but calculated before extrusion.

At present, most enterprises have adopted the long-rod hot shear aluminum rod heating furnace, which reduces the loss of aluminum chips compared with the short-rod heating furnace. Due to the change of the wall thickness of the mold, the control of the casting length is more flexible and accurate, and greatly improves the yield. However, many enterprises neglect the calculation of the casting length after using the long-rod hot shear furnace, and directly hand the work over to the operator for control. However, the operator usually takes the next rod first according to experience and observes the length of the material. If the difference is large, continue to adjust it. Usually, it takes about 3 rods to get the accurate length. In this process, a lot of waste has been produced, which not only reduces the production efficiency, but also reduces the yield.

The correct way is that during the initial production of the mold, the process control department calculates the length of the ingot. During the production of the mold that has been put on the machine for many times, according to the length of the last production bar recorded on the mold card, slightly add about 5-10MM, and observe the length of the ingot during the production. If there is any difference, fine tune it so that the second stick is very accurate. According to the data, using long rod hot shear can increase the yield by 4 percentage points, and it is completely feasible to increase the yield by 2-3 percentage points in actual production.

Measures to improve the yield from the technical level

Improving the level of mold design and manufacturing and reducing the number of mold trials are important technical measures to improve the yield. Generally, 1-3 ingots are consumed without this mold test, which reduces the yield by 0.5-1%. Due to the low level of mold design and manufacturing, some products need to be repaired and tested 3-4 times or more to produce the finished product, which virtually reduces the yield by 2-5%. This will not only cause economic losses, but also prolong the production cycle due to repeated mold test.

The concept of zero mold test is put forward by modern mold, that is, after the mold is manufactured, it is not necessary to test the mold, and it can directly produce qualified products on the machine. Using simulation design software and finite element analysis, the design can be completed in the computer. The mold can also be tested by computer simulation. The mold cavity processing is completed in the automatic machining center. The whole mold processing is completed with high precision. Therefore, the quality of the mold is very high. The qualified rate of the machine is more than 90%, which can improve the yield by 2-6%.

Properly increase the extrusion coefficient of aluminum to improve the yield

Each aluminum factory has a series of machines. According to the extrusion ratio of the products, the length of the cooling bed, the outer section of the products, and the length and diameter of the extrusion cylinder, each factory determines that the products are produced on the corresponding machines. Practice has proved that products of the same specification are produced on different tonnage extruders. Due to the different extrusion coefficients, it has a great impact on the structure and performance of products and production efficiency, and its yield will also vary. When the extruder tonnage is large, the extrusion coefficient is large, the yield is high, and the extrusion cost is close.

Improving ingot quality is the premise to improve the yield

Ingot is the raw material for extrusion production. Ingot has uniform structure, fine grains, no slag inclusion, pores, segregation, cracks and other defects, which can not only reduce extrusion pressure, improve extrusion speed, and improve the internal quality of products. Moreover, it can reduce the defects such as bubbles, pores, scratches, cracks and pits on the product surface. Smaller slag inclusions can be discharged through the slit of the working belt of the mold, but will cause pear marks on the surface of the profile, resulting in a certain length of waste. However, the larger slag inclusion will be stuck in the slit of the working belt and cannot be eliminated, which will cause the plug mold or the product to crack, and the mold will be replaced, which will seriously affect the finished product rate.

When the profile is stretched and straightened, many enterprises have not designed corresponding spacers, especially some large suspended wall profiles and hollow profiles. The deformation of the head and tail of the profile is too large, and when the finished product is sawed, the deformed part must be cut off, which leads to a decline in the yield.

The cushion can be made of hardwood or aluminum blocks. The specification of the cushion should be reduced as much as possible to increase the versatility of the cushion. For the profiles with long overhanging wall and closed section, the cushion shall be inserted into the closed cavity during straightening, and the support frame shall be placed on the overhanging wall. This reduces the amount of deformation in the length direction. Fixture must be designed and managed by specially-assigned person and used by workers.

At the same time, in order to prevent the phenomenon that workers are unwilling to use mattresses because they are too troublesome, it is necessary to establish a reward and punishment mechanism linking the rate of finished products with wages.

Strengthen the management of aluminum profile extrusion dies and production original records

The mold card and the original production record are very important. The mold card must be able to truly display the mold nitriding, maintenance and material production. The original record must be able to truly display the supporting weight, casting length and quantity to provide a reliable basis for the next production.

Reduce geometric waste by using pressureless extrusion

The fixed pad is pressed without residual pressure, which is to fix the extrusion pad on the extrusion rod, and make certain modifications to both.

When the extrusion cylinder does not retreat, the pressure pad is also easy to separate from the ingot, and then the next ingot is directly pushed into the extrusion cylinder and squeezed together with the rest of the previous ingot, so as to avoid shearing and pressing each ingot.

According to the quality requirements and order quantity, the number of casting shears can be determined once, usually 40-50 shears once.

Optimize aluminum extrusion process and reduce technical waste

There are many aspects of the extrusion process that affect the technical waste, which covers the entire extrusion production process. It mainly includes: ingot quality, process temperature, extrusion speed, extrusion tools, molds, transport and loading, aging heat treatment, etc. In addition to formulating advanced and scientific production processes, it is also necessary to correctly and strictly implement the operating procedures and improve the proficiency and sense of responsibility of workers.

Try to reduce the varieties produced in each shift. It is best to arrange only 3-5 varieties per shift to improve the production capacity of a single set of molds.

The impact of moulds on the yield of finished products mainly includes two aspects: the trial of new moulds and the use of production moulds

The more times of mold test, the more mold aluminum taken away, and the lower the yield. Therefore, it is necessary to improve the design and manufacturing level of the mold.

The production mould shall be carefully maintained, reasonably nitrided and maintained in time to ensure high qualification rate, good molding degree and high durability. If 3-4 varieties fail to be put into production due to unqualified mold maintenance in each shift, the yield will be reduced by at least one percentage point.

Aluminum profile extrusion tools include: extrusion barrel, extrusion rod, extrusion pad, die pad, etc. It mainly ensures the concentricity of the extrusion cylinder, rod and die.

Secondly, the extrusion cylinder shall be properly maintained and heated to ensure the flatness of the cylinder end face. Eliminate the phenomenon of poor matching between various extrusion barrels and moulds. Clean the residual aluminum on the inner wall of the extrusion cylinder regularly, check whether the inner hole wall is damaged, use the mold pad correctly, and improve the support strength of the mold.

Extrusion temperature, extrusion speed and cooling have a great impact on the structure, mechanical properties and surface quality of products, and also affect the yield. In addition, the three factors will affect the length of the product. When the casting rod temperature is high, the extrusion speed is fast, and the cooling speed is low, the length of the product after extrusion will increase, with an increase rate of 0.5% - 1%, which also affects the linear density of the profile, so a stable process can improve the yield.

Improve the subsequent extrusion process to avoid technical waste. During the transportation of the subsequent extrusion process, the main attention shall be paid to the scratch and bruise of the profile.

The first mock examination multi hole extrusion can improve the yield

When some products are suitable for multi-air extrusion, porous extrusion can be used as much as possible, which can not only reduce the extrusion coefficient, reduce the extrusion pressure, but also improve the yield. When the technical waste is zero, the yield of double-hole extrusion can be increased by 3% - 4% compared with single-hole extrusion.

Extrusion speed is an important process parameter in extrusion process, which relates to the quality of products and the level of production efficiency. The extrusion speed is not the same as mastering the process temperature. A heat treatment process for an alloy can basically select a different temperature, and the extrusion speed is a process parameter with strong experience. The extrusion speed is different for profiles with different alloy states and different sections. The extrusion speed before and after the same product is also different due to the influence of temperature change during the extrusion process.

To correctly control the extrusion speed, it is necessary to skillfully and flexibly grasp the extrusion speed range of various alloys and various sections (including wall thickness), and pay attention to observe the impact of the extrusion speed on the aluminum profile, such as surface quality, molding degree, etc.

Be familiar with the ability of extrusion equipment to control extrusion speed. Some extruders have constant speed extrusion control and PLC control, some have only PLC control, and some have neither. When a given extrusion speed is given, some extruders can start to extrude at this speed. With the gradual reduction of the blank in the extrusion cylinder, the extrusion pressure decreases, and the outflow speed of the products will become faster and faster, sometimes causing cracks in the rear of the products.

Therefore, it is necessary to adjust the extrusion speed even. Only by understanding the equipment status can the extrusion speed be properly adjusted and controlled.

Reduce the generation of waste products by strengthening the first inspection and process inspection

The scrap of aluminum shape and size, such as wall thickness out-of-tolerance, twisting, plane clearance, opening or closing, mainly depends on the inspection of the first bar after mold test by the master at the time of discharging and the inspection of the quality inspector after stretching to eliminate the generation of such scrap. Generally, the wall thickness tolerance should be controlled from the negative tolerance, because with the continuous production of products, the wall thickness of products will gradually become thicker due to the gradual wear of molds. For sections with large overhanging walls, check carefully against the drawing during stretching and straightening to control the reasonable stretching amount.

Surface waste products, such as scratches, orange peel, tissue articles, black spots, bubbles, etc., often do not appear in every product. It is necessary to check each other and jointly supervise the removal of waste products on the surface through the main machine operator, the quality inspector and the sawing process of the stretched finished products.

If the quality inspector does not find any scratch on the product on the discharge table, and finds any scratch on the product when sawing the finished product, it is necessary to check from the conversion process of the cooling bed to see if some parts such as the transport belt and the feeder are hard and protruded, causing the product scratch.

Quality management is the management of the whole staff and the whole process. Each process must control the quality and achieve the combination of self-inspection, mutual inspection and special inspection, so as to effectively eliminate technical waste in the bud.

Source: aluminum processing