When selecting extrusion equipment, in addition to considering the factors of extrusion speed that produce thermal effects on the extruded metal, one must also consider that the press should have sufficient rigidity and guiding accuracy, as well as the installation of reliable overload protection devices.
When extruding with a friction press, due to differences in the equipment's guiding accuracy, guiding devices need to be added to the mold. For friction presses without an ejection device, an ejection device should also be added.
When extruding with a general-purpose crank press, in order to increase the strength and rigidity of the equipment, the worktable shim should be made of cast steel, and the holes on the table should be reduced. Since the extruded parts remain on the die after extrusion, there is a large clamping force between the extruded parts and the die, and a large ejection force is required, approximately 10%–20% of the nominal pressure. Therefore, the press ejection device should be reinforced. In addition, the extrusion force and stroke should be checked according to the load curve allowed for the press slide. That is, within the entire extrusion stroke range, the extrusion force should be less than the limit value of the press stroke–pressure curve and should not be determined based on the nominal pressure.
The accuracy and extrusion stroke of a general press are not sufficient, and the pressure exerted in the middle of the stroke is only about one-third of the nominal pressure. Therefore, when extruding, it is best to use a specialized industrial aluminum profile extrusion press as the extrusion equipment. The characteristics of a toggle-type industrial aluminum profile extrusion press are a short stroke, a high number of strokes, and a long pressing time, making it suitable for extruding parts with short working strokes. Tensile toggle-type and crank-type industrial aluminum profile extrusion presses are suitable for extruding relatively long parts. Hydraulic industrial aluminum profile extrusion presses can operate at nominal pressure throughout the full stroke, and both the extrusion speed and stroke can be adjusted, making them suitable for extruding parts of large length.
The selection of extrusion equipment should consider the following points:
(1) Select the type of extrusion equipment according to the finalized production plan and the requirements of the production process. Choose the corresponding supporting extrusion equipment based on the production plan, such as for tube production, rod and profile production, or online coil billet production plans. Select extrusion equipment compatible with the process requirements, such as using water-sealed extrusion for easily oxidized copper and copper alloys, using hydrostatic extrusion for extrusion of various coated materials, and using the Conform continuous extrusion process for products that need to achieve lengths of several thousand to tens of thousands of meters, etc.
(2) Choose extrusion equipment according to the product's type, specifications, performance, and quality requirements. For example, when selecting the tonnage of the extrusion press, first determine the range of billet dimensions based on the specifications of the product or intermediate billet, and consider the required degree of deformation to determine the range of ingot sizes and the necessary extrusion cylinder dimensions, thereby determining the tonnage of the extrusion press. In addition, the type of extrusion press is determined according to different product types, specifications, and quality requirements.
(3) Extrusion equipment should be selected based on the technological performance, structural characteristics, and the reasonable matching of various devices. Different performances and structural characteristics determine the different uses of extrusion machines. When selecting extrusion equipment, it is essential to consider the reasonable configuration and balance among the main equipment to fully utilize the equipment's capabilities and achieve higher production efficiency. Generally, it is not allowed to have production stoppages due to the main equipment's capacity being insufficient.
(4) The required level of mechanization and automation of the extrusion equipment must be considered. To improve production efficiency, reduce labor intensity, lower consumption, reduce costs, and improve the quality of extrusion products, the requirements for the mechanization and automation level of extrusion equipment are increasing. Therefore, where conditions permit, advanced technology and equipment should be used as much as possible when selecting extrusion equipment. The selection must go through investigation, demonstration, and proven advanced technology and reliability in production practice. In addition, it should have possible conditions for implementation in enterprise production and should not be adopted blindly. Furthermore, the selected extrusion equipment, while meeting current requirements, should also leave room for development; disregarding this may result in backwardness and passive situations, especially for imported extrusion equipment, which requires even more attention.
(5) It is necessary to consider that the extrusion equipment has a relatively good economic effect when selected:
1) When standard extrusion equipment and general-purpose extrusion equipment are available, try to choose standard equipment and general-purpose equipment. In particular, when introducing extrusion equipment, the localization of spare parts should be considered, which is beneficial for improving economic efficiency, operational effectiveness, and shortening the equipment installation time.
2) In the absence of reference standards and general-purpose equipment, factors such as ease of manufacturing and low cost should be considered, and reasonable technical parameters for the extrusion equipment should be proposed according to process requirements.
3) Consider the factory's civil engineering design conditions and the existing water, electricity, air, and gas conditions, as well as the average temperature and humidity conditions of the factory in winter and summer, and propose reasonable design requirements for the extrusion equipment.
Principles for Choosing an Extruder The selection of an extruder must simultaneously consider the choice and design of the hydraulic system and the control method. When the extruder's working time accounts for more than 70%–80% of the entire extrusion cycle and the extrusion speed does not vary much, using direct drive with a high-pressure pump is more economical. For fast extrusion speeds, short durations, and large extruders or units, using hydraulic accumulator transmission with a pump is more economical. Some modern advanced extruders use hydraulic systems with direct drive by high-pressure oil pumps, eliminating the need for a pump station system and reducing equipment investment costs. The extruder's control system uses a programmable logic control system to achieve program control. In addition to using PLC systems, modern extruders also employ systems for extrusion data monitoring, fault diagnosis, eccentricity monitoring of extruded products, data-based production control, and report printing. The control system is highly reliable, easy to maintain, and flexible for future functional expansions.
Another important aspect to consider when choosing an extruder is the extruder's auxiliary systems, which together with the extruder form a complete production setup. During the operation of the extruder, approximately 30% to 70% of the working time is consumed by auxiliary operations. Often, the production efficiency of the extruder and the quality of extruded products are affected due to imperfect auxiliary machine structures, which also increases the labor intensity for operators. Therefore, carefully considering the selection and design of auxiliary devices is crucial for improving the quality of extruded products and enhancing the automation level of the production line. The main auxiliary devices of an extruder include the feeder mechanism and furnace door sealing device of the heating furnace; the ingot feeding device of the extruder; the die holder device (for replacing working molds); the mechanism for separating extrusion pads, extrusion leftovers, and copper skins; devices for cleaning, repairing, cooling, and lubricating the extrusion mold; and the discharge mechanism of the extruder.
