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Aluminium isothermal extrusion


1 Aluminium isothermal extrusion

Characteristics of isothermal extrusion program

  • Parameter adjustment enables isothermal control with an error of + -1 ° C.
  • Automatic adjustment of isothermal rise is possible due to the proven rise coefficient in constant velocity extrusion.
  • Automatic adjustment of billet temperature (billet taper temperature)
  • There is no risk of runaway extrusion speed as we monitor the maximum extrusion speed.
  • Database creation of isothermal extrusion parameters by extrusion management program (EM).
  • Automatic adjustment of emissivity through extrusion management program (EM).

Fig.1-1 Isothermal extrusion system diagram

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2 Example of isothermal extrusion

2-1 Comparison of isothermal extrusion ON and OFF

    1 Improving productivity
    Isothermal extrusion is faster than constant velocity extrusion because it overshoots at startup.
    In Fig. 2, the ram speed is ramped from the beginning to the end for isothermal extrusion. However, if temperature control is performed using a billet taper or a QR container, the ram speed will approach to constant speed without tilting. Increases productivity by supporting isothermal extrusion of equipment.
    2 Improvement of quality
    Constant velocity extrusion is said to homogenize the aluminum component on the surface of the aluminum profile, and isothermal extrusion is to homogenize the aluminum component inside the aluminum profile. The adjustment of the parameters also enables an isothermal extrusion with an error of + -1 ° C.

Fig.2-1-1 The isothermal extrusion temperature error is set at + -5 ° C. Set temperature 525 ° C, billet temperature 450 ° C. If the temperature error is set to + -1 ° C, the product temperature will be more linear.

Fig.2-1-2 When isothermal extrusion is turned off. Pink product temperature is rising.

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2-2 Isothermal extrusion as inclined extrusion

In the inclined extrusion , in order to prevent the temperature rise of the aluminum profile, the setting speed was made to incline smoothly by the parameters set in the computer. The ram speed follows the slope of its set speed.
The temperature of aluminum profiles can now be measured with a radiation thermometer. Therefore, it is possible to prevent the temperature rise of the profile while monitoring the temperature of the profile directly instead of the inclination parameter preset on the computer.
If you look at FIG12-1 and FIG12-2 of isothermal extrusion, it has a pattern of set speed similar to inclined push. The pattern of the set speed different from that of the inclined push is shown when there is room for the temperature. In this case, the set speed is not inclined but rising as in FIG12-3 and FIG12-4.

Figure 2-2-1 Speed is ramped to prevent product temperature rise

Figure 2-2-2 Speed is ramped to prevent product temperature rise

Figure 2-2-3 Speed has risen due to room for product temperature

Figure 2-2-4 Speed has risen due to room for product temperatureす

Note: The pink line in the figure is the temperature.

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2-3 Increased production and isothermal extrusion

In order to increase the production volume by aluminum extrusion, shorten the ramp speed rise time and increase the setting speed. However, increasing the setting speed will cause product quality defects, so it is a difficult problem to be able to increase the setting speed.

The temperature rise of the product is the cause of the quality defect. Isothermal extrusion prevents extrusion from rising product temperatures after steady state. Therefore, the rise in temperature T after steady state is converted to the set speed ⊿V. And let ⊿V be an increase in the set speed. This can prevent the occurrence of quality defects due to temperature rise, and can increase the production volume. Because the temperature rise of new ⊿ T can be prevented by isothermal extrusion.

The set temperature is the temperature at which extrusion reaches the set speed and reaches steady state. As a result, if the set speed is given, the set temperature is automatically determined by the computer during extrusion control, and there is no need to specify the set temperature.
However, the requirements of the aluminum extrusion plant have been changed to specify the set temperature and control the product temperature to become the set temperature earlier. Fig. 13-4 An example of isothermal extrusion. Therefore, the ram speed of the rising is forced to overshoot.

Fig. 2-3-1 The set speed is higher than constant velocity extrusion. The set temperature is calculated automatically at the rise of the ram. You can see that the ram speed is ramped by isothermal extrusion.

Figure 2-3-2 The product temperature is disturbed in the middle of extrusion. Therefore, it is switched to the constant speed mode automatically. It automatically performs isothermal extrusion when the product temperature becomes normal.

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3 Automation of isothermal extrusion parameter adjustment

The isothermal extrusion parameters are difficult to adjust because there are three parameters: product temperature, ram speed and billet temperature.
Ram speed is just for constant velocity extrusion.
However, many points have been automated compared to manual isothermal extrusion.

  • The rise until the product temperature reaches the set product temperature is automated with the rise time and rise coefficient that were effective in constant velocity extrusion.
  • The billet temperature is automatically adjusted if the rise factor does not work.
  • After the product temperature reaches the set temperature, the temperature is automatically made constant.
  • Even under isothermal conditions, abnormal ram speed or billet temperature will result in failure. See Figure 3-1. By default, isothermal control is performed within plus or minus 10% of the set extrusion speed.
  • Radiation thermometers usually need to be adjusted to ensure that the correct temperature is measured for each extrusion die. The emissivity adjustment was automated for types of radiation thermometers that require emissivity adjustment to obtain the product temperature.

Fig.3-1 The higher the extrusion speed and billet temperature, the smaller the proportion of good products. The ratio varies depending on the material. (Extrusion limit diagram of aluminum alloy).

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4 Parameter input screen for isothermal extrusion program

Fig.4-1 Parameter input screen for isothermal extrusion program
The green input box is entered in the extrusion management program (EM).

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5 Extrusion Management Proguram(EM)

5-1 Extrusion control program (EM) isothermal extrusion screen

  • When the [Set to Machine] button is executed, the extrusion parameters of the screen are set to the machine.
  • The extrusion parameter is registered in the database by executing the [Register database] button. Set the temperature at [Outlet temperature Low] and [Outlet temperature High].
  • When [Auto setting billet temperature] is turned on, the billet temperature is adjusted automatically. The initial value is [Set billet temperature]. The calculated billet temperature is displayed in the green Autoset Billet Temperature. Automatic setting billet temperature is used when the rise of temperature is slow with automatic rise coefficient only.
  • [Error extrusion speed] is the tolerance of [Setting extrusion speed].
  • Error Billet Temperature is the tolerance for Set Billet Temperature.

Fig.5-1 Extrusion management of isothermal extrusion

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5-2 Database of isothermal extrusion parameters

If you want to perform isothermal extrusion using the same extrusion die after the second time, you can perform isothermal extrusion by calling up the first isothermal extrusion parameters.
Since the parameters for isothermal extrusion are difficult to adjust, it is necessary to create a database of parameters to improve productivity.

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5-3 RS232C parameter setting screen

  • Set the communication speed, stop bit, parity, data length and port, and execute [Parameter Set].
  • To start RS232C communication, execute [232C Stat].
  • To stop RS232C communication, execute [232C Stop].

Fig.5-3 RS232C parameter setting screen

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5-4 Adjustment of radiation thermometer

  • Enter the radiation thermometer command in the Send Message text box.
  • Execute the command with [Send Data]. The response from the radiation thermometer is displayed in the Thermometer Received Data text box on the Isothermal Control Screen.
  • If there is a problem with communication, execute [RS232C Reset].

Fig.5-4 Adjustment of radiation thermometer

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5-5 Automatic adjustment of emissivity

Enter the outlet product temperature, calculate the emissivity, and adjust the temperature of the radiation thermometer.

  • Enter the temperature measured with a contact thermometer etc. in [Profile Temperature]
  • Enter the minimum emissivity in [Min emissivity].
  • Enter the maximum emissivity in [Max emissivity].
  • Enter the temperature of the radiation thermometer and the tolerance of the Profile Temperature in [Temperature tolerance].
  • In [timer], specify the emissivity calculation interval.
  • Run Start Calc when the temperature rises to Profile Temperature. The calculation ends when the tolerance reaches Temperature tolerance. You can also end the calculation with [Stop Calc].
  • The calculation history is displayed in [Temperature and Emissivity History].
  • If there is a problem with the communication, execute [RS232C Reset].

Fig.5-5 Automatic adjustment of emissivity

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