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en:grafische_darstellung_der_ergebnisse:aufschmelzverlauf [2024/11/17 19:16] – neelesten:grafische_darstellung_der_ergebnisse:aufschmelzverlauf [2025/09/05 10:25] (aktuell) – neelest
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 ======Melting profile====== ======Melting profile======
  
-The graph of the melting process (ASV) visualises the results of the calculations on the melting behaviour during the plasticising process in the single-screw extruder. The screw length is plotted on the x-axis, while the y-axis represents the dimensionless solid bed width (Y). This is defined as the ratio of the solids bed width to the channel width of the screw flight and can assume values in the range from 0 to 1. +-> [[en:berechnungen:aufschmelzverlauf|To the calculation bases]]
-=====Interpretation of the curves:===== +
-====Plastifizierphase==== +
-  *         The dimensionless solid bed width is represented by the **red curve**. +
-  *         The melted mass fraction is represented by the **blue curve**. +
-====End of the standstill phase (PSI)==== +
-  *         The dimensionless solid bed width is represented here by the **red curve**. +
-  *         The melted mass fraction is shown by the **blue curve**.+
  
-{{ :grafische_darstellung_der_ergebnisse:rex171_grafisch_en_005.png?nolink |}}+===== Illustration of the melting process =====
  
-====Melting curve front/rear (PSI)==== +{{ :grafische_darstellung_der_ergebnisse:rex171_grafisch_en_005.png?nolink&1000 |}}
-The PSI-specific menu item Compare screw positions displays the melting curve for the front and rear screw positions. The same applies to the display of the two curves as for the normal melting curve. The only difference is that the two curves are plotted one below the other in two graphs. The screw moves between the front and rear position during a cycle in the injection moulding process. For this reason, this menu item allows you to view the melting curves calculated for the two screw positions in one graph. +
-=====Peculiarities of the melting process=====+
  
-During the plasticising process, characteristic jumps occur in the melting process, which can be caused by various factors:+=====Interpretation of the curves=====
  
-  * **Cyclical interruptions in screw rotation**: These interruptions, especially in the standstill phase, can lead to sudden changes in the melting rate, which can be seen in the graph by abrupt jumps. +  *   ** Red curve**: The red curve represents the solid bed width. The curve starts at the location of the melt vortex formation with a value of 1. This means that the solid bed occupies 100% of the channel width at the start of the melting process. The solid bed width can increase as part of a compression zone or another reduction of the channel cross-section (start of a barrier zone, change to a 2-start screw zone, reduction of the channel gradient). If the melting model changes to disperse melting (e.g. due to a shearing or mixing section), the solid bed width curve ends here. 
-  * **Geometry changes between zones**: Changes in screw geometry, such as a change in pitch or number of flights between zones, will result in a variation in flight width. This variation directly influences the Y-value (dimensionless solid bed width), which can lead to a sudden increase or decrease.+  *   ** Blue curve**: The blue curve represents the melt fraction. In contrast to the solid bed width, the melt fraction can only increase. If the melt proportion reaches the value 1 (=100 %), the entire plastic has melted. When switching to disperse melting, the melting speed can increase or slow down depending on the circumstances.
  
-{{ :grafische_darstellung_der_ergebnisse:rex171_grafisch_en_014.png?nolink |}}+===== Analysis of the melting process =====
  
-=====Dangers with poorly melting polymers===== +  *   **Solid bed width (red curve)**:  In principle, a high solids bed width is advantageous for the melting rate. However, the solids bed width must not exceed the value of 1, as this would mean that only solids are present in the channel. In this case, the excess solids will first change into the melt channel within a barrier zone. If the solids content in the melt channel also reaches the value 1 or the solids bed width reaches the value 1 outside a barrier zone, the melting calculation is cancelled. 
- +  *   **Melt fraction (blue curve)**: The melting end should be in good time before the end of the screw so that thermal homogenisation can take place within the remaining screw length. The curve shows which zone has what effect on the melting process. 
-For polymers with a high enthalpy that are difficult to melt, undesirable effects can occur in conjunction with early or strong compression. A particular risk is that the Y-curve reaches the value 1, which means that the solid bed width occupies the entire channel width. This occurs when the polymer expands strongly under the strong compression. If the value Y = 1 is reached, the calculation is automatically cancelled at this point. +  *   **In degassing extruders**, the melting end should be **before** the degassing.
-=====Melting process for degassing screws===== +
- +
-In screws that have a degassing zone, the melting process is calculated up to the degassing opening. After this zone, the melting process can only continue if the melted granulate is in a sufficiently small state so that it can easily pass through the gap in the shear elements. However, if the granulate is too large in diameter, it will block the shear elements and the melting process will also be cancelled at this point. +
- +
-=====Representation of the start and end of melting===== +
- +
-Two crucial points are emphasised in the ASV diagram: +
- +
-  * The **start of melting**, which marks the place where the first melt vortices occur in the solid bed. +
-  * The **melting end**, which does not necessarily mean that the entire material is completely melted. This point marks the end of the calculation process, which is achieved either by complete melting or by one of the conditions mentioned above (e.g. Y = 1 or blockage of the shear parts). +
- +
-It is important to note that the actual end of melting is not always an indication that the entire material flow has been completely plasticised. Instead, the graph shows the last point for which the calculation could still be performed validly.+
  
 ===Further topics=== ===Further topics===
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   * [[en:grafische_darstellung_der_ergebnisse:scherdeformationsgradient_und_schergeschwindigkeit]]   * [[en:grafische_darstellung_der_ergebnisse:scherdeformationsgradient_und_schergeschwindigkeit]]
   * [[en:grafische_darstellung_der_ergebnisse:schlepp-druckstroemung]]   * [[en:grafische_darstellung_der_ergebnisse:schlepp-druckstroemung]]
 +  * [[faserlaengenabbau|]]
 +  * [[faserlaengenverteilung|]]
 +  * [[spannungsanalyse|]]
 +  * [[kennlinienfeld|]]
 +  * [[entgasung|]]
 +  * [[zykluszeit|]]
   * [[en:grafische_darstellung_der_ergebnisse:kurzbericht]]   * [[en:grafische_darstellung_der_ergebnisse:kurzbericht]]
   * [[en:grafische_darstellung_der_ergebnisse:langbericht]]   * [[en:grafische_darstellung_der_ergebnisse:langbericht]]