Unterschiede

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--- en:berechnungen:aufschmelzverlauf [2024/11/17 19:38] – [Conventional melting] neelest
+++ en:berechnungen:aufschmelzverlauf [2025/07/03 13:34] (aktuell) – cschall
@@ Zeile 1: / Zeile 1: @@
 ======Melting profile======
+-> [[en:grafische_darstellung_der_ergebnisse:aufschmelzverlauf|For a graphical representation of the melting process]]
 The melting process is divided into three sections. \\
-  - First, the melting calculation is performed, which calculates the location of the melt vortex formation (OSW).
+  - First the location of the melt pool formation (OSW) is calculated
-  - ‘Conventional’ melting begins from the location of the melt vortex formation
+  - ‘Conventional’ melting begins from the location of the melt pool formation
   - From a certain switching point, conventional melting **can** change to disperse melting
 The three sections are described below.
-===== Melting calculation =====
+===== Calculation of melt pool formation location =====
-The content is currently being processed and will be made available shortly. Please be patient.
+The location of the melt pool formation describes the distance from the start of the channel to the position where the melt pool forms. For calculating the melting length, it is assumed that the melt film between the barrel and the solid bed gradually increases. The required melt film thickness for the formation of the melt pool corresponds to the average melt film thickness as determined by the conventional melting calculation. Due to the porous structure of the solid bed, the initial heat flux from the barrel is reduced. The lower the barrel temperature and the bulk density of the material in the channel, the further downstream the location of melt pool formation will be.
 ===== Conventional melting =====
@@ Zeile 18: / Zeile 20: @@
 {{ :berechnungen:aufschmelzverlauf:abb_konv_aufschmelzen_01_en.svg?nolink&500 |}}
-The solid bed is deposited on the non-driving (passive) flank of the screw channel. As the plastic melts, it is carried away to the active flank of the screw channel by the relative movement between the screw and barrel and by the ‘scraping’ by the screw flights. This creates a melt vortex, which simultaneously presses the solid bed against the non-driving flank. \\
+The solid bed is deposited on the non-driving (passive) flank of the screw channel. As the plastic melts, it is carried away to the active flank of the screw channel by the relative movement between the screw and barrel and by the ‘scraping’ by the screw flights. This creates a melt pool, which simultaneously presses the solid bed against the non-driving flank. \\
-As the melting process continues, the solids bed becomes narrower, but retains its height due to the pressure of the melt vortex. The solid bed width therefore decreases as a result of the melting process. If the channel geometry remains constant, the solids bed width decreases continuously. If the channel volume is reduced (wider bars, multi-pass zone, lower channel pitch, limitation to the solids channel in the case of a barrier screw), the solids bed width increases, as the solids volume flow remains constant.
+As the melting process continues, the solids bed becomes narrower, but retains its height due to the pressure of the melt pool. The solid bed width therefore decreases as a result of the melting process. If the channel geometry remains constant, the solids bed width decreases continuously. If the channel volume is reduced (lower channel depth, bigger flights, multi-flight section, lower channel pitch, restriction to the solid channel in barrier screws), the solids bed width increases, as the solids volume flow remains constant.
 The dimensionless solids bed width $y$ shown in REX is normalised to the channel width: $y = \frac{solids bed width}{channel width}$
-==== Clogging of the screw ====
+==== Plugging of the screw ====
+Excessive compression of the screw channel can lead to plugging of the screw.
+If the blockage occurs outside a barrier or maillefer section, the melting calculation is aborted since no further melting progression can be determined. In such cases, it is recommended to use the calculation option “Currently under development: Iterate throughput in case of plugging”, which iteratively adjusts the throughput until a process state without plugging is achieved.
-Excessive compression of the screw channel can cause the screw to clog.\\
+If the solid channel becomes blocked within a barrier or maillefer zone, the excess material is redirected into the melt channel. In the melt channel, a dispersed melting behavior is assumed.
-If the screw clogs outside a barrier or maillefer zone, the melting calculation is cancelled as no further melting process can be calculated. In this case, the calculation option ‘**Currently in progress: Iterate throughput if clogged**’ is recommended, which iterates the throughput until a process is reached that no longer clogs.
+If both the solid and melt channels reach a solid bed width/solid content of $y>1$, the calculation is terminated. If the option “Currently under development: Iterate throughput in case of plugging” is selected, the throughput will be iteratively adjusted to a level at which the solid channel does not become plugged, thus preventing any solid material from entering the melt channel.
-If the solids channel within a barrier or maillefer zone becomes blocked, the excess plastic is transferred to the melt channel. If both the solids channel and the melt channel reach a solids bed width $y > 1$, the calculation is cancelled. If the calculation option ‘**Currently in process: Iterate throughput if clogged**’ is selected, the throughput is iterated at which the solids channel does not clog so that no solids transfer into the melt channel.
 ==== Degassing screws ====
-If a degassing extruder is calculated, there are three options in the event that the plastic has not yet completely melted at the start of degassing:
+If a degassing extruder is calculated, there are three options in the event that the plastic has not yet completely melted at the start of degassing (s. [[en:berechnungen:einfache_berechnung|regular calculation]]):
-  - **Melting up to degassing zone**: The melting calculation is cancelled at the start of the degassing zone
+  - **Melting up to degassing zone**: The melting calculation is cancelled at the start of the degassing section
-  - **Melting from degassing zone conventional**: After the start of the degassing zone, the melting process continues to be calculated using the conventional melting model.
+  - **Melting from degassing zone conventional**: After the start of the degassing section, the melting process continues to be calculated using the conventional melting model.
-  - **Melting from degassing zone dispersed**: After the start of the degassing zone, the melting process is calculated further using the dispersed melting model.
+  - **Melting from degassing zone dispersed**: After the start of the degassing section, the melting process is calculated further using the dispersed melting model.
 ==== Special features in PSI ====
@@ Zeile 40: / Zeile 44: @@
 <dl>
-<dd>$\text{Number of downtimes} = \frac{\text{Channel volume of the leg}}{\text{Dosing volume}}$\\ \\
+<dd>$\text{Number of downtimes} = \frac{\text{Channel volume of the screw}}{\text{Dosing volume}}$\\ \\
-$\text{Total downtime}= \text{Number of downtimes} * \text{Total downtime}$\\ \\
+$\text{Total downtime}= \text{Number of downtimes} * \text{downtime}$\\ \\
-$\text{Normalised standstill time} = \frac{\text{Total standstill time}}{\text{Total throughput time}_{\text{Screw}}}$\\ \\
+$\text{Normalised downtime} = \frac{\text{Total downtime}}{\text{Residence time}_{\text{Screw}}}$\\ \\
-$\text{downtime in interval}=\text{leadtime}_{\text{interval}}*\text{standardised downtime}$</dd>
+$\text{downtime in interval}=\text{Residence time}_{\text{interval}}*\text{Normalised downtime}$</dd>
 </dl>
@@ Zeile 54: / Zeile 58: @@
 ==== Calculation of the melt fraction ====
-The melt fraction is calculated from the current normalised solids bed width $y$, the current channel width $b$, channel height $h$, number of passes $i$, and the current solids bed velocity $v_{fz}$ in relation to the channel geometry at the location of the melt vortex formation and the solids bed velocity $v_{fz,OSW}$ present there
+The melt fraction is calculated from the current normalised solids bed width $y$, the current channel width $b$, channel height $h$, number of channels $i$, and the current solids bed velocity $v_{fz}$ in relation to the channel geometry at the location of the melt pool formation and the solids bed velocity $v_{fz,OSW}$ present there
 <dl>
 <dd>$\text{melt fraction} = 1 - y * \frac{h*b*i*v_{fz}}{(h*b*i*v_{fz})_{OSW}}$</dd>
@@ Zeile 90: / Zeile 94: @@
 ===Further topics===
   * [[en:berechnungen:einfache_berechnung|]]
+  * [[en:berechnungen:prozess_iterieren]]
   * [[en:berechnungen:durchsatz|]]
   * [[en:berechnungen:druckverlauf|]]
@@ Zeile 95: / Zeile 100: @@
   * [[en:berechnungen:temperaturverlauf|]]
   * [[en:berechnungen:leistung_und_schubspannungen|]]
+  * [[en:berechnungen:schergeschwindigkeit]]
   * [[en:berechnungen:verweilzeit|]]
   * [[en:berechnungen:verweilzeitverteilung|]]