Specific Process Knowledge/Back-end processing/Polymer Injection Molder/Nozzle: Difference between revisions

Latest revision as of 15:22, 16 January 2020

Nozzle/tower settings

On the 'Nozzle' screen it is possible to adjust settings for how the nozzle moves back and forth during the injection molding cycle and how it presses against the inlet port of the tool:

Movement of the tower (nozzle) is controlled on the 'Tower' screen.

Advance profile: This parameter controls the speed profile as the tower moves forward to press the nozzle against the mold inlet port. The default settings work fine for most applications.

Retract profile: This parameter controls the speed profile as the tower moves backwards and retracts the nozzle from the mold inlet port. Again, the default settings will work fine for most applications.

Nozzle stroke: This setting controls how far the nozzle moves back between shots. Usually a value between 40 - 100 mm will work fine. If you experience problems with long fine (thin) threads of polymer from the sprue of your samples, it may help to increase the nozzle stroke a little. This will move the nozzle tip further away from the inlet port between injections and thus reduce heat-up of the inlet port. The temperature of the inlet port will also influence polymer flow during injection.

Scrolling down will reveal a few more important settings regarding nozzle control:

Scrolling down on the 'Tower' screen reveals additional nozzle settings.

Force build-up time: This setting defines how long time the machine has to build up the nozzle contact force. A value of 0,2-0,5 sec works fine for most applications

Contact force: This parameter defines how hard the nozzle presses against the inlet port during injection and after/holding pressure. Please do not increase this value above 15 kN without contacting DTU Nanolab as this may damage the nozzle tip or the mold inlet port! For polymers that undergo significant shear thinning (such as PP and PE) contact forces around 14 kN can be required (depends on injection speed) while lower contact forces (10 - 12 kN) will be sufficient for most other polymers.

Delay time retraction: In some cases it may be desirable to maintain the inlet port at high temperature after injection and holding/after pressure. In this case a delay can be entered here (usually 5 - 10 seconds is fine). Keep in mind that if the sum of 'Plasticizing delay time' described earlier and the 'Delay time retraction' on this page exceeds the cooling time, this will cause a delay in the injection molding cycle (thus increasing the effective cooling time).

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 == Nozzle/tower settings ==
-Once the mold has opened, the sample must be ejected from the mold to enable the robot to pick up the sample. This is done by pushing out ejector pins from the mold, which in turn will push out the sample. When samples are picked up reliably by the robot it is usually not necessary to adjust these settings. The settings for the ejector demolding settings are can be found on the 'Mold open' screen:
+On the ''''Nozzle'''' screen it is possible to adjust settings for how the nozzle moves back and forth during the injection molding cycle and how it presses against the inlet port of the tool:
-[[File:09-tower.png|600px|thumb|left|Ejector pin parameters are found on the 'Ejector' screen.]]
+[[File:12-nozzlemove.png|600px|thumb|left|Movement of the tower (nozzle) is controlled on the 'Tower' screen.]]
 <br><br>
-*'''Advance profile''': These settings control how the ejector pins advance. The advance speed (green curve) and advance force (red curve) can be edited using the '=' or arrow buttons or by editing individual points on the graph. Generally it is not advisable to increase the advance speed above a few mm/s. And importantly: '''Under no circumstances should the advance force be increased above 8 kN!''' Otherwise the ejector pins may be damaged (bend or even break)! It is recommended to keep the advance force at 6 kN or below and only increase it to 8 kN if samples cannot be demolded reliably.
+*'''Advance profile''': This parameter controls the speed profile as the tower moves forward to press the nozzle against the mold inlet port. The default settings work fine for most applications.
 <br>
-*'''Retract profile''': These parameters control the ejector pin retraction and is edited in the same way as described for the advance force.
+*'''Retract profile''': This parameter controls the speed profile as the tower moves backwards and retracts the nozzle from the mold inlet port. Again, the default settings will work fine for most applications.
 <br>
-*'''Ejector stroke position''': These settings control the positions of the ejector pins in the retracted and advanced position. It is recommended to leave the 'Ejector retracted position' around 25,6 mm. The 'Ejector pin advanced position' can be fine tuned if you have problems with unreliable robot pickup, but 56,0 mm usually works well. If you make changes to the 'Ejector advanced position' make sure to adjust the robot take-off position as well. Otherwise you risk missing the sample or that the sample is pushed hard into the robot arm and thus risk damaging both the robot and your samples.
+*'''Nozzle stroke''': This setting controls how far the nozzle moves back between shots. Usually a value between 40 - 100 mm will work fine. If you experience problems with long fine (thin) threads of polymer from the sprue of your samples, it may help to increase the nozzle stroke a little. This will move the nozzle tip further away from the inlet port between injections and thus reduce heat-up of the inlet port. The temperature of the inlet port will also influence polymer flow during injection.
-<br><br><br><br><br><br><br><br>
+<br><br><br><br><br><br><br><br><br><br><br><br><br>
-Scrolling down will reveal a few more important settings regarding part removal. The most important are:
+Scrolling down will reveal a few more important settings regarding nozzle control:
+<br>
-[[File:07b-eject.png|600px|thumb|left|Scrolling down on the 'Ejector' screen reveals part removal settings.]]
+[[File:09-tower.png|600px|thumb|left|Scrolling down on the 'Tower' screen reveals additional nozzle settings.]]
-<br><br><br><br>
+<br><br><br><br><br>
-*'''Ejector shake counter''': If samples are difficult to release from the moving part of the mold, this setting makes it possible to move ejector pins in and out several times to help release the sample in order for the robot to be able to grab the sample. Usually leaving it at 1 works fine, but in some cases it may help to increase the shake counter to 2 or 3.
+*'''Force build-up time''': This setting defines how long time the machine has to build up the nozzle contact force. A value of 0,2-0,5 sec works fine for most applications
 <br>
-*'''Ejector shake position''': This position defines the position the ejector pins move to during shake procedures.
+*'''Contact force''': This parameter defines how hard the nozzle presses against the inlet port during injection and after/holding pressure. '''Please do not increase this value above 15 kN without contacting DTU Nanolab as this may damage the nozzle tip or the mold inlet port!''' For polymers that undergo significant shear thinning (such as PP and PE) contact forces around 14 kN can be required (depends on injection speed) while lower contact forces (10 - 12 kN) will be sufficient for most other polymers.
 <br>
-*'''Mold pause time''': This setting is often used when running Variotherm-processes where a delay is required to give the mold time to heat back up to the desired mold temperature before the next cycle can be started. The required time will depend on how cold the mold is at this point in the cycle and the mold temperature setpoint. If the mold has cooled down to 40°C and needs to heat up to 140°C it will usually take several minutes to do so (usually 3-4 minutes). When running constant mold temperature processes, the mold pause time can be set to zero.
+*'''Delay time retraction''': In some cases it may be desirable to maintain the inlet port at high temperature after injection and holding/after pressure. In this case a delay can be entered here (usually 5 - 10 seconds is fine). Keep in mind that if the sum of 'Plasticizing delay time' described earlier and the 'Delay time retraction' on this page exceeds the cooling time, this will cause a delay in the injection molding cycle (thus increasing the effective cooling time).