# Homework Session 1 - Heat Distribution within the Extruder

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## Homework Submission

Submitting all three homework assignments will qualify you for a Certificate of Completion.

Homework 1 - Deadline: Date, 30h of June, 11:59 pm

Homework Submission Form

## Exercise

Our aim is to investigate the heat transfer through the assembly to get insights about the temperature distribution within the extruder. This will help us on the one hand to understand the extrusion process itself and in addition also help us to verify the position of the temperature sensor for the closed-loop control system of the extruder.

In order to help us to get a better understand about this case, we will now perform a thermal simulation regarding to a parametric model at a realistic boundary conditions.
You can modify the parameters of the CAD model as much as you want to create your very own designs, then check and compare the different results.

First, you need to import CAD model from Onshape. To do this, simply click on this link.

Then play with those variables as you wish.

Instructions For The Parametric Model

Take a quick look inside of this model at Onshape , you can see two files, one is the original one as the main ( you can directly import this one to do the first simulation). And the other one named with Set Parameters which contains 5 variables, that are all set initially with a default value of zero, waiting for you to do the modification. These 5 variables together, defines the diameter values and the thickness of the insulator plates, therefore the space gaps between each other. To change the variablesâ€™ value, just double click on the variable, set it to your value, then check.

To modify these 5 variables one by one, you can see the thickness is changing.

One extreme thick case could be (as we present for the second comparing model in this tutorial):

• inner_cylinder : 0.0025
• outer_cylinder : 0.003
• lower_plates : 0.003
• middle_plate : 0.0035
• upper_plate : 0.0035
• PTFE_cylinder : 0.0007

## And modify within these limit values, it can prevent you from the failure of the model building. inner_cylinder : 0.0005 - 0.0025 outer_cylinder : 0.0008 - 0.003 lower_plates : 0.0003 - 0.003 middle_plate : 0.001 - 0.0035 upper_plate : 0.0008 - 0.0035 PTFE_cylinder : 0.0007 - 0.001

Once youâ€™re satisfied with your CAD model, simply hit import button, to import the geometry from Onshape into your SimScale workspace. It may takes several minutes.

### Meshing

• Click on the New Mesh button to start creating mesh.

• Select Tet-dominant from the list and choose the following settings
• Specify the desired mesh order: First order
• Fineness: 3 - Moderate
• Number of computing cores: 4
• Save the settings by clicking on Save button.

In order to get a better mesh, we need to further define mesh refinements at our contact surfaces (see how we define refinements at Tet-Dominant algorithm: Advanced tutorial.

• Click on Mesh Refinements button to start creating it.

• In the refinement settings, make sure the refinement type is Local element size
• Click on Add selection from viewer to assign those contact faces to the refinement (in total you should have 12 faces assigned).
• After that, save the settings by clicking on the Save button.

### Simulation Setup

• Switch to the Simulation Designer by clicking the related button in the main ribbon bar and then click on New button to create a new simulation set up.
• Give the simulation set up a suitable name - Simulation 1(optional)

• Since we are interested in studying the heat distribution of extruder, select Heat transfer - advanced, Steady - state under Thermostructural analysis, and Save.

Next step is to specify the mesh to perform your simulation.

• Click on the Domain item in the project tree and select your Extruder_Mesh under the Available Meshes. Donâ€™t forget to save your selection.

Since we are simulating an assembly of differnt parts, it is necessary to define the interactions within the assembly. We will therefore define Contacts which covers the physical interaction between parts. Without the contacts, the solver wonâ€™t have any information about how different parts are connected to each other.

## Important Note: During the webinar we showed a slightly different workflow for this: Instead of creating Topological Entity Sets first, we will directly assign the faces to the contacts

• Click on the Contacts sub-item in the project tree. This will open a new middle column windows where you can manage existing and create new contacts.

• Next, click on the New button to create a new contact definition.

• For every contact definition given below, select the corresponding faces to assign the Master/Slave relations and click on Add Selection from viewer option at the bottom of the Entity section, after that, as always, Save the settings.

Contact #1 - Heater-nozzle-block and the Nut
This contact is necessary to connect the heat block and the nut with the nozzle.

• Specify the following parameters:
• Name: change default Contact 1 to Heater-nozzle-block & Nut contact
• Tolerance: 0.00001
• Type: Bonded Contact
• Master entity: faceGroupOnGeoFaces_53 (volumeOnGeoVolumes3), faceGroupOnGeoFaces_57 (volumeOnGeoVolumes3)
• Slave entity: faceGroupOnGeoFaces_41 (volumeOnGeoVolumes2), faceGroupOnGeoFaces_43 (volumeOnGeoVolumes2)

Contact #2 - The Nozzle, the PTFE tube and the Insulator
This contact is necessary to connect the insulator with both the nozzle and the tube.

• Specify the following parameters:
• Name: Nozzle & PTFE & Insulator contact
• Tolerance: 0.00001
• Type: Bonded Contact
• Master entity: faceGroupOnGeoFaces_35(volumeOnGeoVolumes1), faceGroupOnGeoFaces_54 (volumeOnGeoVolumes3)
• Slave entity: faceGroupOnGeoFaces_0 (volumeOnGeoVolumes0), faceGroupOnGeoFaces_9(volumeOnGeoVolumes0)

Contact #3 - The PTFE tube and Nozzle

• Specify the following parameters:
• Name: PTFE & Nozzle contact
• Tolerance: 0.00001
• Type: Bonded Contact
• Master entity: faceGroupOnGeoFaces_63(volumeOnGeoVolumes3)
• Slave entity: faceGroupOnGeoFaces_37 (volumeOnGeoVolumes1)

#### Materials

Now we define and assign material properties to the different parts.

• Click on the Material item in the project tree. This will open a middle column menu where you can edit and create materials and assign them to volumes. Click on the New button

Material #1 - Aluminum
use import from material library function, we can assign Aluminum to the mesh volume of heater block

Material #2 - Steel
similarly, assign Steel to the nut

Material #3 - PTFE
define PTFE material properties for the tube:

Material #4 - PEEK
similarly, define PEEK material properties for the insulator:

#### Boundary Conditions

Now you can start to specify the physical behaviour of the extruder and its interaction with the environment by defining the Boundary Conditions for all faces of the mesh.

• Click on the Boundary Condition item in the project tree which will open a new column in the middle of the windows. Here you can see an overview of all boundary conditions which are applied to your mesh.

First we will specify the temperature boundary condition to describe the heat exchange with the environment through the outer surfaces.

• Click on Heat Flux Loads under Boundary Conditons in the project tree and then click on New button.

This will add a sub-item to the project list and open again a new window where you can define the boundary condition. Here you can define a name for the boundary condition, choose the type and assign it to faces by using the list below.

• Specify the following parameters:
• Name: Heater
• Type: Surface heat flux
• qs [W/mÂ˛]: 4023.8
• Please map this boundary condition to the bigger hole of the heat block: faceGroupOnGeoFaces_59 (volumeOnGeoVolumes_3). To assign the face graphically, click on Add selection from viewer after selecting the corresponding face.

• Specify the following parameters:
• Name: Air Convection
• Type: Convective heat flux
• Reference temperature [k]: 297.15
• h[W/(mÂ˛K)]: 10
• Map this boundary condition to all surrounding surfaces of the assembly (except contacts and the surface where you applied the resistor boundary condition). Use Add selection from viewer button to assign the faces graphically as in the previous boundary condition.

• Finally Save the settings after assigning all the faces to the bondary condition.

#### Simulation Control

Before we can start our simulation, we have to define the settings of our simulation under Simulation Control.

• Specify the following parameters:
• Number of computing cores: 4
• Maximum runtime: 3600

#### Result Control

despite the existing temperature result field, letâ€™s add another item of heat flux to the Result Control and save it.

#### Simulation run

• To start the simulation, click on the Simulation Run item in the tree and click on the New button at the top of the middle column menu. This will create a snapshot of your simulation settings as a new sub-item.

.

The run will take approximately 12 minutes to complete. After the run is finished, you will see Finished status at the Job Status corner below.

## For simulating other cases with various CAD models, import another geometry and create a new mesh and simulation. You can skip some manual work by simply right clicking on the former mesh to make a duplicate of it (as well as the simulation setting up), then within this duplicated mesh, change the base geometry from your former geometry to the new one ( for simulation, change the mesh domain ). But do remember that when it comes to entity selections, for example, the mesh refinements, materials and the contacts defines, you have to assign them again.

### Post-processing

• Once your simulation is finished, click on the Post-Processor button in the main ribbon bar and then on Solution field to view the result.

To take a look inside the assembly, we can apply a Clip filter.

• Click on Add Filter button and then select Clip from the list.

• You can control the clip plane by specifying normal and origin.

• Select temperature [point data] in field [1] to view the temperature distribution.

• Select toggle color bar to view the temperature scale [2].

• You can hide the clip plane by unchecking the Show Plane option [3].

Finally we can add the second simulation result to the post-processor, by right-clicking on the Solution fields and selecting Add result to viewer.
In order to be able to show both results at once without overlap, we add a Transform filter which translates the second one by 0.05m in y direction by putting 0.05 into the translate field of the Property Panel.

Now you can compare these two simulation results easily and clear.

### Appendix:

'3D Printer Extruder' simulation project by Deluxee
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#5

Am I missing something???

#6

Hi @debroy84863568,
Yes, for the Air Convection Boundary Condition, we only want to include all the outer large surfaces that exposed in the air, so the inner and narrow surfaces along the tube and nozzle are not included in this case.