Laser Powder Bed Fusion Distortion Simulation in Ansys Mechanical

Hi everyone, this is MingYao from OZEN Engineering. In this video, I'll be looking at how to simulate a laser powder bed fusion process. This is a 3D printing process.

We're going to simulate the process of laser powder bed fusion, which is using powder, fusing powders of metal with lasers to make very complex shapes. ANSYS has made this extremely easy to do, so let's give it a try.

I'll start with this nozzle geometry, and in the custom analysis system section, we have two options: laser powder bed fusion, thermostructural, or inherent strain.

Thermostructural actually models the thermal process during the laser powder bed fusion process and uses that temperature to calculate the inherent strain as we build up the laser. We're going to model the deposition of the 3D printing process layer by layer in this analysis.

I'm going to start up ANSYS Mechanical, and we're going to run some analysis. Here's our model. It's important to make sure that the model is oriented. The build direction is in the Z axis, which makes the simulation easier. I'm modeling the base plate as well as the part I want to print.

So, I'm going to start with the base plate, and I'm going to run some analysis. I'm modeling the base plate as well as the part I want to print. So, there is a very helpful add-on called Laser Powder Bed Fusion Setup Wizard. We're going to use this add-on to do our analysis. Super easy.

Select the part. This is the part we want to build. We are not including any support geometry, and this is the base part. There's no non-built geometry to be included here, no powder geometry, no symmetry defined. So that, you can see, is setting up my analysis as we go.

I have a few different options for meshing. The easiest, fastest one is to do a voxelized part. So, I'm going to, depending on the build height of the build process, you can see that it gives you a lot of description on what the different type is, what different types of meshing can be used.

There's Cartesian, layer tetrahedral, which gives you closely match the geometric shape. Or voxel, which is fast, and reduces material property, with reduced material property, to do fast analysis. Element size is determined by the mesh height, etc.

So, I'm going to specify some sizes based on my model here. Generate the mesh, and let's go. Okay. So, I'm going to do a voxel for the part I'm building, as well as the base here. Select the material. ANSYS has a wide range of commonly used materials.

So let's build Inconel on stainless steel, including nonlinear effects. You can add additional materials as well. Using a Harris Strain would allow you to put in a strain temperature, but here we're not going to use a Harris Strain.

Which means we're going to deposit this model, put in the deposition thickness, and actually model the deposition of the voxel layers.

You can see there's a lot of machine settings for the deposition thickness, hash spacing, scan speed, how long to wait between layers, dwell time, as well as the number of heat sources. So, you can change any of these. I can go from one to two, or four, if I wanted to. I can hit enter.

I can adjust the scan speed. I can reduce the dwell time, or time between layers, to five seconds, for example. So let's change some of these, make it hot.

Build condition, you can specify your preheat temperature, gas flow temperature, your convection coefficient, powder convection coefficient, cool down information, removal, do you want to do heat treatment or base removal.

For base removal, you have the option of instantaneous or directional removal. So I'm going to do instantaneous. So I'm going to do instantaneous. And we're going to look at the distortion of the part after it's been removed from the base.

With the amount of power these things generate, the part is typically welded to the base, so we want to see what the shape is.

Thermal boundary conditions, so this is a base thermal boundary condition, so we're going to say that we're going to heat up the bottom of the base, or we can select multiple surfaces like this. And assign all of these areas to the base. So we're going to do heat treatment.

So we're going to do heat treatment. And assign all of these areas to the base temperature. Structural, so let's say we're going to fix this part. We want to specify three points so that the part doesn't go fly off into space for being under constraint in the static analysis.

So you can just pick any three nodes on the part itself. You can see when I switch to node select, I can pick the nodes that I want. So any nodes that I want. So I can pick the nodes that I want. So I can pick the nodes that I want. So I can pick the nodes that I want.

So I can pick the nodes that I want. And then the nodes will do. Additional setup gets completed. You can choose to set up calibration or not. It tells you some information about how to do calibration. This will obviously make the simulation more accurate.

It'll calibrate it to your particular machine. Go ahead and finish this. And that's it. And that's it. So that's all you need to do to model laser powder bed fusion process to look at the deformation shape. There are numerous options for correction as well, or add-ons.

There's distortion compensation, so if you want the shape such that after the printing stops and you cut it off, you wanted to distort to the shape you want, you can do a whole distortion compensation. I'll show that another day.

You can see there are numerous other options in addition to the laser powder bed fusion process. We also have a direct energy deposition as well as a sintering simulation. But without further ado, let's go ahead and run the simulation on my laptop using four quarters. So small simulation.

As your model gets larger with smaller features, you need smaller voxels. That'll certainly benefit from having a larger simulation workstation. We're going to execute the transient thermophysics and then do a series of statics or structural simulations to look at a deformed shape.

Okay, once the simulation has completed, you get this type of results where you can look at the build-up process for the thermal analysis. You can see we're heating up layer by layer, looking at the temperature and residual temperature as you build up the part.

There's a build-up step and the cool-down step. On the structural deformation side, you can see the amount of residual distortion is 0.6 millimeters.

If I look at the way this is built up, you can see the build-up process with the residual deformation, the cool-down step, finally the removal of the base. We can look at things like stress and any other quantity of interest, stress strain, etc.

Again, building step, followed by cool-down, followed by base removal. So that's a quick demonstration of how we can set up a laser powder bed fusion additive material process. We can also use the manufacturing simulation predicting residual distortion.

As I mentioned earlier, we're able to also take that many steps further by looking at the additive process, generating STLs. We can look at distortion compensation and a variety of other techniques. Some of those I'll show in later videos.

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