[3D Printing for Beginners] SLS Powder Sintering Techniques Guide - How to Position a 3D Model?

[3D Printing for Beginners] SLS Powder Sintering Techniques Guide - How to Position a 3D Model?

The two main factors for success in SLS 3D printing are controlling heat distribution and proper model positioning .
The first factor comes from the experience and improvements made by engineers at 3D printer manufacturers over more than a decade.
The second factor largely depends on the knowledge of the operators who use 3D printers on a daily basis.


Before learning about 3D model placement techniques, let's first understand how SLS laser powder sintering works :
A thin layer of powder is evenly spread on the printing platform. A laser is used to spot-sinter the printing area and directly sinter the powder. Then, the platform is lowered by one layer, and the powder spreading and laser treatment are repeated until printing is complete. After the printer has cooled down, the compacted powder clumps can be peeled off and the finished product can be removed.
 

How to create a flawless 3D model?
This is a common problem, but the reality is that there is no 100% perfect model placement. To achieve optimal results in one area, compromises must be made in another. This is true for all SLS or SLA 3D printing technologies. Therefore, we recommend following these steps and applying SLS placement principles to ensure your model and application achieve the desired results.

Step 1 – Identify Key Features
For each model, identify the most important features, such as edge sharpness, smoothness of a section, or other details that must be printed perfectly. If there are multiple metrics, rank them according to importance. The detailed placement rules described below are often exclusive, which is why prioritization is so important.

Step 2 – Select the most important features
At this stage, the model should be rotated according to the rules mentioned below. Once each model intended for printing in the next job has been rotated, you can proceed to the next step.

Step 3 – Position the model on the printing bed
In this step, your goal is to fill the printed area with the model. Some rules need to be kept in mind, such as accumulating energy at the top and placing elements as evenly as possible.

The principle of uniform model distribution is most important when the models are fairly uniform and easy to pack in a uniform manner. If the models are very different, the smallest should be placed at the bottom of the workspace, and the largest at the top. We do not want to place large models at the bottom because they will release energy during printing and affect other models.

Here are 9 practical SLS placement tips:



2. Various types of holes & round holes
In this case, the plane will be slightly curved. The second scenario is better because the model itself is tall, so it won't bend too much, and the holes will be printed perfectly.

Let's reverse the order for now. Sometimes you'll need the holes to be printed out perfectly. This is important for holes that are specific to the design of a particular screw or nut.
For optimal hole representation, the model should be laid flat with the hole facing upwards. The model surface may be curved.



3. Dimensions of a specific surface
Therefore, you should be able to deduce that in SLS 3D printing technology, the best prints are often along the X and Y axes. Whenever you're aiming for perfect dimensions, lay the model flat so that the side that should maintain its dimensions is facing up. In other words, arrange circular elements appropriately along the Z-axis.

The blue lines in the image show a perfect print of the model's edges. Their dimensions can be accurate to one-tenth of a millimeter, just as you plan. The orange areas may curve slightly upwards, but in this case, it won't affect the object's maneuverability. Do not rotate on the X and Y axes; keep key elements flat.



4. Mechanical strength of specific parts
Let's imagine a model that needs to be particularly strong in certain areas. This is a necessary consideration for all types of handles and hooks, and what we see here is a structure with hooks that must be strong enough to withstand heavy loads. The model will bend slightly when laid flat on the XY axis (in the orange area), but the key parts marked in blue will be the most durable.



5. Sharp details
If you need to print very sharp shapes, such as text, you should position the model upwards. Even if the model's surface is slightly curved upwards, small details like letters will be sharpest.


6. Rounded/smooth surface

On the other hand, we sometimes need to achieve rounded, smooth surfaces. The model in the image below is slightly more complex. The designer's goal is to achieve the smoothest shape possible for the blue area. To ensure a natural, flowing hierarchy without obvious transitions, the model should be placed downwards.
* Smooth and sharp are opposite concepts, so if a sharp element should be placed upwards, a smooth element should be placed downwards.

7. Relative surfaces

The relatively superficial issues were briefly described in the first rule. Let's delve deeper.

In this model, we've marked the surfaces that need to be matched with another model in blue. As you can see, it's rotated according to the 45/45-degree rule, with the upward-facing portion of the opposing surface being sharper than the downward-facing portion.



8. Movable parts

SLS 3D printing technology excels at printing moving parts. For best results, the axis of rotation should be parallel to the Z-axis. The plane may be slightly curved, but this will not affect printing functionality in thicker parts such as nuts.



9. Small and fragile parts Printing small, fragile parts requires some compromises. Our experience suggests placing them downwards. This results in slightly more pour volume on these parts compared to the top of the model , and also provides greater resistance to pressure .

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Additional rules for placing SLS powder sintered 3D printed models
The nine principles mentioned above are formulated for specific design needs. However, when planning SLS 3D printing, you need to understand some important considerations:

1. Place the first element in the middle and at the bottom of the XY layer.
2. If printing many elements at once, keep them centered on the Z-axis, ideally in an inverted pyramid shape.
3. Do not confine energy within the model. For example, when printing tank-like objects, the opening should face upwards.
4. A flat or large-radius curved surface placed at a small angle on the printing bed will have obvious layers.
5. If unsure, follow the golden rule of 45/45 degree rotation.

Energy distribution
SLS 3D printing takes place in a closed, controlled environment where unsintered powder is heated to a temperature slightly below the material's melting point. Heaters specifically designed for this purpose are positioned around the bed. The laser's role is to add additional energy to melt the powder into the desired shape.

The Sinterit printer can print using different materials with varying melting points, so selecting the appropriate powder when preparing for printing in the Sinterit Studio software is important. The printer will then operate accordingly.

Another way to prevent the model from warping is to hollow it out. Hollow models are still quite strong, lighter, and the unsintered powder can be easily removed after printing.


Summarize
SLS 3D printing technology offers a high degree of freedom with few limitations. Following the rules mentioned above makes it easier to achieve your goals, reduce errors, obtain better print results, and produce more usable parts. Contact us today for more detailed information about SLS 3D printers .

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Finished products printed by the Sinterit Nils 480 3D printer :








Finished products printed by Sinterit Lisa X SLS 3D printer

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