【Introduction to 3D Printing】SLS Powder Sintering Technique Guide - How to Orient 3D Models?
The two main factors for success in SLS 3D printing are controlling heat distribution and correct model orientation—
The first factor comes from over a decade of experience and improvements by 3D printer manufacturer engineers.
The second factor largely depends on the knowledge of the daily 3D printer operator.
Before understanding 3D model orientation techniques, let's first understand how SLS laser powder sintering works:
A thin layer of powder is evenly spread on the print platform. A laser then dots the print area and directly sinters the powder. The platform then descends by one layer's height, and the powder spreading and laser process are repeated until printing is complete. After the printer's interior cools, the compacted powder block can be peeled away, and the finished part retrieved.
How to Create a Flawless 3D Model?
This is a common question, but the reality is: there is no 100% perfect model orientation. We must focus on a specific area to get the best results, which means making compromises in other areas. This is true for all SLS or SLA 3D printing technologies. So we recommend following the steps below and combining them with the principles of SLS orientation to ensure your models and applications achieve desired results.
Step One – Identify Key Features
For each model, identify the most important features, such as edge sharpness, smoothness of a certain part, or other details that must be printed perfectly. If there are multiple indicators, prioritize them by importance. The detailed orientation rules described below are often exclusive, which is why prioritization is so important.
Step Two – Select the Most Important Features
At this stage, the model should be rotated according to the rules mentioned below. Once every model you wish to print in the next print job has been rotated, you can proceed to the next step.
Step Three – Position the Model on the Print Bed
In this step, your goal is to fill the print area with models. Some rules need to be remembered, such as accumulating energy at the top and placing elements as evenly as possible.
The principle of uniform model distribution is most important when models are fairly uniform and easily packed in a consistent manner. If 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 volume models at the bottom, as they will release energy during printing and affect other models.
Here are 9 practical SLS orientation tips:
2. Various Holes & Round Holes
Let's reverse it for a moment. Sometimes you need the holes to be perfectly printed. This is important for holes that matter for specific screw or nut designs.
To achieve the best hole presentation, the model should be laid flat, with the hole facing up. The model surface may warp slightly.
3. Dimensions of Specific Surfaces
The blue line in the figure shows the perfect print of the model's edge. Its dimensions can be as accurate as planned, down to a tenth of a millimeter. The orange area may warp slightly upwards, but in this case, it will not affect the object's operation. Do not rotate along the XY axis; keep critical elements flat.
4. Mechanical Strength of Specific Parts
5. Sharp Details
6. Rounded/Smooth Surfaces
On the other hand, we have situations where rounded, smooth surfaces are needed. The model below is a bit more complex. The designer's goal is to achieve the smoothest shape in the blue part. For layers to flow naturally and smoothly without obvious layer lines, the model should be placed facing downwards.
* Smoothness and sharpness are opposite concepts, so if sharp elements should face up, smooth ones should face down.
7. Relative Surfaces
The problem of relative surfaces was briefly described in the first rule. Let's delve deeper into it.
In this model, we've marked the surfaces that need to match another model in blue. As you can see, it has been rotated according to the 45/45 degree rule, and the relative surface is sharper when facing up than when facing down.
8. Moving 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 flat surface may warp slightly, but in thicker parts like nuts, this will not affect print functionality.
9. Small and Fragile Parts
Printing small and fragile parts requires some compromises. In our experience, it is recommended to place them facing downwards. After printing, these parts will have slightly more "pouring" than parts at the top of the model, and their compressive strength will also be stronger.
Additional Rules for SLS Powder Sintering 3D Print Model Orientation
The nine principles 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 bottom of the XY layer.
2. If printing many elements at once, keep them in the middle of the Z-axis, preferably in an inverted pyramid shape.
3. Do not enclose energy within the model; for example, when printing tank-like objects, openings should face upwards.
4. Flat or large-radius curved surfaces placed at small angles on the print bed will show obvious layers.
5. When in doubt, 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 are specifically placed around the bed for this purpose. The laser's role is to add additional energy to melt the powder into the desired shape.
Sinterit printers can print with different materials that have different melting points, so it's important to select the appropriate powder when preparing for printing in Sinterit Studio software. The printer will operate accordingly.
Another way to prevent model warping is to hollow it out. Hollow models are still quite strong, lighter, and the unsintered powder can be easily removed after printing.
Summary
SLS 3D printing technology offers great freedom with few limitations. Following the rules above can make it easier to achieve your goals, reduce errors, and obtain better print results and more practical parts. If needed, you can contact us now to learn more about SLS 3D printers.
Sinterit Nils 480 3D Printer print samples:
Sinterit Lisa X SLS 3D Printer print samples
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