【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 3D printer operator in daily use.
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, and a laser beam targets and directly sinters the powder within the print area. Then, the platform lowers by one layer's height, and the powder spreading and laser process are repeated until printing is complete. After the printer cools down, the compacted powder block can be removed to retrieve the finished product.
How to achieve 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 achieve the best results, which means making compromises in other areas. This is true for all SLS or SLA 3D printing technologies. Therefore, we recommend following the steps below and combining them with SLS orientation principles to ensure ideal results for your model and application.
Step 1 – Identify critical features
For each model, identify the most important features, such as the sharpness of edges, the smoothness of certain parts, or other details that must be perfectly printed. If there are multiple criteria, prioritize them by importance. The detailed orientation 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 every model you wish to print in the next print job has been rotated, you can proceed to the next step.
Step 3 – Orient the models on the print bed
In this step, your goal is to fill the print area with models. 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 even model distribution is most important when models are fairly uniform and easy to pack 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 the printing process and affect other models.
Here are 9 practical SLS orientation tips:
2. Various Holes & Circular Holes
Let's briefly reverse this. Sometimes you need holes to be perfectly printed. This is important for holes that are critical to a specific screw or nut design.
To achieve the best hole presentation, the model should be laid flat, with the hole facing upwards. The model surface may warp.
3. Dimensions of Specific Surfaces
The blue lines in the figure show perfectly printed model edges. Their dimensions can be as accurate as one-tenth of a millimeter as you planned. The orange area might slightly curl upwards, but in this case, it won't affect the object's functionality. 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 required. The model below is slightly more complex. The designer's goal is to achieve the smoothest shape in the blue part. For the layers to flow naturally and smoothly without obvious layer connections, the model should be placed facing downwards.
* Smoothness and sharpness are opposite concepts, so if sharp elements should face upwards, smooth ones should face downwards.
7. Mating Surfaces
The issue of mating surfaces was briefly described in the first rule. Let's delve deeper into it.
In this model, we have marked in blue the surfaces that need to match another model. As you can see, it has been rotated according to the 45/45 degree rule, and the mating surfaces are sharper on the side facing upwards than on the side facing downwards.
8. Moving Parts
SLS 3D printing technology excels at printing moving parts. For optimal results, the axis of rotation should be parallel to the Z-axis. The flat surface might slightly warp, but in thicker parts like nuts, this won't affect print functionality.
9. Small and Fragile Parts
Printing small and fragile parts requires some compromises. Our experience suggests they should be placed downwards. After printing, the pour volume for these parts will be slightly higher than for parts at the top of the model, and they will also be more resistant to pressure.
Additional Rules for SLS Powder Sintering 3D Model Orientation
The nine principles above are tailored for specific design requirements. 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 centered along the Z-axis, preferably in an inverted pyramid shape.
3. Do not enclose energy within the model; for example, when printing tank-like objects, the opening should face upwards.
4. Flat or large-radius curved surfaces placed at a small angle on the print bed will have noticeable layering.
5. When in doubt, follow the golden rule of 45/45 degree rotation.
Energy Distribution
SLS 3D printing takes place in a confined, controlled environment, where unsintered powder is heated to a temperature slightly below the material's melting point. Heaters are placed around the bed specifically for this purpose. The laser's role is to add additional energy to fuse the powder into the desired shape.
Sinterit printers are capable of printing with different materials that have varying 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 functional parts. If needed, you can contact us immediately to learn more about SLS 3D printers.
Sinterit Nils 480 3D Printer printed samples:
Sinterit Lisa X SLS 3D Printer printed samples
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