As with all branches of 3D printing technology, the quality of SLS prints is closely related to the initial design. We have summarized some experience regarding model design and arrangement methods. Before printing, please refer to the following design guidelines to ensure you obtain a product that meets your expectations. For model features or arrangements not covered in these guidelines, please contact after-sales service if you encounter printing problems.
¶ 1.The Influence of TPU Material Properties on Design
SLS printing of TPU is fundamentally different from printing nylon (PA12). TPU is an elastomer, and its low modulus of elasticity and unique thermal behavior dictate the following design principles:
Looser tolerance requirements: TPU parts typically exhibit lower dimensional accuracy than PA12. Typical tolerances are:
- For dimensions within 0–100 mm range: ±0.5 mm in X, Y, and Z directions.
- For dimensions >100 mm: ±0.5% in X and Y directions.
Increased measurement difficulty: Elastomeric parts easily deform under hand pressure during measurement. It is recommended to use dedicated fixtures for dimensional inspection.
¶ 2.Thin wall
For TPU material, wall thickness significantly affects part performance. Thin walls may result in insufficient strength, while thick walls tend to become rigid, significantly reducing elasticity. Recommended minimum wall thickness: 0.6 mm.
Relationship between wall thickness and elasticity:
- ● Thin-walled (<1.5 mm): High elasticity, lightweight
- ● Medium wall thickness (1.5-2.5 mm): Balances elasticity and strength
- ● Thick walls (>3mm): tend to be rigid, with significantly reduced elasticity.
Model design recommendations:
Avoid abrupt changes in wall thickness. Rapid transitions from thin to thick walls can create localized cooling differences and stress concentrations, leading to part distortion or the formation of soft-hard interfaces. Use fillets and gradual transitions instead.
¶ 3.Entity
For models with parts thicker than 10 mm, it is recommended to perform shelling to prevent severe shrinkage and deformation during printing, which could lead to printing failure.
¶ 4.Minimum feature size
To ensure clear features, it is recommended that the minimum feature size should meet the following requirements:
| Feature Type | Minimum Size / mm | Recommended Size / mm | Notes |
|---|---|---|---|
| Raised text/details | 0.6 | 0.8–1.0 | Height/width simultaneously meet |
| Recessed text/details | 0.6 | 0.8–1.0 | If the powder is too fine, it will easily be filled in, resulting in unclear features. |
| Hole diameter | 1.5 | ≥3.5 | The orifice for powder discharge must be ≥8 mm. |
¶ 5.Assembly Clearance
TPU material is an elastomer, which is prone to deformation during sintering. Therefore, when designing assemblies and arranging parts, the spacing needs to be designed to be more spacious than that for rigid materials.
| Feature Type | Minimum Size / mm | Recommended Size / mm | Notes |
|---|---|---|---|
| Clearance between moving parts | 0.5 | 0.6–0.8 | The gaps in rigid PA12 are easily fused within TPU. |
| Gap between parts | 0.5 | 0.8–1.5 | Minimum spacing between walls and parts |
| Buckle fit | - | 0.8–1.0 | Larger tolerances need to be allowed. |
¶ 6.Lattice Structure
The high ductility and resilience of TPU material, combined with a lattice structure, can create a precise elastic response while achieving lightweighting.
Parameter Recommended size/ mm Notes
| Parameter | Recommended Size / mm | Notes |
|---|---|---|
| Cell size | 5–8 | The smaller the cell size, the finer the elastic response; too small a size will affect the powder removal process. |
| Support diameter | 1–1.5 | If the diameter of the support column is too small, it will affect the strength of the component; if it is too large, it will become rigid. |
Design suggestions:
● Print dot matrix samples in key areas for testing to verify whether the strength and elasticity meet the requirements;
● By setting different lattice porosities in different areas of the same part, a hardware-software integrated design can be achieved.
¶ 7.Model Layout
¶ 7.1 Packing density
To prevent thermal effects between printed parts, which could cause shrinkage and deformation, the spacing between parts must be greater than 5mm, and the packing ratio must be ≤20%.
¶ 7.2 Large Plane
Compared to PA12, TPU material shrinks significantly during sintering, and large horizontal surfaces may warp during printing. For large flat surfaces, it is generally recommended to place them at an angle or vertically. For flat plates with a large specific surface area, significant deformation will occur during cooling and shrinkage. Adding supports can help resist internal stress, and heat treatment can also be used to eliminate internal stress and improve deformation.
¶ 7.3 Detailed Features
During the sintering process, the bottom surface of TPU material is prone to slight sinking, resulting in blurred features on the bottom surface. It is recommended to place detailed features on the top or side surface.
¶ 7.4 Small-sized Parts
When arranging small-sized parts (cross-sectional area ≤ 1cm³), please place them as centrally as possible. Since the bonding force between the small molten pool and the powder bed is weak, placing them on the edge may cause defects such as warping and ejection.
¶ 7.5 Saves time and materials
When printing non-flat parts, please place the parts flat on the printing surface as much as possible to reduce the printing height and shorten the printing time and material usage.
