Unprecedented flexibility with TPU 90A: Formlabs launches the Print Settings Editor

The Formlabs TPU 90A SLS powder is used for a wide range of applications: from damping parts to grippers for robotics applications and much more. With the Formlabs Fuse SLS 3D printers, high-quality and durable elastomer parts can be produced with geometric freedom and without multi-stage tooling processes.

Now, Formlabs’ Print Settings Editor (PSE) further expands the possibilities of SLS 3D printed TPU. With the Print Settings Editor – part of Formlabs’ PreForm software – you can change the hardness of TPU 90A to experiment with softer, more compliant parts. Without changing materials or additional cleaning and maintenance, you can now use the PSE to optimize your designs and get closer to your preferred elastomer end material.

Formlabs has tested various combinations of settings to create TPU parts with variable hardness. The results are listed below. The Print Settings Editor is part of our efforts to encourage developers and innovators to try new things. However, based on the suggested combinations, it may take some testing and customization until you get a part with the right hardness and surface finish for your application.

Using the Print Settings Editor

In order to open up new printing possibilities with SLS TPU powder with variable hardness, two important settings must be kept in mind:

– Laser power for the filling: The PSE can control the power of the laser. If the laser power is reduced, the TPU particles will not sinter together as tightly, resulting in a softer part. However, if the laser power for filling is set too low, the part may not be sintered at all and the part will remain brittle and fragile.

– Hatching distance in the filling: The PSE can control the distance of the laser scanning process. A larger distance when scanning with the laser leads to undercrosslinking of the material, resulting in a softer part. If the fill distance is too large, this can lead to visible defects on the surface and some delamination of certain positive features.

To achieve a softer TPU, you can either change the laser power for the infill, the hatch distance in the infill or both. The following results can be achieved by a combination of changes to these two settings.

As the graph shows, a Shore hardness of 38A was achieved during the tests. In general, changing the hatch spacing in the fill has a much greater impact on the hardness of the part, while the laser power for the fill amplifies this effect. For example, to sinter a part with a hardness of 60A, a hatch distance of 0.35 mm and a laser power of 21,000 mW would be a good starting point.

Visible surface effects may occur at very low laser power or large hatching distances. Certain features may not be reproduced and a “blurred” or “crumbly” surface structure may occur. By changing the thickness of a part, the effect on the reproduction of details can be mitigated. Thick parts generally print better, even with larger settings for the hatch distance in the fill. Formlabs recommends not printing thin parts with a gap of more than 0.45 mm.

Tests and analysis of the variable durometer settings with PSE were performed on the Formlabs Fuse 1+ 30W printer model. Although PSE is also available for the predecessor model Fuse 1, the results may not exactly match the above.

Effect on the mechanical properties

When parts become softer, their bulk density decreases – the part becomes more foam-like on a microscopic level. This affects both the mechanical properties and the watertightness. If you want to use the part in an application that requires a certain mechanical resistance or wear resistance, you should test the part thoroughly.

The elongation at break (EAB), the tensile strength (UTS) and the stiffness are particularly influenced by changes in the laser power for the filling and the hatching distance in the filling.

This can be seen particularly clearly with long strips such as these tension rods: The rear bar (40A), the middle bar (60A) and the front bar (80A) have different degrees of stiffness.

To quantify this effect more precisely, take a look at the following graphs. By reducing the hardness from 90A to 80A, the UTS and maximum elongation of the parts are also reduced by over 50 percent. This increases the likelihood of parts cracking during the depowdering process and damaging fine structures.

The reduction in hardness from 90A to 80A also has a significant effect on the tensile strength of the parts, with those of higher hardness being closer to the nominal tensile strength of 66 kN/m and those of lower hardness showing a rapid drop in strength.

PSE enables completely new material properties

TPU 90A powder has enabled leading footwear designers, sporting goods manufacturers and aerospace engineers, among others, to prototype a wider range of materials more accurately and earlier in their design process. With variable Shore hardness now possible – without having to change your printer or perform additional cleaning or maintenance – completely new material properties are possible. With the right test protocol for your individual settings, softer, more resilient parts with a good surface finish can be achieved.

To learn more about TPU 90A powder or to request an SLS 3D printed TPU sample with a different hardness, contact our team. For more information on PSE, visit the Formlabs support page.

Raw data from tests

The following table contains raw data from Formlabs tests on the effect of laser power and hatching distance on Shore hardness. Refer to this data when developing your own print settings.

Laser power for the fill (Fill Laser Power)	Distance of the fill hatching (Fill Hatch Spacing)	Hardness
15000	0.35	37.7
18000	0.12	90.1
18625	0.26	66.3
19400	0.43	40.4
20000	0.12	88.5
21100	0.33	62.7
22160	0.48	43.6
23150	0.22	78.6
24000	0.38	62.3
25000	0.12	89.8
25250	0.52	45.3
25800	0.28	74.9
27000	0.12	90.6
28500	0.12	89.8
28500	0.12	91.4
28500	0.13	90.7
28500	0.1325	89.5