A laser beam is then directed into the liquid, (guided by the 3d file you ve made), solidifying the areas it comes in contact with.

Transcription

1 1 Stereolithography is a technique where the parts are manufactured by building up successive thin layers of hardening resin. The process takes place in a large tank, and begins when a layer of liquid polymer is spread over a platform. A laser beam is then directed into the liquid, (guided by the 3d file you ve made), solidifying the areas it comes in contact with. Once the laser is finished, the platform with the solid areas resting on it, shifts down, and the process begins again: liquid is spread; a laser beam hardens specific points in the liquid; and the platform and completed layers of the object move down. In this way, layer by layer, an object is drawn in the liquid by the beam, with the layers being consolidated throughout the process. When the object is complete, it is raised out of the tank via the supporting platform much like a submarine rising to the surface of the water with the excess liquid flowing away.

2 2 Surface quality & orientation Due to the stereolithopgraphy process, a lot of the characteristics of your 3d print will depend on it. Because your object will be printed layer by layer, the orientation will influence the surface quality and strength. Below you can see two parts of the same shape but one build horizontally and the other vertically. CAD layer based CAD layer based On the horizontal you ll see the so called staircase effect. The surface will be close to a topographic map. If the part is turned vertical, the surface quality will be better. So it s good to allready think of which surface need to be best and chose the orientation accordely.

3 3 Support Since the process of stereolithography takes place in a tank with liquid resin, the parts need to be attached to the supporting platform to prevent the piece from floating away. This attachment is called support and is needed for any part build in stereo lithography. Next to this function of keeping the part in place it also allows to build elements which are hanging over.

4 4 External support To keep your part in place and prevent it from collapsing while it s being build, the parts which are below an angle of 30 degrees needs to be supported. In our example this means the bottom of the vase need to be supported because it is below an angle of 30 degrees. The rest of design doesn t need extra support because it stays above the angle of 30 degrees.

5 5 Internal support Also on the inside of your part, the 30 degrees rule is applied. So any part below an angle of 30 degrees needs to be supported. In our example the vase has a part on top which need to be supported to prevent it from collapsing during the building process. As you might suppect the removal of internal support is far more difficult than extrenal support because it s usually less accessible by hand.

6 6 Rule of 30 degrees In the diagram on the right, you can see a symbolic representation when an part will need support our not. The safe zone is called self supporting and here no support is needed to build the part. For most parts this areas range from 150 degrees untill 30 degrees. If your part is below 30 degrees or 150 the part will need to be supported to be constructed. Try to keep this in mind when designing a object you would want printed in resin. 180 o 150 o 90 self supporting o 30 o 0 o support needed A great way of avoiding support is applying a fillet. In a lot of cases this solves the issue but be aware that horizontal surfaces do still need support when they are sticking out more than 2mm.

7 7 Examples To illustrate the different kinds of support, we have printed a dog in transparant resin. You can see how the part looks when the support is manually removed. Next to that you see the dog still with all the support it needed to be build in a resin. On the 2 images on the right you see the external support for the belly and the ear and the internal support for the back of the dog. As you see only for transparant pieces the internal support is an issue. Most parts are finished off with a paint so then this support won t be visible

8 8 Finishing Depending on your wishes, the part will be finished. This consist of taking away the support, sanding it and possibly painting it. The support removal is a manual process so this means the support has to be accesible by hand somehow. So for internal support this ussualy means leavin in a hole to be able to take the support out. In case the support needs to be taken out for example because of the transparancy of the piece, we advice to leave a hole with a diameter of at least 80mm. in other case removing the internal support is not needed, the support is left on the inside and won t be visible at all. Other option is to build the part without any hollow space on the inside but keep in mind this is ussually more expensive because more material is used to produce the part. After that the small residue for the support is sanded away manually. Here the same applies as for the internal support, if it isn t accesible we won t be able to sand it away. Depending on the material and color you selected, your part can now be painted.

9 9 Extra Here you can find some supplementary information on 3D printing with resins. In most cases the techniques the resins used are foto sensitive this means they react to a light to harden. But due to this material, the parts printed might change color over time. That s the main reason we advice you to paint your print to protect it from UV light. Unlike polyamide, chains and joints can t be produced in one piece due to the support they would need.