Always make sure your model meets the design guidelines of your desired material, and focus mostly on these features:
- maintain a wall thickness of at least 1mm
- accuracy is 0.15mm + 0.15% of the longest axis
- always keep a clearance of at least 0.5 mm
When designing something mechanical that has to be 3D printed or when adding a mechanical feature to your model there are several main considerations.
Material properties & limitations
For the purpose of this tutorial, consider Versatile Plastic as the material you'll be working with. It's printed using the Selective Laser Sintering technique (SLS). Different 3D printing materials and processes have very different material properties, limitations and strengths. Please refer to our Material pages for further information and design guidelines of each material.
Versatile Plastic is made of a Polyamide 12 powder that is sintered together by a laser. After it has been printed, your model is then taken out of the resulting big block of powder. With this process, there is no need to print distinct support material since the unused build medium - the powder - provides support.
The examples used here are close to the recommendations published in the material guidelines, it's highly recommended that you attempt to exceed these minimums whenever possible. To understand why this is we need to look at process limitations.
SLS is one of the most accurate 3D printing processes available. The process has a layer thickness of 0.1mm. Therefore the maximum accuracy of any detail on any part will be 0.1mm in any direction. The laser is more accurate than 0.1mm so the surface that is exposed to the laser will display higher accuracy. This is why orientation has an impact on models.
Orientation refers to the way in which your model is positioned inside the build area of the 3D printer. How a part is oriented can have an impact on the surface and dimensions of the final product. To use the set 3D print orientation tool, please follow these steps:
1. Visit https://www.shapeways.com/mymodels and click the 3 vertical dots to the right of the model.
2. Select "Open in 3D tools" from the popup.
3. On the page that follows, click on the "SET 3D PRINTING ORIENTATION" button.
4. A popup window will appear, with a navigational button on the bottom left hand corner. Use this to set the orientation and then click "SAVE ORIENTATION" when done.
Keep in mind that this will have to be done for each material you wish to set orientation for. These settings will not carry over to the other material options.
Previously, our team of engineers picked the best orientation for products. Now we give you the ability to choose it in 90 degree increments at your own discretion. Once you set orientation, we will save that selection for the same material each time you order it.
Below is an example of a tray build where some parts are oriented for accuracy, and others for smoothness:
SLS is a very accurate process, but because of the layered construction there are some specific limitations with holes. If a hole is constructed vertically, it will be based out of lots of layers within the diameter of the hole. This means that the hole will not be as flush (and round) as you might like it. Therefore the best orientation for holes is horizontal - where the laser is constructing each hole from the top.
Larger holes (1mm and up) are also more accurate than smaller ones.
Since Versatile Plastic models are made up of powder, they will always feel grainy, similar to terracotta or limestone.
You can choose extra post processing like Processed or Premium finishes to achieve smoother models. You can also smooth your model using sandpaper, or apply transparent varnish to achieve smoother finish. Please note that this will affect the accuracy of the dimensions.
Due to the print process, parts printed in SLS shrink. The shrinkage depends on ambient temperature and humidity of the print environment. The accuracy of Versatile plastic is ±0.15 mm + 0.15% of the longest axis.
For example: a product with dimensions of 50x50x100 mm can be 0.15 mm + 0.0015*100 mm = 0.3 mm bigger or smaller in any direction. Due to the limitations of this technology we are not able to guarantee a 100% fit.
Clearance is the distance between a door and the door frame when the door is shut. If you make a peg with a diameter of 3mm, and a hole with a diameter of 3mm, the peg will not fit into the hole. There has to be some kind of clearance for it to work.
The amount of clearance depends on the functionality of the part. The higher the clearance, the more likely it is to fit. When developing complex moving mechanical parts though, the more clearance, the more inefficient the part. A good balance between clearance and efficiency is crucial for your design decisions.
The minimum clearance is 0.5 mm for Versatile plastic. Making the clearance below this point will cause your parts to fuse together.
For more information please refer to the Design guidelines tab on the Versatile plastic material page.