Design guidelines for 3D printing – part II: Design tips to excel print quality

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Design guidelines for 3D printing – part II: Design tips to excel print quality
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In the current rapidly advancing era of home-based manufacturing, it is a requisite for every one of us to understand the intricacies of 3D printing and adapt our designs in order to get sound prints. Previously in the article Design guidelines for 3D printing – design tips to improve quality of print, we saw some basic guidelines to be followed to obtain good quality prints. Now we explore further in order to better control and customise our prints.

Directional strengthening
The parts produced by 3D printing are generally anisotropic, i.e. they exhibit directional properties. It is a layer by layer process, with each layer in the x-y plane (horizontal plane) joined together along the z axis (vertical direction). Due to this process, there is very good adherence within a layer than between the layers. The end effect is that the part exhibits very good tensile and compressive strengths along x-y direction, and poor strength along z direction. So if you design a part which has to carry some load or withstand some stress, ensure that the orientation of the part is designed in such a way that the load acting direction lies along x or y directions.

Design orientation for directional strength

Design orientation for directional strength

Threads
Threads are extremely useful to create assemblies. But good care has to be taken in order not to spoil the threading features. Sharp edges and perpendicular surfaces (90 degree angles) act as high stress concentrators, hence they need to be avoided. Minimum threading size of at least 0.8 or 1 mm is recommendable. Also standardised ACME threads are known to work quite well with 3D printing; hence they can be used with adequate tolerance for the mating parts.

Acme thread

Acme thread

Another technique is to use external threaded inserts. Normally you can add a nut, washer or any insert after the part is printed. But in case you need a nut embedded inside the body of the part, just create a cavity or hole that will contain the nut. Ensure that the dimensions of the cavity are not smaller than that of the nut. Then as the part is getting printed, pause the print, place the nut in its cavity and continue the print. In this way the nut is now integrated with your part.



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