SLICING – Creating custom support structures with CAD

Description:

This Solution will show how to generate custom support structures utilising CAD software. Sometimes, the slicing software will not generate clean support or it will not support certain overhangs/features. By creating custom support structures, fully supported parts and clean interface points can be assured. This tutorial is completed using SolidWorks but, the process should transfer to other solid modeling programs with ease. Section 4d of the HD2x User Manual (pages 34 – 36), will also be referenced during this tutorial.


Problem: 

Support generation through the slicing software will sometimes (part dependant) produce inadequate support structures resulting in failed parts. Evidence of this is: 1) skipped support layers 2) support not reaching the part and 3) unclean Interface layers.


 

These parts were generated using the “HD DUAL ABS HIPS” settings in Cura. However, this is not a limitation of the printer but rather the slicing software.


Solution:

The solution for this issue is to create custom support structures in CAD. This is done by creating a separate STL file that occupies the void between model and print bed. When the custom supports are created, the “Dual extrusion merge” function in Cura, will align the support and the model STL files together. Once aligned, the Model STL will be printed with the first nozzle and the Support STL will be printed with the second nozzle.

With this method, there will be no voids or missing sections of support because it is now recognizing the Support STL as a part. Essentially the need to generate support has been removed.

Please follow below for the process used to create these custom supports.


Process:

The following is the process used to create the custom supports for this particular model The CAD program used in this Solution is SOlidWorks. This process should be able to be applied to any CAD software capable of solid modeling. Also, this was the process used for this part specifically, it is not necessarily the best “end-all” process for every part. Different parts will require different process.

1) Extrusions were created in the Z direction up to the undersides of the part. In this case the extrusions penetrated through the entire part, the cavity for the Model will be created in the next step. It is important to remember that in this step, the option to “Merge Bodies/Features” should be left unchecked (if left checked, the Model will not remain as a separate body).

In this case, the support had to be created with 2 separate extrusions.
2) Now that there are multiple bodies, a “Combine Subtraction” feature is used to cut a cavity out of the extruded support pieces. Select only the bodies on the underside of the part to save as these are the only ones required for the support structures.
Blue is being subtracted from Green.

3) Now there should only be the support body(s) and the Model body(s) left. Save each one as a separate STL file.

4) Import the STL files into Cura and use the “DUAL HEAD PRINTING WITH 2 COLORS / MATERIALS” process described in section 4d of the HD2x User Manual (pages 34 – 36). Save the GCODE and check the file in Repetier Host.

Extruder 1 = Yellow

Extruder 2 = Red

5) Check the file in Repetier Host. All the previous issues with the Cura generated support should no longer be present.
With CAD generated support:

With Cura generated support:

6) Load ABS + HIPS and print.


Conclusion:

Thank you for taking the time to read this Solution for generating CAD support structures. Please let us know if you have any questions regarding this process by Creating a New Ticket.
Also, if you have any suggestions or have found a better process, we would love to hear about it, so please let us know.
in Working With 3D Models