Modelling support in CAD program?

I have something I want to make where one part of the model supports another part. The “support” part has a specific shape and will continue to be part of the model, but I want to be able to separate it from the part it is supporting.

If I model it in CAD with the appropriate spacing for supports, will it translate properly in the slicer and simulate a support?

try a simplified test piece.

I will. I was just hoping somebody knew the answer.

trial and error. Find what works for you and/or what ever it is you are printing. Explore. Sometimes what works on one print doesn’t work for another. Another way to put it is nobody has an answer to your specific need, especially without an example to go from.

I believe there are three parts to this question;

  1. How can you simulate support with an imported geometry. Adjusting infill and outer layers?
  2. How do you separate them? I understand that if the geometries are separate by 0.02m they will separate. Something to experiment on.
    3 how do you import a geometry where you can adjust infill on specific regions? Or colors? There is a lot of information on this. What CAD program are you using?

Actually, this is an area I spent quite some time on. I was inspired by this articulating arm example that I found on Printables. I was struggling to get these to print without the slicer supports seriously impeding the joint’s movement. It seemed like nothing would work. Then I noticed that he had a number of STL files that had the word “support” in the filename.

His approach was shear generous in my opinion. He understood that his models need to have almost completely smooth surfaces for his joints to work. However, doing supports with the slicer is a blunt instrument as we all know. His approach was to architect-in supports in such a manner that their connections would be easy to snap off while at the same time, providing the supported needed to print well.

The process worked so well I went back and took a couple of models that I kept around for precisely this reason. These were resin-oriented prints that defied FDM printing. I took his queue and brought the STL into CAD and devised a structure, then I used a boolean union to create a negative part which I then applied to the scaffold.

Now having said that, after I took on this project, Orca introduced Boolean functions which work fantastic for this purpose, if and only if the model did not have any intricate nooks and crannies. I also had some success in using negative parts of the original model which worked somewhat well but for only the simplest of models. In the end, CAD is much more precise but for a quick method, the slicer can be bent to your will. If there’s interest, I’ll post a quick tutorial here just let me know which method, CAD or Slicer there’s interest.


I would be interested in learning the CAD method.

Well it is also a bit up to your CAD system in use.

Of course it can by done and then a lot more precise than in the slicer. as well as additional hold-down brackets, which I can then break away more easily than removing entire brims.

You can even load 2 objects synchronously into the slicer, which are aligned exactly to each other. Than you can handled it as 2 different objects. In my CAD it’s calld layer, in Autodesk Objects. But always the same you have to draw aligned and also export it correctly from the CAD - so stay on the crodinates.

May this one will help you:

video starts by 390 seconds:

and than you can handel it in objects, video starts by 519 seconds:

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Thanks, I will take a look at the videos.

Ok. Here’s an example of a test I did back in August using OnShape but the principles should be the same for almost any CAD. I used only three features, Sketch, Extrude, and Boolean. Transform was only used to pivot the import into a more desirable orientation to work on. That was before there was a Boolean function in Orca. Truth is, the Boolean function in Orca handles an STL mesh than OnShape does. OnShape does better with STEP files.

In the end, I gave in to doing this all now in Orca now that it has a Boolean function. I’ll show an example of one at the end where I had to embed magnets into an organic shape that was very hard to do in CAD and eventually I moved most of the model into Orca.

Step 1 - create a simple square geometry and extrude to a height that will cover enough of the model

Step 2 - Bring in the STL that I had imported previously

Step 3 - Apply a Boolean subtract function using the imported STL as the tool. This will create a cavity in the block that matches the object later to be supported.

Step 4 - Now if you didn’t check “keep tools” the STL will be deleted which is what we want but there is still material in the way. So in this example, I created a simple sketch that outlined the lines of the model and then extruded down to the face of the cavity.

In this example I created a second sketch to widen and extrude to provide more gap. This part is very important because it’s where the trial and error occurs. You want to create a large enough cavity so that the supports inside the slicer will break off easily but not too much so that they can’t come off clean. At 0.28 layer height, I found 1.5 - 2mm space to be ideal with PLA.

Step 5 - Export to a step file as this will retain the most details and import that into the slicer. Now this is where it’s a judgement call. I experimented with making my own supported using a pattern wrap. Truth is, that turned out to be a little too much work mainly because of the tedium of exporting/loading/exporting etc… So I found that by using the slicer supports but modifying the angle, I could get a similar affect.

The other modifications to the supports.

Here’s an earlier example are other examples of where I did the scaffolding solely in CAD.

And this model came directly for the original Printables upload.

Here’s an example of doing it in CAD and them moving it to Orcas for the final assembly. The function here was to create magnet brackets that could be glued seamlessly into a interior of a medical skull model such that the glue could set up without gaps. Click to zoom in on the details in the Green box