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Stop Using a Brim!

Do you have lifting corners?

Are you spending time on post print clean up?

STOP USING BRIM in your slicer!

This is a very simple part. It’s just a triangular prism but when you try to 3D print it, or more importantly print it at scale. There’s a number of challenges around these three corners that I will show you a solution for today.

So this type of part is a very simple part, this is a very simple example that we’re going to use but we’re looking at these sharp corners. 

Sharp corners when put down on the very first layer are not something that’s desirable, they cause dragging where the nozzle will reach out to a point and then drag the corner back with it. Which will cause a little bit of a warp or if you’re creating a very dense part if you were to print this totally solid, then these corners break up from the bed and you start to have a little bit of curling which is also not desirable. 

This error can come up a lot especially in mass production of a part like this, so we want to address it. Also there’s a lot of more complicated types of designs out there than this simple triangle. There’s things as simple as a gear where warping at corners can be an issue. 

Now the traditional type of solution to help with warping is to put a brim on this, where you have a single strip all the way around the outer side of the part. 

And that’s fine, but it doesn’t always work and it adds a lot of post-processing because that brim has to be removed from the entire exterior of the part. When really the only thing we care about are these corners, so the other problem is also that the brim is a print setting and you want the design to not be dependent upon the printer settings or the printer tuning itself. 

A good design can be manufactured basically with any printer at any time and at any scale. So how can we change this CAD so that it doesn’t need a software generated brim? 

Well these!

The most common solution is actually called mouse ears and mouse ears are these very simple circles that you place at very sharp corners. Which gives a round outline to the part, so that it doesn’t have the drag feature. And also creates a very high surface area for adhesion right here so that the corner is held against the bed very well.

The way you design them is you can place them on the corner and then you make them as thick as whatever the first layer would be. Generally 0.2 is a very good thickness for these types of features, so that the software can catch them. Most softwares will catch them very reliably this way, instead of having a brim all the way around that needs to be cleaned off, you have just a small area that can be trimmed off very quickly. 

But this can be optimized even more, this still has quite a bit of touch and can leave residue on that tip. So there’s an evolution to this that can be utilized. Which is to actually put kind of a sprue off the end of the corner. This way instead of having to trim two edges, you instead just literally snip off the tip of this. 

However this one has been exaggerated in order to show that sprue. This is a little bit far spaced and a little bit long, because what would happen is if this part was very dense and had a lot of warping or a lot of internal stresses it would start to pull up on this little sprue. It would kind of stretch it and it would still potentially warp. 

So you want to make sure that this surface area of the disc, is as close to the corner as possible. What we can do is edit our model and you’ll basically move it in, right to the edge. 

This is a very good sprue where you have a very tight controlled part, but again it snips off in a half a second. You can produce thousands of these inside of large print farms and not have to worry about a bunch of post-processing labor cost or additional cost.

That helps a huge amount with a part, because 3D printed parts are really just the cost of the machine time and the material. But then a lot more cost comes in with post-processing, so rather than using software generated brims or these kinds of basic designs of the mouse ears. You can create these sprue design mouse ears which will hold together sharp corners that have a high potential to warp or to fail in the first layer. They add very minimal extra post processing to the part.

Try these on your next 3D model with sharp corners!

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