(Updated)Unlocking the Potential of Multi-Axis CNC Milling with ZBrush .

"Updated" 12/31/2019 (The release of ZBrush 2020 came with some amazing new features that are extremely helpful for using ZBrush for CNC milling purposes so I updated my article to include those. For those that have already read the original article, I posted the updates at the bottom so feel free to jump to that section.)

When you think of CNC milling do you think of ZBrush? If not, then you should. When most people think of 3D models for CNC milling they think of 3D models created in software like Vectric, Fusion 360, ArtCam, Mastercam, Solidworks, etc. These types of programs have been the main players for CNC milling because most CAM programs couldn't create tool paths from .stl or .obj files. Over the past few years though a lot of CAM programs have upgraded so that they can now create tool paths directly from .stl or .obj files. So why is that so important to the CNC industry? Because it opens the doors to 3D digital sculpting and modeling software programs like ZBrush, an industry standard in the film, video game, and 3D printing industry. It officially bridges the gap between CAD/CAM programs/3D models and digital sculpting.

When I first started creating 3D models using ZBrush for CNC milled limestone 3 1/2 years ago, it was a very small niche market. The CNC industry was huge of course, but using ZBrush in it was almost non-existent. Today, even though there are more digital sculptors/3d modelers that use ZBrush for CNC work, it is still a very small market with a lot of untapped potential. I use to think that a lot of companies just didn't need ZBrush artists, but I'm finding that assumption to be quite wrong. They need digital sculptors, they just aren't aware that they can use us yet. The problem is that a lot of companies don't realize yet that their CAM software can most likely use .stl and .obj files now.

I actually spent a few days calling and emailing CNC machining companies to see if they used programs like ZBrush or if they use .stl or .obj files, and almost every single one of them weren't aware that those were available options to them now or the benefits that those capabilities would give them. I won't lie, I was surprised because I thought to myself "How much potential work are they missing out on?".

If you are not familiar with ZBrush then you are probably thinking, "What's the big deal?". The majority of highly detailed and realistic 3D models(characters, creatures, robots, etc.) that you see in video games, TV shows, and movies are now created in ZBrush. Those same kind of high polycount and detailed digital sculpts, can be applied to CNC milling(depending on your CNC machine and your material of course). The same tools that are used to optimize a digital sculpt for 3D printing are the same tools that I use to design digital sculpts and 3D models for CNC milling.

ZBrush can handle a model consisting of millions of polygons and tons of separate parts with ease. You can easily create an organic(creatures, characters, cloth/ribbons, plants, flourishes, acanthus leaves, etc.) or hard surface model(vehicles, robots, scroll work, architectural trim, columns and capitals, etc.) inside of ZBrush. Because of things like subdivisions, polygroups, folders, Sculptris Pro, Live Boolean, deformers, ZRemesher, etc. you can quickly revise a model if a client requests it. If you prefer hard surface modeling techniques then the ZModeler tool will improve the efficiency of your workflow. I usually like to design my models in a bunch of separate pieces, which then mill as one solid piece.

You can also use ZBrush in conjunction with 3D models created in CAD programs. For example you can import a 3D model that you designed in Revit, Fusion 360, Inventor, AutoCad, etc. into ZBrush and run ZRemesher on it which turns it into a quad polygon based model and work on it from there, or cut pieces from the model or add to the model. ZBrush can be used to repair digitally scanned models such as how I've used it in the past to repair 3D scanned ornamental architecture pieces(that had weather damage) which were then CNC milled out of limestone. When ZBrush and CNC milling are combined, the possibilities are endless.

"ZBrush 2020 Article Updates"

When ZBrush 2020 was released on November 12, 2019 it included new features that I've been wanting for my CNC work for the past few years. My favorite new feature is the Move Infinite Depth Brush. In ZBrush being able to evenly adjust the silhouette of a 3D model that consisted of a few million polygons was almost impossible and doing so took a lot of time and required a lot of correction afterwards. With the new Move Infinite Depth feature you can now do exactly that quickly and easily. When working with a model that consists of numerous separate elements, being able to adjust the silhouette of each element is extremely important when using ZBrush for CNC milling.

Another important issue that I have to tackle a lot(in creating digital sculpts/3d models for CNC milling and jewelry design) is being able to identify and eliminate undercuts. That's where the new Draw Draft Analysis comes into play. It allows you to to choose your own "pull direction" and it displays on your model where the undercuts would be. The best part of this new feature is that you can fix those issues in "real time" so that as you work the Draw Draft Analysis updates in real time. This is also a superb tool for mold making as well.

The next one that I find helpful, both for CNC milling and 3d printing, is the new Polypaint From Thickness feature. Using polypaint, it identifies parts that might be too thin to print or that might break during CNC milling. You set the maximum and minimum thickness that you are looking for and ZBrush will identify those areas on your model. This eliminates guess work and future revisions which saves time and as we all know in the line of work, time is money.

There are a ton of other new features that I've yet to experiment with, but these are the main ones that I've found that help speed up my workflow. Here's a link to Pixolgic's website where it explains all of the new features, and how to use them, in more detail.

https://docs.pixologic.com/features/whats-new-in-zbrush-2020/