Oct. 4, 2017
Mills are like the opposite of 3D printers. Instead of laying down material, they cut it away. This is referred to as subtractive manufacturing (as opposed to additive manufacturing).
Milling machines have been around much longer than 3D printers have. Manually controlled milling machines, like the Bridgeport mill, have been a staple of machine shops for nearly a century. In the 1950s, the first efforts were made to automate milling machines using computers. Thus, the CNC (Computer Numerical Control) mill was born. A language called G-Code was developed for controlling CNC mills, and many years later this language was adopted by 3D printers as well.
Milling is an art form and takes years to master. Setting up a project for CNC milling is actually much more involved than 3D printing. Take your time when learning to use the Nomad or any milling machine.
The Nomad comes with several different software programs you will need to be familiar with in order to succeed.
This is the program you use for actually running the machine. It has manual controls for moving things around and setting your origin point. Once you are ready to start cutting, you bring your G-Code file (.nc) into Carbide Motion and it feeds the instructions to the machine.
Carbide Create is a basic 2D design tool for getting you started. It allows you to draw your design and then convert that design to G-Code. You can also import .svg files which you have created in other drawing programs, like Inkscape or Adobe Illustrator.
Carbide Create is good as long as you are just doing simple design using soft materials, however, we quickly outgrew it’s capabilities when we moved to more difficult projects. For instance, Carbide Create will have the spindle plunge straight down into the material. This is fine for soft materials like wood or plastic, but for metal it is best to make helical cuts. This is because endmills are designed to cut with their sides, not their bottom like a drill. We broke a few bits because of this.
The Nomad comes with a free license for MeshCAM, which is more like a 3D printing slicer than a traditional CAM tool. MeshCAM lets you import 3D models (.stl files). Here we cut out a bust of my coworker Ryan from the RenShape block that came with the Nomad 883. MeshCAM lets you cut out complicated shapes like this, at the expense of the speed and precision of traditional milling.
Most CAM tools allow you to do 2D (or 2.5D) milling. This is where all the cuts are done to a certain depth. You can have multiple cuts at different depths, creating a stair step effect, but you cannot have a ramp. 3D milling allows the spindle to move up and down along the Z axis at the same time that it is moving side to side. This allows you to cut inclined surfaces.
Fusion 360 is professional grade CAD/CAM software made by Autodesk. It is free for startups, hobbyists, and enthusiasts. Fusion 360 allows you to do both 2D and 3D milling. It gives you more control and allows you to create more advanced toolpaths, however it also has a significant learning curve. You will want Fusion 360 if you are cutting metal, since it uses techniques that put less stress on the endmill and prevent it from breaking prematurely.
Easel is a free online tool made by Inventables for running the X-Carve and the Carvey. It lets you make simple designs for scratch or import SVG files. It also has a number of plugins for creating things like inlays, stamps, gears, puzzles, and more. Although it is not made for controlling the Nomad, you can use it to create G-Code which you can run through Carbide Motion.
The Nomad 883 can use a wide variety of materials. You'll want to be careful with every material that you cut on the machine - double check to make sure the material you are using is compatible.
Aluminium is the most difficult to cut of these materials. Correct speeds and feeds are especially important for aluminium. We recommend getting plenty of experience with the softer materials first before trying to cut metal.
Steel can be cut with the use of coolant, however this is difficult and we only recommend it for people who have machining experience and know what they are doing.
FR-4 circuit board contains glass fibers, which are highly abrasive and quickly wear out your endmill. For this reason, we recommend avoiding FR-4 board and using FR-1 instead, which does not have the fiber.
The Nomad uses standard endmills with an ⅛” shank. You can purchase them from McMaster-Carr. Although there are many different endmills available, the following are the most common.
Square endmills have flat ends and are good for when you are cutting all the way through materials. They are also good for facing the surface of your material, or cutting pieces that need to fit together.
Ball mills have a rounded end. They are good for 3D milling or making stylish cuts.
Before you can start cutting you must consider how you are going to hold the material down. This is called fixturing. Included in the box with the Nomad 883 is a roll of double sided carpet tape. This is a simple and effective way of holding down your material. There are also several add-ons available from Carbide 3D for holding materials in various ways.
This table has a grid of threaded holes which you can use to screw down your workpiece. You can also use it to attach fixturing clamps, like the ones that come with the Carvey.
This low profile vice lets you hold block or pieces that don’t have a flat bottom surface.
The flip jig allows you to make perfectly aligned two sided cuts.
There are two important things to keep in mind when figuring out how to fixture your material.
This is a term you will hear quite often in the machining world. Speeds and feeds refers to how fast the spindle is spinning (speed), and the rate the cutter is moving through the material (feed rate). The relationship between these settings is very important and depends on the material you are cutting and the end mill you are using.
Let’s use aluminium as an example, since it is the most difficult material you might be cutting on the Carbide 3D Nomad 883. If you cut too fast or the spindle is spinning too slow, then the endmill will be taking a bigger bite with each pass. This means that you will get a rougher surface. If it is especially bad, you may hear a chattering sound. You will also be putting more load on the endmill, and might break it prematurely.
On the other hand, if you cut too slowly or the spindle is going to fast, there will be excessive friction and heat will build up. This will cause aluminium to melt, or wood to burn.
Choosing the right speeds and feeds is really an art form. Carbide Create will give you recommendations for many materials. Nevertheless, you should only consider this a starting point. You will need to do some experimentation to find what works best for you. You should also check any reference charts you can find. More about speeds and feeds.
Milling is much more dangerous than 3D printing. When things go wrong, they go very wrong, so it is important to use correct safety procedures.
Carbide 3D's Nomad 883 desktop mill is a great addition to any workshop. It's compatible with many different materials and endmills, making it a precise and versatile machine.
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