Understanding how your CAM software understands and sees the axes and tool orientations that is physically on the CNC machine can be tricky. Often, it is not explicitly explained leading to much confusion for new CAM technicians. This is particularly evident when it comes to CNC turning, where directions and rotations can get tricky pretty quickly.
As a result, we thought we’d create a guide to understanding the setup and tool selection process.
This should help you understand:
- How your stock/workpiece should be setup
- Why the position of spindles and turrets on your physical CNC machine matters
- How Fusion 360 will display changes made
- How to ensure your tool isn’t facing the wrong way
- How to create custom tool orientations
The image below shows a simplification of your primary axes on a CNC lathe. These are
- Rotation of spindle
Other orientations to pay attention to are:
- Tool direction
- Tool Type -[Left hand tool, Right hand tool, Boring tool, Drilling tool]
It is important to understand your equipment and make note of the various capabilities. For example, you may have a single chuck, single head machine with your tool moving leftward toward the spindle (as shown in simplified model below). In this case, you would find that:
- Your tool holder is either on side C or D in the diagram below.
- This affects your toolholder type – Right-hand tool or Left Hand tool
- This also affects Spindle Rotation since the spindle must rotate the piece into the tooltip to cut (see figure 2)
Fusion 360 CAM turning setup
When you begin any CAM workflow by moving into the MANUFACTURE workspace in Fusion 360, the first step is always to create your setup.
This defines your stock size, tells the machine where axes and your origin points are and indicates the front/back of your workpiece.
When setting up your workpiece, it is important to define
- The front of your stock by indicating where the chuck is using the Chuck sub-tab. This will move the origin point selected, so it’s best to define where the chuck is first.
- The direction of your axis, remembering:
- The positive side of an axis is the one where the red/blue/green arrow on the triad is.
- The toolpaths generated will always have the tool approach from the positive X-axis.
- Positive Z-axis must be in direction away from spindle.
If you have multiple bodies in your design, be sure to select only the body to be machined as your model under the Model sub-tab.
Under the stock tab, you can choose from various options to define the stock, mainly fixed sized or relative sized options.
- Fixed size allows you to input absolute lengths, radii and centres
- Variable size allows you to use the model as a reference and add offsets to each dimension
If you are continuing from a previous setup, you also have the option to continue rest machining so that Fusion will know what was cut already and start with that as your stock for this setup.
Selecting the solid option allows you to use rest machining.
There are various tool types to consider, but depending on your machine, you will choose either a right hand tool, left hand tool or a neutral tool.
Here is a picture of the tool library showing some of the various types. Notice for the
With RHT & LHT, you have to consider your setup, since we already established that the toolpaths generated will approach from positive X-axis.
In our example above (figure 1), I chose a right hand tool. This means that if I hold my tool in my right hand, it will cut something on my left and vice versa for a left hand tool.
Since the positive X-axis is setup towards direction C (figure 1), our tool will be placed on that side, ready to approach and cut. So what would happen if I choose a left hand tool? As you can see in Figure 3 below, the tool flips, but remains on positive X-axis as per setup.
So how do I use a left hand tool on my machine? Well, the only way you can achieve that is if the left hand tool is used upside down i.e the tooltip will move to the bottom left so it can approach the spindle in the Z axis. But the reason it did not show this way is because of the spindle rotation!
See, the spindle rotation is tied to the tool. This makes sense because your spindle must rotate into the tooltip. So you need to edit the tool and ensure that the rotation is reversed in order for it to put the tooltip in the correct place. In this case, the left hand tool’s insert tip is on the top right because the spindle rotation is already set to ACW.
The only way this LHT can be used is if the rotation is reversed, in which case, it will rotate the tool 180 degrees about the X-axis, putting the tip on the bottom left.
Once that is done, you should find that your tool is orientated correctly to cut the piece according to your setup. Now, there may be dangers to using your tool “upside down” and there may be advantage too. That is a debate for the machining purists, but this is just to highlight how Fusion 360s tool, spindle and setup works.