In order to properly machine a part it is important to set the work coordinate system (WCS) properly in Fusion 360. This tutorial runs the user through how to set this WCS using the B-table and vise, along with the square part that is produced in the ‘First Part Tutorial.’ A user can use any part that they are milling, and it would be set in the same way just using a different part for reference.
Setting the B-Table Offset Value
To set the origin you will need the B-table offset value that comes in the Quick Start Guide with your machine. There is a B-table offset value written in and this is specific to each machine. Locate this number. In Fusion 360 go to the ‘Model’ environment, as shown in the upper left corner of the screen in the photo below.
Then within the B-Table with Vise title there is a section labeled ‘Sketches’ expand that and then right click on the B-Table Offset and select ‘Edit Sketch’. Then you can click on the dimension that is highlighted when Edit Sketch is selected and type in the B-table offset for your particular machine. Press enter to store it. Now, your B-table offset is set correctly however you need to set the work coordinate system to recognize this point as the origin of your model.
Setting the WCS
The next part takes place in the CAM environment, so go back to the Model and click the drop down menu to select CAM. Next, directly to the right of the CAM button reads a button called ‘Setup’. Click this and select ‘New Setup’. From here a box pops up on the right hand side that is called Setup: Setup1. Within this box is a section titled ‘Work Coordinate System (WCS).’ Select the drop down next to the Orientation title and “Select Z axis/plane & X axis” as shown below.
Two pieces of geometry will need to be selected to complete the “Orientation” field, one for the Z Axis and one for the X Axis. To do this, select the box next to the “Z Axis” labeled “Nothing”, then select geometry (a straight line) on the vise perpendicular to the moveable axis of the jaw and parallel to the work table. Repeat the operation for the X Axis, selecting a feature perpendicular to the work table. When finished users should have a WCS that looks like the image below. If you need to change the directions of the axes, use the “flip _ Axis” check boxes to flip them.
The orientation of the B axis is flat or (perpendicular) to the spindle of the Pocket NC when homed. This needs to be reflected by the WCS. On the Pocket NC, the Y Axis moves the table up and down this must be reflected in the setup for the output code to work with the machine. The positive Y direction of the WCS should point straight up from the the B table.
Next, you will select the origin of the machine within the model. The origin of the machine is represented by the point about 0.839 inches off the surface of the table at the center of rotation. This point varies slightly from machine to machine and is the value we just set in the previous section based on the B table offset
In the Setup menu change the Origin type to “Selected Point.” Then select the top point of the B table offset sketch. Your origin is now correctly set for your machine.
Note: By selecting the top of the B-table offset sketch as the WCS Origin, you are setting your CAM up for “Center of Rotation” programming. This means that your real-world setup must match your 3D model setup as closely as possible for the machine to cut the stock in the right place. Alternatively, you may choose to select a WCS Origin point that is relative to the stock or part you are cutting, which does not require your real-world setup to match your 3D model setup as closely. This method would require you to use Pocket NC’s RWO (Rotated Work Offsets) feature. More information on RWO can be found in the RWO Tutorial.