Set Spindle Speed and Feed Rate in FreeCAD Path

Configuring accurate spindle speeds and feed rates in FreeCAD's Path (CAM) Workbench is essential for achieving clean cuts, protecting cutting tools, and preventing machine damage. This guide explains how to set and adjust these cutting parameters directly through the Tool Controller, modify them for specific machining operations, and understand the core speed and feed values required by your CNC machine.

Setting Parameters in the Tool Controller

In FreeCAD Path, feed rates and spindle speeds are primarily managed by the Tool Controller assigned to your Job.

  1. Open your CAM Job: Expand your active Job in the Tree view on the left-hand panel.
  2. Locate the Tool Controller: Look for the Tool Controller associated with the tool you are using (e.g., TC: Default Tool or a custom-named controller).
  3. Open the Controller Properties: Double-click the Tool Controller, or select it and review the Data tab in the Property View below the tree.
  4. Adjust the Values:
    • Spindle Speed: Set the rotational speed of your spindle in revolutions per minute (RPM).
    • Spindle Direction: Choose between Forward (clockwise) or Reverse (counter-clockwise).
    • Horizontal Feed (HorizFeed): Set the cutting feed rate for horizontal movements along the X and Y axes (typically measured in mm/min or in/min).
    • Vertical Feed (VertFeed): Set the plunge rate for vertical movements along the Z axis into the stock material.
    • Rapid Speeds: Adjust horizontal and vertical rapid positioning speeds if your post-processor or machine requires software-defined rapid travel instead of G0 defaults.
  5. Click OK to apply the changes.

Overriding Speeds and Feeds for Specific Operations

If a single tool needs to run at different speeds or feeds for distinct operations (such as roughing versus finishing), you can assign dedicated controllers or adjust parameters per operation.

  1. Add an Additional Tool Controller: Right-click your Tool in the Job's Tool list or use the Path menu to create another Tool Controller referencing the same physical tool bit.
  2. Differentiate Parameters: Set one controller with aggressive feeds for roughing (e.g., a high horizontal feed rate) and another with lower feeds and higher RPM for finishing passes.
  3. Assign to the Operation:
    • Click on the specific Path operation (e.g., Pocketing, Profiling, or Adaptive).
    • In the Data tab, find the Tool Controller property.
    • Use the drop-down menu to select the specific controller configured for that operation.

Core Speed and Feed Parameters Explained

  • Spindle Speed (RPM): Determines how fast the cutting tool rotates. Calculated using the recommended surface speed (SFM or m/min) for the material and the cutter's diameter.
  • Horizontal Cutting Feed (HorizFeed): The linear speed at which the tool moves sideways through the stock. It is calculated by multiplying the spindle RPM by the number of flutes and the recommended chip load per tooth.
  • Vertical Plunge Feed (VertFeed): The downward entry rate into the material. Because endmills are less efficient at drilling downwards than cutting sideways, plunge rates are typically set between 25% and 50% of the horizontal feed rate, unless using dedicated ramping or helix entries.