DesignForCNC/resources/tools

Tools

Each tool is stored as a JSON file which has the shape's path and values for all attributes of the shape. It also includes all additional parameters and their values.

Storing a tool as a JSON file sounds great but eliminates the option of an accurate thumbnail. On the other hand, storing each tool as a *.fcstd file requires more space, and does not allow for generating tools. If a person has an extensive tool arsenal, they might want to script the generation of tools, which is easily done for a *.json file but practically impossible for *.fcstd files.

When a tool is instantiated in a job the PartDesign body is created from the shape, and the attributes and constraints are set according to the values from the JSON file. All additional parameters are created as properties on the object. This provides the correct shape and dimensions which can be used to generate a point cloud or mesh for advanced algorithms (and potentially simulation).

Tool Libraries

Due to each tool being stored in its own file, and the storage/organization of those files being quite flexible, the importance of a tool library for organisational purposes is quite diminished. The user is free to organise their tools in whichever directory hierarchy they see fit, and can also name them as best fits their use and organisation. A tool library is nevertheless a great representation for a physical grouping of tools, such as in an automatic tool changer.

A tool library is a (JSON) file with a mapping of tool ID to the path of the tool file. As a consequence, each tool can be in multiple libraries and doesn't have an ID of its own. The ID is a property of the library

If a tool from a tool library (or an entire tool library) is added to a job it retains its ID from the library as a property. Adding a tool bit directly results in the tool getting the next free ID assigned.

Tool Controllers

Tool controllers largely stay the same as they are today. As an additional feature, it should be possible to copy a tool controller, which allows for easy feed and speed changes for the same tool.

The above requirement highlights one change though, that the ID should be a property of the tool bit, and not of the tool controller. There are two requirements that are currently mapped to a single ID. There needs to be an identification of which tool controller is being used by a certain op, and which tool number to use for a M6 command.

Paths and Extensibility

The following directory structure is used for supplied (shipped with FreeCAD) tools:

  Tools
    + Bit
    + Library
    + Shape

Strictly speaking, a user is free to store their tools wherever they want and however they want. By default, the file dialog will open the corresponding directory (depending on context), or whichever directory the user opened last.

The above directory structure with the most common default tools shipped with FreeCAD should be installed analogous to TechDraw's templates.

How to create a new tool

1. Set the tool's Label, this will show up in the object tree.
2. Select a tool shape from the existing shape files. If your tool shape doesn't exist, you'll have to create a new shape, see below for details.
3. Each tool bit shape has its own set of parameters, fill them with the tool's values.
4. Select additional parameters.
5. Save the tool under the path/file that makes sense to you.

How to create a new tool bit Shape

The shape file for a tool bit is expected to contain a PartDesign body which represents the tool as a 3D solid. The PartDesign body should be parametric based on a PropertyBag object so that, when the properties of the PropertyBag are changed the solid is updated to the correct representation.

1. Create a new FreeCAD document.
2. Open the PartDesign workbench, create a body, and give the body a label you want to show up in the bit selection.
3. Open the Path workbench and (with the PartDesign body selected) create a PropertyBag: menu 'Path' -> 'Utils' -> 'Property Bag'
   • This creates a PropertyBag object inside the Body (assuming it was selected).
   • Add properties that define the tool bit's shape, and put those into the group 'Shape'.
   • Add any other properties to the bag which might be useful for the tool bit.
4. Construct the body of the tool bit and assign expressions referencing properties from the PropertyBag (in the Shape Group) for all constraints.
   • Position the tip of the tool bit on the origin (0,0).
5. Save the document as a new file in the Shape directory.
   • Before saving the document, make sure you have Save Thumbnail selected, and Add program logo deselected in FreeCAD's preferences.
   • Also, make sure to switch to Front View and Fit content to screen .
   • Whatever you see when saving the document will end up being the visual representation of tool bits with this shape.

Not that 'Shape' is the only property group which has special meaning for tool bits. All other property groups are copied verbatim to the tool bit object when one is created.