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Material Only gibbscam

Material Only calculates toolpath for all remaining material left on walls by prior operations only. Remaining material is stored for 2D operations including contouring, roughing and drilling. Remaining material is NOT stored for 3D operations including Lace, Surface Flow and 2 Curve Flow cuts. Material Only supports custom stock definitions, sharp/bullnose/tapered/ball endmills and most form tools. Undercutting tools are not supported. Material Only may be used as a single operation or as part of a multiple process group.

When the Material Only option is selected, the system tracks the areas where material is left during an operation by creating closed shapes with both “wall” and “air” features or a combination shape for each occurrence of remaining material. During subsequent operations, the system generates toolpath to remove only the material within these shapes. Toolpath generated in these areas is based upon an open-sided pocket configuration.

Machining preferences

The Allow Mill Material Only checkbox in the Machining Prefs tab of the Preferences must be active in order to track and store the condition of remaining materials. It is strongly recommended that this option be deselected if the Material Only option is not going to be used in operations.

When this option is active, the system performs the necessary calculations for a Material Only operation, even if the calculations are not applied. This information is also saved with the part file.

Material Only Pockets

There are two different types of pockets when calculating toolpath for Material Only machining operations—closed and open. When generating toolpath for a solid that has closed and/or open pockets, SolidSurfacer uses the Multiple Shapes method described below. For more information on Material Only and cutting geometry, see the Mill manual.

Multiple Shapes Method:

This is the recommended method for assuring the best toolpath when generating toolpath for Material Only machining. This method requires at least two shapes. The first is an all “air” shape, which represents the stock, and another shape representing the pocket as an island. This second shape is an all “wall” shape. Using this method, the system treats the pocket as an island inside the stock.

To generate these shapes, SolidSurfacer performs a horizontal slice of the solid at each Z-level cut depth defined in the process dialog box. The all “air” shape is based on the stock condition at each Z-level step and the all “wall” shape(s) is based on the part condition at each Z-level step.

The following part shows what the “air” and “wall” shapes would look like at two different Z-level steps for the part. The part consists of a floor at Z0 and four walls with the tallest at Z25.

1. Part model
2. Custom Stock
3. Air geometry for stock
4. Material at Z20
5. Material at Z10

Material Only—Multiple Shapes – air and wall shapes

Optimizing Material Only for Solids

  • Avoid full solid selections. Only select the area (faces) to be cut.
  • Use Create 2D toolpath. This produces better toolpath (not just G1s but G2s and G3s) and also allows for a tighter Surface Tolerance setting. Avoid undercuts when using the Create 2D toolpath feature.
  • Select Ignore Tool Profile when permissible (see the Mill manual for more information on Ignore Tool Profile).

Material Only Limitations:

  • Undercutting tools
  • Custom Stock with undercuts
  • Depth First


  • If wasteful toolpath is generated, the Past Stock value for this operation may be too large. The recommended value for Past Stock is the tool diameter minus 2.5 times the maximum surface tolerance of the previous operation.
  • If no toolpath is generated, the final cut depth may be below the stock bottom. Redefine the stock definition for this operation, then move the stock bottom to the desired final cut’s Z-depth.
  • If all else fails, extract edge geometry and machine as geometry. When extracting the edge geometry, specify a small tolerance so that the edges will be extracted as lines, arcs, and circles (analytics). Then use the Multiple Shapes method described in Material Only—Multiple Shapes – air and wall shapes.

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