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PyCAM currently supports only rectangular processing bounds. This can cause unnecessary machine moves in unused corners of this rectangle. Additionally it makes it harder to use support bridges, since they need to be connected with the remaining material outside of the bounding box. See the screenshot for an example of three objects that are supposed to be cutted out of a solid block.
The new toolpath cropping feature (currently only available in the development repository – to be released with v0.4.1) allows you to crop the toolpath to the required minimum. This can reduce machine time significantly.
This new feature resides quite well hidden in the Toolpath tab. Just select a toolpath of your choice and then click the Crop button. After some seconds of processing you will see the reduced toolpath in the 3D preview. Also notice the change of machine displayed in the toolpath table. The original toolpath corresponding to the image above is shown below.
Toolpath cropping is a side-product of the new 3D to 2D projection. It turns a 3D object into the polygons resulting from a cut through the xy-plane. In case of the model being positioned completely above or below this plane, the bottom of the model will be used as the cutting plane instead. The diameter of the toolpath’s tool will be added as an offset to these projected polygons. This should be suitable for most real-world applications of toolpath cropping.
Alternatively you can also load a 2D contour model (e.g. from an SVG or DXF file) as the toolpath cropping area definition.
The next screenshot shows the toolpath of a triangle-like shaped 3D model. The machine’s moves on the right side (top and bottom corner) are useless for the result. Removing these moves by cropping the toolpath saves around 30% of the machine time required for this object.
The future release v0.5 will probably feature non-rectangular bounding boxes, but until then you will need to live with the current simple implementation. Hopefully it will suit your needs!