Rest machining

A large tool clears a pocket fast, but leaves material where it doesn’t fit:

• inside corners rounded to its radius;
• slots and gaps narrower than the tool.

A rest pass with a smaller tool cuts only that material, instead of clearing the whole pocket again. (Design: docs/specs/rest-passes.md.)

Adding one

• Right-click the pocket in the Browser, then Add rest pass ▸, and pick a smaller endmill: the project’s tools come first, then those in your tool library. A library tool is copied into the project’s Tools. When the entry is greyed out, point at it to see why: no smaller endmill in the project or your library, or the pocket has dogbone corners. Command line: chipload op add-rest part.chipload --op 1 --tool 2 (copy a library tool in first with chipload tool use).
• It belongs to the pocket: it shows as a leaf under it, numbered after it (1.1, 1.2), and takes the pocket’s shapes, depths, oversize and direction. Change the pocket and the pass follows; turn the pocket off and its passes aren’t cut either.
• Its own: the tool, feed, plunge feed, step down, stepover, entry, and on/off. Click the pass to change them; its right-click menu removes it.
• Feeds and step down come from your tool library’s values for the small tool when it has them. Otherwise they’re copied from the pocket: check them.
• Several passes: a pocket can have more than one, each with a smaller tool than the one before (12, then 6, then 3 mm). Each clears what the one before it left.

Command line: chipload op rest-pass part.chipload --op 1 lists a pocket’s passes, and with --pass 1 changes one (--tool, --feed, --plunge-feed, --step-down, --stepover, --enabled false) or removes it (--remove).

When it is cut

A rest pass waits for the pockets next to its pocket that use the same tool. After the last of them come all their rest passes, the larger tools first, then the operations after them. So with two pockets and an outline, all cut with a 12 mm tool, and a 4 mm rest pass on each pocket:

The small tool comes in once, and the outline, which frees the part, stays last. The report, the G-code headers and the setup sheet show the passes where they are cut.

What it cuts

• Worked out from the tool’s size: Chipload works out what a tool of the larger tool’s size can’t reach in the pocket’s shapes. It looks at the size, not at what the pocket’s toolpath did.
• Rings: around each piece of that material, the small tool clears a small pocket with rings, within its own diameter. Along the real walls it follows the walls, so the corners come out with the small tool’s radius.
• Pieces too small for the small tool too are skipped, with a note giving their size.
• Nothing left: if the large tool reaches the whole pocket (a circle wider than it), the pass cuts nothing and says so.

View > Show stock shows the result: the corners cut by the small tool.

Rules

• A smaller endmill: a pass’s tool must be an endmill smaller than the tool before it.
• No dogbones: a pocket with dogbones can’t have rest passes; its corners need no rest.

A rest pocket on its own

When the large pocket is cut elsewhere, in another project or another program, a pocket can rest after a tool by itself: Clearing > Rest after in its properties (command line: chipload op rest part.chipload --op 2 --after-tool 1). It is an ordinary operation in the list, cut where it stands. Chipload warns when no earlier, enabled pocket cuts the same shapes with that tool at least as deep; it is still safe, it just leaves the bulk of the material.

A rest pocket that copies an earlier pocket of the project (same shapes, depths, oversize and direction, after its tool), as Add rest pocket made them before rest passes, can become that pocket’s rest pass: right-click it, Make it a rest pass of operation N (command line: chipload op make-rest-pass part.chipload --op 2). It is then cut after the run of pockets it belongs to.