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ajandClaude Opus 5.5
6f555345e3
Breakoffs are now picked by their joining line, default to the smaller side as scrap (flippable), and cut that line between tabs on a new Break layer instead of slots. Plan Cutting and Assign Lead-ins enter each cut from the scrap with the nest's internal lead-in, or pierce on the line without one; checks treat break cuts as intentional open cuts that are not material. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
65 lines
3.7 KiB
Markdown
65 lines
3.7 KiB
Markdown
# Breakoffs
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A breakoff is scrap drawn on a part, such as a forming backgauge tab, that must stay
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attached through cutting and forming and is snapped off afterwards. In the CAD
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Converter's **Breakoffs** panel, **Add Breakoff**, then click the line that joins the
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part and the scrap. Lines or arcs that end partway along another visible line or arc
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first split it there (the first piece keeps its entity ID), so a joining line can end
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exactly where it meets the outline. The clicked entity then grows into the chain that
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continues as a single path. Its ends must touch, within 0.001, one closed outline
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drawn around both part and scrap, and the chain must run inside it: either a separate
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line drawn across the outline, or a section of the part outline with the scrap's
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outside edges drawn separately.
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The smaller side is the scrap; **Flip** (or "Larger side is scrap" in the dialog)
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swaps it. The dialog sets the tab count (both end tabs included, at least 2) and tab
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width; tabs start evenly spaced and can be dragged along the joining line. Edit
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re-spaces the tabs only when the count or width changes. The view shades the scrap,
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draws the cuts and marks where each cut is pierced.
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## Geometry contract
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`BreakoffBuilder` (`OpenNest.Core/Breakoffs`) resolves each `Drawing.Breakoffs` entry
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against the entities being cut:
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- The two sides are the outline from one end of the joining line to the other, closed
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back along the joining line. They must add up to the outline within 1%. Tab
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positions are measured from the joining line's end with the smaller X (then Y).
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- The outline is kept, with every joint snapped exact (lines move their endpoint; a
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short connecting line is added between arcs), because the planner closes contours within
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1e-6 and the program is re-chained from any entity.
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- The joining line between consecutive tabs becomes open cuts on the `Break` layer
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(`LayerType.Break`, `SpecialLayers.Break`), each travelling with the scrap on its
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left. The joining line itself is not cut at the tabs; end tabs keep cuts off the
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outline.
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## Cutting break cuts
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Break cuts cut like `Cut` motions but are not material: `SpecialLayers.IsMaterial`,
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material capture, overlap checks, nesting and area ignore them. `ShapeProfile` and
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`ConvertGeometry` pass them through in order without re-chaining or re-winding.
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Both Plan Cutting (`PreparedContours`, emitted after scribes and before contours in
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every full or prefix emission, never in single-contour probes) and Assign Lead-ins
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(`ContourCuttingStrategy.Apply`/`ApplySingle`) emit them through
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`ContourCuttingStrategy.EmitBreakCuts`:
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- Each cut is entered from its scrap side with the internal lead-in; `NoLeadIn`
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pierces on the line. There is no lead-out, since the cut ends at a tab.
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- It is entered at whichever end has more scrap before the part's contours along the
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scrap direction (`BreakCutEntry`), because the scrap narrows to a wedge near the
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outline. Entering at the far end cuts it in reverse.
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Checks treat them as intentional open cuts retained by tabs: `ReleasedContourState`
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never makes them rapid obstacles or "open fragment" warnings, but reports a missing
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lead-in like any contour. `LeadPathValidator` lets a lead into a break cut run
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through its own part's material, and still refuses one that touches any of the part's
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boundaries or another part. The posts cut them: Gravograph IS maps `Break` to its cut
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settings; CI Fiber and Cincinnati treat any non-lead, non-scribe layer as cut.
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Breakoffs that do not resolve (hidden or missing joining line, overlapping tabs) are
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listed with the reason and not applied, but stay on the drawing.
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`CadImporter.BuildDrawing` applies breakoffs and copies them to the drawing;
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`SourceEntities` keep the original geometry so a reopened drawing can be edited. Split
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pieces get no breakoffs.
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