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ajandClaude Opus 5.5
48863d51c8
Slats are strips of a set thickness running the full length or width of the table, one every pitch. A part's contacts are the corners of where its material crosses a slat, so the support check and support tabs work as on the grid. Nest > Support Bed... picks grid or slats; nest files store type "slats" and support-grid.json keeps both layouts' values. Draw Support shows the slats cut off to the sheet. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
135 lines
8.8 KiB
Markdown
135 lines
8.8 KiB
Markdown
# Support grid and support tabs
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A cut part drops onto the machine's support bed. If its center of gravity is not over the
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points it rests on, it can tip into the head's path or fall through. OpenNest models the bed,
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checks every part against it, and can tab only the parts the bed cannot hold level, at the
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perimeter point where one tab steadies the part most.
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## The support bed
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`OpenNest.Support.SupportBed` is the machine's bed, fixed to the machine and measured from the
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plate origin into the sheet; a sheet in another quadrant sees it mirrored. The built-in layout
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is one of two layouts; a layout only reports its contacts under a part's material. Lengths are
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in the nest's units.
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- The laser grid, `SupportGrid`: one contact point every `PitchX` along X and `PitchY` along
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Y, the first at (`OffsetX`, `OffsetY`).
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- Straight slats, `SupportSlats` (as on the plasma table): each slat a strip `Thickness` wide
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running the full length (`Axis` X) or width (`Axis` Y) of the table, one every `Pitch`
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across it, the first centered `Offset` from the origin. A part rests on the region where its
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material crosses a slat, so its contacts are that region's corners: where the outline and
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holes cross each slat's two edges, and the outline and hole vertices on a slat. A part
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narrower than a slat rests on its own corners; one balanced across a single slat has a margin
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of at most half the thickness, which the stability margin rejects.
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Curved slats imported from a CAD layout are not modeled yet.
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Every bed also carries:
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- `RegistrationTolerance`: how far a sheet may sit from its nominal place. The bed is checked
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shifted by up to this much along X, Y and both diagonals, and the worst result is kept.
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- `StabilityMargin`: how far inside its contacts the center of gravity must lie to count as
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supported, allowing for slag, gas pressure and worn contacts.
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The bed belongs to the nest (`Nest.SetSupportBed`); every plate follows it, including plates
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added later. It is display, analysis and tab placement only: never material, spacing or a
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keep-out. Nest > Support Bed... edits it and picks the grid or slats; Save as Machine Defaults
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writes it to the nest's machine configuration (`MachineConfig.SupportGrid`: both layouts' values
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and which one is in use; settings saved before slats existed are a grid), which nests assigned that
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machine receive while it is enabled: File > New and BOM import assign the Tools > Nest Defaults
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machine (the first by name when none is chosen), and Nest > Machine (or the status bar's machine
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label) reassigns a nest and replaces its bed with the new machine's (none when that machine gives
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nests no bed). A machine with no bed saved yet uses the legacy shared
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`%APPDATA%\OpenNest\support-grid.json`. The nest file stores the bed in
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`plateDefaults.supportBed` and the machine in `machine` (see [nest file format](nest-file-format.md)).
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## The support check
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`SupportAnalyzer.Analyze` takes a placed part's material (`SupportMaterial`: outline minus
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holes, chorded at 0.001; leads, rapids, scribes and break cuts are not material, and a tabbed
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cutout's slug counts as part since it stays attached). Plate is of even thickness, so the
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center of gravity is the area centroid. The part rests on the bed contacts inside its material;
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the margin is the signed distance of the center of gravity inside the convex hull of those
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contacts (negative outside). Fewer than three contacts that are not in line can only balance a
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part, so their margin is at most zero; no contacts at all is negative infinity. A part is
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supported when its worst margin is positive and at least the stability margin.
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A perimeter tab holds the part at the tab, so a tab point counts as one more contact.
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`PartSupport.MarginWith(point)` is the worst margin with a tab there, and `BestTabPoint` the
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outline point (vertices plus 256 even samples) that maximizes it. A tab cannot lift the margin
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past the contacts' own hull edges, so a whole stretch of outline often ties; among samples
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within `Tolerance.Epsilon` of the best, the one nearest the line through the center of gravity
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across the long side of the outline's minimum-area bounding rectangle wins. The search itself
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is not narrowed, so a part held only near one end is still tabbed at the far end. `AcceptsTabAt(point)` accepts
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any point that reaches the stability margin, or, when no single tab can, only points as good as
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the best one found. A tab's bending strength is ignored: it is a support point, not a cantilever.
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A tab never goes in an inside corner, where its nub cannot be ground flush. An inside corner is
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a run of consecutive inward-turning outline vertices that turn at least 30 degrees together, so a
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chorded fillet counts while a shallow bend does not. Tab points keep the analysis's inside-corner
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clearance from those vertices (Plan Cutting and the overlay use twice the tab size; 0 keeps a tab
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off the corner only), and `AcceptsTabAt` rejects closer points. The tie-break above runs over
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the clear points only; points equally near the center line go to the one farthest from an
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inside corner. Only when every outline point is too close does the clearance give way.
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View > Draw Support shows the grid or the slats, cut off to the sheet (while its points or slats
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are at least 6 pixels apart), each part's
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contacts, and its center of gravity: green when supported, red when it can tip, with an orange
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diamond on a red part's best tab point (keeping the plate's tab-size clearance).
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## Support tabs in Plan Cutting
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Cutting Settings > Tabs > "Tab parts the support grid cannot hold level" sets
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`CuttingParameters.SupportTabs`. With it and a plate support bed, `CuttingPlanService` capture
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analyzes each regenerated part (`SupportTabCapture`). A part the bed cannot hold level gets a
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tabbed perimeter (`PreparedContours.WithSupportTab`), using `TabConfig` for the tab size; all
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other parts keep the plate settings, so supported parts are not tabbed.
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The emitter tabs a perimeter at its entry: the cut stops short of the entry by the tab size.
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A support-tabbed perimeter's automatic entries are therefore limited to catalogue points the
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analysis accepts, plus the closest native point to its best tab point (`AutomaticEntryKind.SupportTab`,
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never on a reflex or cusp vertex). Ranking and lead checks are unchanged.
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If none of those entries has a lead-in that fits, the part is still tabbed. The search falls
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back first to every catalogue entry clear of inside corners, then to every entry
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(`SupportEntries`), each ordered by how well the tab steadies the part; of the entries whose
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lead-in fits, it keeps every one that holds the part level, or else only the steadiest. The
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open-scrap pierce fallback then tries the last of those catalogues.
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A drawing pin on the perimeter wins: its entry, leads and tab are kept as pinned, and the
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analysis is only carried for review. Replay and best-effort plans (`SupportTabCapture.Review`)
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warn with `PostVerificationKind.PartSupport` whenever an unsupported part's emitted perimeter is
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untabbed or its entry does not steady the part: its pin has no tab or a tab elsewhere, no
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steadying entry had a lead-in that fits, or no single tab can steady it. Like every planner
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warning, this makes the proposal UNVERIFIED, so applying it needs explicit acceptance.
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A planned tab that sits in an inside corner, because no lead-in fits clear of one, gets an
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advisory note instead (`SupportTabCapture.Notes`; never for a pin): a Ready plan keeps its
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status and lists it in Plan Cutting's warnings, and the console and MCP summaries print it under
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the plate.
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## Lead-ins placed by hand
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Plate > Place Lead-in cuts where it is clicked. Under "Tab parts the support grid cannot hold
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level", `SupportTabSettings.ForManualLeadIn` enables tabs on a copy of the settings when the
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plate's bed cannot hold the clicked part level, so the tab sits at the clicked entry. The
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overlay's orange diamond shows where it steadies the part; the pre-post review checks the
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result. Plan Cutting is the only automatic lead-in assignment.
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## Pre-post review
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`PartSupportReview` runs in every pre-post verification and in Validate Nest. On a plate with a
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support bed, each part whose settings (its own, else the plate's) ask for support tabs and that
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the bed cannot hold level is checked, however its program was made. The tab is the gap between
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the end and the start of the program's outside cut (the chain of cutting motions with the
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largest extent). A part with no such gap, or whose gap does not steady it, gets a
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`PartSupport` warning at its center of gravity naming the best tab point; posting needs
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consent as for every warning. A part whose material cannot be read is reported as not checked.
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Not covered yet:
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- Locked or ineligible parts keep their programs in Plan Cutting; the pre-post review still
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checks them.
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- Only one perimeter tab per part. A part that needs more (one tab cannot reach the stability
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margin) gets the best single tab and a warning.
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