AutoCAD Tip: AutoCAD JOIN Workflow: Create Closed, Edit-Ready Contours

Today’s tip streamlines geometry cleanup and preparation: use JOIN to combine lines, arcs, and polylines into reliable, edit-ready contours.

Why JOIN matters:

• Create closed boundaries that hatch correctly and calculate areas without gaps.
• Prepare clean offset paths for walls, kerbs, and toolpaths.
• Reduce object count and simplify selection, properties control, and layer management.
• Eliminate tiny gaps that break trims, extends, and associative annotations.

What JOIN can combine:

• Lines, arcs, 2D polylines, and 3D polylines (like-to-like only; 2D and 3D polylines don’t mix).
• Geometry must touch end-to-end or be within a small “fuzz” distance.
• Polylines must be coplanar and share compatible widths/elevations.

Fast workflow (reliable results):

1. Clean first:
   • Run OVERKILL to remove duplicates and overlaps.
   • Flatten z-elevations if needed (FLATTEN, or set Elevation = 0 in Properties). Mixed Z often blocks joins.
2. Use JOIN directly:
   • Type JOIN, select all candidate objects, then specify a small fuzz distance (e.g., 0.01 or suitable for your units).
   • Result inherits properties from the first selected object.
3. Or use PEDIT > Join for polylines:
   • Start PEDIT, select a polyline (or accept conversion for lines), choose Join, select adjoining objects, set fuzz distance.
   • Use Close to seal a nearly finished loop.

Troubleshooting common failures:

• Still not joining? Check:
  • Endpoints aren’t touching: use FILLET with radius 0 to “snap” corners together.
  • Gap larger than fuzz: extend/trim or temporarily increase fuzz (within reason).
  • Mixed widths or elevations: normalize via Properties palette.
  • Non-coplanar or 3D vs 2D mismatch: convert with CONVERT3DPOLYS or FLATTEN to a single plane.
• Hatch leaks after join:
  • Verify the polyline is truly closed (PEDIT > Close).
  • Run AUDIT if geometry behaves oddly.

Power tips:

• Pre-isolate relevant layers (LAYISO) before joining to avoid grabbing stray objects.
• Use Quick Select to target only Lines/Arcs in a layer or area, then JOIN for batch cleanup.
• Build a macro for one-click cleanup:
  ^C^C_overkill;_pedit;m;_join;0;;_close;
• BOUNDARY is a good fallback: pick inside a closed region to generate a fresh polyline, then purge the old fragments.

Standards and deliverables:

• Closed polylines simplify area schedules, data extraction, and downstream CAM/CNC processes.
• Fewer objects mean smaller DWGs and faster edits, plotting, and xref performance.

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