FreeCAD Build Guide

Summary¶

After following this guide, the builder has a complete, validated FreeCAD parametric model of their specific libdrone configuration, with all parts ready to export for slicing. This skeleton is the 3.0.0 replacement for the V2.4.6 FreeCAD Cookbook — a 2,083-line step-by-step guide. The skeleton provides the arc; the atoms provide the reference; the Cookbook provides the detailed click-map for each modelling operation.

This guide requires the V2.4.6 FreeCAD Cookbook open on your second screen. The Cookbook contains FreeCAD-version-specific UI interactions (menu paths, dialog names, constraint tools) that change between FreeCAD versions. This skeleton provides the conceptual structure and decision points; the Cookbook provides the exact click sequence.

Concept¶

Why parametric before printing¶

→ parametric-modelling-philosophy explains the fundamental principle: every dimension of every part traces back to a single named variable. Before any modelling begins, every variable in → variable-table-values must be entered into the FreeCAD spreadsheet and the model must update cleanly. An incorrect variable produces incorrect geometry in every part that depends on it — and the error is silent until you try to print and assemble.

The parametric approach also means that scaling the platform — changing the wheelbase for a 5-inch or 8-inch build — is a variable edit, not a redesign. → variable-table-structure covers the variable organisation. → freecad-parametric-scaling explains the two-variable classes (frame-driven vs electronics-driven) and the scaling sequence — which variables change when the wheelbase changes and which must stay fixed regardless of airframe scale. The Cookbook's Scaling Philosophy section is the source material for that atom.

FreeCAD orientation¶

→ freecad-ui-110 covers the FreeCAD 1.1-specific interface elements: where the workbench selector is, how to set CAD navigation mode, the macro path for Flatpak Linux installs. → freecad-workbenches explains the workbenches you will use: Spreadsheet (variable entry), Part Design (solid bodies), Part (boolean operations), Assembly.

→ freecad-document-setup covers the one-time global setup: units (mm/kg/s, 3 decimal places), navigation style (CAD), zoom at cursor. Do this before creating any geometry.

Robust modelling discipline¶

Before touching any sketch or extrusion, internalize three habits from the Cookbook:

Name every feature as you create it. A Model Tree reading "Sketch002, Pocket003, Mirror004" is a debugging nightmare. A Model Tree reading "ArmProfile, PinchSlit, RodChannelLeft" is self-documenting.

Fully constrain every sketch before closing it. Underconstrained sketches (shown in yellow/white) produce geometry that drifts when variables change. The sketch must show "Fully constrained" in green before you close it.

Use =Variables.VariableName for every dimension. Never type a number directly into a dimension dialog. Always reference the spreadsheet variable. This is what makes the model parametric. A typed number is a hardcoded constant that breaks when variables change.

Reference¶

Modelling sequence and atom map¶

Pre-modelling checklist¶

Before opening FreeCAD:

1. Variables file open: → variable-table-values
2. FreeCAD 1.1 installed (Flatpak or native)
3. Macro file (LD_V343_Variables.FCMacro) copied to macro path
4. Second screen ready for the Cookbook

Variable entry gate¶

After running the macro and entering all variables:

• Open every Part Studio in the Model Tree
• Confirm no red cells in the Spreadsheet
• Confirm "Recomputed" or "Up to date" for all bodies — no yellow warning icons
• Spot-check three critical dimensions against the Variables file:
• ArmBoreOD (motor bore): should match MotorBoreOD + MotorBoreClearance
• GX12ChimneyBore: should show D-shape, not round circle
• TSlotWidth: should match ArmTabWidth + TSlotClearance

If any check fails: fix the variable first, then remodel. Do not proceed with incorrect variables.

Part-by-part decision gates¶

Arm shaft (Part 5) Before padding: confirm the dovetail groove is on the BOTTOM face, not top. The dovetail routes motor phase wires for EMC separation — wrong face means wires will be on the wrong side after assembly.

Platform (Part 7) Three features are EMC requirements. Before exporting Platform STL, confirm: - LEFT wire channel present (signal zone): Y = −20mm - RIGHT wire channel present (power zone): Y = +20mm - MIPI centreline channel fully enclosed (camera cable route)

If any feature is missing: do not proceed to production print. → power-signal-separation explains why these features cannot be retrofitted after printing.

GX12 chimney bores (Part 7) Each GX12-7 connector bore must have a D-D profile (flat on one side), not a round circle. The D-D prevents the connector from rotating and backing off the retention nut. → gx12-connector-standard explains the rotation prevention requirement. If the bore is round: check the GX12ChimneyFlat variable.

Procedure¶

Session setup for each modelling session¶

1. Open FreeCAD document — do not open from a backup; open the current saved version
2. Check for any yellow warning icons in the Model Tree — resolve before editing
3. File → Save a Copy before any major edit (creates a restore point)
4. Ctrl+S after completing each Part Studio successfully

Recovering from a broken model¶

FreeCAD's topological naming problem (→ topological-naming-problem) can cause features to detach from their reference geometry when upstream features change. Symptoms: red cells in Model Tree, error dialogs on recompute.

Recovery sequence: 1. Ctrl+Z to undo the last change 2. If undo is not possible: open the backup copy from before the edit 3. Identify which feature broke (the first red item in the tree) 4. Re-apply the constraint or reference using the current geometry 5. Do not rename features mid-model — this compounds TNP errors

Rationale¶

The FreeCAD Cookbook (V2.4.6) is 2,083 lines of step-by-step UI click maps that are necessarily version-specific — the menu paths and dialog layouts change between FreeCAD versions. This skeleton separates the stable conceptual content (modelling sequence, decision gates, EMC geometry requirements) from the version-specific click maps in the Cookbook. When FreeCAD 1.2 releases, only the UI atom (freecad-ui-110) and the Cookbook need updating, not this skeleton.

Connections¶

requires: [] related: - sk-complete-build-guide - sk-hardware-reference - sk-master-specification leads_to: - sk-complete-build-guide