Sketch Basics

Open with the big idea: the entire CAD pipeline rests on sketches. Show a finished bumper bracket, then click its first sketch in the timeline to reveal the flat outline underneath. Tell students: if your sketch is messy, every feature downstream inherits that mess. This is the most important hour of the unit.

Expand the Origin folder in the browser so they see the three planes plus the center point. Demo: start a sketch, pick the XY plane. Stress that the very first line or point should snap to the origin. The single most common beginner mistake is drawing a part floating in space, then it spins or moves unexpectedly when joined later. Origin = home base.

Teach the workflow: sketch loosely, then constrain. Beginners try to draw perfectly with the mouse and get frustrated. Show a sloppy blue quad. Explain the color code right now: blue lines can still move (under-defined), black lines are locked (fully defined). Our goal every time is to turn the whole sketch black.

Walk the constraint toolbar in the Sketch Palette one icon at a time. Apply Horizontal and Vertical to the sloppy quad and watch it snap square. Apply Equal to two sides to make a true square. Emphasize: constraints are RELATIONSHIPS, dimensions are NUMBERS. Use constraints first because they hold up when you change dimensions later. Keyboard tip: hover shows the shortcut letters.

Tangent is essential for slots and rounded brackets so lines flow into arcs without a sharp corner. Demo a slot. Symmetric is huge for FRC: pick two holes and a centerline, and they mirror perfectly so the part stays balanced. Common mistake: selecting the entities in the wrong order. For Symmetric, pick the two objects first, then the axis line.

D is the shortcut to memorize. Click an edge, drag out, type the number, Enter. Show how each new dimension turns more lines black. FRC tip: type units explicitly. Fusion will respect 'in' even if the document default differs, and you can type fractions like 1/2 in. Mention you can reference User Parameters here by name, which we cover in a later lesson.

Construction lines are scaffolding. Demo: draw a diagonal corner-to-corner construction line, place a center point where it crosses, and put a bolt hole there. Toggle a normal line to construction with X. Critical point: construction geometry does NOT create faces, so it won't accidentally split your extrude. Use it for centerlines and the mirror axis for Symmetric.

Demonstrate the drag test: grab a blue endpoint and wiggle it. If it moves, the sketch isn't locked. Add what's missing until everything is black. Reassure students that over-defining throws a warning (a conflict) and they should undo, not pile on more dimensions. A fully-defined sketch is the mark of a careful CAD engineer and it won't surprise you later.