Drawings and Manufacturing Documentation

Why drawings still matter#

Even in a 3D world, a drawing is how you tell a person (or a machine operator) exactly how to make a part. Some manufacturing is fully model-driven (export the part straight to a CNC), but drawings remain essential for hand fabrication, communicating tolerances, and creating a permanent record. A good drawing removes ambiguity so the person at the band saw or mill builds the right thing.

What goes on a drawing#

In Onshape you add a Drawing tab and place views of your part or assembly. A complete part drawing typically includes:

• Orthographic views — front, top, right (and isometric for clarity).
• Dimensions — every measurement needed to make the part, applied to the views.
• Hole callouts — diameter, quantity, and whether holes are tapped or clearance.
• Tolerances — how much variation is acceptable (e.g., +/- 0.005 in on a critical bore). Tight tolerances cost time; only apply them where they matter.
• A title block — part name, material (e.g., 6061-T6 aluminum), quantity, units, designer, and date.
• Section and detail views — to show internal features or zoom in on small details.

Dimension what the machinist needs#

A classic beginner mistake is to dimension a drawing the way the part was sketched rather than the way it will be measured and made. Dimension from clear reference edges (datums), group related dimensions, and make sure the part is fully defined by the dimensions shown — no more, no less. Avoid duplicate or conflicting dimensions.

Tolerances and GD&T#

Tolerance is the allowable variation in a dimension. For most FRC parts a general tolerance note (e.g., 'all dimensions +/- 0.01 in unless noted') plus tighter callouts on critical features is plenty. GD&T (Geometric Dimensioning and Tolerancing) is a more formal symbol-based system used in industry to control position, flatness, concentricity, and more. Most FRC teams use only light GD&T (mainly hole position), but understanding the concept helps when parts must fit precisely, like bearing bores and gear meshes.

Drawings stay linked to the model#

A major advantage of CAD drawings is that they are associative: change the 3D model and the drawing views and dimensions update. This keeps your documentation honest as the design evolves during the season — a paper drawing would go stale, but a CAD drawing tracks the model.

Practical tips#

• Only dimension critical features tightly. Over-tight tolerances waste shop time and may exceed your machines' capability.
• Use one drawing per part for fabrication, plus assembly drawings to show how parts go together.
• Export to PDF for the shop and keep the source drawing in Onshape.
• Check the drawing against the model and a sample part before cutting a batch.

Clear drawings are how the design team hands off cleanly to the build team without standing over their shoulder.