Board CNC Processing Service Guide

A board part starts as flat stock: sheet, plate, or panel. The finished geometry may still be flat, or it may be a flat base with pockets, bosses, bores, and slots machined into it. The common thread is that one dimension is much smaller than the other two, and that changes everything about how the part is held and cut.

Typical examples we run include mounting plates, manifold blocks, heat-sink bases, PCB stiffeners and frames, control panel faces, gasket and seal plates, robot end-effector plates, battery module separators, and enclosure panels with machined openings. Aerospace ribs, automotive bracket plates, and medical instrument bases land in the same family.

Work like this rarely needs a five-axis center to be efficient, though the extra rotary axes help when a plate carries angled faces or compound holes. Two or three setups on a three-axis machine often cost less. The choice depends on feature count, positional tolerance between faces, and how many parts you need.

Thin sheet under roughly 0.5 mm deflects under cutting force. Climb milling with light radial engagement helps, but a laser or waterjet may hold the outline better and faster. Machining only makes sense when you need pockets, countersinks, tapped holes, or a controlled edge.

Parts with deep, narrow cavities relative to their thickness are better suited to a block. A tall rib standing on a thin base will chatter no matter how slowly you feed it. If the design calls for a 10:1 height-to-thickness ratio on a free-standing wall, expect to redesign the wall or accept a slower, more expensive process.

Very large panels with only a few holes are usually a sheet metal job. Press brake tooling and a punch press will beat a milling machine on cost per part once quantities climb. We will say so rather than quote a process that does not fit.

Flat parts move when you clamp them. A vise squeezes the middle and lifts the ends. Six clamps around the perimeter can bow a 3 mm plate by a few tenths before the tool touches it. The first operation usually removes stock from one face, flips the part, and then the released stresses let it curl.

We prefer vacuum chucks for panels wider than 300 mm, with a sacrificial spoil board machined flat in place. For smaller plates, a fixture plate with dowel pins and low-profile clamps keeps the part seated. Tape mounting works for thin stock when cutting forces stay light.

Rough and finish in separate operations where flatness matters. Take 0.3 mm off both faces first, let the part rest, then finish. On aluminum plate, this alone often recovers 0.05 mm of flatness that a single heavy pass would lose.

Aluminum plate is the default. Grades 6061 and 6061-T6 machine cleanly, hold a good finish, and resist distortion when the stock is stress-relieved. Grade 7075 is stronger and harder, which suits structural brackets, but it is more prone to movement after heavy stock removal.

Stainless 303 and 304 are common for plates that see moisture or chemicals. Both work-harden, so we keep radial engagement low and never let the tool rub. Grade 17-4PH is the pick for high-strength, corrosion-resistant parts, though it needs slower speeds and more tool changes.

Copper and brass plate parts appear in busbars, heat spreaders, and RF housings. They cut fast but grab the tool and throw chips, so chip evacuation and coolant flow matter more than speed. Titanium and Inconel plate take the longest cycle times and belong in a separate cost bracket entirely.

Send a 3D model plus a 2D drawing, or a STEP file with a tolerance table if the part is simple. The model defines geometry; the drawing defines what is actually inspected. A PDF or DWG/DXF is fine for the drawing itself.

Call out the datum faces. On a plate, the primary datum is almost always the largest flat face, and the second datum controls rotation in the plane. Without datums, an inspector picks their own and your positional tolerances mean nothing.

State the material grade and temper, not just aluminum. List critical features with their tolerances, surface finish, and any thread or chamfer requirements. Note the quantity and when you need the parts. Anything you leave out becomes an assumption, and assumptions get quoted twice.