CNC router processing guide

• 1
  How a CNC router removes material
• 2
  What part shapes fit CNC router processing
• 3
  Materials that cut well and materials that fight back
• 4
  Feeds, speeds and depth of cut
• 5
  What accuracy a CNC router can hold
• 6
  CAM choices that change the result
• 7
  Router or milling center? Pick by part and callout

A CNC router spins a fluted cutter and moves it along programmed paths. The cutting edge shears material away chip by chip. On a gantry machine the spindle travels over a fixed bed, so sheet stock stays put while the tool does the work.

In CNC router processing the cutting force pushes mostly sideways. That is why the workholding matters as much as the spindle. A part that lifts or chatters during a pass will show marks that no finishing step can hide.

A router is a milling machine with a different geometry. Long travels and a large bed suit flat, wide parts. The trade is stiffness: the gantry flexes more than a cast column, so deep cuts in hard metal need lighter passes.

• 1
  Shear, not scrapeSharp flutes cut; dull ones rub and burnish.
• 2
  Climb vs conventionalClimb milling usually gives a better wall finish.
• 3
  Chip evacuationRecut chips dull the edge and spoil the floor finish.

Routers earn their keep on flat and shallow parts: panels, brackets, plates, housings, jigs, signs, and long rails. If the part fits inside the bed and the depth of cut stays modest, the work is quick and repeatable.

Tall, thin walls are the weak point. A 3 mm wall standing 80 mm high will deflect under side load. If the drawing calls for that geometry, plan a support or expect to move the job to a machining center.

Pockets and profiles are straightforward. Deep narrow slots are not, because a long small-diameter cutter bends. Keep the cutter as short as the geometry allows, and the same slot will hold tolerance.

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  Good fitPlates, panels, brackets, fixtures, long rails.
• 2
  Watch closelyThin tall walls, deep slots, tight inside corners.
• 3
  Move to a millSmall 3D features with tight true position.

Wood, MDF, acrylic, ABS, polycarbonate, POM and HDPE cut cleanly and fast. Aluminum 6061 and 6082 also route well when the spindle has enough speed and the feed keeps the chip thick.

Stainless 304 and 316 work-harden at the cutting edge. If the feed drops or the cutter dwells, the surface gets harder and the next pass is worse. Take a full chip load and keep moving.

Titanium, Inconel and hardened tool steel belong on a rigid machine with coolant and a rigid setup. On a gantry router they chatter, and chatter is a scrapped part, not a cosmetic issue.

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  EasyWood, MDF, acrylic, ABS, POM, HDPE, 6061 aluminum.
• 2
  Moderate6082, 7075, 303 stainless, brass, carbon fibre.
• 3
  Hard on tooling316L, 17-4PH, titanium, Inconel, tool steel.

Three numbers set the cut: spindle speed, feed rate and depth of cut. They are linked. Raise the feed without raising the speed and the chip gets too thick. Raise the speed without the feed and the edge rubs.

Chip load is the number to watch. If the chip is thinner than about 0.05 mm in aluminum, the cutter is rubbing rather than cutting. Heat builds in the tool, not in the chip, and edge life drops fast.

For a 6 mm carbide cutter in 6061 aluminum, a starting point is 12,000–18,000 rpm and 1,500–2,500 mm/min, with a 0.5–1.5 mm axial depth and 40–50 percent radial engagement. Tune from there.

In plastic, run faster and take bigger chips to keep heat out. In wood, depth of cut can be aggressive because the material is soft and the chips clear well.

On a well-set-up router cutting aluminum, ±0.05 mm is realistic on profile and pocket dimensions. Position error grows with part size because the gantry sees more thermal drift over a long pass.

Across a 500 mm span, ±0.1 mm is a fair expectation. Across 4,000 mm, ±0.25 mm is more honest. That is not a machine fault; it is thermal growth and rail straightness over a long travel.

When a drawing calls for ±0.005 mm, the job belongs on a precision CNC mill or a 5-axis machining center. Those machines close the loop on the tool tip and control the cut directly. A router is not the tool for that callout.

• 1
  Router, small part±0.05 mm in aluminum, good setup.
• 2
  Router, long part±0.25 mm across 4,000 mm.
• 3
  Precision mill±0.005 mm on GreatLight equipment.

Toolpath strategy decides as much as the machine. A constant-engagement path keeps the cutter loaded evenly, which holds finish and tool life. A simple offset path spikes the load at every corner.

Lead-in and lead-out matter on hard materials. Plunging straight down into aluminum or stainless leaves a witness mark. Ramp or helical entry spreads the load and protects the cutter.

Leave stock for a finish pass. Roughing at 0.3 mm radial and finishing at 0.1 mm gives a clean wall. Trying to hit the final size in one pass usually shows chatter in the surface.

• 1
  Constant engagementEven load, better finish, longer tool life.
• 2
  Ramp entryAvoids plunge marks in metal.
• 3
  Finish allowance0.1–0.2 mm left for the last pass.