TOOLPATHSToolpath types

A toolpath (tool path) is the route that the tool's cutting edge or center follows^[1][2]. Choose a machining method suited to the shape and have CAM calculate it. Usually you layerroughing → semi-finishing → finishing → rest machining in that order^{[3][4][5][1][6]}. The figures are schematics and are not drawn to scale.

▭2.5D toolpaths

Cuts flat contours and pockets by stepping Z down to a set depth. You draw the contour in XY and only change the depth of cut in Z. Mainly for prismatic parts and drilling.^[1][7][8]

Contour (outer edge, profile)

Pocket

Facing

Hole machining (drilling, tapping)

Trochoid

Contour (outer edge, profile):Moves the tool around the outer or inner edge of a shape. Used for finishing side walls and cutting out the outline.^[1][9]
Pocket:Digs down inside a closed contour, cutting layer by layer to a set depth.One source / reference^[1]
Facing:Cuts the top surface flat. Used for removing mill scale from stock and bringing it to height.^[1][9]
Hole machining (drilling, tapping, helical):Picks up hole positions and outputs drilling and tapping with canned cycles and the like. There are also paths that enlarge a hole by helical interpolation.^[1][9][6][7]
Trochoidal milling:Advances while drawing small circles and removes thin chips bit by bit. Cuts slots and pockets with a small radial depth of cut and a large axial depth of cut. A method devised for hardened steel and heat-resistant alloys.One source / reference^[10]

Canned cycles for hole machining:G81,G83,G84(G/M code dictionary)

≋High-efficiency roughing (adaptive / dynamic type)

With constant-spacing paths (conventional), the engagement (red) increases suddenly at corners

Conventionally small ap and large ae. High-efficiency roughing uses a small ae and a deep ap (axial depth of cut) (red = engaged area)

High-efficiency roughing (adaptive / dynamic type):Roughs while varying the pass spacing from place to place so that the load on the tool (engagement) stays below a set limit. Takes a deep depth of cut (Z direction) and can use the whole side of the tool.^[3][9][1]
Axial depth of cut ap, radial depth of cut ae:ap is the amount the tool engages in the axial direction, and ae in the radial direction. High-efficiency roughing and trochoidal milling use a small ae and a large ap.^[10][3]

For a guide to the first depth of cut, see thecalculation below.

◠3D finishing toolpaths

Moves the X, Y, and Z axes simultaneously to cut along curved surfaces. For dies and molds and freeform parts. Finishing passes at a fine pitch are stacked with a ball end mill.^[7][8][6][1]

The figures show the points (blue) the path passes through on the same mountain-shaped cross-section.

Waterline: at each constant height (good for steep slopes)

Raster: parallel lines in XY (good for gentle surfaces)

Surface-following (scallop): equal spacing on the surface

Pencil: only the valleys and corners (red) the previous tool cannot reach

Rest machining: a small tool cuts what the large tool left (red)

Waterline (Z-level, contour):Traces the contour of the shape at each constant height (Z). Suited to finishing steep slopes and vertical walls.^[4][6][1]
Raster (parallel):Reciprocates along parallel lines in the XY plane, with Z following the curved surface. Suited to finishing gentle surfaces.^[4][6][11]
Surface-following (scallop, constant pitch):Cuts while offsetting inward so that the spacing between passes stays constant on a curved surface. Often used to finish areas left by waterline and raster.^[4][6]
Pencil (corner machining):Creates a path along small-radius corners and valleys to cut corners the previous tool could not reach.^[4][6]
Rest machining (leftover machining):Uses a small tool to cut only the areas left uncut by the previous operation (with the larger tool).^[5][6][3]

Stepover (pitch):The spacing between adjacent passes. It affects the height of the cusps (ridges) on the finished surface.^[4][10][12]

For ball end mill speed and feed, see theBall end mill calculator.

⟲5-axis toolpaths

Swarf (side cutting):Cuts with simultaneous 5-axis, placing the side of the tool against an inclined wall.^[6][8]

For how to decide the tool orientation, machine configurations, and how to check for collisions, see5-axis machiningpage.

◎Trochoidal slot milling guide

Tool diameter Dc(mm)Slot width(mm; may be left blank)

Upper limit of ae (0.20Dc)—mm

ae in the G1 segment (0.10Dc)—mm

Upper limit of advance per loop (0.10Dc)—mm

Radius of entry and exit arcs (0.50Dc)—mm

Lower limit of slot width (Dc ÷ 0.70)—mm

Dc ÷ slot width—

ae_max = 0.20 × Dc / rad_m = 0.50 × Dc / w_max = 0.10 × Dc / Dc ÷ slot width < 0.70^[10]

Dc: tool diameter (mm)
ae_max: upper limit of radial depth of cut (mm)
rad_m: radius of the entry and exit arcs (mm)
w_max: upper limit of advance per loop (stepover) (mm)

This is a guide.It is a calculation that only multiplies the ratios in the Sandvik Coromant material by the values you enter; the material gives no worked example. The same material lists an ae upper limit of 20% Dc, ae of 0.1 × Dc in the G1 segment, and a stepover upper limit of 10% Dc, so all three are shown.

↧Guide to the first depth of cut in high-efficiency roughing

Tool diameter D(mm)Effective flute length of the tool(mm)

Aluminum: ap (1.5–2.0 × D, up to flute length)—mm

Steel: upper limit of ap (up to flute length)—mm

Steel: ap ≤ flute length / Aluminum: ap = 1.5–2.0 × D (but up to flute length)^[3]

ap: axial depth of cut (mm)
D: tool diameter (mm)

This is a guide.The Autodesk Fusion help gives the tool's effective flute length as the guide for the first depth of cut: up to the flute length for steel, and 1.5 to 2 times the tool diameter (up to flute length) for aluminum. This is one manufacturer's guideline, and the material gives no worked example. For speed and feed, see theEnd mill and milling cutter calculator.

Other CAD/CAM pages

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📚Sources

Toolpath names differ by software (for example: Z-level = contour = waterline). Check the names in the help of your CAM.

TOOLPATHSToolpath types

▭2.5D toolpaths

≋High-efficiency roughing (adaptive / dynamic type)

◠3D finishing toolpaths

⟲5-axis toolpaths

◎Trochoidal slot milling guide

↧Guide to the first depth of cut in high-efficiency roughing

Other CAD/CAM pages

CAD/CAM basics

CAD/CAM software list

Data formats

Coordinate systems, post, DNC

5-axis machining

📚Sources