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Printed from Kezuriba (kezuriba.net/en/nc/g40/)

G40

Machining center, LatheModal, group 07

Cutter compensation cancel (lathe: tool nose radius compensation cancel)

⌨On machining centers

G40 G01 X_ Y_ (cancel in a block that includes a move)

Diagram: Cutter radius compensation: left (G41) and right (G42) of travel direction

Programmed pathG41 (left)G42 (right)Tool center path (dotted)Facing the traveldirection (arrow):Tool on left → G41Tool on right → G42No compensation → G40With spindle CW (M03):G41 = climb millingG42 = conventional millingOffset amount is thetool radius under the D no.
When canceled with G40, the tool center runs on the programmed path (the contour is undercut by the tool radius). Cancel with a straight lead-out move, not an arc.

◎On lathes: Tool nose radius compensation cancel

The same number means something different on lathes (FANUC-type G-code system A). Group 07.

Diagram (lathe): tool nose radius compensation, imaginary tip and nose center

ZXG42 nose-center pathImaginary tipWithout compensation, tapers and arcsare left undercut (orange)OD toward Z− (tool on the right) → G42ID toward Z−, face toward X− → G41
With G40 (no compensation) the imaginary tip follows the program path. Faces parallel to X and Z come out to size, but tapers and arcs are left uncut as shown in orange (overcut on the inside).

📚Sources

The meaning shown agrees in at least two sources (agreement confirmed). Explanations are written in our own words.

  1. Siemens AG — SINUMERIK 802D sl/840D/840D sl/840Di/840Di sl/810D Programming Manual ISO Milling, 04.2007 Edition (6FC5398-7BP10-0BA0) cache.industry.siemens.com
  2. Haas Automation, Inc. — Mill Operator's Manual – 17 Mill G-Codes (online version) haascnc.com
  3. National Institute of Standards and Technology (NIST), USA — The NIST RS274NGC Interpreter – Version 3 (NISTIR 6556, 2000) nvlpubs.nist.gov
  4. Saitama University, Faculty of Engineering, Department of Mechanical Engineering, practical training — Machining center program 2019 (training NC program O19-0101, with comments) jisshu.mech.saitama-u.ac.jp
  5. Siemens AG — SINUMERIK 802D sl/840D/840D sl/840Di/840Di sl/810D Programming Manual ISO Turning, 04.2007 Edition cache.industry.siemens.com
  6. Haas Automation, Inc. — Lathe Operator's Manual – 16 Lathe G-Codes (online version) haascnc.com
  7. Ministry of Health, Labour and Welfare (MHLW), Human Resources Development Bureau, Office of the Councillor for Skills Evaluation — Human resource development manual using the practical exam tasks of the Grade 3 Skilled Worker Test: CNC lathe work (March 2018) waza.mhlw.go.jp