Can I simulate a 5-axis CNC program for free?

Yes. The simulator on this page runs entirely in the browser with no sign-up or installation. Paste a program and press Run to see the tool motion and the cut part in 3D, with line-numbered warnings for TCP-off drift, singularities, rapid moves into the stock and holder collisions. You can share a program as a link.

What is the difference between G43.4 and G43.5?

Both are tool centre point control and treat X/Y/Z as the tool tip. G43.4 (type 1) gives the tool direction as rotary angles (A/C or B/C); G43.5 (type 2) gives it as a vector I/J/K and lets the control work out the angles. G43.5 depends less on the machine layout, but which of the two angle solutions is used is left to the control.

What do I, J and K mean in G68.2?

They are Euler angles for the plane: rotate the coordinates I degrees about Z, then J degrees about the new X, then K degrees about the new Z. For example, G68.2 X0 Y15. Z0 I0 J-45. K0 puts the origin at Y15 and tilts the plane -45° about X, giving a 45° face whose normal points between +Y and +Z.

Can I check undercuts and side holes that 3-axis simulators cannot show?

Yes. Many 3-axis simulators store the part as a height map seen from above, so they cannot draw sideways holes or overhanging walls. This one keeps the stock as a 3D grid, so cuts from any direction remain as they are. Use the Section button to slice at X=0 or Y=0 and look inside.

5-Axis CNC Simulator: G43.4, G43.5 and G68.2 Examples

Free play

The starting program tilts the same ball end mill by 30° with tool centre point control on (G43.4) and off (G43). At X-15 the tip stays put while only the tool leans; at X15 the tip swings through a big arc and gouges the top face. Press "Machine view" to see how the table actually tilts. Switch the machine layout and you will find that a program written with the A axis does not run on a head-type machine — it stops with an error.

X—

Y—

Z—

A—

C—

T—

—

—0:00—

Rotation directions (signs), the zero of C and the position of the rotation centre differ between machines; the values here are illustrative.

Commands this simulator reads

Command	Meaning	How it is simulated
G43.4 H_	Tool centre point control, type 1. X/Y/Z are the tool tip; A/B/C are the rotary-axis angles	The tip moves on a straight line in work coordinates; the angles change evenly within the block
G43.5 H_ I_ J_ K_	Type 2. The tool direction is a vector I/J/K; the control works out the rotary angles from the machine layout	Write all three of I/J/K. Of the two possible angle solutions, the one closer to the current angles is used
G49	Cancels tool length offset and tool centre point control	After it, X/Y/Z are read as positions of the machine’s linear axes
G68.2 X_ Y_ Z_ I_ J_ K_	Defines the tilted working plane (feature coordinate system). X/Y/Z is the origin; I/J/K are Euler angles (rotate about Z, then the new X, then the new Z)	Euler angles only; roll-pitch-yaw, three-point and two-vector forms are not read
G53.1	Points the tool normal to the tilted plane (indexes the rotary axes)	Only the rotary axes move; a warning appears if the tool is close to the stock
G69	Cancels the tilted working plane	Coordinates return to the ordinary work system
A / B / C	Rotary axes: A (about X) and C (about Z) on a table-table machine; B (about Y) and C on head-table and head-head machines	Naming an axis the machine lacks is an error. The tilt axis travels ±120°; C turns without limit
G41 / G42 / G73–G89 / # / WHILE	Cutter compensation, canned cycles and Custom Macro B work as on a 3-axis machine	Inside a tilted plane they act in plane coordinates. 3D tool radius compensation for a tilted tool is not simulated

Each control maker names and writes the same functions differently. This simulator reads only the FANUC-style syntax.

NC	Tool centre point control	Tilted working plane
Siemens SINUMERIK	TRAORI	CYCLE800
Heidenhain TNC	M128 / FUNCTION TCPM	PLANE SPATIAL and others
Haas	G234 (TCPC)	G268
Mitsubishi Electric	G43.4 / G43.5	inclined surface machining command

Code numbers and availability depend on the control model and the machine builder’s options. Always check the manual for the real machine.

13+2: a 45° face and a hole normal to it

Cut the top +Y edge of the block to a 45° face, then drill a φ6 hole 12 mm deep normal to that face at its centre. Tilt the coordinates with G68.2, point the tool with G53.1, and the rest is written like 3-axis code.

Hint

G68.2 X0 Y15. Z0 I0 J-45. K0 puts the origin on the top edge of the face with Z pointing out of it. The face spans Y' 0 to 21.2 mm; the hole is at Y' 10.607.

X—

Y—

Z—

A—

C—

T—

—

—0:00—

O5001 (3+2 KEISHAMEN TO ANA)
G21 G90 G17 G40 G49 G80 G69
G54 G00 A0 C0
T1 M06 (FLAT D12)
S5000 M03 M08
G68.2 X0 Y15. Z0 I0 J-45. K0
G53.1
G43 H1 Z50.
#1 = 7.
WHILE [#1 GE 0] DO1
G00 X-40. Y2.
Z[#1 + 5.]
G01 Z#1 F600
X40. F1200
Y10.
X-40.
Y18.
X40.
G00 Z[#1 + 5.]
#1 = #1 - 3.5
END1
G00 Z50.
M05 M09
G69
G49
G00 Z100.
A0 C0
T2 M06 (DRILL D6)
S2000 M03 M08
G68.2 X0 Y15. Z0 I0 J-45. K0
G53.1
G43 H2 Z50.
G00 X0 Y10.607
G98 G81 Z-12. R3. F150
G80
G00 Z50.
M05 M09
G69
G49
G00 Z100.
A0 C0
M30

23+2: a side hole and a side slot (hidden from above)

Drill a φ8 hole 15 mm deep into the middle of the +Y side (Z-20) and mill a slot 10 wide, 5 deep and 30 long into the -X side. A height-map simulator cannot show these; here the sideways features are cut as they are. Use "Section" to look inside.

Hint

For the -X side use G68.2 X-30. Y0 Z-20. I90. J-90. K0. The first rotation I (about Z) swings Z' round to -X; X' is then work +Y and Y' is work -Z.

X—

Y—

Z—

A—

C—

T—

—

—0:00—

O5002 (3+2 SOKUMEN NO ANA TO MIZO)
G21 G90 G17 G40 G49 G80 G69
G54 G00 A0 C0
T1 M06 (FLAT D10)
S6000 M03 M08
(-X NO SOKUMEN : Z' GA -X MUKI)
G68.2 X-30. Y0 Z-20. I90. J-90. K0
G53.1
G43 H1 Z50.
G00 X-15. Y0
Z3.
G01 Z-2.5 F200
X15. F800
Z-5. F200
X-15. F800
G00 Z50.
M05 M09
G69
G49
G00 Z100.
A0 C0
T2 M06 (DRILL D8)
S1600 M03 M08
(+Y NO SOKUMEN)
G68.2 X0 Y30. Z-20. I0 J-90. K0
G53.1
G43 H2 Z50.
G00 X0 Y0
G98 G83 Z-15. R3. Q5. F160
G80
G00 Z50.
M05 M09
G69
G49
G00 Z100.
A0 C0
M30

3Simultaneous 5-axis: swarf-cut a 10° draft wall

Turn the φ56 round blank into a frustum with a 50 mm base and a 10° draft, 20 mm deep. The side of the tool rides on the wall, so use G43.5 (tool axis given by I/J/K) and step the tip position and direction every 5° round the part. The floor corner (Z-20 to -17.6) is not graded.

Hint

The outward wall normal is (cos10°·cosφ, cos10°·sinφ, sin10°) and the tool axis (−sin10°·cosφ, −sin10°·sinφ, cos10°). The tip centre sits one tool radius out along the normal from the foot of the wall.

X—

Y—

Z—

A—

C—

T—

—

—0:00—

O5003 (DOUJI 5JIKU SWARF)
G21 G90 G17 G40 G49 G80 G69
G54 G00 A0 C0
T1 M06 (FLAT D10)
S6000 M03 M08
#1 = 10. (KOUBAI)
#2 = 5. (KOUGU NO HANKEI)
#3 = 25. (SOKO NO HANKEI)
#4 = -20. (SOKO NO Z)
#10 = #3 + #2 * COS[#1]
#11 = #4 + #2 * SIN[#1]
G43.5 H1 X[#10 + 20.] Y0 Z50. I[-SIN[#1]] J0 K[COS[#1]]
G00 Z#11
G01 X#10 F400
#5 = 5.
WHILE [#5 LE 360.] DO1
X[#10 * COS[#5]] Y[#10 * SIN[#5]] I[-SIN[#1] * COS[#5]] J[-SIN[#1] * SIN[#5]] K[COS[#1]] F800
#5 = #5 + 5.
END1
G01 X[#10 + 20.] F800
G00 Z50.
G49
M05 M09
G00 A0 C0
M30

4Undercut: a 15° dovetail with a tilted tool

Cut a dovetail 16 mm wide at the top and 10 mm deep along X, with walls leaning in by 15°. The walls overhang, so a vertical tool cannot reach them. Slot the middle with φ12, then tilt φ6 by ±15° on the A axis and cut each wall with the side of the tool. The floor corners are not graded.

Hint

Right wall A-15., left wall A15. (C0). The tip centre is at Y±7.366, Z-9.224. Go down and up outside the stock (X±40) so the overhanging walls are not gouged.

X—

Y—

Z—

A—

C—

T—

—

—0:00—

O5004 (ARIMIZO 15DO)
G21 G90 G17 G40 G49 G80 G69
G54 G00 A0 C0
T1 M06 (FLAT D12)
S5000 M03 M08
G43 H1 Z50.
G00 X-40. Y0
Z2.
G01 Z-5. F300
X40. F800
Z-10. F300
X-40. F800
G00 Z50.
M05 M09
G49
T2 M06 (FLAT D6)
S8000 M03 M08
(MIGI NO KABE : A-15)
G43.4 H2 X-40. Y7.366 Z50. A-15. C0
G00 Z-9.224
G01 X40. F600
G00 Z50.
(HIDARI NO KABE : A15)
G00 Y-7.366 A15.
Z-9.224
G01 X-40. F600
G00 Z50.
G49
M05 M09
G00 A0 C0
M30

Tips for writing 5-axis programs

3+2: G68.2, then G53.1, then G43. Cancel the tool length offset (G49) before defining the plane, move the tool clear of the stock, then index the rotary axes with G53.1. G53.1 swings the rotary axes, so commanding it just above the part can drive the tool into it. Generic CAM post-processors output the same order: retract, cancel compensation, G68.2, G53.1.
Prefer machine-independent code. G68.2 and G43.5 describe the tool direction, so the same program runs on machines of other layouts (exercises 1 and 3 cut the same shape on a head-type machine too). G43.4 with explicit A and C is tied to one machine’s layout and rotation directions.
Watch how you retract from an undercut. Lifting a tilted tool straight up in Z gouges an overhanging wall. Go up and down outside the stock, or retract along the tool axis. The section view shows at once where a gouge happened.
Avoid changing direction near vertical. Changing the direction slightly while the tool is almost vertical makes the C axis swing a long way at once (the singularity), which slows the feed and can mark the surface. The simulator warns when C turns more than 30° in one block.
Do not move rotary axes without TCP near the part. Without tool centre point control the linear axes do not follow when the rotary axes turn, so the tip swings round the rotation centre. Do rotary moves at a safe height away from the stock.

Assumptions and limits

The stock is a 3D grid at 0.5 mm spacing, each point holding its distance to the surface. Features finer than 0.5 mm look rounded. Grading counts places more than 0.15 mm off the drawing and fails anything 0.25 mm or more off.
Collisions are checked only between the tool, shank and holder and the stock — not with fixtures, the table, the spindle head or the machine body.
Rotation directions, zeros, travel (±120°), the rotation centre (about 80 mm below the table top) and the head pivot length (150 mm) are illustrative. How the linear axes behave on G53.1, which of the two solutions G43.5 picks and how feed is computed with rotary motion all depend on control parameters on a real machine.
Inverse time feed (G93), 3D tool radius compensation, tilted-plane definitions other than Euler angles and inch input (G20) are not supported.
Before cutting on a real machine, always verify with a collision-checking simulation from the machine builder or CAM vendor, plus a dry run and single-block. This page is for learning how the code is written and how the machine moves.

FAQ

Can I simulate a 5-axis CNC program for free?: Yes. The simulator on this page runs entirely in the browser with no sign-up or installation. Paste a program and press Run to see the tool motion and the cut part in 3D, with line-numbered warnings for TCP-off drift, singularities, rapid moves into the stock and holder collisions. You can share a program as a link.
What is the difference between G43.4 and G43.5?: Both are tool centre point control and treat X/Y/Z as the tool tip. G43.4 (type 1) gives the tool direction as rotary angles (A/C or B/C); G43.5 (type 2) gives it as a vector I/J/K and lets the control work out the angles. G43.5 depends less on the machine layout, but which of the two angle solutions is used is left to the control.
What do I, J and K mean in G68.2?: They are Euler angles for the plane: rotate the coordinates I degrees about Z, then J degrees about the new X, then K degrees about the new Z. For example, G68.2 X0 Y15. Z0 I0 J-45. K0 puts the origin at Y15 and tilts the plane -45° about X, giving a 45° face whose normal points between +Y and +Z.
Can I check undercuts and side holes that 3-axis simulators cannot show?: Yes. Many 3-axis simulators store the part as a height map seen from above, so they cannot draw sideways holes or overhanging walls. This one keeps the stock as a 3D grid, so cuts from any direction remain as they are. Use the Section button to slice at X=0 or Y=0 and look inside.

Related pages

Sources

Command names and behaviour were checked against public material from control and machine makers and the output of a CAM vendor’s FANUC post-processor. No manual text or examples were copied.

5-AXIS NC SIMULATOR5-Axis CNC Simulator

Free play

Commands this simulator reads

Exercises

13+2: a 45° face and a hole normal to it

23+2: a side hole and a side slot (hidden from above)

3Simultaneous 5-axis: swarf-cut a 10° draft wall

4Undercut: a 15° dovetail with a tilted tool

Tips for writing 5-axis programs

Assumptions and limits

FAQ

Related pages

Sources