A CNC simulator shows the toolpath of a program on screen without touching the machine. Mentor CNC offers 14 free simulators that run in the browser with no installation or sign-up: twelve CNC lathe cycle simulators, a 2-axis lathe CAM simulator and a 3-axis milling CAM simulator. Each one draws a live toolpath from the dimensions you enter and generates ready G-code in FANUC format. This page explains what each simulator is for, in which order to use them, and what to check before taking the generated code to a machine.
What Is a CNC Simulator and What Is It For?
The most expensive mistake on the first run of a CNC program is a collision: a Z value with the wrong sign, a forgotten diameter/radius difference or a missing retract line damages the tool, the chuck or the part. A simulator shows that mistake on screen, at no cost. For a learner it has a second benefit: seeing where each line of G-code takes the tool is far more durable than memorising commands. Mentor CNC simulators do a third job as well: they calculate every address of the cycle (P, Q, U, W, R, F) from the dimensions you enter and write the program themselves, so you learn how the cycle is built by reading the generated code.
How the Mentor CNC Simulators Work
- They run in the browser: open the page on a computer, tablet or phone; there is nothing to download, install or sign up for.
- You enter dimensions, a program comes out: stock diameter, finished diameter, length, depth of cut, finish allowance, feed and spindle speed go into form fields; the simulator writes the cycle lines.
- Live toolpath: every pass is drawn on screen; roughing passes, the finish pass and retracts are shown separately.
- FANUC format: the lathe simulators generate code in FANUC 0i-TC syntax (diameter programming, two-line G71/G70 and G76 formats). Copy the code into your program editor.
- Matched to the cycle guides: each simulator has a companion cycle guide that explains the addresses, parameters, alarms and limits. What you see in the simulator, you can read in the guide.
The 14 Simulators and What Each One Is For
CNC lathe cycle simulators
| Simulator | What it teaches / generates |
|---|---|
| G0 / G1 Basic Moves | Your first program: enter stock diameter, target diameter, length, pass depth, feed and speed; see the difference between G0 and G1 and the modal-command logic line by line in the generated program. |
| G90 Turning Cycle (OD / ID) | Single-pass turning cycle for outside and inside diameters; incremental U/W usage. |
| G94 Face Turning Cycle | Facing in stepped passes; short program with modal Z lines. |
| G71 Rough Turning Cycle | Multi-pass roughing from profile stages, depth of cut and finish allowances; two-line P/Q format. |
| G72 Face Roughing Cycle | Roughing from the face inward; ideal for seeing the direction difference against G71. |
| G73 Pattern Repeating Cycle | Repeating the profile on castings and forgings; X/Z relief allowances and pass count. |
| G74 Peck Drilling Cycle | Axial drilling with Q peck depth and R retract; chip-breaking logic. |
| G75 Grooving Cycle | Single and multiple grooves; pass plan with P and Q steps. |
| G92 Threading Cycle | Single-line threading cycle; metric threads from nominal diameter, pitch and pass depth. |
| G76 Threading Cycle | Two-line multi-pass threading; pick a standard and pitch and angle fill in, then set first-pass depth and finish allowance. |
| G32 / G33 Zigzag Threading | Produces every pass as explicit blocks without G76; alternates flank load on rough passes. |
| FANUC Macro Threading | Load-split pass plan and Custom Macro B program for trapezoidal, coarse-pitch, tapered and multi-start threads. |
CAM simulators (the whole operation)
| Simulator | What it teaches / generates |
|---|---|
| CNC Lathe CAM Simulator (2-axis) | Material group, stock, jaw grip, OD/ID feature cards, tool and nose-radius selection; complete program with solved speeds and feeds. |
| CNC Milling CAM Simulator (3-axis) | One operation on a vertical machining center: material, stock, G54 work zero, feature definition and the generated G-code. |
In Which Order Should I Use Them?
- G0/G1 Basic Moves: modal commands, diameter programming, safe approach and retract. The logic under every cycle lives here.
- G90 and G94: single-line turning and facing cycles; you see how one line becomes many passes.
- G71 / G70 and G72: multi-pass roughing and finishing; P/Q block logic, finish allowances, direction difference.
- G73: pattern repeating; how it differs from G71 on castings and forgings.
- G74 and G75: axial drilling and grooving; chip-breaking steps.
- G92, G76, G32/G33 and macro threading: a comparison of single-line, two-line, explicit-block and macro approaches to threading.
- CAM simulators: the whole operation with material group, stock, workholding, tool and cutting data.
Before You Take the Generated Code to the Machine
The simulator writes a correct cycle for the geometry you entered, but it does not know your machine. Check the following before running the program:
- Confirm that the cycle format matches your control: on the old FANUC 0 series G71 is a single-line cycle, on 0i and later it is two-line; the same distinction applies to G76.
- Tool numbers, offset numbers and the work zero (G54 or G50) must be edited for your machine; the simulator uses example values.
- Chuck jaws, tailstock and tool-holder dimensions are not in the simulation; check approach and retract points against them.
- Watch the program on the machine’s graphic screen first, then dry run, then machine the first part in single block at reduced feed.
- Builder parameters can change cycle behaviour (for example the G71 retract amount or the number of G76 finishing passes). Compare the values in the manual with your own parameter list.
Differences Between the Simulator and a Real Machine
The simulator shows the toolpath; it does not show cutting force, vibration, tool wear, coolant or chip flow. Collision detection covers only the drawn toolpath against the part profile; the holder body, the turret and the chuck are not considered. Speed and feed values are suggestions; material, insert grade and machine rigidity change the outcome. The simulator therefore does not replace time at the machine; it makes that time safer and more productive.
Frequently Asked Questions About CNC Simulators
What is a CNC simulator?
A CNC simulator is software that draws the toolpath of a CNC program on screen and shows the result before the program is run on a machine. Mentor CNC simulators also generate the G-code in FANUC format from the dimensions you enter, so they are both a learning tool and a program-preparation tool.
Are the simulators free, and do I need to install anything?
Yes, all of them are free and run in the browser; there is no download, installation or sign-up. They open on a computer, tablet or phone; a large screen is recommended for following the toolpath comfortably.
Which control is the generated G-code written for?
The lathe cycle simulators generate code in FANUC 0i-TC syntax (two-line G71/G70 format, two-line G76 format, diameter programming). On Siemens, Mitsubishi or Haas controls the same cycles use different addresses and some different behaviour, so the code must be adapted using that control's manual.
Can I run the generated program directly on my machine?
No, check it first. The simulator does not know about tool-to-part collisions with the chuck jaws, tool holder dimensions or machine-specific parameter settings. After loading the program, watch it on the machine's graphic screen, do a dry run, and machine the first part in single block at reduced feed.
Which simulator should I start with?
Start with G0/G1 Basic Moves; modal commands, diameter programming and safe approach are learned there. Then G90 and G94, then G71/G70, then grooving (G75), drilling (G74) and the threading cycles (G92, G76). Leave the CAM simulators for last, because they combine all of this in one operation.
Does a simulator replace CAM software?
For single-operation 2-axis lathe and 3-axis milling jobs it is enough for learning and quick programs. Multi-operation parts, 3D surfaces, 5-axis work and tool-library management need a real CAM package.
Disclaimer
The simulators on this page and the programs they generate are for training purposes. CNC programs cause physical machine movements; the same code can behave differently on different control units and with different parameter settings. Before running any program on a real machine, follow the machine builder’s manual and test with graphic check, dry run and single block. Mentor CNC cannot be held liable for damage or loss arising from the use of these tools.