--- title: "Why Did My CNC Crash on G00? Common Beginner Causes" description: "A G00 rapid moves at full speed, so a wrong offset, tool length, or start point turns a small mistake into a crash. Here are the usual causes, explained for learners." url: https://gcodepractice.com/journal/why-did-my-cnc-crash-on-g00/ canonical: https://gcodepractice.com/journal/why-did-my-cnc-crash-on-g00/ author: "Lawrence Arya" authorUrl: https://www.linkedin.com/in/vibecoding/ published: 2026-06-02 updated: 2026-06-02 category: "Guides" tags: ["g00", "crash", "safety basics", "beginner"] lang: en --- # Why Did My CNC Crash on G00? Common Beginner Causes > **TL;DR** A CNC usually crashes on G00 because the rapid move went somewhere you did not intend, at full speed: a wrong work offset (G54), a missing or wrong tool length offset, a rapid commanded into the stock or a clamp, or absolute and incremental modes mixed up. G00 does not cut, but it moves fast, so a bad coordinate becomes a collision. This is an educational overview, not operating or safety advice. This is an educational explanation of why beginners see crashes on a `G00` line. It is not operating instructions or safety advice for your specific machine. Always work under your instructor or employer and follow the machine manual. A `G00` is a rapid: it moves to a coordinate as fast as the machine can. It does not cut, which is exactly why beginners are surprised when it crashes. The code did nothing wrong; it went fast to the wrong place. ## The usual causes Most `G00` crashes trace back to a mismatch between what the program assumes and what the machine actually knows: - **Wrong work offset.** If `G54` (or whichever work offset is active) is set wrong, the machine's part zero is in the wrong spot, so every rapid is shifted. - **Wrong or missing tool length offset.** The Z rapid assumes a tool length. If that offset is off, the tool rapids too low. - **Rapid into the stock or a fixture.** A rapid planned for clear air becomes a collision if the stock, vise, or clamps are taller or positioned differently than assumed. - **Absolute vs incremental mix-up.** With `G91` (incremental) left active when the program expected `G90` (absolute), a rapid lands somewhere completely different. See [G90 vs G91 crash prevention](/journal/g90-vs-g91-crash-prevention/). - **A non-straight rapid path.** On many controls a `G00` does not move in a straight diagonal, so a path you assumed was clear can clip something. ## At a glance | Cause | What is actually wrong | The concept to learn | | --- | --- | --- | | Wrong work offset | Part zero is in the wrong place | `G54`-`G59` work offsets | | Wrong tool length | Z assumes the wrong tool height | Tool length compensation (`G43`) | | Rapid into stock/fixture | Path not actually clear | Clearance planning | | Absolute/incremental mix-up | Mode not what the program expects | `G90` vs `G91` (modal state) | | Dogleg rapid path | Path is not a straight diagonal | How `G00` actually moves | ## Why this is a recall problem too Notice every cause is a code or concept you can know cold: what `G00` does, how `G90`/`G91` change it, what `G54` sets. Beginners who can read [G00 vs G01](/journal/g00-vs-g01/) and the [common G-codes](/journal/common-g-codes-for-cnc-beginners/) without hesitating are far less likely to misread a setup. Recall does not replace careful checking on the machine, but it removes the confusion that causes many beginner mistakes. Building that recall is what [beginner CNC code practice](/journal/beginner-cnc-code-practice/) is for. A closely related failure mode worth understanding is the [Z-axis plunge crash](/journal/z-axis-plunge-crash-g-code-mistake/). ## Bottom line A `G00` crash is almost always a wrong number reaching a fast move: an offset, a tool length, a mode, or a path that was not really clear. Learn the setup codes cold, verify offsets, and use your machine's safe-checking features under supervision. ## Sources - [LinuxCNC G-code reference (G0, coordinate systems)](https://linuxcnc.org/docs/html/gcode/g-code.html) - [Wikipedia: G-code](https://en.wikipedia.org/wiki/G-code) - [CNCCookbook: G-code and M-code cheat sheet](https://www.cnccookbook.com/g-code-m-code-cnc-list-cheat-sheet/) ## Frequently asked questions ### Does G00 cause crashes because it is a cutting move? No. `G00` does not cut. It crashes things because it moves at the machine's maximum rapid rate, so a wrong coordinate, offset, or mode sends the tool somewhere fast, with no time to react. ### What is the most common G00 crash cause for beginners? A wrong or missing offset: the wrong work offset (`G54` to `G59`) or a tool length offset that does not match the tool. The program is fine, but the machine's idea of zero is wrong, so the rapid goes to the wrong place. ### How can I avoid G00 crashes while learning? Learn what each setup code does, verify offsets, and use your machine's safe checking features under supervision. A practice tool like G-Code Sprint helps you recall what codes like `G00`, `G90`, and `G54` mean, but it is not a controller or a safety system. Always follow your instructor and machine manual. *G-Code Sprint is a study and practice tool only. It is not a CNC simulator, machine controller, or safety authority. Always follow your instructor, employer, machine manual, and shop safety procedures.* --- Source: https://gcodepractice.com/journal/why-did-my-cnc-crash-on-g00/ Author: Lawrence Arya — https://www.linkedin.com/in/vibecoding/