The toolpath is perfect. The axis still runs out of travel getting there
Overtravel is a strange kind of crash: nothing hits anything. There’s no fixture in the way, no tool clipping a clamp, no collision at all in the usual sense. The machine simply commands an axis past the end of its physical travel, and either faults out mid-program — stopping a run cold — or, worse, forces its way there and damages the axis. The toolpath that got there can be geometrically flawless. The problem is the machine, not the path: this particular machine can’t reach that orientation from that position.
That’s why overtravel slips past the checks most programmers trust. It isn’t a geometry error, so a geometry check doesn’t see it. And it gets dramatically more likely the moment rotary and B-axis motion enter the picture — which is to say, on exactly the multi-channel and multi-axis turning machines where a mid-run fault is most expensive.
Why rotary and B-axis multiply the risk
On a 3-axis mill, travel limits are simple boxes and rarely surprising. Add a rotary axis, a B-axis, a sub-spindle, and multiple channels, and the ways to run out of travel multiply:
- Rotary wind-up. A C-axis that keeps rotating in one direction across many operations can accumulate toward a rotational limit — fine for a while, then suddenly past it.
- B-axis reach. Orienting a tool with a B-axis changes what linear travel remains. An orientation that’s reachable at one position runs an axis off its limit at another.
- Combined-axis moves. A simultaneous move distributes travel across several axes at once; one of them can hit its limit while the others have room to spare, and it’s not obvious which from the code.
- Sub-spindle and tailstock intrusion into travel. The usable travel of one element depends on where another is — the sub-spindle’s position changes how far the main-side axes can move.
- Kinematics-specific limits. Head-head, table-table, and mixed kinematics each impose different travel envelopes for the same nominal geometry.
Every one of these depends on the *specific machine’s* travels and kinematics — not on the part, and not on the toolpath.
Why the listing and the CAM sim miss it
Reading the code doesn’t reveal it. A commanded position is just a number; whether it’s inside this machine’s travel envelope isn’t visible from the line. Combined-axis and rotary limits are effectively impossible to check by eye.
A toolpath simulation doesn’t model your machine’s travels. A CAM’s toolpath render is about the shape being cut, not the physical limits of the specific machine and kinematics the program will run on. If the simulation doesn’t carry your machine’s real travel envelope and its real kinematics, an axis running past its limit isn’t represented — the toolpath looks clean because, as a path, it is. The overtravel only exists relative to this machine, which the toolpath sim isn’t checking against.
Catching it needs the real program executed against a twin that has the actual machine’s travels, kinematics, and the position of every element — spindle, sub-spindle, rotary, B-axis — at each moment.
Where Eureka G-Code fits
Eureka G-Code builds a twin of your real machine and kinematics, head-head, table-table, mixed, with rotary and B-axis, sub-spindle and multiple channels, and executes the true ISO against it. Because the twin carries the machine’s actual travel envelopes and follows the real position of every axis and element as the program runs, an overtravel / end-of-travel condition surfaces on the twin before the machine faults mid-run or forces an axis past its stop. Rotary wind-up, a B-axis orientation that runs out of linear travel, a combined move where one axis hits its limit — all of them appear where the machine will actually hit them.
And because it’s the same run that checks collisions, you get the full picture at once: hard collision, near-miss between cutting edge and equipment, holder-vs-blank, finished part vs model, pre-holes for tapping — and overtravel — on the real kinematics, at any number of axes. On complex turning machines, that’s the difference between a program that looks reachable and one you’ve confirmed the machine can actually execute end to end.
> Take the job with your tightest transfer, the short part, the fast pickup, the back-working operation that starts the instant the sub has it, and run the real ISO on a twin of your machine in Eureka G-Code. Watching the handoff sequence the way the control runs it, before the spindles do it for real, is how the drop gets caught at a desk.
FAQ
What causes an overtravel / end-of-travel crash?
A program commands an axis past the end of its physical travel. Nothing collides — the machine either faults mid-program and stops the run, or forces the axis to its limit and damages it. It’s common on rotary and B-axis moves, where reachable travel depends on the machine’s kinematics and the position of other axes.
Why doesn't my CAM catch overtravel?
A CAM toolpath simulation checks the shape being cut, not the physical travel limits of the specific machine and kinematics the program runs on. Overtravel exists only relative to that machine, so a toolpath render that doesn’t model the real travel envelope doesn’t see it.
Does Eureka G-Code check axis travel limits?
Yes. It executes the real ISO against a twin of your actual machine and kinematics, following the position of every axis and element, so overtravel and end-of-travel conditions surface before the machine hits them — alongside collision and near-miss checks in the same run.
Does it handle different machine kinematics?
Yes. It reproduces head-head, table-table, and mixed kinematics, with rotary and B-axis, sub-spindle and multiple channels, so the travel envelope checked matches the machine that will run the program.
Is overtravel a geometry problem?
No — that’s why it’s easy to miss. The toolpath can be geometrically perfect; the fault is that this specific machine can’t reach that position or orientation within its travel. It only shows up when the program is checked against the real machine’s limits.
Next step
Request a demonstration on a digital twin of your own machine
Verify the real ISO against your machine’s real travels — on a digital twin, before an axis finds its limit