Table of Contents

Step Field Reference

Every simulated step carries a row of output: the NC line it came from, the kinematics, the load, and what that load did to the cutter. The field-by-field definitions are generated — MachiningStep is the complete and current list, and it is not copied here. This page states what each group covers, how the numbers are to be read, and the two readings that are most often misread.

How a Step's Numbers Are Formed

A step's data covers the time interval between two consecutive steps — from the previous step to this one — not an instant. Most fields are therefore a simplification over that period, and the prefix says which: Avg (average), Min / Max (extremes), Delta (range) and MaxAbs (maximum absolute value).

A field that depends on a frame carries the frame in its name: [W] workpiece, [TR] tool running, [SR] spindle rotation. The frames themselves are defined in Milling Physics Coordinates.

The machine coordinates of a rotary axis are continuous angles, on the step and in the step file: a table that turned twice the same way reads 720°, which is what an analysis needs. For an axis that wraps around, the Step Properties panel and the Color Index Time Chart show the same axis folded into 0–360°, as the controller's position screen does.

Field Groups

Group What it covers
Source The file, line, line text and flags of the NC command that produced the step, its index in the run, and the active tool id
Time and motion End-of-step timecode, step duration (one spindle revolution in the default per-revolution mode), spindle angle at the start, the cutter location with its IJK normal, the machine coordinates, the displacement in program coordinates, the feed / spindle-speed / cutting-speed / per-tooth family, whether the controller commanded the step as a rapid traverse (IsRapid: G00, Heidenhain FMAX, a CL RAPID, G28 and the travel to a tool-change position — the controller's modal state at the step, so the tool change's own step reads the travel's rapid when the change moves, else the state of the block before it; a CSV replay carries no rapid semantic and reads false), and whether a rapid step cut stock (IsRapidCut: true on the touched rapid steps of a line the play reported as Play-RapidCut--Detected, a line whose removed volume reached the project's RapidCutVolumeThreshold_mm3, by default any touch; false until the line is reported — when a feed step or another line follows it, or the play ends — and on a CSV replay; a changed threshold reaches it with the next play, as it reaches the warning)
Engagement and removal Whether the cutter was engaged at all, radial and axial engagement (ae, ap), material removal rate, and the program-side cusp height and its distribution
Chip Chip thickness, volume and mass
Force and torque Average and maximum force on the tool, torques about the tool tip and about the sensor point in each frame, and the mapping-comparison fields that put a measured signal beside the simulated one — error ratios and symbolic error correlation
Power and energy Spindle input power (what enters the spindle for the cut) and output power (what reaches the cut after spindle losses; the ratio between them is the spindle's configured EnergyEfficiency(API)), the spindle meter power (the output power plus the spindle's loss, the dry-run power of a turning spindle included: what a power reading on the machine shows, in air as well), the instantaneous and continuous power and torque ratios against the spindle capability curve, two accumulated energies: the input energy of the cut, and the meter energy of the whole play, the max breakage ratio (MaxBreakageRatio): the largest known of the yielding stress ratio and the instantaneous spindle torque and power ratios — NaN when the physics ran and none of the three is known, and empty like the three ratios on a step the physics did not run on, and the overload runs: the spindle revolutions (SpindleOverloadRevolutions; each step adds its seconds × its rpm / 60, so a change of speed does not break the run) and the peak ratio (SpindleOverloadPeakRatio) of the run of consecutive steps whose spindle ratio — the larger known of the instantaneous torque and power ratios — is above 1, and the spindle revolutions of the run whose yielding stress ratio is above 1 (YieldingStressOverloadRevolutions); every step of a run reads the run's value once the run closes (at a step whose ratio is 1 or below or unknown, at a rapid step, or at the end of the play) and the value so far while it is open (a stopped play leaves its last run open until the next play starts); 0 on a step in no run whose ratio is known, NaN when the physics ran and the ratio is unknown, and empty on a step the physics did not run on
Thermal Cutter body, cutter surface, workpiece surface and chip temperatures, cutter subsurface temperature at a given depth, and thermal stress with its yield ratio
Wear and deflection Instantaneous and accumulated crater wear, accumulated flank wear depth and width (the three accumulated values are those of the tool now mounted and start from zero at each tool change), tool tip and bottom-edge deflection, the height above the tip at which the step's cutting force is placed on the cutter beam for that deflection (the centroid of the engaged cutting edge), and re-cut depth

For what the thermal yield ratio implies about breakage risk see Evaluating Process Machinability; for the wear model behind the wear fields see Tool Life and Wear.

Note

EndTimecode was named AccumulatedTime before the rename, and step CSVs written with the legacy header are still read.

Two Readings That Are Usually Misread

A cusp spike is usually a rapid-move collision, not a finish result

The program-side cusp is computed from the ideal program feedrate while the cutter is engaged with the workpiece. A rapid traverse is not meant to touch material; when it does, the cusp formula is fed the (very high) rapid feedrate, so the value spikes far above any real cutting cusp. Treat an isolated cusp peak at a rapid / G00 line as a likely gouge or collision to investigate. The same engagement-during-rapid usually shows up beside it as spikes in the availability ratios — yielding stress, spindle torque, spindle power.

A power or torque ratio over 100% is load damage, and it is read by duration

A ratio above 100% means the spindle cannot supply the demanded load at the commanded rpm, so it droops: with feed held, rpm drops, feed-per-tooth rises, and forces climb further — a runaway loop that, left unchecked, grows the chip until the cutter breaks and the spindle and drive are overstressed. That is load damage, not a tool-versus-workpiece collision (see NC optimization).

Read it by duration, not just by height. A one-revolution overshoot usually still completes the pass, leaving a slightly insufficient cut there; a ratio that stays above 100% across many consecutive spindle revolutions is a genuine overload to fix. A high-load step typically also shows large cutter–workpiece engagement, large tip deflection, and more vibration and noise. Because the ratio is normalized by the spindle-capability curve, a placeholder or guessed spindle skews it — confirm against the real spindle's speed–power and speed–torque curves before calling a cut overloaded.

See Also