Machinery TwinMotion profile reference
Automatic point constraints and expert Poly5, Poly3, Cubic and Straight intervals.
| Type | Degree | Continuity at joins | Use for |
|---|---|---|---|
| Poly5 | 5th order | C², position, velocity and acceleration | The default for real motion between dwells |
| Poly3 | 3rd order | C¹, position and velocity | Lighter curve when acceleration continuity doesn't matter |
| Cubic | 3rd order | C¹ | Spline-style interpolation through intermediate points |
| Straight | 1st order | C⁰, position only | Dwells and constant-velocity zones |
New cams are authored with shared points. Auto, Stop, and Pass through choose the appropriate law automatically. Select Manual / expert on a point to choose the motion profile of the interval from that point to the next and to enter slope/curvature boundary values.
The shared point owns one position, slope and curvature for both adjacent intervals, eliminating contradictory duplicated boundaries.
Rules of thumb
- Rest-to-rest moves: use Stop points at both ends; the compiler selects Poly5.
- Dwells: Straight with equal start/end positions.
- Constant-velocity zones (synchronization windows, the cutting stroke of a flying shear, the sealing zone of a cross sealer): Straight with the required slope; enter/exit via Poly5 segments whose boundary velocity matches the zone's slope.
- Poly3 vs Poly5: Poly3 can't enforce curvature boundary conditions, so joins are only slope-smooth. Acceptable for gentle motions; visible (and on a real machine, audible) for fast ones.
Common profile smells
- Sawtooth position (Straight up, Straight down), infinite acceleration at every corner. Fine for a rough block-out, never for the final profile.
- Vel-matched but accel-stepped joins, looks fine in position, shows as kinks in the visualizer's acceleration plot; upgrade the joins to Poly5.
- A single huge Poly5 doing three jobs, split into phases instead; boundary conditions per phase are easier to reason about than one over-constrained curve.