The X20SM1446-1 current trace does not report amperes. Its current datapoint is an enumeration that identifies the selected current mode, so trace values of 3 during acceleration/deceleration, 2 at constant speed, and 1 at standstill cannot be interpreted as 3 A, 2 A, and 1 A. Diagnose the separate standstill-motion problem through position-control timing and lag-error traces.
Interpret the current trace correctly
| Trace result | Supported interpretation | Engineering decision |
|---|---|---|
| 0, 1, 2, or 3 | Selected current-mode enumeration | Do not label the value as amperes. |
| Actual winding current | Not available from this trace datapoint | Measure at the motor wires with a multimeter. |
The 80MPD5.600S014-01 is described as internally parallel-wired and capable of running at 6 A, but that rating does not prove that the module is delivering 6 A. The supplied configuration images do not expose their numeric settings, so the configured current limits cannot be audited from the available evidence.
Diagnose slow movement at standstill
An active position controller can command corrective movement in any powered-on state, including standstill. This provides a supported explanation for slow motion—sometimes opposite the preceding move—even when the displayed position appears to remain at zero. Treat that explanation as a hypothesis until a trace correlates the command, feedback, and error.
- Trace set position, actual position, and lag error together through the end of a commanded move and the following standstill period.
- Repeat the measurement with position control disabled and compare the result. If the creeping stops, the position-control path is implicated.
- Confirm that position control and prediction time are configured intentionally, then verify that all timing values match the network configuration.
- If position control remains active at standstill, consider matching the standstill and constant-speed current settings. Configure the acceleration/deceleration current similarly or higher only when the load requires it; more current can increase resonance behavior with small loads.
Calculate and verify prediction time
The stated network calculation uses a 4 ms cycle and eight cycles of delay:
Prediction time = 0.004 s × 8 = 0.032 s
Equivalent delay = 32 msA trial value of 0.04 s did not eliminate the standstill movement. Prediction values must follow available cycle-time increments. Incorrect timing can create false lag errors and drive incorrect position-controller behavior. A 32 ms total delay also limits achievable controller performance; reducing cycle time or placing the stepper modules on a more direct X2X path are supported improvement paths when faster control is required.
Tune proportional gain from lag error
A gain is acceptable when lag error remains within the application's required limits and the control loop remains stable; merely oscillating around zero does not establish correct tuning. The reported gain range of 1 to 3.5 produced lag-error oscillation around zero, but the evidence does not define the required error limit or identify one value as correct. Compare set position, actual position, and lag error after each adjustment, rejecting gains that create sustained or growing oscillation.
Feedback resolution can impose an additional limit. If the motor uses the stated standard ABR encoder with 1024 increments, its resolution is 0.35156 degrees per increment. Confirm the installed encoder before applying that value; a controller cannot resolve corrections finer than the available feedback resolution.
FAQ
Why does the X20SM1446-1 trace show 3 instead of 6 A?
The traced datapoint reports current-mode enumeration values 0 through 3, not amperes. Measure current at the motor wires with a multimeter if an actual current value is required.
Why does my B&R stepper motor creep after the move finishes?
An active position controller can issue corrective movement during standstill. Trace set position, actual position, and lag error, then compare the behavior with position control disabled and verify the prediction-time configuration.
How do I know whether the stepper proportional gain is correct?
Accept the gain only when lag error stays inside the required limit without unstable or sustained oscillation. Oscillation around zero alone is not sufficient evidence of correct tuning.