Siemens SINUMERIK codes
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Siemens SINUMERIK Controller

Servo/Axis · Intermediate · 30-60 minutes

Alarm 10891

Siemens 840D 10891 - Channel block multiplicity of node is greater than its order

In the B spline the distance between nodes PL (node = point on spline at which 2 polynomials meet) has been programmed with zero too often in succession (i.e. the "multiplicity" of a node is too great). In the quadratic B spline the node distance may not be specified more than twice with 0 in succes

Siemens SINUMERIKServo/AxisIntermediate30-60 minutes

10891

Siemens 840D 10891 - Channel block multiplicity of node is greater than its order

Channel block multiplicity of node is greater than its order

In the B spline the distance between nodes PL (node = point on spline at which 2 polynomials meet) has been programmed with zero too often in succession (i.e. the "multiplicity" of a node is too great). In the quadratic B spline the node distance may not be specified more than twice with 0 in succes

Safety

  • Refer to Siemens documentation
  • Ensure qualified technician performs repairs

Common Causes

  • B-spline node definition contains consecutive zero distances exceeding the spline order
  • Programmer specified duplicate knot values more times than allowed by spline degree
  • Knot vector multiplicity violates B-spline mathematical constraints for the specified order
  • Copy-paste error in spline definition resulted in repeated zero node spacing values
  • Incorrect knot sequence generated by CAM software without proper validation

Troubleshooting Steps

  1. 1Review the part program block referenced in alarm (channel %1, block %2) and locate the B-spline NURBS definition
  2. 2Examine the knot vector values and count consecutive zero distances - verify multiplicity does not exceed spline order (typically order + 1 for clamped splines)
  3. 3Consult the original CAM source file and regenerate the toolpath with B-spline export validation enabled
  4. 4Compare knot vector against spline degree specification - for quadratic splines (degree 2), no knot may repeat more than 3 times total
  5. 5Correct the knot vector in the part program to ensure node multiplicity complies with B-spline order constraints, then reload and test

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