Laser scan micrometer for die swell measurement

Intended use

High-precision continuous, non-contact die swell measurement


  • Calculation of the swell value
  • High-precision, non contact measurement
  • Continous diameter measurement
  • With diagram printout


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Avoiding rejections and deviations in quality due to swelling of extrudates

The Brabender® Swelltest provides high-precision, non-contact measurement of the diameter of objects with a circular cross-section and any transparency by means of a visible parallel laser beam with continuous diameter measurement on round profiles.

The Brabender® Swelltest provides:

  • High-precision, non-contact measurement of the diameter of objects with a circular cross section and any transparency by means of a visible parallel laser beam
  • Continuous diameter measurement on round profiles

The measuring system is attached to the Swelltest die head by means of an adaptation kit. The distance to the die head can be adjusted between 12 and 50 mm. A red laser beam emitted from the laser diode in the transmitter is converged into a parallel beam by the transmitter lens. This parallel beam passes through the measuring area before it meets a CCD image sensor in the receiver.

During processing, the extrudate runs through the measuring sector. When the laser beam meets the extrudate, its cross-section is interrupted. This interruption projects a shadow with an area proportional to the diameter of the extrudate on the receiver. The one-dimensional CCD image sensor scans and calculates the shadow area from which
the sample dimensions are calculated by the controller.

  • Calculation of the swell value swelling coefficient)
  • Determination of the swell behaviour as a function of shear rate and temperature
  • Possible combination with the measurement of stationary flow curves
  • Calculation of the 1st normal stress difference from the swell value determination of the conditions for critical swell values (melt fracture)

Apart from die swell measurement, the Swelltest offers a number of other applications:

  • Band width measurement (e.g. for film extrusion)
  • Film edge control or measurement of shaft eccentricity
  • Measurement of clearance (e.g. roller gap, cutter blade height)
  • Measurement of position or dimensions of complex shapes
Measuring window30 * 300 mm
Measuring range0.5...10 mm (option: 30 mm)
Measuring resolution5 μm
Accuracy± 0.03 mm
Sampling rate780 c/s
Display resolution5 μm
Serial portRS 232C, baud rate 300...9,600 b/s adjustable (option)
Analog voltage output6 V
Light sourcevisible semiconductor laser beam, wavelength 670 nm
Ambient temp. at sensor0...40 °C
Power supply85...264 VAC, 47...63 Hz
Enclosure ratingIP 60

Die Heads PRN BRO EN