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Monday, September 14, 2015

Solutions to Common Parker Print Surf Problems

Since Dr. John Parker introduced the Parker Print-Surf (PPS) instrument in the early 1970's, strategies have developed to improve the repeatability (measurement to measurement agreement) and reproducibility (instrument to instrument agreement). Even though there have been many iterations and generations of the original PPS instrument, Technidyne developed a brand new instrument in 2001 that resolved many, if not all of these issues.

Below you can see the list of issues with traditional PPS instruments and the Technidyne solution/approach:

Potential Causes for Error in                          Technidyne's Solution with
PPS Testing                                                        PROFILE/Plus PPS

Air flow measuring device
   - devices are non-linear                                   =>    Multi-point restrictor calibration & paper
   - dummy heads are used to calibrate this               verification

Sealing the measuring head
   - petroleum jelly typically used
       * too little = leaks & high readings           =>    Rubber o-rings
       * too much = clogs & low readings

Flatness of the head                                           =>     Manual lapping

Protective collar
   - burrs on collar may not allow proper seal  =>    No collar
   - collar can pull & cause small creases

Concentricity of guar land                                =>     Each head is mechanically fitted by hand

Instrument air
   - blows on paper, usually mill air                   =>     Dedicated, filtered air source
      that is not clean

Backing material
   - highly variable
   - wears out i.e. becomes heavily                   =>      IRHD hardness is measured on every
      embossed                                                                 backing

Clamping pressure
   - not easy to check                                         =>      External load cell
   - pressure too high = low readings