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High speed analysis of Twist (or lead) for shaft sealing applications

Monday, February 22, 2016

World leading analysis of texture and lead in dynamic sealing systems

The surface finish of a rotating shaft can give rise to seal leakage or premature failure. Twist analysis is important in the early detection of any issues. It has many applications in industries such as automotive, domestic appliances (such as washing machines) and the food processing industry – in fact almost anywhere rotating shafts are used.
The biggest influence on leakage is the presence of spiraling marks along the rotating shaft. These marks can cause a pumping action and depending on depth and wavelength they may bridge the seal allowing ingress of water or loss of oil.

Twist measurement
Traditional contact techniques have been very successful in controlling the surface characteristics of rotating shafts. A recent development in the measurement of Twist is the use of Taylor Hobson's Luphos non-contact probe on a Talyrond instrument. The system has the same level of accuracy as traditional contact techniques but the measurement is up to 4 times faster. This approach to high speed twist measurement is compliant with MBN 31007-7 and removes the need for estimates based on incomplete measurements. Analysis based on an incomplete measurement can give rise to errors due to variation in the surface over the circumference of the part, affecting process control.

What is Twist analysis?
It is a method of quantifying the twist on the shaft

  • Developed and patented by Daimler
  • Uses a 3D map of the surface
  • Measurements taken using Talyrond or a Talysurf instrument

Twist Analysis technique
A series of traces is taken in the axial direction of the part, after each trace the spindle is rotated by a given amount in degrees and a new trace is taken until the measurement is complete. A special analysis routine is applied to the 3D surface in order to detect any spiraling effects on the surface.

Parameters include:

  • Cross sectional area
  • Number of threads/leads
  • Lead depth
  • Evaluation Length
  • Period length

Luphos Probe on Talyrond

The unparalleled measurement capability of the Talyrond 500 Series instruments combined with the accuracy and ease of use of the LuphoSmart gauge provide unbeatable non-contact and contact measurement solutions.

Features include:


  • High speed measurement
    • High sample throughput
  • Non - contact measurement
    • Zero contract force - for fragile samples
    • No tip wear
    • Lowers cost of ownership
  • Long working distance
    • Detailed knowledge of component dimensions unnecessary
    • Large form deviation measurement possible
    • Less chance of damaging the probe
  • Proven correlation with contact metrology

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