Page 18 - RB-66-13-3

TECHNOLOGY
Shamrock Marketing Take On Raven Engineering DVS 1220 Differometry Casing Analyzer Technology
Shamrock Marketing’s headquarter building
Shamrock Marketing Inc have announced that they are to take on the sole distributorship of the DVS 1220 Differometric casing analyser manufactured by Raven Engineering of Oxford Michigan. The DVS 1220 is a non- destructive laser testing machine that can achieve complete casing analysis in under 90 seconds generating precise image output that is simple to understand. The machine is designed so that any retreader can now offer affordable complete casing integrity to their customers and prospective customers.
According to Raven Engineering the key to the DVS-1220 is the speed of the test cycle and ease of
process without moving the camera. The vacuum cycle causes the voids or separations in the tyre to expand. Then, by using the special DVS-1220 software to process the images, it is possible
(error of parallax) where one eye looks straight the other looks at a slight angle. In our brain the two separate images are processed to appear as one image with the perception of depth. However, in Shearography this produces a laterally displaced image with fringes resulting in noisy output making interpretation difficult for the operator. Additionally most other methods of Interferometr y require multiple vacuum cycles during the process increasing time to analyze the tyre often in excess of 3 minutes.
Differometr y is not a form of Interferometr y because it requires only one source of information and does not produce the interference and fringe patterns. This is part of what makes the DVS 1220 interpretation easier, says Raven and Shamrock. The optics utilise a straight reflection from the test object and then the computer compares the difference of the reflected light from two or more images during a stressed and unstressed condition. A basic law of physics
(Reflection Law)
explains that
during the
vacuum cycle,
when the surface
of the tyre
moves, each
individual
reflective ray of
light moves to a
different
position on the
sensor causing a
change
(difference)
between the
image captures.
Using an
algorithm to
process these
images the anomalous regions can be viewed without the confusion of fringes or a double image. The DVS 1220 software allows for processing of the data to measure and count the anomalies, display just the anomalies or display the anomalies with the tyre image overlain.
The components are small enough that four cameras and sixteen lasers can easily fit inside a passenger car tyre for a full 360 degree view allowing cycle times of just a few seconds. The DVS 1220 footprint is only 3048 mm x 1524 mm x 2121 mm and can accommodate tyres up to 1,168 mm in OD with maximum weight of 118 kg.
Differometry could be an alternative to shearography
interpretation of the results. Although the same basic information is provided as other types of non-destructive tyre testing equipment, the machine is claimed to be much quicker and easier to use, both in terms of operation and interpretation.
to see what is different or what has moved. The Differometry process then utilises the ability of the computer to capture images in a defined sequence of time and to analyse them. Any identified anomaly is scalable in exact size, shape, and dimensions allowing for easier interpretation by the computer and by the operator. All this can be achieved in a tyre floor to floor time of around 90 seconds.
Other forms of Interferometry such as Shearography require two sources of information in order to have the constructive and destructive interference and to produce fringe patterns. An optical element is placed in front of the lens bending approximately 50% of the incoming light from the viewed area. This produces an effect much like human vision
The DVS-1220 operates using Differometry, which was developed in 2003 specifically the testing of tyres and differs from various forms of Interferometry such as Shearography and Holography that it relies on the power of computers to analyse results rather than on optics.
for
in
So what are the benefits of Differometr y over other forms non-destructive casing analysis? Differometry works by taking two images of a casing at slightly different times during a vacuum
18 Retreading Business
of