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Technical
cleanliness –
ISO 16232 / VDA19
Modern
manufacturing processes require better technical cleanliness therefore
improved methods applied in industrial cleaning systems. Cleaning systems
according to contemporary industrial standards are limited in performance
and often do not achieve reliably the cleanliness of parts as required.
Residual magnetism has an important impact on the success of cleaning
processes since its effect is not immediately obvious. Due to magnetic
attraction, ferromagnetic particles in the form of chips, dust, or fibers,
stick to the workpiece. The smaller these particles, the more pronounced
appears this sticking effect. This magnetic attraction force on the particles
impedes, even prevents their removal by the washing process.
The impact of residual magnetism on the efficiency of cleaning
methods
Any industrial cleaning process, such as ultrasonic cleaning, aqueous
or solvent based cleaning, spraying or brushing, is improved in efficiency
if the workpieces are completely demagnetized prior to cleaning. The target
is to keep residual magnetism of the workpiece at any place below 2A/cm
(= 2.5 Gauss) to assure the success of the cleaning procedure.
| Cleaning
of a rotating part in an aqueous cleaning system (text made by a leading
manufacturer of cleaning systems) |
| |
Particle
number bigger than 100μm |
Cleaning
efficiency |
| Before
cleaning |
1200 |
|
| After
cleaning |
|
|
| Remaining
magnetism lower than 20-50 A/cm (=25-62.5 Gauss) |
more than 200 |
lower than 83% |
Remaining
magnetism lower than
2 A/cm, workpiece contaminated with magnetic particles |
65 |
95% |
| Remaining
magnetism lower than 3-5 A/cm (=3.75-6.25 Gauss) |
20 |
98% |
Remaining
magnetism lower than
2 A/cm (=2.5 Gauss) |
1 |
99.9% |
Measurement of the residual magnetism of workpieces
Residual magnetism should be measured as closely as possible to the surface
of the workpiece. The Gaussmeter should be equipped with a probe on which
the transducer element may directly touch the surface on the critical
location. On residual magnetic fields below 4 A/cm (=5 Gauss), the earth's
magnetic field impacts significantly result. This makes measurement of
residual magnetism poorly reproducible. To eliminate the disturbance created
by the Earth's magnetic field, measurements should be made inside a zero
gauss chamber. We recommend for these tests our specially developed instruments
"M-Test LR" and "zero-gauss chamber”.
The following tables,
charts, and pictures demonstrate how particles adhere to a steel blade
at different strengths of residual magnetism. Cleaning was carried out
by compressed air.
Information
on cleanness testing:
As a partner in the field of the demagnetizing technology, we have a consulting
function at the Frauenhofer-Institut
of production technology and automation. We recommend this link for
further information on cleanness testing. 
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