Special solutions

FISCHER has already developed numerous customized solutions for the automobile industry. These include among others the determination of layer thicknesses of sound insulation foam or other organic layers such as oil. If you need a solution for coating thickness measurement, material analysis, material testing or microhardness determination in the automotive sector, please contact us!

Special solutions

Application notes

Measurement of SAM (sprayable acoustic material) coatings for the automotive industry

In the automotive industry, a great deal of effort goes into reducing vehicle weight by using lighter components. An example is the use of SAM (sprayable acoustic material) coatings in vehicle interiors. These locally applied insulation layers replace the larger and heavier soundproofing mats previously used. However, in order to meet the targets for sound protection, weight, clearance and cost, the thickness of these coatings must be carefully monitored. 

In addition to its light weight, sprayed-in acoustical insulation has the further advantage that it can be applied precisely and selectively by robots, allowing a full automatic manufacturing process. Typically, these SAM coatings are between 2 and 4.5 mm thick, very often located in places that are difficult to reach, and found on top of either aluminum or steel – that is, on both ferrous and non-ferrous substrates.

Developed by FISCHER for just this measurement task, the FA14 probe employs the eddy current method, which is effective for measuring non-conductive coatings of up to 5 mm thickness on conductive base materials.

But above and beyond these fundamental specifications, the FA14’s compact elbow design also makes it possible to take accurate readings even in very close areas: The sensor has an external casing with a total diameter of 20 mm, and its field focus is optimized such that measurements can be taken – without edge influence – on spots no bigger than the probe itself.

Of course, as do all FISCHER eddy current probes, the FA14 compensates for conductivity. In practice, this means that differences in the conductivity of the base material, e.g. when various aluminum alloys are used, exert no influence on the coating thickness measurement. The probe of FA 14 can be connected to the handheld instruments of the FMP-family, either DUALSCOPE® or ISOSCOPE® models.

Measuring point

Target Min (mm)

Target Max (mm)

Actual (mm)

MP1

2.7

3.5

2.8

MP2

2.7

3.5

2.9

MP3

2.7

3.5

3.1

MP4

1.7

2.5

2.0

MP5

2.7

3.5

2.9

MP6

2.7

3.5

2.9

MP7

3.7

4.5

3.4 !

MP8

1.7

2.5

2.1

Fig. 2: Example of typical measurement values from quality control of SAM coatings on eight predefined measuring points, where MP7 is outside the tolerance

With the handheld instruments of the FISCHER FMP-family and the specially developed FA14 probe, SAM coatings can be measured accurately and easily even in hard-to-reach areas and on varying base materials (aluminum or steel). Your local FISCHER representative will gladly answer further questions.

Measuring the thickness of lubricants used in chipless metal processing

Whether rolling, pressing, drawing or stamping, chipless coldforming of sheet metals simply does not work without lubrication. Especially in the automotive industry, the need for ever reduced air resistance and to meet ever more challenging design requirements continues to grow. The result of the forming process depends largely on proper lubrication, which is used, for example, to reduce friction between the forming tool and the workpiece to prevent them from sticking together – a condition that can exert negative impacts on both the workpiece and the expensive forming dies used. The thickness of the lubricant film must therefore meet specifications within a narrow tolerance range.

Besides reducing friction, lubricants help prevent typical process-induced flaws such as cracks, scratches and dents. The oils are applied by roller to the sheets in process and distributed evenly over the entire surface – in sheet metal forming, about 0.5- 2 g/m2. The respective predetermined tolerances must be closely monitored through measurement. The most suitable, non-destructive method uses the principle of beta backscatter, in which beta particles (electrons) are given off by a radionuclide (emitter); some of them are then scattered back by the oil layer and the metal substrate.

Fig.1: FISCHERSCOPE® MMS® PC2 with Z15NG probe for contactless measuring of oil and lubricating films on metals

The measurement effect consists of the number of backscattered electrons, which in turn is dependent on the mass per unit of the coating and the atomic numbers of the coating and base material. This is the method that has been implemented in the modular coating thickness gauge, FISCHERSCOPE® MMS® PC2, to be used in conjunction with the probe Z15NG and a C14 beta emitter. A three-point support that touches only outside the recognized measurement area ensures a stable, reproducible probe placement and the optimal working distance of approximately 4 mm between probe and measured surface – allowing for the contactless measuring that is essential with these coatings.

Fig.2: Schematic representation of an oil film measurement using the probe Z15NG and the beta backscatter method

Table 1 shows measurement examples of an oil film on two different base materials. The higher standard deviation in the sample “oil/Al/Fe” is caused by variations in the thickness of the aluminium.

 

oil/Fe

oil/Al/Fe

Oil film

3.8 g/m²

1.9 g/m²

Standard variation

0.07 g/m²

0.3 g/m2

Number of measurements

10

5

Measurement time

5 s

20 s

Tab.1: Measurement with Z15NG probe according to the beta backscatter method

With the FISCHERSCOPE® MMS® PC2 and the probe Z15NG, it is possible to measure the thickness of lubricants on metals to ensure optimal workflows for chipless sheet metal forming. For more information, please contact your local sales representative from FISCHER.

Your contact to FISCHER

Fischer Technology Inc.
Windsor/United States

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Phone: (860) 683-0781
E-Mail: info@fischer-technology.com
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