Certificate of Accuracy

Certificate of Accuracy

Certificate of accuracy given by independent measurement laboratory, makes our devices referential, just like CMM machines – thus they can be used in application where certificate of accuracy is required. It can also be used as a bargaining chip between subcontractors.

Link to the accredited measurement laboratory:

Laboratory of Coordinated Metrology

Accuracy testing of SMARTTECH 3d scanners.

Certification according to the recommendations of the German PTB according to VDI / VDE 2634

Each 3D scanner manufactured by SMARTTECH is tested according to the standard above. For customers who require additional accuracy documentation  , scanner can be tested and certified by  by an accredited Measurement & Inspection laboratory, thus gave the same referentiality like standard CMM and can be used in specific aplication that requires referential devices.

Certification and maintain measurement accuracy over the lifetime of a 3D scanner is possible only  in the case of scanners permanently calibrated for a particular volume and held in sealed cover.

Why we calibrate scanners, according to the standard?

To meet customers requirements  our company has introduced a standardization of calibration and inspection of 3D scanners, according to the German standard VDI / VDE 2634, created by the German Association of Physicists and Engineers. This standard is clear and measurable for all, so it gives the opportunity to compare and choose  the best 3D optical scanning system.

Guideline VDI / VDE 2634

The guidelines define the following parameters:

the error of the optical head – executed on a single sphere,

the error of the length – executed on the standard ball bar

the flatness error – performed on a flat plate.


The first parameter

It describes the error characteristic of the optical 3D measurement systems, based on scanning the surface in a small measuring range, which is the distance between the center of the sphere determined using the Gaussian criterion (least squares method) – an element of the combination, based on a finite number of measurement points on the adjusted the spherical pattern of the material dimension – and measuring point adjusted on the same spherical pattern material dimension.

As the pattern is applied sphere of diameter Wed material light scattering, respectively:

rys1

Av = (0.1 … 0.2) L0

where: L0 – diagonal smaller rectangular parallelepiped covering space measurement.

The procedure consists in measuring the sphere at least 10  within the space of setting measurement.

rys2'

In the next stage, by using the “best fit” designates the radius of the sphere, and then calculates the difference between the actual calibrated radius of the sphere and the result achieved. These operations are performed separately for each of the 10 items.

The data is calculated for each of the spheres and entered into the table.

tab1

The outcome of the trial will be positive if none of the errors listed in the array is not greater than the maximum permissible value of up to fifth dimensional characteristic pattern of the ball, and the uncertainty of measurement determines the highest value from the resulting differences.


The second parameter

Another parameter is the error of the length specified pattern “ball bar” (two balls made of a suitable material). Dimensions patterns arise from the relationship shown in the figure below.

rys4

Schematic pattern to test the length of the fault indications:

No. ˃ 0.3 L0Dp = (0,1 … 0,2)

L0L0 – Diagonal cuboid describing the range
No. – the distance between the centers of spheres
Dp – diameter of a sphere

This parameter is used to verify the correct playback 3D scanner length. According to the recommendations of VDI / VDE is the difference in length between the measured and calibrated (actual) between the centers of the spheres. It is determined from the formula:

Δl = lm-lk

where:
Δl – error distance between the centers of the balls
lm – measured length value
lk – calibrated length value

In order to determine the parameter to be measured in the test pattern positions.

rys5'rys6

For each of the two pattern balls  by using the “best fit” is matched sphere. Automatically in the Mesh3D, calculated is the radius of the sphere and its center coordinates.

rys7'

With these data it is possible to calculate the value of the length between the balls and the formula is determined distance error.

tab2

Just as the first parameter, the value should not exceed 1/5 dimension checked in the pattern. As the uncertainty of this parameter selects the highest value.


The third parameter

The last parameter is the  flatness error.

VDI / VDE define it as the distance range of the measured points from the plane constructed by least squares. The pattern is made of a material with low reflectivity, whose width can not be less than 50 mm, and the length – from 30% of the diagonal body describing range.

rys8

In order to determine the flatness error pattern should be measured at 6 positions.

ryss9'rys10

Then, using the “best fit”, set a threshold of uncertainty for all positions and calculate the difference between the values: the master and the resulting options for each pattern position.

rys11

Flatness error should not be greater than 1/5 of the measured characteristics. We choose the highest value, which is about the unit of measurement uncertainty

tab3
Movie showing the certifying process ofthe scanning device

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