Many times customers attempt to determine the variation of their product to assist in determining reasonable production tolerances. Below is an evaluation that we assisted a customer with on some deep red paper samples.
Technidyne Data – Evaluation of red paper samples
A variety of measurements
were made on the red paper samples provided by the customer to better
understand the characteristics of the samples.
Similar measurements were made on the 90 range, white calibration
standard paper to provide a basis for comparison.
Sample Variability (single
direction): One single red sample sheet was measured 30 times in
various locations but in the same orientation to look at the sample
variability. All three parameters, L*,
a* and b*, had a range (high minus low) of about 0.25 units. Using the standard deviation, the values in
L* had the most variation followed by a* and finally b*.
TABLE A.1 – Red Sample Variability (single direction)
After taking 30
readings (all with the sample in the same orientation)
|
L*
|
a*
|
b*
|
Range (High – Low)
|
0.25
|
0.25
|
0.22
|
Standard Deviation
|
0.073
|
0.066
|
0.053
|
Similar measurements (12
instead of 30 since the physical size is smaller) were made of the white,
non-fluorescent paper calibration standard.
The L*, a* and b* range was less than 0.05, or about 20% the spread seen
with the red sample. The standard
deviations were on the order of 3 to 12 times smaller than those of the red
sample.
TABLE B.1 – White Paper Sample Variability (single direction)
After taking 12
readings (all with the sample in the same orientation)
|
L*
|
a*
|
b*
|
Range (High – Low)
|
0.04
|
0.02
|
0.05
|
Standard Deviation
|
0.011
|
0.005
|
0.017
|
Sample Variability
(directionality; MD vs. CD): The same sample sheet was then measured 15
times in machine direction (MD) and then 15 times in cross-machine direction
(CD). L* and b* showed slightly higher
directionality as determined by looking at the range and standard deviation of
the measurements. All of these values
were higher than those achieved in the single direction test described above.
TABLE A.2 – Red Sample Variability (directionality; MD vs. CD)
After taking 30
readings (15 MD and 15 CD)
|
L*
|
a*
|
b*
|
Range (High – Low)
|
0.36
|
0.32
|
0.23
|
Standard Deviation
|
0.080
|
0.086
|
0.059
|
A series of 12
measurements were made of the white, non-fluorescent paper calibration
standard. There is no real
directionality when compared to the single direction data above. However, the results are orders of magnitude
better then the red sample which shows some measurable directionality.
TABLE B.2 – White Paper Sample Variability (directionality; MD vs. CD)
After taking 12
readings (6 MD and 6 CD)
|
L*
|
a*
|
b*
|
Range (High – Low)
|
0.02
|
0.02
|
0.04
|
Standard Deviation
|
0.008
|
0.006
|
0.015
|
These kind of evaluations are important to help in determining reasonable variations and production tolerances. This information can also be useful to help communicate with the end user on acceptability tolerances.
Feel free to contact me at toddp@technidyne.com.