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Weighing Balance Accuracy for Plastic Moulded Parts variation study

J

JPDaniel

#1
Dear forum members,

Can you please suggest the required accuracy of weighting machine for studying part to part variation and estimating moisture absorption in plastic parts? We have part weights ranging from 3 grams to 80 grams.

0.001 mg, 0.1 mg or 1 mg readability are choices given by some vendors. What is the practical precision required?

Thanks and Regards,
Daniel
 
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dgriffith

Quite Involved in Discussions
#2
Dear forum members,

Can you please suggest the required accuracy of weighting machine for studying part to part variation and estimating moisture absorption in plastic parts? We have part weights ranging from 3 grams to 80 grams.

0.001 mg, 0.1 mg or 1 mg readability are choices given by some vendors. What is the practical precision required?

Thanks and Regards,
Daniel
I should think 1 mg (0.001 g) would give you plenty of resolution. However, just because it can sense a change of 1 mg (sensitivity) doesn't mean it will be accurate to 1 mg. In the end, how much change do you expect to see if the part gains or loses moisture may be the determining factor.
 
J

JPDaniel

#3
Thankyou. 0.001 g resolution that you suggested should be the right value. I looked at ASTM standard D570-98 (google search) on water absoprtion by plastics and they too recommend that the parts be weighed to nearest 0.001 g.
If a part weighing 4g absorbs say, 1% moisture by weight, it would amount to 0.04 g increase in weight and this would be able to detect. Of course, no problems with parts of larger sizes. (We are trying to correlate dimensional variation due to moisutre absoption). Sorry about the units, should have been 0.001 grams. Also noted your point that the accuracy would not be the same:thanx:

Best Regards,
Daniel
 
L

Lukasas

#4
I also was searching for a long time for a weighing scales for plastic, and finally i found it! Look- moris.lt/lt/bendra-iranga/svarstykles.html . What do you think? Maybe you could suggest me smth? :bigwave:
 
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