can we match mass property of this object?
i have attached one file, which will give you dimensions for parts. by using solidworks 2019 i got mass property 51609.75 grams. nothing is wrong. material is right, dimensions are right. but still not getting exact value. i had same problem before on CSWP preparation exam on site. that module also have some value which has fraction between two value and comes with more 6 digits after decimal point.
in this model value z=(c=e)/3 =(60+10)/7= 23.33333333. i am confused, when having this kind of value in model it always not matching exact same value in answer. for CSWP exam we have to match right value, if we close to that value from option and select it then next question of modification will need to answer fill in the blank will be wrong. can someone guide me for this problem plese?
thank you
yatharth
9 Answers
attached file will show my part. if i did something wrong in it which affect my mass property of part and if you want to let me know.
thanks
yatharth
I don't have SW 2019, so I can't review your part.
I did build my own part, and I got the correct mass. I'll confidently say there is a problem with your model.
Download my part, review how it was made. See where/how it differs from your method.
Models like this are "hard" because they require the sketches and features to be created in a certain way. If you don't anticipate how the sketches, planes, and features all relate to each other, it is very easy to make a tiny mistake which will alter the mass by a little.
Simple models like this should follow the best modeling practices.
Make all extrusions
Make all cuts
Add small details like fillets/chamfers (if required)
Using a Rib feature for this seems much too hard. The Rib tool is great, but I'd use a solid extrusion in this case.
Upload a step or parasolid of your model and I can look at it (minus the feature tree). I suspect you'll find the error(s) if you make some section views. Chances are the "rib" does not fully interface with the curvature of the pipes. Or, maybe there is a solid web of material where the pipes intersect?
Check the indicated areas in the image attached.
I remodeled the part to make use of a Rib feature. It works, but it is more difficult than using an extrusion.
The model faces are identical according to the Compare Documents tool.
The mass differs slightly between the models
Mass = 51608.54731285 grams for the first model
Mass = 51608.54814788 grams for the model using a rib
This is odd, but not unheard of. I have not tried it in recent releases, but I found that rotating a simple sphere results in a different mass depending on if it rotates around a horizontal or vertical axis.
Attached is my version which uses a rib. It is based on the original model, so some unneeded features have been suppressed. I'd delete them, but it is a pain to edit/fix the equations.
THIS ARE MY STEPS FROM FIRST PART. IT HAS MASS PROPERTY OF 51609.75 GRMS.
THANK YOU FOR YOUR SUPORT SIR
HI FredSWUG,
I HAVE MADE Part in solidworks 2016. you might open this part in your sw. i have remove 2019. it was evaluated copy.
can you please check this part for me?
thanks a lot
I'd call it a defect in the software.
The last feature in our parts is the only feature which leads to the mass difference.
I started from the middle, and cut through all to the outside.
You started at the outside and cut Up to Next.
The resulting geometry is the same (according to the part comparison), but the mass is different.
This is a great reason to not base the test answers on tiny differences in mass, or moments of inertia. The model is "close enough" that you'd get the answer right, but I can't see a reason for the mass to be different simply by changing the sketch location, and feature end condition (in this case).
