weight of 3D prints

[rdsk 0]

I printed in PLA two similarly shaped components, one with a 5cm by 5cm right angle triangle cross section extruded by 1 cm and the other  the same but with a slight parabolic concave on the hypotenuse (ie slightly less volume).  I set the infill density to 90% and so was surprised that the latter parabolic one weighed 50% more than the triangle.    It should have weighed 18% less.  I cleaned the nozzle before printing the parabolic one which may have meant the triangular shape was using less PLA and certainly the print looked less smooth.  Are there any other explanations why the weights would be so different from expected?

[geert_2 557]

I think you will need to provide images of the models, of the cross sections, and of the layer-views while slicing, and project files and parameters. Otherwise it would just be wild guessing.

 

[rdsk 0]

Here is photo of  the 3d prints.  They're same thickness.  Even though they're both 90% infill the left parabolic curve is 50% heavier than the right triangle.  I can only think that the nozzle need cleaning when I printed the triangle.  The volume of the parabolic shape is 18% less than the triangle which feels lighter and a bit less solid.

I was hoping to balance these on a see saw (per archimedes method of mechanical theorems on wikipedia)  as a math toy and so the weight needs to be accurate.

I'll try reprinting the triangle.

So my question is how accurate should I be able to get the weights if the print density is set at 90%?

Perhaps I'd be better of with some other material than PLA - they shapes are so light anyway but its a proof of concept and so I'd like to get it to work.

[Framar 38]

Cura give you theorical weight one you have slice your model. Maybe you can start by comparing what Cura estimates with what you get; one model at a time.

[geert_2 557]

Also, shells are 100% filled, and the shell in the curved part is longer than in the straight, which could give a bit difference. But so much...?

 

I think you would best print them at the same time, on the same bed, and 100% filled. So there are no differences in infill-pattern, and no differences in shell vs. infill, and no differences in speed, temp, extrusion-rate (or underextrusion), etc...

 

Maybe scale it down to 50%, for a quick test, so you don't waste too much material?