Weight is off on 3D printed Parts?

[Anonymous]

Ok, wondering if I'm doing something wrong or overlooking something.

I'm making some quadcopter parts for 3d printing.  The entire copter needs to be less than 100g and the frame under 25g. 

I made a custom material and set the right density of 1g/cm2 for my filament.  Fusion reported the weight of the parts as 23.4g, but when printed they were just 18g which is about 30% lighter.

The two parts are basically flat plates with holes in them with a thickness varying from .8 to 3mm thick, printed solid with no infill.

Is this sort of difference normal?  Maybe because the 3d printer is printing the parts slightly thinner or something?  Or is this an error?

Not too concerned but if I had an accurate weight estimate I could have added some more plastic to stiffen the part.

[innovatenate]

Out of curiosity, where are you getting the material density number from? In Fusion, the weight calculation is simply density x volume = mass.

I think some of the 3D slicing applications such as Cura and other do some calculations using the length of the filament, filament type (material, dia, etc), infill, etc..  to calculate the final weight of the 3d object.

That would be my best guess as to what is happening. I hope that helps.

[dieselguy65]

my first thought.

in Fusion the model is solid.

in your slicer you are using less than 100% infill

there is your difference.

try printing one at 100% infill and see if Fusion is now accurate

[Anonymous]

Some more detail for you guys....

The material density of 1g/cc came from the filament manufacturer's data sheet.

24g was fusion's calculated weight

18g was the actual weight when printed, measured on a scale with 1g accuracy

The slicer was set to 100% infill,

There are 2 parts, one 2mm thick and the other 3mm thick.

The main thing here is that I'm trying to hit a target weight with these designs, so I'm trying to figure out why Fusion is estimating them heaver.  I haven't printed/weighed enough parts to see if this is off by consistently the same amount or if the % amount it's off varies with the shape/size of the part.

[dieselguy65]

Under extrusion, will cause that. Your extruder not being calibrated very
precise will also.
There is alot of variables. Filament diameter variations, etc

[Anonymous]

Is there more than one part or body in your model? If you check properties it will include all parts even if they are hidden away.