When starting 3D printing you might not pay much attention to the fill density percent in your slicing software, but this metric is very important. It will have a major impact on how quickly your prints come out, their strength, and the amount of material used.

Starting out, I was once asked if I was trying to hold up a car with my 3D printed figures. The density was so high, they were nearly indestructible.

If your fill density is one hundred percent, your 3D printed part, figure, etc… will be a solid block. If your fill density is zero percent, the part will be hollow.

Do you plan on making models or replicas? You’ll probably do well with a low percentage fill density. Anywhere from two percent to fifteen percent should be fine. This assumes you do not intend on putting these models through rigorous physical trials. I usually print out models between four and five inches tall, using fill density between two and five percent. The models come out fairly strong, they are finished faster, and use less materials than higher settings.

Do you plan on making a part for everyday or mechanical uses? Then try using a higher fill density percentage. For household items like a cup holder, light switch, etc… experiment with thirty to fifty percent fill densities. You’ll find fill densities in that range create very strong models and parts. If you intend to use a part for heavy physical tasks, start with fifty percent, and see how they come out. You can always print your part again at a higher percent.

Another important consideration is material usage and costs. If you plan to make lots of parts or models for sale or use, you’ll need want the lowest possible fill density to get the job done. This will take experimentation. I have found that different models come out better with different fill densities, but it usually required some failed experiments to figure out the optimal amount. You don’t want to spend a whole roll of filament on one model, unless you really want to.

Remember, fill density determines how much material will be used in your model. Lower percentages print faster, use less materials, but will be weaker than using higher percentage fill densities. DO NOT BE AFRAID TO FAIL. Test out different density settings, it will save you time and materials in the long run.