Noob Question - More Explanation on DENSITY?

Discussion in 'Design and Modeling' started by Toysoldier, Dec 18, 2014.

  1. Toysoldier
    Toysoldier Member
    Hi all, I am new here and new to 3D printing....

    I a, also sure this question has been asked but so far I could not find a good description of what the Model Density % is when I upload a model and the number shows up on the edit screen. I uploaded my first model and although I am not 100% sure, I suspect my model's pricing might be too high for its size and shape ($50 for the cheapest material). I suspect it has something to do with the density at 23% and that I have no hole in the model to drain internal material. But I could be wrong.

    But the edit page does not have any help description that explains exactly what the DENSITY value is or means. I searched the tutorials for Density but I could not find a basic description of it there either.

    So can someone explain basically what DENSITY mean as a percentage? Also, I attached a snapshot of my first model dimensions ... is $50 too high for my model using it cheapest material or is that about right?

    I exported my model from Zbrush as an STL file and the exporting options did not mention any variables like wall thickness.

    Thanks!

     

    Attached Files:

  2. mkroeker
    mkroeker Well-Known Member
    Density is the fraction of the bounding box (closest box-shaped volume around the part) that is actually occupied by the part, in other words the "material volume" divided by w*d*h. This value used to be much more important before shapeways changed the pricing scheme for strong&flexible - they even offered a discount on big models above a certain density,but then found out that it was not commercially feasible for them.
    Nowadays you are charged based on a combination of actual material used (the 75ccm of your model at 28 cent each) and "machine space", i.e. the empty space immediately around your model where they cannot put anything else for printing. Perhaps you could save a bit by hollowing out if it does not matter that the statue will then need to have a big hole in its back, but chances are the hollow area then just counts as "machine space".
    On the other hand, if you just want one copy for yourself, the easier solution would be to use the 20 percent discount currently offered with the promo code at the top of the webpage.
     
  3. Toysoldier
    Toysoldier Member
    Thank you very much.. That helps me understand what Density is and how important it is to the price in Shapeways.

    My plan is to take my 3D art models I created for the virtual world of SecondLife and print them for Real World art sculpture sales to my art customers. So the objective is for sale to others.

    If cost wasn't a big factor I would love it to be solid but if hollowing drastically reduces the price then I would entertain it, but creating a hole in this model (really anywhere in the model) would not be desirable.

    I have already had it printed by a customer of mine with a MakerBot 2 printer and the ABS material print was hollow and looked awesome. But I assume this person knew how to take my STL file and modify the STL to hollow it out prior to printing. Since it was extruded, there was no need for a drain hole. as it only printed the walls.

    I really want to see this model sculpture printed in metal... but i am nervous at the cost and if it doesn't work like it worked outside Shapeways.
     
  4. CybranKNight
    CybranKNight Well-Known Member
    The biggest issue is simply the overall size, remember that making something twice the size results in it having four times the volume. It would help if you could make it hollow but as you kinda mentioned it currently just doesn't have a suitable area for the escape hole(s). You could re-design it in assorted ways to allow it to be made hollow to really cut down on the cost but it wouldn't really be all that "easy".
     
  5. Make that eight times the volume.

    Shel M
    NH, USA

     
  6. Toysoldier
    Toysoldier Member
    Thanks for the advice. So as they say... SIZE DOES MATTER. :)

    I would hate to make this model smaller as the one I have printed now is 3.5" tall and I cant imagine the statue being much smaller. I love its size as it sits on my desk and if it were 1/2 the size it would just get lost wherever it sat.

    So because of the size - hollowing and an escape hole might be a big factor in cost reducing for printers that use a dust bonding method. Correct? For the extruding printers only hollowing would help as there is no need for an escape hole if I understand correctly. And right now I assume my model is not hollow and therefore the cost of even the most simple materials are high (i.e. 75cm of material).
     
  7. CybranKNight
    CybranKNight Well-Known Member
    Ah quite right, my bad, I'll go back and fix it.

    You could try "redoing" the legs so there isn't a gap between them then you could hollow out the bottom of the legs and expand that up into the torso(I wouldn't do the hands/head) and what would probably help cut down the cost a bit, but regardless of how hollow the model is the machine space won't really change without changing the size of the model.