Hollowing out made no price difference.

Discussion in 'My Work In Progress' started by 3dinLeiden, Mar 26, 2013.

  1. 3dinLeiden
    3dinLeiden New Member
    Hi everyone, (project game pieces)

    I have uploaded a model. It passed auto check, price $80.30. I need 2 sets to play test it, so I thought I would try hollowing out the bases.
    That uploaded ok and the auto 3d-rotate model-viewer shows the hollowed out bases.

    I think this should be about at least 1/5 reduction in material . The price calc show the same.

    I am using file format *.obj in 3ds 9. Boolean subtraction. I noticed the Oriented Bounds Vol had reduced, see below;

    V1: un-hollowed :price $80.30.

    Oriented Bounds (used for determining printability)
    In: 7.4 w x 1.5 d x 3.7 h
    Cm: 18.9 w x 3.9 d x 9.4 h
    Vol: 92.58 cm³

    V2: hollowed bases :price $80.30.

    Oriented Bounds (used for determining printability)
    In: 7.4 w x 1.5 d x 3.7 h
    Cm: 18.9 w x 3.9 d x 9.4 h
    Vol: 56.28 cm³

    Any ideas about this?

  2. virtox
    virtox Active Member Moderator
    That seems very strange, which material are you working with?
  3. 3dinLeiden
    3dinLeiden New Member
    White Strong & Flexible

    I am guessing that there is an issue with the 3ds9 boolean in my model, and that the shapeways rendering anim recognises it, but the algoritm for price doesn't.

    ...but then the volume has changed.

    Is this the volume that is proportional to the price?
    Oriented Bounds (used for determining printability)
    In: 7.4 w x 1.5 d x 3.7 h
    Cm: 18.9 w x 3.9 d x 9.4 h
    Vol: 56.28 cm³
    Last edited: Mar 26, 2013
  4. virtox
    virtox Active Member Moderator
    Should the boolean made such a mess of the mesh that the upload at filter at Shapeways would need to fix it, it would show that in the previews as well.

    But as you note the volume does change so, either the price is delayed or broken?

    The pricing has some linear elements, but there is also a density discount. But would be very coincidental to hit the exact same price;-)
    Are the prices for the other materials identical as well?
  5. stonysmith
    stonysmith Well-Known Member Moderator
    We'd need to see the model to try to offer any suggestions..

    Can you upload a copy of your model here in the forum, and/or make the model in your shop public?
    If you'd rather keep the model private, you could PM a copy of it to me.

    Most such cases are caused by bad boolean operations, but yes, if the volume changed, then the price should have also.
  6. virtox
    virtox Active Member Moderator
    Hmm, but density discount is something to take into account as your models are just below and just above the threshold of 10%

    So the first model is

    Cm: 18.9 w x 3.9 d x 9.4 h
    Vol: 92.58 cm³

    92.58/(18.9*3.9*3.9)=13.36% density

    Meaning the price will be
    1.50 + 20*1.40 + 72.58*0.70 = 80.306

    the second is
    Cm: 18.9 w x 3.9 d x 9.4 h
    Vol: 56.28 cm³
    56.28/(18.9*3.9*3.9) =8.12%

    1.50 + 56.28*1.40 = 80.292

    WOW, you did hit the exact sweet spot ;)

  7. 3dinLeiden
    3dinLeiden New Member
    Good point virtox, only the price of top two materials are the same but the rest look to have nearly halved, in line with the volume reduction.
    These are only prototype pieces and I will need two sets to playtest, so I am trying to keep the price low.

    ...of these, sandstone now looks the cheapest. 72.44 reduced to 45.21

    However the pieces have lids which I want to clip onto the bottom part, like a russian doll.
    I am not sure sandstone will be good for this, perhaps thin walls (approx 4m) are likely to crack?

    How does this affect peoples opinions of the issue (White Strong & Flexible + Black Strong & Flexible, no price change)

    Thanks for the quick responses people.
  8. 3dinLeiden
    3dinLeiden New Member
    Hi virtox, (I posted my last reply befoe getting your 'density discount' reply so maybe this one will also come through after a new one)

    I was not aware of that discount. I think i can greatly reduce the bounding box but am not sure how the print works.
    I can put the lids (nearly) on the pieces... Say hovering 5mm above them but with the pieces inside the hollow lids?

    If I reduce the boundary box, that will increase the density, so I'm not clear on how that discount works.
  9. 3dinLeiden
    3dinLeiden New Member
    The above approach worked. Placing the pieces inside their lids to reduce the bounding box triggered the aforementioned discount ( presumably ).
    The White Strong & Flexible new price down to $ 54.90.

    I am new to this, but I don't think shapeways have been good at publising this factor, as most of the things I have read are indicating that the bounding box makes zero difference to price. Also I still am not sure why the other prices reduced previously and the White/black Strong & Flexible didn't, guess only they get density discount.

    If I have now triggered a density price reduction... is it a flat reduction once I have gone under a 10% density, so packing them in futher I think will not get any further price reduction. I plan to try another more packed-in to check if it will reduce further.

    Thanks for the advice, perhap someone can summarise what they think its going on with this as it has left me still a little confused.
    Last edited: Mar 27, 2013
  10. bartv
    bartv New Member
    Hi 3dinLeiden,

    You're absolutely right, we need to promote this more. As higher density models are actually more efficient for us to produce, this would be a win for us, too.


  11. virtox
    virtox Active Member Moderator
    To be clear, the density discount applies when you go above 10%.
    Once you get the discount, packing further will make no difference.

    This is for basic black and white nylon:
    If the volume/(optimal bounding box) >10% and model has more than 20cm3 volume:
    the first 20cm3 will cost $1.40 all cm3 above will cost you $0.70

    If you drop below 10% you pay $1.40 for all cm3
    So for some models it is actually cheaper to add some waste material in the model to increase the density :-S
    This is a side effect of the current implementation by Shapeways.