Assembled model

Discussion in 'Software and Applications' started by grahamarrol, Feb 27, 2014.

  1. grahamarrol
    grahamarrol New Member
    I am a new user to Shapeways and was looking for help.

    I am using Autodesk Inventor to create 3D models of USB flash drive cases with pupils in my school. I was looking at the possiblity of getting these cases made for the pupils using shapeways but dont know how to go about it.

    The models consist of two parts (a top and bottom casing) which will enclose the USB and memory board which I have purchased. Do I have to sent two seperate models for the top and bottom of the casing and asseble myself or can I send the assembled model as an STL file and both parts will be made?


  2. HOLDEN8702
    HOLDEN8702 Well-Known Member
    Hi, Graham.

    You can upload a .stl file with all multiple parts you want.

    This is true for all plastic materials, but not for all the metalic ones.

    Check the materials portfolio

    With white strong flexible (or colors strong flexible) it hasn't problem to do it.

    As you know, you can do an ensemble or derive a part to add two or more parts to create your file in inventor.

    Best if you compress to .zip your .stl file. Then the shappy software ables you to choose between milimetres and inches to size your file.

    Ask me if you have issues. I'm working with inventor too.


  3. stonysmith
    stonysmith Well-Known Member Moderator
    It is BEST if your parts are connected together by a thin connecting piece (called a sprue).
    "All the parts you want" is a bit of a misnomer... you need to consider that these parts must be handled by human hands.
    Very very tiny parts can get broken/lost unless something is holding them together.

    Also, Shapeways has warned us.. don't abuse the process. Too many disconnected shells drives their labor costs up significantly.

    Look at this model.. it contains 50 separate parts and would without a question be rejected if it didn't have the containing cage - there's no way human fingers can pickup all 50 of those parts without breaking some, of them.. I'd be likely to receive 47 of them instead of 50.

    For USB shells, I'd recommend (at least) connecting the halves together with a sprue so that they stay together.. that would reduce the likelyhood of a part going missing.
  4. stop4stuff
    stop4stuff Well-Known Member
    If your flash drive halves have a hole in them say for a lanyard, or keychain split ring to go through, then the cleanest way I've found is to put a loop through the hole, creating 3 seperate shells within one model file. This ensures your parts stay together and there are no sprue marks that might upset the asthectics or fit of the design. The loop should be at least 1mm diameter 'wire', this can then be cut easily with scissors.

    The above only applies to plactics.

    For metals, Shapeways does allow a maximum of two parts in one file if the print is intended as a matched pair, e.g. cufflinks or earrings.

  5. HOLDEN8702
    HOLDEN8702 Well-Known Member
    I've only trying to help a novice to do his first printing experience.

    My intention was not at all to give him evil ideas or to reopen a crusade for or against the sprues. All we work in Z scale, we know.

    But Graham only ask for an usb case, this isn't a try to do an infinitesimal part file. Not jump things out of proportion.


  6. stop4stuff
    stop4stuff Well-Known Member
    Luis, chill, in one way or another we are all still learning.
    I've been guilty of abusing utlilising multiple shells in one file.
    Some of us are just like big kids in a new sandpit, seeing how far we can push things.
    Its natural.

    You have some amazingly detailed tiny detailed models in your shop - awesome stuff!

  7. HOLDEN8702
    HOLDEN8702 Well-Known Member
    Thanks, Paul. Yours too.

    Best we can talk about this in another topic. Many others are open about this.

    I wish to know if Graham finally could do his best. Have you read it, Graham?
  8. grahamarrol
    grahamarrol New Member
    Thanks everybody for the advice. I will try using sprue pins and and see what I get back. I am only experimenting and looking at costs to see if it is a viable school product, affordable to pupils.
    I really just wanted to know if you send a constrained model of two parts, if they would be made that they could be taken apart (opened) or would they be one solid model.
  9. HOLDEN8702
    HOLDEN8702 Well-Known Member
    Hi, Graham.

    You can upload a model in two parts, with or without sprues.

    If you makes a two parts case, it could be printed and being opened if you let enough space between the parts. It depends on the material and you got the optimal separation after some test.

    I have had some luck on it, and I've obtained mobile parts interlocked in my models.

    But the bad news is that if you makes a closed case, you have to open escape holes to pour off the auxiliar powder or wax from the manufacturing process. Take a look in the material portfolio information: tic

    My opinion is that sprues are an expensive and useless nonsense for a big part as a usb case. Obviously you have watched that another designers thought in contrary. My experience supports my assertion, but don't worry, if the model can't be printed because it lacks the sprue, shapeways will let you know, reject printing and ask for you to change your design.
  10. barkingdigger
    barkingdigger Well-Known Member
    Not sure it it's too late to help, but if you want to use two interlocking halves they need to be separated by a few mms in the file so they don't accidentally fuse together during printing. (There is a small minimum "clearance" distance quoted in the Guidelines, but I like to err on the cautious side and move the items far enough apart to see clear "daylight" between them on the CAD screen...)

    Either sprue up the halves, trap them in a cage, or tie them together on a keyring-style loop through a convenient hole so each printed "unit" has all the parts for one USB case - that way you save the mental health of the poor tech that has to handle/clean/pack them, and don't need to waste time matching up parts when the kids are getting restless.

    One thing to keep in mind is how the parts will connect - the printed parts are immune to solvent glues. You can use superglue (always fun when you need to supervise others...) or design in some kind of mechanical tab-based fixtures to secure them.

    There's no discount for multiple copies. Just looking at a USB stick here, I'm guessing it is about 1 or 1.5 cubic cms of material (assuming a 1mm-thick skin), so in FD at $2.39/cm3 that's under $4 each. Much more expensive than injected plastic, but not much set-up cost for limited runs. (IM plastics tooling runs in the 10s of thousands of dollars, before a single item is ready for sale...)

    Hope this helps!