Making a casing for an electronic print

Discussion in 'Design and Modeling' started by dennis013, Sep 4, 2008.

  1. dennis013
    dennis013 New Member
    Hi, I was giving the task to create a model for a casing of a electronic print. The size of this model is 30x50x15mm and i have successfully upload a copy to this website

    Modelled in 3d Studio Max:
    [​IMG]

    Unfortunately I ran into some problems with which I could really use some help.

    First of. The model is essentially a box / container. So it's needs to open up in some way that it can be closed easy and firmly. A colleague of mine suggested to use gripping edges for about 2cm on each long side of the module:
    [​IMG]

    To be honest, I'm doubtful this will work properly on the first dozen attempts and I'm also not sure how to precisely model this in 3d studio. Can anyone advise some strategy on this?

    Second part of my question:
    My model has deformed during the conversion process from 3D Max to shapeways. The holes for the speaker aren't round any more and the extruded text isn't as crisp as I would like it to be.

    See the result here: http://www.shapeways.com/model/4589/.html

    Any input or advice is greatly appreciated!!
     
    Last edited: Sep 4, 2008
  2. svenpb
    svenpb New Member
    If this is not a mass product I would suggest using hex screws to close the container. If it is a mass product (and having no experience with gripping edges), I would suggest several snap connections. My gut feeling says they can be made bigger for equal closing force than a gripping edge and hence tolerances are less strict.

    Can you explain more about the deformation. I can not get a feeling from it from the pictures.
     
  3. dennis013
    dennis013 New Member
    Hi Sven, thanks for replying

    Using snap connections is a good idea! I will talk to my collegue about this. Could you direct me to some kind of blueprint for this?
    I will google for this too.

    The deformation takes place when my model is imported. If you follow the link i gave earlier to the shapeways model and view it in 3d, you will see what i mean.
     
  4. robert
    robert New Member
    Don't worry about the deformation. It is actually an annoying rendering artefact. There is more on this topic in the forum.

    I can assure that we print it exactly as you uploaded it.

    And yes, we are working on fixing the 3D viewer and thumbnail generator to better portray the actual 3D meshes we import.

    Cheers!

    Robert
     
  5. Dalhimar
    Dalhimar New Member
    Ok first off, the locking edges might not work to well without adhesive used on them, which would make it so you could not open again.
    I would suggest using at least 2 locking tabs on each of the long sides.
    Heres a basic pic and file
    [​IMG]



    This would allow you to open the case/box by applying pressure at just the right areas to lift the tabs off the pegs.
     

    Attached Files:

    Last edited: Sep 5, 2008
  6. svenpb
    svenpb New Member
    Something like Dalhimar.

    I've drawn what I had in mind, but this is just a first idea of a process. For example, the walls will bend because of the force and so additional support ribs will be necessary I guess. Also you want the thickening for the snap to be local and not to be part of an increased wall thickness. Same is true for the guidance that is now part of the wall. Don't think you want it the way it is drawn.

    Guidelines exist, e.g. you should calculate the allowable deformation of the material while the snap occurs. And calculate the angles of the snap.

    Maybe you better buy some stuff in your local shop, take it apart and learn from it. I actually think you'll end up with Dalhimar's design or something similar.

     

    Attached Files:

    Last edited: Sep 6, 2008
  7. Dalhimar
    Dalhimar New Member
    I only see one real problem with your idea Svenpb.
    The Lighter blue could easily slide down into the space between the tab and wall.
    But that is a good idea, Go get some cheap cases or whatnot and look at how they are held together, this will give you an idea on how to design you locking structure. The one i did a rough design of is just that of a really common design. Look at as many sources as you can, then decide on what would fit your project the best.
     
  8. dennis013
    dennis013 New Member
    Sven en Dalhimar, thanks to you both for the input! You have helped me a great deal. Even though I'm still not sure it is going to work on the first try when i read this page:
    http://www.efunda.com/designstandards/plastic_design/snaps.c fm

    The math is way too complicated for me, but there are some good tips on that page. I'm going to try and do it with real models. If anyone got some tips.... that is always welcome and appreciated!
     
  9. svenpb
    svenpb New Member
    That's a very concise website. Good find.

    What they are trying to calculate (from scanning the page) is to be sure the bend is within the range of elastic deformation. If the bend is too large, the deformation is plastic, which means that the latch will not return completly to its initial position. [edit: they are trying to calculate the force, sorry]

    I'm not sure if this calculation is very important for prototyping.

    The locking -angle from what I understand starts at about 60 degrees. If the angle is bigger, you can not disassemble te part.
     
    Last edited: Sep 8, 2008