Material and method advice needed

Discussion in 'Technologies and Hardware' started by BrianH, Jan 8, 2012.

  1. BrianH
    BrianH New Member

    I'm in the planning stages of a personal project that involves creating a cellphone mount. Its going to end up being made up of a number of different pieces, and while I have a small history of 3d modeling, I have never designed anything with the purpose of it being made in real life, and this will be my first foray into 3d printing.

    First question, screws. Is it a good idea to make 3d-printed screws? Can the threads be represented accurately, can they survive small amounts of trauma? It seems like this would be the easiest way to solve some of the design challenges I'm coming across, as I could simply make a screw and screw hole match each other perfectly.

    If printed screws are not advisable, what about making unthreaded holes with the purpose of driving a metal screw into them? Should the hole match the shaft of the screw, or should it be somewhere between the shaft and the apex of the thread?

    Alternately, are there any commonly-used designs for fastening pieces together?

    What about hinges? I was thinking about simply having the pin with a cap on one end and a threaded tip in the other, to allow for a sort of screw-on cap. If threaded objects are not advisable, though, I really don't know what I would do for the hinge.

    Also related, what should I expect when designing two pieces that are meant to play on each other? In the case of a hinge, can I make a pin with a diameter of 3mm, and a hinge with a hole of 3mm and expect them to fit perfectly? Stiff? Snug? Not fit at all? Does it depend on the material?

    Thanks for your time!
  2. crabigailrose
    crabigailrose New Member

    Sounds like you have a neat project going on! Here's a bit of advice for ya

    Instead of having so many parts and extra hardware (hinges, pins, fasteners, etc) try to incorporate those functions into your actual design. Instead of adding a hinge after your project is printed, why don't you design it with a living hinge and eliminate that extra peice of hardware? A living hinge is where the plastic thins out where you want the hinge to be, and because of the natural properties of plastic your part will easily flex there and become a hinge. Shampoo bottles, film canisters, and a lot of packaging (like those plastic clam-shell containers) all use this kind of hinge.

    As for fasteners, what do you need them for? 3d printing is interesting, because you can print parts that are already assembled. I don't know if you can print screws accurately, but depending on how your design works you may be able to cut them out completely. Do you have drawings of your design? Maybe I could help better if I could see what you're trying to do with the screws.

    Good luck! hope I could help at least a little =-)
  3. BrianH
    BrianH New Member
    Thanks for the advice!

    After digging around, I found that somebody else has done a project similar to mine, to get a basic understanding of it see this link: ixed_.html?gid=mg

    However, there are two areas in which I would like to expand upon. First, I would like it to be more portable. My first thought was to make the clamp fold up, but I recently came up with another approach, to have the clamp detachable with a dock at the bottom of the device to hold the clamp arm. I basically want to be able to toss the dock + controller combination into my bag without any protruding parts sticking out and potentially breaking from everyday wear and tear.

    I'm assuming in this application a living hinge would not be appropriate? I did some searching through the help files and found that incorporated hinges, where they are printed as they are with no external pieces, is a possibility. Perhaps that would be the simplest approach. Do you know of any examples of such heavy incorporated hinges floating around the stores?

    The second area I would like to expand upon is to make the dock universal. I was thinking of using a telescoping arm to do this, with the locking mechanism being a screw attached to the outer sleeve that you would tighten to prevent the inner arm from sliding. See diagram 1 to get a better idea of what I'm talking about, the cylinder at the bottom is the screw.

    As for fasteners, if you look at the front of the 3d model on the link I provided, you'll notice that its blank, while on the photos the person who made it did something to fasten it around the controller. What I was thinking of doing is having a fastener with a natural catch, see diagram number 2 for a better idea.

    What I would still like to know is, what is the most robust material that can handle moving parts, and what kind of distances should I allow for when modeling? I know there's lots of discussion about integrated moving parts, so the distances on the hinge is probably well-covered (as long as I can see a good hinge design to allow for cleaning) but what I would like to know is what about the telescoping arm? It is my intention to print the sleeve and the inner arm as separate pieces, should there be any gap at all between the pieces if there's no threat of them fusing in printing? Should I still allow a gap? What about the use of the screw? should I try using a printed plastic screw, or would I be better off having an unthreaded hole and simply jamming a screw in the hole? How big of a hole should it be relative to the metal screw?

    Anyway, thanks for your time. Still want to hear some solid advice before I start hammering out the details on this.

    Attached Files:

  4. Tamert
    Tamert New Member
    I only make functional models unlike many here who create artistic designs. I have found:

    1. If you want to create a threaded hole, buy a tap set and just leave the correct diameter hole in the model for your tap set. Nylon bolts are cheap, widely available, and and provide sufficient friction to lock tight before stripping the threads for most of the printed materials (I have used WSF, aluminide, UFD, and SS).

    2. You can't count on making a functional hinge because of the print to print variation. The only way that you can guarantee success is to print the hole too small and the pin too large and then drill/sand them to fit well (don't forget to lubricate).

    It's best to think of all of this printing as more of a rough casting that needs to be machined for precision fit.

    Hope this is helpful.
  5. BrianH
    BrianH New Member
    I appreciate your taking time to reply, but there are still a lot of unanswered questions.

    About threaded holes, is it reasonable at all to simply make an unthreaded hole the diameter of the screw, and force a screw in the hole to give it threads? Is the material that pliable? Its not going to be used as a major support fastener, I just need it to lock the telescoping arm to a certain length.

    And as for the telescoping arm, what kind of gaps between the two pieces should I design for? The sleeve and inner arm are going to be separate parts so I don't need to worry about them fusing, but I would like it to be a very snug fit (as snug as possible!)

    As for the hinge, it can be a bit loose if I design it correctly I think, I'm mostly worried about it being robust while still being able to be cleaned. Pleas see the attachment. Does this look like a good hinge design for these purposes?

    Attached Files:

  6. Roy_Stevens
    Roy_Stevens New Member
    You can print threads. I would suggest using Acme style with a fair amount of slop.
    You can drive sheet metal or similar screws into it. Some experimentation will be necessary, but I would start with the hole at the diameter of the shaft plus 30% of the thread to give some place for the deformed material to go.
    You can't bend it far, certainly not like a shampoo bottle top. I doubt the living hinge concept would last for very many cycles.

    My question is: Why make it universal? The beauty of rapid prototyping is the that you can make everything personalized. I can buy a lousy universal mount at any box store. What I can't buy is something that fits my oddball Android device like a glove.
  7. BrianH
    BrianH New Member
    Thanks for the advice about screws. I was going to use a simple PC-case screw, they're around 3mm. But now that I look at them, their threading is pretty fine, so I should probably use a different screw size, I have a few others sitting around that are 3.5mm without threads, 5mm with. Those would probably work better, with a 4mm hole to dig into.

    So finally, any advice on the telescoping arm + hinge? That's all I really need before I commit to my design.

    Oh, and I want it universal so other people can use them as well. I don't think there are any cellphone docks that are made to pair up with PS3 controllers out there, so another beauty of 3d printing is that I can fill that void myself :)
  8. BrianH
    BrianH New Member
    Still hoping I could get some help on gap spaces for separate components...