Is Printing Articulated Projects Possible?

Discussion in 'My Work In Progress' started by zrowngctr, Mar 5, 2020.

  1. zrowngctr
    zrowngctr Member
    I'm working on a generic articulated hand for a Transformers Combiner toy:

    While unlikely and probably impossible, I want to know if Shapeways can print articulated objects, where it's not just one solid block object.

    This is the first joint I am working on, where the post in the middle of the thumb support is intended to allow the support to rotate around it, so the hand can be folded into a fist.

    Is this possible to print several unconnected shapes in one print job?
  2. SemperVaporo
    SemperVaporo Well-Known Member
    It depends on the material you want to use. Do a search of the marketplace (the search text box above) for "Articulated hand", and you will find many products, including some "hands", that others have made available for sale. Look to see what materials they used.
    Look at the Materials page of this site (hover the mouse over "Start Making" and select the bottom item, "3D materials guide") and read about many of the materials available. There will be words that explain whether they can be printed as one object and how close together the parts can be and still be separate items in one print. Be sure to check the 2 tabs ("Material info", and "Design Guidelines") at the top of each material's page to see the minimum sizes, tolerances, etc..
  3. zrowngctr
    zrowngctr Member
    I'm thinking given how firmly the pieces need to snap together, there isn't really a tolerance for adding airgaps, as it would affect the stability of the joint:
    This is a simulation of how the thumb joint will rotate on the printed product.
    if the post isn't the same size as the hole in the rotational socket, it'll wobble a bit when printed.

    At the moment, I'm considering printing the finished product in such a way that the pieces can be assembled by hand afterwards, with the use of some superglue that is.
  4. SemperVaporo
    SemperVaporo Well-Known Member
    Take a look at this product (not mine)

    Watch the video on that page. I bought one to prove to myself that it really is what I see in the video (besides, I am a steam locomotive nut and just had to have yet another model of one!). I have it in my hands right now and it is boggling how detailed it is and how rigid the wheels are in the frame, yet they roll! (The axels rotate in the frame yet it is not assembled after the print, but is printed with the axels "IN" the frame holes!)

    The side rods and the main drive rod pivot on the drive pins on the wheels and the main rod cross head slides in the cross head frame behind the steam cylinders. The front truck (4 wheels) pivots on a center pin and has some "slop" on that pin, but that may be intentional since on real locomotives like this, the truck did shift on that connection to the frame (i.e.: the truck can turn to follow curves in the track as well as tip up and down to follow vertical undulations in the track and keep all 4 wheels in contact with the rails).

    I still think you will want to read about the various materials and what tolerances there are for specific printed sizes. And some materials are actually a casting of one material after using another material to make a mold, and as such there are two (or even 3) times when parts can vary from the size specified in the print file.

    And again, I suggest that you look at "hand" type products others have available for printing. They may not meet your purpose, but you can see the tolerance effects on how to hinge parts and such.

    I am right now trying a new material (same as the steam loco, "Smooth Fine Detail Plastic") to remake one of my items in a much smaller size since this material has much smaller possible gaps between parts than what I have been using ("Versatile Plastic").

    But you may need to use some other material, depending on the strength you need for the articulated hand... are you just going to make it for show, or is it to be part of a "super human robot"?

    You may also have to just print the parts separate, and drill holes to fit the shafts that are to be in them if you require absolute minimum tolerances... or even fit them with ball or roller-bearing races to obtain smoothness of operation and minimal slop in the articulated joints. But that is all lots of post print work.
  5. zrowngctr
    zrowngctr Member
    I did search for some similar products, but could only find dissembled ones that need assembly after printing.

    The product I am designing is not intended to be for display only, but for functionality and play value, hence why I am trying to articulate the joints, for posing and to emulate closing the fist around the weapon of the Combiner the hand will be attached to.
    There's actually a 5mm shaft running through the fist which will actually be holding the weapon, the digits aren't necessary to hold it.

    In case anyone is unfamiliar with what a Combiner is, they're a gestalt mechanoid formed from 5-6 seperate mechanoids, with the smaller units becoming the arms and lower legs with a main larger unit forming the torso/upper legs.
    The hands and feet are seperate modules which have to be attached after Combination, but the toy versions aren't very detailed or scale accurate, hence why there's such an interest in manufacturing third party versions to replace these modules.

    I haven't figured out how to make a ball joint assembly with 3D printing yet, hence why my design is rotational based.
  6. Andrusi
    Andrusi Member
    The short answer is you can't print two separate pieces that are zero distance apart, and if you try Shapeways will interpret it as all one big static piece. (Heck, I don't think that's even possible through regular manufacturing. If you look at the official hands you're replacing, you'll see they've been assembled after the fact, too--if they're the ones I'm thinking of, they're actually held together by metal pins.) You can print "pieces" that are multiple separate parts, but they have to be far enough apart that they'll be loose--good for free-rolling wheels, not so good for articulated fingers that you want to be able to hold a pose.

    The good news is that once you've accepted that some assembly is going to be required, there are several ways to do it without even needing glue. Probably the easiest way is to have the end of the finger that attaches to the hand be a C shape instead of a full circle, so they can just clip onto the rod like putting a tool in a LEGO minifig's hand. It won't work well at all scales, but chances are they'll work for what you're doing.

    Regardless of what you go with, be prepared to print slightly different variations on your product three or four times, as tolerances for this sort of thing have a way of working out slightly differently than you expected. There might be other considerations depending on your material--in Versatile Plastic for instance you'll want to find a way to sprue all these little pieces together so Shapeways doesn't charge you an extra two bucks each.
  7. zrowngctr
    zrowngctr Member
    Here's some samples of Combiner hands:
    The grey on is an official one, with a metal pin.
    The black one is a third party product and uses plastic extruded posts to lock the joints together.

    I'm currently working on emulating the black one at the moment.

    I had considered the C clip path, if that can lock the joints stable enough for posing and can be slotted on without breaking the clip.

    I genuinely hope I don't have to print this product 4 times, on average it takes Shapeways 2 months to ship my prints to me (because they're in America and I live in Australia).
    4 different prints would be a combined mailing time of 8 months total.

    I wish I had a way to do the test prints locally, for a faster turnaround time, then when I've solved all the problems, submit the refined model to Shapeways for a genuine print.

    Unfortunately, the local printers (and local is a misnomer, since they're all in the next state!) charge a fortune for prints, much more then Shapeways would ever ask.
    I think it's because these businesses are geared towards mechanical engineering prototyping and aren't intended for toy prototyping or the home hobbyist market.
  8. Temjin
    Temjin Well-Known Member
    Why not fixed pose hands, can you do some really fun stuff with them.