Multiple Instances Same Model

Discussion in 'Design and Modeling' started by riopoliciea2020, Mar 7, 2020.

  1. Hello everyone,,

    I know that it is possible to print multi-piece models. Is it considered the same thing if the pieces are identical?

    That is, if I want to have several copies of a small (let's call it) "doo-dad," is it possible to lay these doo-dads out in an array in one model file in order to more efficiently (and presumably more economically) print several of them at one time?????
    Last edited: Mar 11, 2020
  2. stonysmith
    stonysmith Well-Known Member Moderator
    It's very possible, I do it quite often. Part of the trick though, is that for the humans handling the parts, the more there parts there are, the more work for them to find them, and it gets problematic if even one single part goes missing - they have to wait out another print batch before they can complete your order.

    For that reason, several years ago, SW implemented a minimum charge PER PART. If you have a file with 20 separate meshes inside it, they'll happily/easily print the whole thing, but it's going to run up the price if a human can't pickup all of the pieces in a single motion. There's a whole thread about it up in the forum.

    That's why I do this: (click to see the model)
    The connectors here are called sprues - they keep the parts from floating away from each other.
    mhristau likes this.
  3. SemperVaporo
    SemperVaporo Well-Known Member
    I have a strange experience with what you are questioning. I have done several multi-item prints where I have drawn one, then duplicated it many times and connected all the pieces together with very short sprues. It has worked well in the sintered nylon stuff (Versatile Plastic), which is all I have ever used for my designs.

    My latest escapade with this was making several model "connecting plates" for a model that several RR club members are building. Each model needs about 50 plates in 3 different sizes. So I drew one plate in each size and duplicated them the number of times necessary and made one large flat plate of them, all connected with short sprues. I uploaded this design to check for problems, (fixed them!) and, then figuring that connecting these 5 sets of plates into one mass of parts would be cheaper (or at least easier to do), I stacked 5 sets on top of each other with sprues connecting the sets together vertically. I uploaded that and it would not print. It just listed the error as "Model is not manifold.".

    I studied and studied the stack of five and could not find the problem. So I deleted 3 sets from the stack of 5 and they were okay to print. So I went back to the stack of 5 and just deleted the top set. This also was accepted as printable.

    So I added the 5th layer back in (from scratch)… Hmmm... "Not manifold". I tried all sorts of things to fix it and nothing helped.

    In an act of desperation, I deleted the bottom layer, leaving just 4 layers (2 thru 5 of the original file). It was acceptable, no error! The problem was not in the 5th layer if layers 2 thru 5 would print and not in layer 1 if 1 thru 4 would print.


    I tried several things and as long as there were just 4 layers it was okay, but adding a 5th layer (above or below) caused the same error.

    I gave up and ordered a single set and a 4 layer set. No problem... EXCEPT...

    Then I checked the prices. The 4 layer set was about 62 cents MORE expensive that 4 times the single layer.

    I don't figure that there was that much material in the sprues connecting the layers together, but I guess it might have been. The sprues were 1/32-inch square and 1/8-inch long and there were about 10 of them between the layers, so 30 total in a stack of 4 and 40 total in a stack of 5.

    Do remember that you are paying for material and sprues are material you pay for and then throw away.

    Another item for this same project requires 180 identical items. I drew one, then duplicated it to a stack of 10 (with short sprues between them, then duplicated that stack 9 more times to make a matrix of 100 of the items with sprues connecting the stacks. Then I duplicated that array and stacked it on top of the 1st array (again with sprues connecting the two matrices, to have 200 total (a few extra would not hurt!). I also needed 112 of a similar, but slightly smaller, item, so I created a 10x12 matrix of those. I knew my sprues were pretty small and the stacks of parts might cause a problem with cleaning the unsintered powder from them after printing, so I checked the 'Print it anyway' checkbox. If the matrices fell apart, there was no need for SW to reprint them... I was going to cut them all apart anyway.

    The smaller parts came with only one of the "parts" broken out of the matrix, but it was in the bag with the rest of them, no problem.

    However, the larger, 2 stack array was all in pieces! I think there were at most only 6 parts still connected together, many groups of 2 or 3 and the rest already alone in the bag. Just a bag of parts (saved me having to cut them apart!). But there were only 180 of the 200 parts in the bag. And there were lots and lots of bits and pieces of the sprues that connected the stacks of 10 side-by-side, as well as two teeny-tiny bits that were not part of my print! One of the two parts was a flat plate about 1/8 inch wide, 3/8 inch long and 1/32 inch thick, with two tiny pips on one flat surface that might have been remnants of sprues it was connected to. The other item was 1/8 inch diameter disk, 1/32 inch thick with a single pip in the center of one surface, also possibly the remnant of a sprue... but I have no idea what they are or where they came from. They were not a part of my drawing.

    The missing 20 parts are not a problem since I only needed 180, (unless one of the club members drops one and we can't find it) so I didn't complain about it. I got what I wanted and learned more about this process.

    As they say; "Your mileage may vary.".

    EDITED: to correct the price different between 1 item and 4 copies in a stack
    Last edited: Mar 7, 2020
  4. mhristau
    mhristau Member
    please provide link to thread & Thanks
  5. stonysmith
    stonysmith Well-Known Member Moderator
  6. stonysmith
    stonysmith Well-Known Member Moderator
    Non-manifold was the bane of my existence when I started this 10 years ago.

    Blender has an add-on tool to find non-manifold. Netfabb Basic will warn you (and try to fix) about non-manifold while you try to export a model. Windows 3d Builder will offer to "fix" the non-manifold sections. Probably other options out there, but that's what I use.

    Basically (though there are several situations) being non-manifold means that you either have confusing or overlapping geometry.

    Imagine two cubes sitting on the platform, with a single common edge between them. That can sometimes get flagged as non-manifold, because the software and the printer can't figure out what "direction to turn" as it approaches that corner. I can't quite explain why, but it does happen. Overlap the edges by .00001 and the manifold error will go away.

    The other situation is when you have two surfaces that EXACTLY overlap in the same plane. Sort of like two sheets of paper you drop on top of each other on the ground. The software wants to make it a single plane, but there's not enough information to decide what to do as it works thru the overlap.
  7. mhristau
    mhristau Member