German 3D printed RC submarine

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  • cheapsub
    Member
    • Feb 2011
    • 196

    German 3D printed RC submarine

    You can download files from Thingiverse
  • X Bubblehead
    Member
    • Sep 2017
    • 59

    #2
    Not a fan, this is an amateur design (looks like a kid's toy) and 3D print with too many issues. He has to go to extra lengths just to ensure alignment of the parts. That's to be expected with fiberglass hulls, but a good printer can get 50 micron accuracy. There are better boats available that require a lot less work to get right. Thanks for sharing as there is still plenty to learn from the videos and completed hull.

    This contributor - a mechanical engineer, puts a level of thought into his designs that are rare, (at least with free, downloadable boats.) They look and print well and all of the parts align without noticeable gaps:

    DSRV: https://www.thingiverse.com/thing:4676024

    MK-8 SDV: https://www.thingiverse.com/thing:4575440

    1/48 Gotland: https://www.thingiverse.com/thing:3324010

    He's optimized his designs for printing speed, but used good design practices for assembly.


    This is pretty typical: a nice-looking boat with a lot of detail - until you get close and look at the model. https://www.thingiverse.com/thing:4782972

    Things to look for:

    1. There's noticeable faceting in the curved portions of the hull, which is a dead giveaway the model is probably more trouble than it's worth to print. You can't remove it with a slicer - the model's mesh has to be re-designed or the CAD file STL conversion must be much finer. There's no way to sand out the faceting without damaging the rivets and weld beads, unless you want to spend more time sanding than it took to print.

    2. The hull thickness looks good - unlike the model above, which is too thin and has alignment issues. (But prints faster.) A minimum of 3mm (with 100% infill) ensures strength - especially if printing with PLA, which warps very easily in direct sun (or a warm car interior.) A better choice, (but works best with an enclosed printer) is ASA plastic.

    3. The mesh is pretty ugly and needs a lot of work. Hull mating joints are not flush with geometry protruding where flat surfaces are required. Round limber holes are octogonal. 36 to 48 sides are a good start, depending on scale. The interior is smoother than the exterior. STL files are composed of triangles to smooth out imperfections. There is no flow in the base mesh, just a bunch of disjointed interconnects to create the shape. This is why CAD models can look good on a computer screen (using the app's smoothing protocol) but when converted for 3D printing fall apart mesh-wise, which ups the (triangle) poly count. Every vertex is converted to GCode by a slicer, so a smooth, efficiently built mesh will print faster, since the print head responds to each point in the model.

    There are increasing numbers of (free and paid) 3D printer-friendly RC-submarine hulls becoming available, which is a good thing, and cannot hurt making this hobby more accessible and less expensive to more people. Unfortunately, the vast majority of 3D printer owners cannot create content or modify existing files and are forced to purchase or download free files that may (but aren't guaranteed to) be designed properly or print without an inordinate amount of cleanup to complete. Creating hulls with RC in mind requires designers to take into consideration design features for the installation of bearings, linkages, WTCs, air and water management among others.

    Amateur modeling mistakes are excusable with free models, but unforgiveable when paying for a hull - which is unfortunately all too common. This is one reason professionally-designed models take weeks - or months to create.

    This brings up another good topic for discussion in a new thread - What goes into the creation of the CAD file of a good 3D-printed model?

    I look forward to seeing what designers come up with next as more are posted online.
    Last edited by X Bubblehead; 03-29-2021, 07:37 AM.

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    • cheapsub
      Member
      • Feb 2011
      • 196

      #3
      Still hesitated to jump back in to 3D printing; software, hardware and supply.
      But you don't touch it, you never learn.

      Comment

      • X Bubblehead
        Member
        • Sep 2017
        • 59

        #4
        Great point and explains why so many people can't climb the first part of the learning curve that motivates them to move to the next level. Modeling takes a lot of work and motivation. Once you get to a certain point, it gets a lot easier but the beginning is tough.

        Creating (good) models takes a lot of time and practice. When I went to school for modeling, there were 31 students on the first day. Every one of them had paid big bucks to be there and all were fired up. Two weeks later, there were fifteen. I caught the school's director in the hallway and asked him if a 50% attrition level after two weeks was typical, and he confirmed it was. After a year, five more had dropped.

        It's important to note the difference between CAD and modeling software, because the terms often end up being used interchangeably, and despite some similarities, they're very different types of software.

        Engineering CAD-level programs, which can cost $15,000 per license create 3D objects that are dimensionally accurate but lack the tools to "sculpt" a mesh with certain types of details. The can perform stress and thermal analysis of materials and create technical drawing packages. When saving a file in a compatible format, 3D prints can be created.

        Examples include SolidWorks, & ProE.

        Dedicated 3D modeling / rendering / animation programs, (which range from free, like the light version of Fusion 360, and Blender to $1700 a year for Maya) differ in that the mesh (or wires) that make up the polygons are directly controlled, and can be shaped to easily create organic models, --making them ideal for ship's hulls. (US nukes being a notable exception- they're fairly symmetrical.)


        CAD programs are more concerned with measurements; the resulting mesh is not directly manipulated on a polygon, edge or point (vertex) level, so polygon flow is irrelevant. When 3D printing, polygon flow is very important, especially when sub-division modeling techniques are used. You can compensate using coarseness when exporting to STL with a CAD program to some degree, but a well-built 3D modeling program's geometry is based on quad polys (4-sided polygons) and when built properly, lends itself well to 3D printing.

        Both types of programs can be used for ship modeling and 3D printing, they just go about creating the objects in very different ways.

        Whichever software is used, the STL conversion always sub-divides quads to triangles, so any repair of an STL is usually more complicated. I usually combine all of the triangles to get back to quads for simplicity.

        Here is a render of the mesh of a well-constructed ship hull --this doesn't imply that it will 3D print well because all of the parts need to be broken down, but the point of this render is to demonstrate the smooth flowing polygons
        that make up the all-quad mesh.

        Click image for larger version

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        And here are a few shots of the U-boat I mentioned, with the camera getting progressively closer, showing a file that will not print well and would require too much of my life to sand and fill and sand and . . . --you get the point.

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        Never forget, your health and time are the most valuable things in your life, with time being the most under one's control. Everything else good in our lives flow from those two things. The ridiculous amount of sanding required to get this model presentable is a waste of precious time -unless one is exceptionally bored.

        I'm spending the next 30 days evaluating another thousand dollar investment in modeling software because in the long run, being more productive due to the added features saves me valuable time. I don't care how good you are, 3D modeling is a huge time suck. The good thing is, once you learn how to model, the learning curve when using a new app is much flatter because good modeling practices are universal.
        Last edited by X Bubblehead; 03-30-2021, 07:26 AM.

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        • X Bubblehead
          Member
          • Sep 2017
          • 59

          #5
          More educational examples of the same boat - only showing the mesh in more detail.

          The first shot of the bow has an external detail highlighted. Notice how it isn't connected to the hull? It's just placed there - meaning there's junk geometry inside the hull, which can cause printing errors, and adds to the print time.

          The last pic of the bow interior illustrates an important mistake - lack of symmetry.

          Since the exterior is the same on both sides, only one half needs to be modeled, then mirrored. This is a huge time-saver when building any symmetrical model!! This clearly shows different mesh topology on each side when viewing the interior. A mirrored mesh typically has a line running down the center where the two halves of the mirrored mesh join.

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          Last edited by X Bubblehead; 03-29-2021, 01:53 PM.

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          • X Bubblehead
            Member
            • Sep 2017
            • 59

            #6
            Last entry before I apologize for thread-jacking, which wasn't the intent. I just saw a good opportunity to throw some info out there for anyone interested in 3D printing, since it is increasing in popularity for this hobby. But I'll apologize anyway.

            This is a locking pin included in the previously-mentioned U-Boat files. The first pic shows three locking pins that appear identical to the eye when viewed in texture mode without the mesh visible. The pin on the left is the original STL. The other two are pins I modeled while eating lunch.

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            The second pic shows a big difference between the three when the mesh is visible. The original STL is an all-triangle mesh, as is normal for that format, but notice how much redundant the mesh is on what is essentially a cylindrical part. It is sub-divided into groups of triangles that carry the same shape. The middle pin is a mostly quad (four-point poly) mesh - except for the four end faces which have multiple points.

            The pin on the right is the quad mesh, turned into triangles. Compare the point count of each. The 3D printer head has to move to each point to complete the print in small segments - the lines between each point. More points mean more movement, which causes longer print times. All will look the same when printed - as depicted in the first picture, but the remodeled pin with fewer polys will print in a shorter time.

            Click image for larger version

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            For a small pin like this, the printing time savings aren't noticeable, but on a 12-hour or longer print with hundreds of thousands of points, they can be considerable. Being able to remove 75% of a model's points while retaining an acceptable shape for an aesthetically pleasing-to-the-eye 3D print is highly desirable once you know how and why.
            Last edited by X Bubblehead; 03-30-2021, 12:14 PM.

            Comment

            • cheapsub
              Member
              • Feb 2011
              • 196

              #7
              Cool with me.
              3D printing is not just cut and paste.
              May be the old job as a copier service tech, got to me, after work don't want to work on another box.
              Now I am out of a job, thinking about start a print farm.

              Comment

              • subdude
                Official Peon
                • Feb 2003
                • 664

                #8
                X-B,

                Cool with me as well. Great explanations. As someone who has been driving 3D CAD / Solid Modeling for most of my adult life ( I'm 65, started in 3D in '88) it's easy to forget that it's all Greek to many folks. I would encourage you to keep up the lessons, maybe even start a new thread / forum for it. With the current popularity of 3D Printing, I'm certain that it would be helpful to many. Carry on!

                Jim
                SubCommittee member #0069 (since the dawn of time.....)

                Comment

                • salmon
                  Treasurer
                  • Jul 2011
                  • 2304

                  #9
                  I agree with Jim!
                  If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

                  Comment

                  • X Bubblehead
                    Member
                    • Sep 2017
                    • 59

                    #10
                    Having taught 3D modeling and animation classes, I vividly remember how completely confusing this technology was for me when I first started. My modeling instructor was very well-known but displayed that empathetic attitude with all of us polywogs. I'm using some of his online training today as I evaluate another modeling app. His teaching style that jumps off the screen hasn't changed one iota from when I sat in the front row of his class furiously taking notes, --not just of the substance, but the style in which he taught.

                    3D printing audiences come in two flavors - Those who can create objects to print and those who use 3D files created by others.

                    I really enjoy the entire modeling process, from gathering reference material to the problem-solving that goes with creating the most efficient workflow results in the least amount of time. Being able to hold a physical representation of an object you create yourself is the icing on the cake. Having said that, I understand why the tedium that I find so relaxing could drive others insane.

                    3D Modeling is not for everyone.

                    It's challenging to teach the basics of 3D modeling without the students having an app to practice what they learn, but I suppose I could keep the information generic for anyone who wants to pick up a free 3D modeling program and apply the concepts to their situation - since all 3D apps do essentially the same thing with similar tools. A lot of the paid apps have free, full-featured 30-day trials, so I could provide a link to the software I use for anyone to jump in and be productive . . . for thirty days at least.

                    If there's a demand for it, I'd consider creating a multi-lesson, submarine-themed series geared for beginners, starting with the basics of 3D modeling, choosing a printer, followed by slicing a model we create to obtain a 3D print.

                    I concur - a new 3D Printing and Digital Design section here could make it a lot easier for viewers to quickly locate this type of information, rather than dig through the other thread sections.
                    Last edited by X Bubblehead; 03-30-2021, 06:28 PM.

                    Comment

                    • X Bubblehead
                      Member
                      • Sep 2017
                      • 59

                      #11
                      Originally posted by salmon View Post
                      I agree with Jim!
                      If you can create a new, "Digital Design and 3D Printing" section in the forums, I'll begin work. I would ask that it remain in an open forum for all to access.

                      Deal?
                      Last edited by X Bubblehead; 03-31-2021, 06:34 AM.

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