Week 6 3D Scanning and Printing

This week we are going to learn a core concept of fablab: using 3D printing and 3D scanning technology than change our physical world (atoms) to malleable as our digital world (bits).

Weekly Assignment

  • Group assignment: test the design rules for your 3D printer(s)
  • Individual assignment: 1 design and 3D print an object (small, few cm3, limited by printer time) that could not be made subtractively. 2 3D scan an object (and optionally print it)

Main Manufacturing Processes

  • Formative manufacturing: uses molds, the initial costs are very high but lows when the volume increases.
  • Subtractive manufacturing: a process where the material is being removed, such as the CNC milling machine we used for last weeks assignment. The material used is for actual functional prototypes (such as wodd, and metal).
  • Additive manufacturing: it adds material, and the only technology that currently does this is 3D Printing. 3D Printing is a process that builds an object by adding material layer by layer. These manufacturing process is mostly used for prototyping, it has some limitations when it comes to the material (although nowadays there have been many advances and there are a number of printers that use material for actual products, like metal, bio compatible materials, and so on). But a great advantage is the speed and costs for building a 3D printed prototype.

    • 3D Print Limitations

    Your digital design will become a physical object. In the digital design environment, there are no laws of physics to adhere to, such as gravity.Anything can be "drawn" in 3D on a digital canvas, but not everything can be 3D printed.

    General Design Consideration for 3D Printing

  • Overhangs: All 3D printing processes build parts layer-by-layer. Material cannot be deposited onto thin air, so every layer must be printed over some underline material;Overhangs are areas of a model that are either partially supported by the layer below or not supported at all. There is a limit on the angle every printer can produce without the need of support material. For example, for FDM and SLA this angle is approximately 45o degrees.
  • Wall thickness: Every 3D printing process can produce accurately features that are thin up to a certain point.As a good practice, always add thickness to your models. Walls with thickness greater than 0.8 mm can be printed successfully with all processes.Generally, designs with a uniform and consistent wall thickness decrease the chance of warping or shrinkage.
  • Warping: Something that is often easily overlooked while designing a 3D model is the fact that the materials used for 3D printing undertake physical change: they are melted, sintered or scanned with a laser and solidified. The heating and cooling of material can cause the parts to warp while printing. A good practice is to avoid large flat surfaces and add rounded corners to your 3D models.
  • Level of detail: When you are creating a 3D model with intricate details, it is important to keep in mind what is the minimum feature size each 3D printing process can produce. The minimum level of detail is connected to the capabilities and mechanics of each 3D printing process and to the selected layer height.
  • Corners: Because the printing nozzle in FDM is circular, corners and edges will have a radius that is equal to the size of the nozzle. This means that these features will never be perfectly square. For sharp edges and corners, the first layers of a print are particularly important. As discussed above for vertical holes, as the nozzle prints each layer, it compresses the print material down to improve adhesion. For the initial print layer, this creates a flare often called an “elephant's foot”. This can impact the ability to assemble FDM parts as this flare protrudes outside the specified dimensions.
  • Vertical pins: Vertical pins are often printed in FDM when assembly of parts or alignment is required.Considering that these features are often functional, it is important to understand the size of vertical pins that FDM can print accurately. If your design contains pins smaller than 5 mm diameter, add a small fillet at the base of the pin. If function is critical, consider including a hole in your design in the location of the pin, drill the hole to the correct size and insert an off the shelf pin.

    • Design Rules

    Layerheight

  • Select a lower layer height for parts with curved surfaces or when visual appearance is important.
  • Higher layer height is faster and more cost-effective and will result in parts with improved mechanical properties.
  • If the parts will be post processed, layer height is not as important.

    • Level of Detail

  • Avoid overhangs in your design when possible, by using angles smaller than 45o.
  • Add at least 0.8 mm wall thickness to your models.
  • Avoid large flat surfaces and use rounded corners to avoid warping.
  • Decide what is the minimum level of detail your models require and choose a 3D printing process accordingly.

    • More Reference:

    More Design Rules: How to design parts for FDM 3D printing

    More Design Rules For Different Filement

    What are the 3D model design guidelines for printed parts?

    More 3D print explaining on 3DHubs.

    Group Assignment

    Group assignment is documentd by Jin Group assignment link:Test the design rules for your printer(s)

    Individual Assignment

    3D Scanning

    We use Kinect 2.0 for 3D scanning.

    Skanect is a software that for scanning, and Meshmix is a software for edit model.

    3D Scanning collects data of a real object and translates it into a virtual 3D model. There are different types of 3D scanners, the one we used is a KINECT from Windows. This one works best with big surfaces, ie: a human body, if you are looking to scan smaller objects such as jewelry, this is not the scanner you would use. 3D scanning is quite fun, but you need to know that after scanning your object, you will have to repair the mesh. This is because when we scan, the precision is not perfect and the surface can have "holes". Among the softwares you could use to repair your mesh once you did the scanning, is MESHMIXER from Autodesk.

    Meshmixer operates on triangle meshes, which consist of three types of elements: vertices, edges, and triangles.

    • Vertices are points in 3D space. We can also associate other information with vertices -- for example, color.
    • Edges are connections between pairs of vertices.
    • Triangles are triples of vertices.

    More Meshimix tutoriel.

    Scanning Process:
    1. Have a clear background behind object for scanning.
    2. It works better if the scanner is fixed on a tripod and the object to scan spins on a fixed axis.
    3. Think of the best position to begin scanning your object. Remember that this process is like take thousands of photos that in the end are "stitched" together to build the object. And the stitch will be slightly visible, so keep in mind where you want to the stitch to be. In this case, when scanning a person, is a good idea to start recording from the side, this wat the stitch will be on the back of your head.

    3D Printing

    For 3D printing, I tried tindcad and fusion360 for design, also I used mini printer, Raise 3D and ultimaker.

    Tinkercad and Mini printer.

    Tinkercad is a very easy 3D modeling software for kids, I played it with my students. We failed several times, becasue we did do the right support and filling setting. In the end we got a good key chain.

    Iphone case printing

    I also decide to print an iphone 11 case. I download a model from thingsgiver and print it on Raise 3D printer. It seeems printing well but the side part is easy to break. The reason is that printer is printing layer by layer, so when you print a thin part vertical, its fragile between layers. This printing is just for fun, so I learned that FDM 3D printing in generral for prototype, it not that stronge. When we design things we need to make our design thick enough for the function.

    Final project printing

    My final project also need a case, I design it in fusion360, here is my first design.

    The first print failed because I forgot to put raft to make object stick on plate, so when nozzle print more layers on the base it start to move a little bit. I stop printing when I found out this mistake.

    Then I print again, this time printing goes well but you can see those two pieces actually can not been assemble together well. I caculate size wrong. It took about 12 hours to print, I am wasting materirels and time.

    In this design, I have several problems. 1 It's not easy to assmeble two parts together well. 2 I design tube for buttons and force sensor, but they can not fit in this case properly. 3 It takes too long to print. So I change my design and make second version design.

    In this design, I only print one part, and use laser cuter to cut a bottom board, also I can put button through these holes properly, so I measure button size carefuly and make sure they can fit in those holes without problems. Also I decide to use soft materiels to print a soft part, and put it on force resistor, so kids can hit on it to show the level of their emotion and willings. I designed a platform for force resistor, the sofe print part will be on the force resistor.

    The last print works well:

    Here are First print VS Second print VS the last one.

    Download Link: