CEO & Founder. Mechanical engineer with PG in Tool Design and Manufacturing; Varied experience in global companies; CEO of MNC for over 17 years; Strong process background.

  • How to design fractals for 3DPrinting

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    Using fractals to design complex shapes

    Fractals Intro

    Fractals are geometric patterns that repeat at different scales. They exhibit the property of “self-similarity”. Fractals appear complex in shape. But they are just iterations of simple geometries in a pattern. Consider an equilateral triangle, inscribe another equilateral triangle within and continue doing this. You will end up with a Seirpinski’s Triangle. This is a simple geometric fractal.

    Sierpinski's Triange

     Fractalfoundation.org: “A fractal is a never-ending pattern. Fractals are infinitely complex patterns that are self-similar across different scales. They are created by repeating a simple process over and over in an ongoing feedback loop. Driven by recursion, fractals are images of dynamic systems – the pictures of Chaos. Geometrically, they exist in between our familiar dimensions.” 

    Fractals appear all over nature from microscopic to cosmic scales. The arrangement of cells in living organism and stars show fractal-like patterns. A simple example in your daily life is branches of trees or lightning on a stormy day.

    Origin of fractals

    The term fractal was first coined by Benoit Mandelbrot in 1975. It derives its origin from the Latin word fract meaning broken or fragmented. Fractals are able to describe complexity in nature better than Euclidean geometry. According to James Gleick ,”In the mind’s eye, a fractal is a way of seeing infinity”- from Chaos (1987), 98. Fractals are powerful tools. Various fields such as architecture, biology, weather modeling, astronomy, networking, digital art, etc. use fractal as a tool.

    Application of fractals

    Fractals have been applied in several fields of human knowledge including architecture, antena design and mechanical cross section of ropes. Fractals also appear in  nature in several locations including the human lungs, propogation of lightning, tree branches and coastlines.

    Exploiting fractals in engineering design

    3D printing can be used for creating complex shapes. Since shape is not a limitation for 3D printing, fractal design helps in creating complex shapes to solve engineering problems. In here we will be discussing the design aspects and will not be covering the actual 3D printing process by itself.

    The principle of fractals can be exploited in engineering design in many ways. Some of the typical examples are weight reduction in structural members, compaction in antenna designs, heat transfer applications, equalised fluid flow paths etc.

    Here is an example for fractal fluid path creation. The objective here is to divide fluid paths in an equalised patterns keeping the overall flow area constant and minimise friction losses to due changes in the flow of length or directions.

    Fractal Fluid Path Design

     

    Design steps for creating fractal fluid path

    I have described the main design steps in Fusion360, without some of the intermediate steps.

    1. Create a pattern of 16 nos 3 mm squares in a plane with a pitch of 10 mm between them in X and Y directions ( Fig 1) . Create another plane at a distance of 25 mm in the Z axis. Project the mid point of the 4 shaded squares to the second plane. And draw a square of 6 mm in the second plane with the projected point as the centre (Fig 2). Please note that this is an important step. The 6 mm square will have the same area as  the sum of four 3 mm squares. ( 4* 3^2= 6^2) . One could accordingly change the dimensions to suit the application. Loft one of the corner 3 mm squares in the first plane to the corresponding quadrant of the 6 mm square in the second plane. This creates the first fluid passage  (Fig 3). The design still has not added any wall thickness, which will come in the subsequent steps. 
    2. Fig1-3Extrude the top square after lofting by 3 mm. This is done to minimise the impact of direction changes by equalising after every step of the fractal division.  (Fig4) . Create a circular pattern around the center axis and create 4 identical bodies of fluid passage (Fig 5). Wall thickness is still not added. The next step is t0 combine the 4 bodies into a single body and shell outward with 2 mm wall thickness (Fig 6). Now we have created 4 flow paths of equal size and flow distance and deflection angles, with wall thickness.
    3. fig4-6The next step will include creating another plane at 25 mm from the top of the body (created above) and draw a square of 12 mm . As explained in step 1 this is to account for the same area as four 6 mm square flow areas. ( 4*6^2= 12^2).(Fig 7). As, before the 6 mm square passage is lofted to the corresponding quadrant of the 12 mm square. ( Fig 8). Again the top surface is extruded by 3 mm.
    4. fig7-9Similar to what was done for Fig 5 in we again create a circular pattern to create 4 bodies. (Fig 10). These 4 bodies are combined and shelled outward with 2 mm wall thickness. (fig 11). The next step is to circular pattern the first set of combined body cluster in Fig 7 around the axis which passes through the center of the 12 mm square.
      fig10-12
    5. We are almost there. We need to add another body to convert the square 12 mm opening to 13.543 diameter opening to again keep the area constant. ( 12*12 = π/4*13.543^2) . This is done to facilitate connection to round pipes. Create an offset plane by 30 mm and draw a circle of dia. 13.543 . (Fig 13). Loft the 12mm square to the 13.543 dia. circle. (Fig 14). The final step is shell the body outward by 2 mm and combine all the bodies (Fig 15) and it is done.
    Fig13-15 Stratnel-Cross-Section-fractal-fluid-path

     

    Conclusion

    These parts are suitable for 3d printing. One could also add other features to this part like threads and or other features. With such complex shapes, making such a product through any process other than 3D printing involves several limitations including design, machining, patterns, overall costs, etc. 3D printing is elegantly suited for manufacturing such fractal-based designs.

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  • How to 3D print single and multi-colored backlit surfaces

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    backlit 3D printed light switch banner

    3D print backlit surfaces

    3D printing does not always have to be opaque. There are several applications where a transparent or translucent part is needed and a backlight is used to highlight that part.

    Common instances include power switches, face plates, and UI indicators. A power switch needs visual feedback to show the user if it is off or on. This is more important if the switch is in a toggle mode.

    Let us discuss how we can create a custom part for backlighting. The backlighting should provide visual relief only in specific locations. What this means is that some parts of the switch need to be transparent or translucent while other parts are opaque.

    Materials to use

    Depending on the application, one could use PLA, ABS, Polycarbonate(PC), PETG, etc.. All these materials are available as opaque or translucent filaments. In translucent filaments, there is also a choice of clear or colored filaments.

    In this experiment, we use PLA. The same method will apply for other materials too.

    We could achieve similar results with different methods. We will examine two different approaches here.

    The first method uses translucent filament for printing. Applying masks, opaque areas are painted and translucent areas are not.

    The second method is to use two different materials. A translucent material for the light window and an opaque material for the mask.

    Both approaches have their merits.

    Method 1 – Single Translucent Material

    Design your whole fixture including the opaque and translucent areas as one single part. 3D print the switch in a translucent material of choice. After doing this, the whole part will appear translucent and look like this.

    stratnel-single-transparent-material-light-switch

    We can now paint the part to have a translucent window, in two different ways.

    Paint the whole part with an opaque paint color of your choice – maybe black. After painting , laser etch to remove paint only in areas that need to be translucent.

    We could also first apply mask(s) on the areas of the part that need to be translucent. Then paint the part and peel off the mask to get the required translucent windows.

    stratnel-painted-light-switch-unlit

    Translucent material, painted and laser etched – unlit
    stratnel-painted-light-switch-lit

    Translucent material, painted and laser etched – with backlight

    Method 2 – Multiple materials, opaque and translucent

    It is possible to use different materials for the opaque area and the translucent area in the part. This method is much more elegant and reduces further process steps. We do not need to resort to masking or painting.

    Another advantage of this method is that it is also possible to add light guides into the design. This will help homogenous illumination of the desired area, even when the light source is away from the pattern. We can also illuminate several patterns with a single light source if we use light guides.

    stratnel-light-switch-multiple-material

    Multiple material – opaque and translucent
    The final choice of whether to use painting or multiple materials will depend on the pattern of light. If the pattern is simple, using multiple materials is the way to go. If the pattern is intricate, laser etching provides better detail and resolution.

    Choice of Lighting

    As for the backlighting, a simple LED is the usual light of choice. LEDs are available across the color spectrum and are well suited for the application.

    The transparent material chosen for the part can also be colorless in appearance and the LED light can be colored to provide the desired effect. By using multi-colored or RGB LEDs, it is possible to design a panel that can emit several colors.

    This gives the designer the option to indicate different states of operational readiness by changing the light color, say orange for warm and red for hot.

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  • A starter guide on designing for additive manufacturing

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    3d-printed-drill-jig

    Additive manufacturing is for every one. Not just big companies.

    Are additive manufacturing methods meant only for high end product companies like large aerospace, automotive or medical devices companies and/or hobbyists? NOT ANY MORE. It is getting to be more mainstream in almost all industries regardless of complexity, sophistication, segment or size.

    Why is it that some industries are benefitting more from additive manufacturing than others? One big reason is that they have learnt the lessons to design differently for 3D printing. Here we will talk about how product designing processes have to be different.

    The set of “Design Principles” traditionally used must be revisited to take full advantage of additive manufacturing/3D printing.

    Traditional design principles will not work with 3DP

    The following traditional design principles will not apply when you are designing to leverage 3D printing.

    • Existing designs can be tried for additive manufacturing effectiveness. This approach is most likely to fail because existing design was designed for traditional manufacturing methods.
    • Avoid complex shapes in products; use simple geometries for DFM considerations.

    3d-printed-complex-shapes
    Image © Stratnel Technologies LLP

    Traditional manufacture may require a lot of machining for a complex shape like this, but with 3D printing this product is straightforward to design and print.

    • Doing multiple iterations to optimize design is very time consuming and expensive in traditional manufacturing.
    • Since additive manufacturing does not involve expensive tooling for making the part you could run iterations to optimize your design within a short span, compared to traditional methods
    • Using multiple materials in one part is almost impossible without very complex manufacturing and/or assembly methods.
    • Standard parts are better than custom parts for subtractive manufacturing. In additive manufacturing, parts are made anew every time. There is no such thing as a 3D printed standard part.
    • Additive manufacturing aficionados have to give up their fixation on materials. They cannot afford to have statements such as “all our parts have to be in aluminium only”. Additive manufacturing can come up with high rigidity by using composites. Carbon fiber reinforcement is very much a reality. Open minds will pave the way not only for newer materials, but also gain weight reductions as a bonus.
    • There is this standard notion that “3D printing is expensive”. It will not be expensive if we consider the total applied cost (which includes tooling costs, lead times, inventory carrying costs, factory footprint savings, productivity levels, etc).

     

    All these may appear difficult to the uninitiated . But the benefits are substantial . Imagine the advantages of replacing an engineering process costing $800 and taking 10 days with another more elegant solution that costs only $200 and takes only 2 days. If such economies are in fact realisable, how many different processes in your work place could you deploy additive manufacturing to gain competitive advantage?

    Let us talk specifics. Here is a design example to understand this better. Consider a drill jig for drilling axial holes in a spherical object in all the three axes. The idea here is that one first drills a hole by centering the sphere in a conical locator and locates the first drilled hole on two pins resting on the V block and repeat the same exercise on another orientation for the third axis.

    Part drawing
    3d-printed-part-design
    Image © Stratnel Technologies LLP

    A traditionally made and assembled Jig may look like this. This design is a representative of the idea and will need some more work to ensure clamping and other requirements.

    traditional-drill-jig
    Image © Stratnel Technologies LLP

    A 3D printed jig will be a lot easier to make with just two parts.
    1) A structure to locate the parts , the pins and the jig bush.
    2) The jig bush itself.

    3d-printed-drill-jig
    Image © Stratnel Technologies LLP

    Design steps for Additive Manufacturing

    The design steps in Fusion 360 will be:

    1. Create the base with the conical locator and the V groove for the pins. And locate the bush at the correct position. Generate a ring body around the bush to house the bush.

    design-drill-jig-step-1
    Image © Stratnel Technologies LLP

    1. Generate the starting area of the pillars on the top surface of the base plate. Generate a plane normal to the base and at 45 deg to the edge of the plate where you can draw the spline path for the pillar . Create a plane normal to the spline path at the end of the spline close to the jig bush.

    design-drill-jig-step-2
    Image © Stratnel Technologies LLP

    1. You can generate a new body by lofting the starting area of the pillars and the profile at the termination end, along the spline path to create a new body. Generate a circular pattern of the new body to get the four pillars.

    design-drill-jig-step-3
    Image © Stratnel Technologies LLP

    1. Combine the bodies – the base plate, the ring around the jig bush and the pillars to get one body and convert to a component and the job is done.
    design-drill-jig-step-4

    Image © Stratnel Technologies LLP

    Shift in design paradigm for 3D printing

    Designers have to be innovative and think out of the box when designing for 3D printing. This is new learning and challenges the traditional concepts learnt so far by designers. Of course, additive manufacturing does challenge traditional manufacturing and designers have to make suitable changes in their thinking in order to be successful.

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  • How to design parabolic, hyperbolic, elliptical reflectors for 3D printing

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    Parabolic reflectors

    Designing parabolic reflectors for 3D printing

    In this article, we show you how you can design parabolic reflectors from first principles with any CAD software. Here at Stratnel, we offer design advisory and printing services and enable designers to use additive manufacturing to move quickly and get more done.

    Applications

    Reflectors are used in applications like industrial lighting, stage spotlights, home lighting, signal collection in antennas, directional microphones, speaker enclosures, infrared heaters, ultrasound sensors, etc.

    The common geometrical shapes used are spherical, ellipsoidal, paraboloidal and hyperboloidal. These shapes are simple conic sections. Reflectors use any of these shapes or sometimes a combination of these shapes to increase the effectiveness of signal collection and transmission.

    Conical sections explained

    Source: Wikipedia, modified by Stratnel.

    All of them have different characteristics. These geometrical shapes can be used appropriately to increase the effectiveness of the design. For instance a parabolic reflector will generate parallel beams when the source is in the focal point. We will discuss designing parabolic reflectors/collectors and 3D printing them. Any conical section shape can be designed and 3Dprinted with additional features, using similar principles.

    From equations to CAD

    Modeling in Autodesk Fusion 360

    Designing Parabolic reflector Fusion 360
    Image © Stratnel Technologies LLP

    Here is a way to model in Autodesk Fusion 360 from first principles.

    Andrew Sears from Autodesk support mentioned this method in the Fusion360 user forum. I have explained the steps involved in more detail.

    The design steps in Autodesk Fusion 360 are based on the space available. We may start with some basic parameters like the diameter D and height h. Let us consider D=80 and h=30.

    Step 1
    Construct a triangle with Base=D=80 and height=2h=60.

    Draw a line from the mid point of base which is perpendicular to the hypotenuse. Let us call this offset distance and measure it. In this case it happens to be distance=33.282.

    Parabolic reflector design steps 1, 2 & 3

    Image © Stratnel Technologies LLP

    Step 2
    Revolve the area enclosed by hypotenuse, base and axis around the axis line to generate a conical body.

    Generate a tangent plane and copy (or move) it by the offset distance (33.282) so that it will pass through the intersection of offset distance line and the base line and split the body.

    Step 3
    The splitting plane has the parabola we need. We now copy the parabolic curve and offset the curve outside for required thickness ( say 3 mm) and revolve the section to get the parabolic reflector we started with.

    Designing parabolic reflector Step 3

     

    Designing parabolic reflector Step 3

    Images © Stratnel Technologies LLP

    From CAD to prototype

    3D printing is a great way to get from design validation, through functional testing, and manufacturing small batches.

    You may also consider aesthetics, ease of printing, mounting arrangements etc. as you iterate with your 3D printing service provider. Here is an example of a parabolic reflector with integrated mounting fixture.

    Parabolic Reflector with mounting fxiture

    Image © Stratnel Technologies LLP

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  • How to save measurement time with custom 3D printed fixtures

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    frustration

    Photo: nasrul ekram on Flickr

    Have you been asked to do a Cpk analysis and spent hours of time measuring each part in your sample set?

    There are less painful, and more reliable ways to do this sort of thing.

    We’ll show you how we improve reliability and save hours of measurement time with 3D printed fixtures.

    Cpk is an index (a simple number) which measures how close a process is running to its specification limits, relative to the natural variability of the process. The larger the index, the less likely it is that any item will be outside the specs.

    — Neil Polhemus

    Traditional fixture design is expensive

    Traditional fixture design, manufacturing, and assembly pieces and assembling them could be quite cumbersome and time consuming.

    Repeated manual measurements are risky

    To get an accurate measure of CP or Cpk for your manufacturing process, you need to make multiple repeat measurements of parts in your sample size.

    Take this stamped part that needs to be measured, for example.

    Stamped Part:1
    Stam

    Stamped Part:2

    stamped-part-2

     

    Sample size, 32 nos.

    What you do typically to measure is like this:

    1. For each sample, align it against a fixture.
    2. Measure each side carefully.

    This traditional alignment process constantly nags your mind with repeatability doubts.

    Design and print your own fixtures

    Delicate pieces, like this stamped part, are measured easily with fixtures. Fixtures take away both the problems of alignment time and repeatability doubts.

    Example

    Here’s a fixture we designed internally at Stratnel for this part.

    3d=printed-fixture 3d-printed-fixture

     

    This 3D printed fixture can be made in a matter of hours and 1/4 the cost of a traditionally manufactured one.

    More on this, in the next part of this series.

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