Design Rules of 3D Printing (DFAM)
In any type of manufacturing, there are specific rules and limitations that dictate how you must design your product before manufacturing process. As in 3D printing processes, whether it is for prototyping or for manufacturing end-use products, has different capabilities and different design restrictions. 3D printing can be a bit confusing. There are numerous different software, different materials, and not only the use of different printers but also various printing technologies used for 3D printing. So, it is clear that there is no one size fits for all approach. The limitations in 3D printing are related to the primary mechanics of additive manufacturing process.
3D printing is no different at all. There are characteristics of hardware, software, temperature, and filament and many other factors that should be focused in detail while designingin order to transform your digital model into a 3D printed object.
In this article, we will be discussingcritical design considerations for a designer to avoid any mistakes while turning a 3D model into a 3D object. That what are the elements that should be looked after while creating components and parts for 3D printing? Understanding of these elements and the guidelines of each 3D printing process will help the designer to master the process and able to manufacture certain 3D objects through 3D printing.
Digital vs. Physical
When designing for 3D printing, is it essential to keep in mind the fact that your digital design will end up as a tangible physical object? As far as digital designing is concerned, there’s no law of physics to abide by, and the prime example is the gravity.
As what the experts say: “You can design any 3D object in a digital designing environment, but there is no such possibility or guarantee that you can print anything as a physical object especially in 3D printing.”
Every 3D printing technology has their own set of limits for printing procedure. Every 3D printing engineer must keep in mind the following things in prior consideration when printing a digital 3D object into a physical 3D object:
Every 3D printing procedure will deliberately go by end-to-end layering and designing. It is nearly impossible to draw the 3D material on thin air which is the main reason that every 3D layer of the object must use some underline or withstanding material as support before the 3D object will get printed.
Talking about overhangs, they are an area of the 3D model which might occur to support the object layer or may not support the object at all. Most of the 3D printers usually have a limit of an angle which they can adjust when printing the object without needing to help the 3D material until the allowed object anglegets exceed. The mere examples are FDM and SLA because these technologies can hold up the object angle for not more than 45 degrees only.
It is better to keep the angel degree limits in consideration when 3D printing an object to avoid overhangs.
Wall thickness is the second most important thing to keep in mind when designing a 3D object for printing. Most of the 3D printing procedure mainly compose the precise features of the 3D object which might be thin up to a certain level when printing them into a physical object.
For the better results, it is wise always to check the wall thickness of your models. For The successful printing of a 3D model, it is suggested to keep the wall thickness more than 0.8 millimeters.
Sometimes the thing which mostly overlooked while designing a 3D object is the materials. The fact they are unnoticed can make a lot of physical modification in your 3D model such as:
- They may get melt
- They may get sintered
- They may get scanned by a laser and solidified
The warping of the 3D objects may occur during printing due to the heating and cooling of the materials.
The warping is more likely to happen when printing on a broad or flat surface. To avoid the warping while 3D printing your model, you must use an adequate surface area in grip with the proper usage of machine calibration. It is recommended to use a more circular edge for your 3D models for printing than using large and flat surfaces.
Whenever printing a 3D model with a sophisticated level of details, it is essential to keep in the mind what can be the required feature size which 3D printer might be able to print.
The primary link of the mechanism of your 3D printer of the required level of detail for 3D printing is with the competences of the selected height of your object layers.
The material you will use in your 3D printing will decide the impact of your final 3D model. So, always try to make sure you have an adequate level of details set when 3D printing a design into a physical object.
What is an overhang in 3d printing? They are geometric shapes in a 3D model that have no material underneath them making layer-based 3D printing challenging. Overhangs are areas of a model that are partially supported by the layer below or not supported at all. There is a limit on the angle in every printer can produce out of support material. Some personal 3D printers must print support structures below to avoid the overhangs from immediately collapsing during printing. Some overhangs are acceptable still you can often
safely 3D print overhangs with as much as a 45degrees angle overhang without any issue. If you are increasing the angle from 45 to above, then you are in the state of trouble, which in this case means droopy filament strands.
Another thing to keep in mind when designing a part to be 3D printed is wall thickness. Wall thickness is the value that gives a 3D model strength and durability. Thin walls for larger surfaces can be crumbling by the printer just because it is unable to print it accurately. The thinner the wall is, the more fragile and disposed to damage and warping the model is. For the avoidance of getting damage figurine, setting up a thicker wall thickness will ensure resistance to the pressure you apply when removing support and processing the model after printing.
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.
The process and materials used will have an impact on the speed and cost of your print, so determining whether smaller details are critical to your model is an important design decision.
Horizontal Bridge Gap
Bridging is when we print a flat, horizontal part of the model midair. While using a support structure for such a role could be a solution, it often works to bridge the gap without using support. We will have to drag lines of plastic between already printed parts, in a way that the plastic won’t fall down when being printed.
Fused Deposition Modeling happens on a building platform. Since models will be “built in the air”, they should be affixed to the supporting platform to keep them from crumbling. This joining is indicated as the “support” and is required for any model built utilizing this innovation. While keeping the model set up, it additionally empowers the development of components that stand out. After the making of building procedure is finished, the help is physically expelled. If it’s not too much trouble take note of that your model may show noticeable confirmation of the removed support structures.
An escape hole is usually involved when creating an object with a hollowed-out center. A borehole diameter of 2mm is recommended these type of escape holes is required to remove unfused material from the interior, just leaving the printed object behind. A technique that saves on price, since less material is the result.
The minimum pin diameter is known to be 1 millimeter. Even though smaller diameters are possible, 1 mm is the advised diameter to be used as it helps in maintaining the contour shape of the object.
Connecting and Moving Parts
3D printing encloses a wide range of technologies. Some more than others are particularly efficient to create complicated assemblies. However, as the technologies are evolving, we’ve reached a point where almost all of them can create part with moving components like a hinge or a joint. If we’re often looking at SLS 3D printing as the best solution for that, since we only need to remove the uninterred powder to “free” the moving parts, technologies like FDM or Polyjet have also brought solutions to add a “support material” that will be removed
with a solvent after the printing process. In any cases, regardless to the technologies you’re using, it’s now widely accepted that 3D printing technologies allow for integrated assemblies. Some with more facilities than other.
the tolerances and precisions of some 3D printing technologies are sufficient to create assembly that will simply “snap” together or will even be used for high performance goals. As a example, General Electric released a video showing how they successfully used additive manufacturing to create a fully working jet engine. The result is astonishing.With appropriate tolerances, parts with functional hinges, chain-link style textiles, and other types of moving components can be fabricated in a single print without the need for post-print assembly. This is one of the main upside of 3D printing when you want to manufacture a product since it can considerably reduce the number of necessary components to create your end product.
Rule of thumb
There are different 3D printing processes, but the basic rules and guidelines are more or less the same in each process and vary depending on the material and type of 3D printing process being used. DfAM (Design for Additive Manufacturing) is a big umbrella which includes all the rules, considerations and parametersneeded inadditive manufacturing processes.
3D printing technology is advancing rapidly,and there are demand and need of designing and making more intricate, elaborate and workable objects. There are specific procedures which are necessary when making a physical object and similar guidelines are mentioned in the DfAM ‘Rule of Thumb’. These rules are fundamental when designing and implementing your 3D model.
The 3D models to be designed must firstly fit the 3D printer build volume and either lie flat on the build plate or be supported. Support is one of the most keys, and critical part of the metal printing process and the measurements, placement, and geometry should be correct to prevent waste of materials, printing time and cost. The alignment and positioning must consider during the design stages as upward facing surfaces have sharper edges and a better surface finish.
The rule of thumb or limitations for designing metal printed part features are:
|Wall Thickness||Minimum 0.4mm to 1mm in diameter. For FDM 0.8mm|
|Pin Diameter||More than 1.5 mm in diameter|
|Hole Size||Without supports, 0.5 mm to 6 mm but diameter more than 6 mm will require support|
|Escape Holes||Minimum of 2 mm to 5 mm in diameter|
|Overhangs||One should avoid overhangs in the design and use more than 45-degree angle fromhorizontal for unsupported surfaces|
|Unsupported Edges||Maximum limitation 0.5 mm|
|Aspect Ratio||8:1 ratio is allowed for build height to section width|
|Aspect Ratio||On a 3D plain allowed thickness in Z-direction is ± 1-layer whereas in XY plane it is ± 0.1 mm|
The process and materials used will affect the speed and cost of your 3D print, so it is better to determinethe smaller details which are critical to your design. One should avoid large flat surfaces and round the corners to prevent warping. Determine the minimum level of detail your 3D model require and choose the 3D printing process accordingly.
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