Traditional manufacturing design principles stem from traditional subtractive manufacturing processes such as milling or turning. The rise of additive manufacturing and 3D printing calls for an adaptation of design principles to ensure that the technology is being utilized to its fullest capacity.
To understand this concept further we must first begin by understanding what both subtractive and additive manufacturing is. As the name suggests, subtractive manufacturing utilizes tooling to cut into (remove/subtract) material from a blank part. An effortless way to understand this is a sculptor cutting away at a block of clay to make their sculpture. This manufacturing methodology has been the industrial standard since the industrial revolution began.
Recently however, additive manufacturing processes have been developed and tuned and is now accepted as a feasible manufacturing method for its respective industries. In contrast to subtractive manufacturing, additive manufacturing enables electromechanical systems to add and incorporate material to precise locations to build the part. A good analogy for this technology is building a sandcastle. When building a sandcastle, you must continuously incorporate new sand to pre-existing geometries in a precise orientation to define features like walls and doors.
To take full advantage of the technology, designers must carefully consider both the advantages and disadvantages with the tooling and modify their designs accordingly. The following are things to consider when designing parts for additive manufacturing.
Tip One: Build Plate Orientation
As previously mentioned, additive manufacturing incorporates and builds on top of each successive layer. Due to this it is important to design/orient your parts with all the larger, flatter features on the build plate and have the smaller taller features grow from the larger ones. This will provide the part with an adequate foundation to build the part up vertically. Consider the two images below. Although the image on the right has a flat base, it also has several features that protrude out of the part. These parts have large overhangs which would result in requiring a lot of support material and would have inconsistent, messy layer lines which will result in a poor surface finish. In contrast, the part orientation shown in the left image has a much more refined build plate orientation. Here it can be identifying that the largest flat surface is in contact with the build plate. Furthermore, it should also be noted that all features have a sufficient foundation to grow upon. This orientation will result in a much smoother surface finish and limit the need for support material, reducing the overall post processing time.
Tip Two: Self Supporting Geometry
In order to both reduce the amount of support material and the overall time required to print and post process the part, designers must utilize the self supporting capability of additive manufacturing. Self supporting geometry is a specific maximum angle that provides the new material with a solid foundation to continue building the part without stepping, stringing and other surface defects. Generally in Fused Filament Fabrication (FFF) printing, this angle is known to be positive 45 degrees from the build plate. This figure however will change slightly depending on individual printer mechanics as well as material type and quality.
Tip Three: Segmenting Parts
Although 3D printing and additive manufacturing have been known to have the ability to print geometries that wouldn’t be possible using traditional manufacturing methods, it doesn’t mean that you are able to print anything you want without careful consideration. One of the main design constraints that people will have is that their design is limited to the build size of their printer. Despite having a set build volume, doesn’t necessarily mean that as a designer you are limited to only designing parts that fit that envelope. A popular technique to building larger parts is called segmenting and is implemented in the design phase of the project. Using CAD, designers will simply cut the part at the set location and will insert a tongue and groove or dovetail geometry that will allow for easy assembly once the parts are printed. Depending on the material, over the counter adhesives and two part epoxy’s have been known to be very effective at bonding and joining 3D printed parts together.
Tip Four: Corners and Rounds
In respects to FFF additive manufacturing, corners can be modified to help speed up the printing process and help maintain the structural integrity of the part. When printing a sharp corner with FDM printing, the print head will have to rapidly ramp down in speed and then rapidly accelerate out of the corner. This change in speed will result in excess tool wear, increase vibration and will increase the time of the print. In order to mitigate this, it is common for additive designers to incorporate fillets into their design.
This in turn helps reduce the speed differential of the print head, minimizes vibrations and increases the part strength by reducing stress concentrating geometries. When incorporating fillets it should be noted that the larger the radius the more these negative impacts will be reduced.
Tip Five: Combine components to minimize assembly time
One of the advantages additive manufacturing has over other manufacturing methods is the ability to combine components of assemblies into one component. One famous example by Stratasys is the end of arm tool. This tool uses a vacuum to lift and carry components though its assembly process. Traditionally this component is machined and then components like vacuum lines and other components are assembled to it. When designed for additive manufacturing, designers were able to utilize the space and internal geometries to incorporate tunnels which will act as the vacuum lines. This helped improve the system as it reduced the time required for post assembly and integration into the machine.
Hopefully, this post will help you think additively during the design phase and will help streamline your design process while reducing your time to market.
