The leap from small to large format 3D printing opens a world of opportunities but also requires different printing guidelines to ensure optimal results
The leap from small to large format 3D printing opens a world of opportunities but also requires different printing guidelines to ensure optimal results. Large format 3D printing presents a unique set of challenges and opportunities that must be considered when transitioning from small format printing.
Following the guidelines described in this article will help to make the transition from small to large scale 3D printing. This enables you to produce high-quality, large scale prints with higher mechanical strengths, more finishing options and save time and material.
1. EVERYTHING IS BIGGER
The possibilities of large scale additive manufacturing start at the limits of desktop printers. Desktop printers are generally able to print objects up to 300 mm x 300 mm x 300 mm. With large format additive manufacturing, printing starts at this size. For example, the smallest configuration of the Flexbot already provides you with a print bed of 2 x 1 meters.
This reach can be increased due to the modularity of CEAD’s robotic LFAM solutions. A larger print bed or placing the robot on a linear track, increases the build volume and therefore the printing size. The Flexbot set-up is customizable, an example of this can be seen in the photo above, where the largest Flexbot system has been installed at Al Seer Marine, with a build area of 4 x 36 meters and two robots moving along a linear track.
As additive manufacturing moves from small to large scale, there is a significant increase in nozzle sizes, layer height and width. Typically, desktop printers can handle nozzles with a maximum diameter of 0,8 mm.
However, the nozzles that fit on CEAD’s extruders range from 2 mm to 24 mm, depending on the extruder. The use of larger nozzles leads to the creation of thicker and wider layers during the printing process. Extrusion output also determines the size of the part, which is significantly larger in LFAM applications.
2. COOLING THE PRINTED LAYERS
In smaller desktop printers, a fan is often included to cool the part during printing. This helps to regulate the temperature of the previous layer, or bead, which allows for shorter layer times and faster printing.
While external cooling provides a benefit for small scale, for large scale 3D printing cooling with a fan is undesired, from a mechanical perspective. With LFAM, your printing strategies are focused on adjusting layer times to allow for proper cooling and solidification of the material.
3. PELLET VERSUS FILAMENT 3D PRINTING
When it comes to raw materials for this type of 3D printing, there are two main options: pellets / granulate or filament. Desktop printers usually melt plastic filament while CEAD’s additive manufacturing systems use pellet-based 3D printing.
Filament is made of pellets by material suppliers. The material used for LFAM thus requires less processing, since the pellets can be used directly for 3D printing. Simplifying the production process of printing material decrease the costs of this material.
Unlike filament extruders, CEAD’s pellet extruders use a screw mechanism to melt and transport pelletized material through a heated and nitrated barrel towards the nozzle. The nitrated barrel inside CEAD’s extruders offers resistance against abrasive materials. This allows processing of a wide variety of short-fiber reinforced thermoplastic composites offering many applications in different industries.
Just like filament, most thermoplastic pellets also need to by dry when printed. An external dryer is used to ensure that the material is dry and free of moisture. After the drying process, the pellets are loaded into a feeder inlet and pushed through a barrel with multiple independent heating sections, where they are heated until they melt.
Pellet based extrusion has several benefits over filament based 3D printing:
- Lower costs: because it requires less processing than filament, pellet material generally has a lower cost. Materials for existing production methods, such as injection molding, can also be used. Decreasing the costs further.
- Higher production speed: higher production speed is obtained by the higher output of LFAM. Additionally, during printing new pellets can be added to the dryer. Filament printers need to be paused to change a filament spool.
- Wider range of available materials: because pellets are widely used in the plastic industry, the range of available materials is larger than filament.
- Milling possibility: because LFAM is larger and therefore coarser than small scale printing, you can mill the print it back to a smooth whole. Larger beads provide more opportunities for milling.
Click to read more about thermoplastic pellets for large scale 3D printing.
4. CONTINUOUS TOOLPATH
When working with large format 3D printing, start and stop points become more visible compared to smaller formats. This is why it is important to design prints with a continuous tool path, allowing for the entire print to be completed in one go. When the extruder follows a continues toolpath and thus not perform any start-stops while printing, any potential defects in the print will be less noticeable. By utilizing a continuous tool path, large format 3D prints can thus be produced with fewer visible flaws and a higher level of quality.
CEAD’s robot extruders and Flexbot can be equipped with Dynamic Flow Control (DFC). The DFC allows you to calculate very precisely how much thermoplastic material you are extruding. This add on provides more consistency in output and therefore enables higher quality start and stops in your prints.
These start and stops can be used to print various parts simultaneously, increasing overall production time of the parts. Additionally, a doubly bead can be implemented in your designs using start and stop. This provides more milling opportunities while saving weight and thus production time, material and production costs. Read more about increasing large scale 3D printing accuracy with Dynamic Flow Control.
5. PRINTING WITHOUT SUPPORTS
In large format 3D printing, the only necessary support comes from the engineers on the CEAD support team. While smaller 3D prints can use supports to achieve unique designs, large scale printing requires a different approach.
Removing supports on smaller prints can be done with a simple pair of pliers, but this is not practical for larger prints. The amount of material needed to print the supports at this scale is substantial and can result in a significant waste of resources. In these cases, you either print without supports (for example in 45 degrees, as seen in the video below) or you mill the supports away after printing.
6. VARIOUS PRINTING STRATEGIES
The robotic aspect of robot based 3D printing enables the use of various printing strategies. Examples of printing strategies are non-planer, multi-planer or 45 degree printing, as seen in the video above.
45 degrees printing opens new possibilities for design. Despite the larger scale, the overhang angle remains the same as in small format 3D printing, typically around 45 degrees. This applies to both small and large scale 3D printing, regardless of whether the extruder is placed at an angle.
When the extruder is positioned at an angle, the overhang angle remains at 45 degrees, but rotates relative to the bottom layer. This should be considered during the design process to ensure that the overhangs can be successfully printed without collapsing or distorting. An example of this type of printing can be seen in the video above.
7. PRINTING ONE MATERIAL AT A TIME
Similar to small scale 3D printing, large format 3D printing involves printing layer by layer. Printing with small scale filament printers allows the possibility to pause the print and change filament. This enables printing an object with multiple materials.
With large scale pellet based printing, material can not be changed that easily. The printer’s barrel needs to be emptied and purged before new material can be used.
A common application of printing two different materials at the same time can be found in printing supports. This ensures that the supports can be dissolved in water or are easily removable. This however does not cause a limitation for large scale 3D printing, since printing with supports is not a common practice.
8. MODULAR PRINTING SYSTEMS
An advantage that large scale robotic printing offers is the modularity of printing systems. For example, an existing Flexbot robot solution can be equipped with various robot extruders and milling options. Additionally, CEAD offers modular print beds, increasing the print potential. Combining this with placing the robot on a linear track results in a significant increase in print volume.
The modularity not only relates to upgrades related to the robot and equipment. Multiple robot based Flexbots can also be combined to print the same object from two different angles, as seen in the picture below. Click to read more about the 36 by 4 meter large robotic 3D printing system seen in the photo below.
The modularity of robotic based large scale additive manufacturing enables you to adjust the printing system to your application and printing facility.
9. FORGET ABOUT INFILL
Traditional smaller 3D printing requires hollow prints to contain an internal structure, called an infill. This internal pattern of material is printed inside the shape of a 3D print, in order to provide the final print with more additional support and strength.
When printing at a large format, the use of infill is usually not required. Generally. large scale additive manufacturing prints are strong enough when printed hollow. The strength of the prints is attributed to the larger size of the prints and the presence of fibers in the material. The absence of infill saves printing time and the use of material.
However, the size and application of some prints could require additional strength, such as the bridge seen in the picture below. To increase strength, LFAM prints can be designed with an internal ribbed structured. This supports critical points. Another application of this can be found with prints that are used under elevated temperatures (eg. Autoclave).
Read more about large format 3D printing and infill at CEAD’s knowledge base.
10. LARGE SCALE IS LARGE SCALE
It’s important to keep in mind that the printed objects shouldn’t be smaller than 300 mm x 300 mm x 300 mm in general. While you can print longer objects that are shorter than 300 mm, this is the general guideline.
Additionally, it’s not recommended to print details that are smaller than 10 mm, due to the limitations of the smallest possible layer width and the complete circle that can be made with the toolpath. Large scale additive manufacturing should thus focus on large projects.
TRANSITIONING FROM SMALL SCALE TO LARGE SCALE 3D PRINTING
The guidelines elaborated in this article help you to achieve high quality large format prints. Are you looking into the possibilities for LFAM for your organization?
CEAD’s innovative approach to large format 3D printing is revolutionizing the industry and paving the way for new possibilities in design and manufacturing. Please contact CEAD’s specialists to learn more about the possibilities that this approach can offer for your production facility or research.