Best practices for composite 3d printing
By Nishant Pal
Every engineering application require the components designed and manufactured to satisfy two basic needs
1. Effective & Efficient solution to the engineering problem.
2. The solution should be cost-effective to manufacture at a large scale with minimal impact on the environment from its manufacturing.
Engineers always try to keep the above two conditions in mind when designing and manufacturing a solution to any problem. Technologies and material development progress to have an effective solution at a reasonable price with a bare minimum effect on the environment. To this extent, the use of composite material is increasing exponentially to manufacture functional parts and to some extent replace existing materials such as metal components entirely from the solution.
A composite material is basically a mixture of two or more individual constituent materials with distinct chemical & physical makeup which when combined together form an entirely new material with properties of all the individual materials that made up the composite itself.
A number of composite materials are currently in use in a lot of different industries, think of materials such as Plywood, reinforced concrete, etc.
The composite material thus when made up with competency can yield a material that is stronger, flexible, more durable, and in most cases less expensive. The process of making composite materials and the technologies that are used to fabricate parts using these composites are in constant development in order to make them environmentally friendly as well.
The technology available in the Market:
Different technologies are available in the market that uses composite material in different ways in order to produce a functional part. For the sake of this article, we will be focusing on 3D PRINTING as our primary technology.
Fused Filament Fabrication or FFF is a commercially available technology that deals primarily with composite materials.
The technology involves deposition of melted thermoplastic either by itself or reinforced with continuous strands of fiber on a build platform via an extruder. The part is manufactured by repeating the deposition process layer by layer (called “slices”) over and over until the total height of the part is deposited on the build plate.
Material available in FFF technology:
The materials available in FFF 3D printing are either a single constituent material such as ABS/PLA or it’s a composite material of a base thermoplastic mixed with chopped fibers (usually a millimeter in length). The strength of this composite material is dependent on the percentage of fiber used in the creation of the material.
Example- Markforged ONYX composite material is a mixture of nylon and chopped carbon fiber, the resultant material is 25x stronger than ABS which makes it ideal for making functional parts.
One advantage of FFF technology is its capability of using reinforcement fibers along with the base thermoplastic to increase the strength of the parts 10 fold. These reinforcement fibers are usually in a continuous strand which greatly enhances the strength when used strategically to the applied force on the part.
Example- Markforged ONYX reinforced with Carbon fiber can achieve a strength comparable to that of Al 6061 making it an ideal solution to replace metal without any loss of strength and imparting lightness to the part as well.
Needs and best practices for composite 3d printing:
Composite materials provide a lot of benefits to the engineers in terms of their strength, stiffness, lightness as well as their economics. Because of these benefits many industries such as automotive, aerospace, construction have started implementing and experimenting with composite materials using technologies like 3D printing.
However, technologies like 3D printing FFF have inherent weaknesses such as the parts manufactured using the technology are anisotropic in nature meaning they have different mechanical properties along different axes. Due to this certain considerations are required to be taken in order to manufacture a part with adequate strength viz
A) Use of dowel pins:
Wear surfaces
Dowel pins provide a hardened steel wear surface for areas of parts that interact with abrasive surfaces. For example, a robotic end-effector grips a threaded pipe coupling. The dowel pins prevent the threads from cutting into the printed plastic, increasing the lifetime of the grippers.
Alignment
Use pressed-in dowel pins or shoulder bolts to precisely align multiple components. Press-fit dowel pins are used to line up a component with its assembly, while screws secure it. Use dowel pins for alignment before gluing or bolting the components together to attach multiple printed parts precisely. Thus a big assembly part can be broken into smaller segments and secured together.
Use of metal inserts and bushings
Threads and inserts
Instead of printing or tapping threads into plastic, add a metal heat-set insert where you need threads. These inserts get pressed in with a soldering iron to reflow the plastic around the part for local isotropic strength. Inserts are stronger and last longer than printed or tapped plastic threads.
Bushings
Bushings or sleeve bearings provide high cylindrical precision and smooth concentric clearance fits. Off-axis loads distribute to the printed part with the bushing’s larger surface area. The bushing cavity can be reinforced with continuous strand composite fibers for higher torsional resistance.
B) Splitting up the parts:
Sometimes it is more effective to split up a part than to print it as one piece. The part can be split in two, with each piece printed in order to prioritize the strength of each segment.
Here are some reasons to consider splitting a part up
• Parts with many iterations or customization can be designed with a core base geometry and interchangeable modules
• Elements of parts that undergo increased wear or strain can be isolated into components that can be changed out regularly
• Designs requiring specific strength profiles across multiple axes can be printed in sub-components in different orientations and joined post-print
• Complex prints with critical features on multiple planes can be split into sections to reduce supports, decrease print time, and ensure print success.
Conclusion
Continued improvement in the technology to minimize or eliminate these issues is ongoing and at the rate, the technology is advancing soon we will have all the major industries using 3D printing with composite material support to replace metal components.
To know more about it, contact us for 3D printers and services in India contact us at www.4dsindia.com or Email us at info@4dsindia.com
