Polymers can replace metals, and this practice is becoming more and more common. Modern high-performance polymers and composites are lighter and have mechanical qualities that are comparable to those of aluminum. Additionally, the capacity of high temperature 3D printers like the AON M2+ to additively produce parts from these polymers has accelerated adoption by lowering the complexity, lead times, and financial constraints of conventional manufacturing processes.
What differentiates metals and polymers?
We need to have realistic expectations before we can discuss which polymers can replace metals. Some businesses could exaggerate the abilities of high-performance polymers while overlooking the underlying differences between metals and polymers. These are the following differences:
The thermoplastics that are used to create 3D printed polymers are formed of chemically distinct polymer chains (no molecular bonding between chains). Since these chains are intertwined, the material has mechanical integrity. Due to stronger intermolecular contact pressures, the chains can also arrange and fold into a crystal structure that is more difficult to break apart. Due to this, semi-crystalline polymers outperform amorphous polymers in terms of strength and stiffness.
A common metal would have a structure like that seen in image A below if you were to examine it under a microscope. Small grains of a crystal lattice make up each of the tiny grains that make up metals (image B). These crystals are composed of a variety of metal atoms that are strongly bonded to one another. Metals are inherently stiff and powerful due to atoms' interatomic bonds and crystallization. These grains frequently differ from one another in terms of size and orientation, both of which have an impact on the metal's bulk characteristics.
In conclusion, although metals include several crystals (grains) with varying inclinations, semi-crystalline polymers are partially comprised of crystals. The attraction force between thermoplastic polymer chains is less than that between metallic crystals because the chains are chemically distinct. Metals are therefore often more temperature resistant and more rigid to elastic deformation. Metals have historically been the material of choice for mechanical and thermal applications because of this. But as we develop thermoplastics, their effective strength starts to catch up with and, in some circumstances, even surpass that of metals.
Two Suitable Metal Replacement Materials: PEEK and ULTEM™
Two of the most well-liked polymers that have been considered as metal substitutes are PEEK and ULTEMTM 9085. Aluminum 6061, an alloy used to make consumer goods, automobile parts, maritime constructions, and structural components for airplanes. Carbon fiber makes up 10% of CF PEEK, enhancing its stiffness and strength over standard PEEK. These are a few industries where switching to alternative metals can significantly reduce weight while keeping the necessary mechanical and thermal qualities. These high temperature thermoplastics also outperform standard in-service metals in terms of chemical and corrosion resistance.
How to 3D Print PEEK and ULTEM™
It is not a guarantee that items made by 3D printing high performance materials will have specified mechanical, thermal, and chemical qualities. The chosen 3D printer must have a precision-controlled high temperature build chamber (minimum 132°C), 500°C extruders, and programmable print surfaces to match these properties. Printing at lower temperatures than 132°C can severely diminish a part's strength and chemical resistance and necessitate additional annealing, which inevitably results in warping.
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