According to Analisa Russo of Formlabs, electroplating can turn 3D printed plastic parts into powerful end-use parts.
The company’s technical community manager first participated in the electroplating of additive manufacturing parts, while working on the project to recreate the Volkswagen’s 1962 minibus version.
Volkswagen and Autodesk (Autodesk) designed the 3D printed wheel cover. Next, the Russo team at Formlabs in Somerville, Massachusetts printed the hub caps on a stereolithography (SLA) style 3D printer. Then, RePliForm (a custom electroplating shop in Halethorpe, Maryland) applied a 0.004 inch thick layer of copper and nickel to the surface.
The resulting parts look and feel like metal. But compared with 3D printed metal hub caps, the plastic resin/plated version can be produced quickly with the development of the design with minimal geometric constraints.
Electroplating 3D printing resin is a good choice for many applications. Russo said: “The strength and stiffness data of electroplating resins fill the huge gap between plastics and metals.”
In addition to automotive equipment, hybrid technology can also be used to manufacture fixtures that require long-term dimensional stability, as well as equipment that manufactures lightweight electrical components (such as antennas).
Russo said: “The antenna is a beautiful example of combining the geometric complexity of 3D printing with the function of metal coating.” She said: “We have seen some antenna designs with very complex internal channels, which can only pass through 3D The printing is completed, and then a high-purity, high-conductivity copper coating is applied.”
Sean Wise, founder and CEO of RePliForm, has electroplated SLA parts since 2002. Tests conducted by his company showed that electroplating increased the tensile strength of SLA prints by three times, the bending strength by nearly ten times, and the stiffness by four times.
Wise said: “People don’t realize the strength of the electroplated coating.” “We can get very strong parts because the metal shell of the composite material we are manufacturing is 10 to 15 times stronger than the plastic substrate.”
Regarding cost, the price of electroplated plastic parts with 50 to 75 micron non-cosmetic copper and nickel coatings will be about the same as the retail price of the service bureau printed plastic parts. He added that other factors will increase or decrease costs, and as the number of parts increases, plating costs will also decrease.
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Wise estimates that the total cost of ordering four SLA parts plated with 50 microns of copper and nickel is $456, while the total cost of four 3D printed stainless steel parts is $1,600.
Surface treatment
Wise said that when appearance is critical, parts printed with SLA technology are more suitable for electroplating than parts printed with selective laser sintering or filament patterns. He added that his workshop plated parts printed with all three technologies.
Wise said: “The real advantage of stereolithography is that by curing the photopolymer resin with ultraviolet lasers, you can get extremely high resolution.” Very smooth surface, this is a good starting point.”
However, when a thin metal plating layer is applied to a printed part, problems may arise. One is that shiny metal surfaces can even show the smallest flaws, including layer lines and other flaws left during the printing process.
Russo explained: “With SLA printing, you always have a supporting scaffold that fixes the part to the build platform.” “Usually, it is removed by shearing and grinding the support points, even after removing the structure, these artifacts will be Keep it. She continued: “I learned that it is difficult to highlight the smallest surface defects and make them have high contrast through electroplating. “In order to prevent these marks from appearing on the decorative surface, it is important to position the parts in the printer to hide them in areas that are not visible during final use. ”
Electroplating steps
According to Wise, primers and conductive paints can be used to mask surface defects. The disadvantage is that fine or refined functions will be lost. In order to prevent this and also form a better bond with the resin, his workshop uses the room temperature chemical nickel (RTEN) process to directly electroplate the plastic parts. This is the standard production process used for electroplated injection molded parts.
Wise said: “First, you put the palladium dispersion on the surface of the part.” “Then put the part in the RTEN tank with the nickel ion reducing agent, and then it will automatically start to deposit nickel on the surface.”
Once the metal completely covers the object, it is possible to allow current to pass. This is essential for the first electroplating step: the copper bath. In the molten pool, the power flowing through the parts will reduce the copper ions in the solution, so they will be plated on the parts like copper metal. The rate at which they decrease depends on the current density on the surface.
Wise said: “Outside the most prominent area of the part, the current density is highest, while inside the part and the least prominent area.” The result is “you get different deposition rates.” This can become a problem, especially when plating antennas and other parts that have inner surfaces that need to be plated.
The first advantage of using copper is that it is a good interface layer for plastics. It tends to adhere better, the plating goes into fine details, and is much better than nickel at the corners.
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After the copper layer, one or more different types of metals can be electroplated onto the workpiece according to the required characteristics. For example, nickel is much stronger than copper and more resistant to corrosion, so it is usually used after copper. Then other finishes (such as gold, silver or chrome) can be used as the final cosmetic layer.
Coating design
Before printing the final part to be coated, it is important to consider the thickness of the electroplated coating and other factors.
Russo said: “Depending on your application, the coating will add a fairly uniform shell around your part, and its thickness may be between 25 and 300 microns.” “Therefore, you need to make the appropriate shell in the CAD model Offset.”
She added that designing parts is a common work and an iterative process, which is very important for additive manufacturers to cooperate with electroplaters before printing.
“When someone submits a part to us for a quote, we will ask questions about the purpose of the coating, how strong the coating is, the type of surface required and the temperature it will see,” Wise said.
He said: “Sometimes we tell people that we can’t do it, and other times as long as everyone plans ahead, it’s relatively easy to do.”
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