RePliForm combines plating methods with additive manufactured resin prints to enhance the engineering performance of resin parts. Boston Micro Fabrication (BMF) has extended fabrication of AM resin or ceramic prints to much smaller, higher resolution parts. Recently, RePliForm and BMF have been examining how combining these technologies can extend the applications of each into new areas.
Mechanical properties of plated parts
RePliForm employs a simple composite model called the “rule of mixtures” to estimate the strength of plated AM parts based on the properties and volume fraction of their constituents.
Therefore, if you know the component properties and their respective volumes, you can estimate the plated part properties. The capsules have wall thicknesses that range between 150 and 250 microns with an average of ~200 microns. When plated with 50 microns of Cu and Nickel, the average wall thickness should increase by about 50%. Since the coating alone is more than 12x stronger (900 MPa for plating vs. 70 MPa for resin) and 50x stiffer (132 GPa for metal vs. 2.4 GPa for resin) the plated capsules will be at least 4x stronger and 15x stiffer after plating with 10 microns of Cu and 40 microns of nickel.
To get a rough estimation of the volume of metal and plastic on a plated part, weigh the part before and after plating. The weight before divided by the resin density is the part volume, the weight after, minus the initial weight divided by the metal density (~8.92 g/cc) is the metal volume.
Making room for the plated coating using surface offsets
Ideally, if parts are to be coated, the part’s design needs to be modified to make allowances for the coating thickness added. This would mean doing surface offsets which would make the walls thinner by 2x the coating thickness. For a part with 150 micron walls that would results in 50 micron walls while the 250 micron wall thickness section would drop to 150 microns. If the walls are too thin to build and handle reliably, a thinner coating might have to be used or just the surfaces with critical dimension might be offset prior to printing.
Surface resolution and plated part electronic performance
The surface of a plated plastic part is a reflection of the finish that is in the plastic substrate. That’s why molded parts needing cosmetic finishes are shot in polished injection mold tooling. AM parts generally have layer lines and other build artifacts (support marks) that print through the coating. In some applications like antennas, the presence of these build artifacts will limit the usable frequency range of the device. The very high resolution of the BMF 3D printed parts has been shown to open up the frequency range of antennas to greater than 85 GHz.
Plating on ceramic materials
By adjusting the ceramic abrasive etch step, RePliForm can also plate on ceramic materials as shown with two alumina ceramic samples below. The smaller sample was plated with 10 microns of Cu and 40 microns of nickel and the larger samples was plated with 25 microns of semi-bright copper then 6 microns of electroless nickel.
For more information on BMF’s micro-precision 3D printers, please visit our product page.
For more information on RePliForm and their plating services, please visit their website.
