Electroplating 3D Printing: A Way to Enhance 3D Printed Parts

Electroplating is the process of coating a thin layer of real metal (such as copper, nickel, gold) on the surface of 3D printed parts, which not only improves the appearance of the product and obtains a metallic luster, but also enhances its functionality and durability. Although this post-processing process is complex and requires careful operation, it is an economical and efficient alternative to metal printing. This article will introduce in detail the principles and operation procedures of electroplating 3D printed parts.

Source:  https://www.instructables.com/Copper-Electroforming-on-3d-Printed-PLAABS-Objects/

Basic principles of electroplating

Electroplating uses electrolysis to make metal ions migrate and deposit on the surface of the target object under the drive of an electric field. The specific process includes:

Immersing the 3D printed part (usually a non-conductive material such as plastic or resin) in an electrolyte containing metal salts (such as copper, nickel, gold, etc.).

By applying an electric current, the anode metal (such as a copper plate) undergoes an oxidation reaction, releasing metal cations into the solution; the negatively charged 3D printed part acts as a cathode, attracting cations and reducing them to metal atoms, and depositing layer by layer to form a coating.

Conductive pretreatment: Since non-metallic materials such as plastics are not conductive, they must first be made conductive by chemical plating or spraying conductive coatings (such as graphite) to ensure that the electroplating reaction proceeds smoothly.

Process of electroplating 3D printed parts

Pretreatment of 3D printed parts

The surface of the 3D printed parts needs to be cleaned before electroplating. The dust and grease on the surface of the printed parts will affect the uniform adhesion of the conductive paint and metal coating to the parts, thereby affecting the effect of electroplating. In addition, surface smoothness is also very important. The smoother the surface, the glossier the final metal coating. Therefore, it is necessary to pretreat the 3D printed parts before electroplating:

Cleaning: Remove support residues, grease or powder on the surface of the parts (ultrasonic cleaning or alcohol wiping).

Polishing: Grinding or chemical polishing (such as acetone vapor polishing ABS) to eliminate layer lines and improve surface finish.

Detail repair: Fill printing defects (such as pores and cracks) to ensure uniformity of electroplating.

The technologies used for 3D printed parts for electroplating are usually SLA and FDM. Common 3D printing materials include plastics and photosensitive resins. For this non-conductive material, additional conductive treatment is required. The treatment methods include spraying conductive paint (spraying conductive paint containing metal particles), chemical plating (using chemical deposition to form a thin metal layer on the surface, such as chemical nickel plating and copper plating to provide a conductive base) and graphite spraying (spraying graphite powder on the surface of resin parts to form a temporary conductive layer).

Electroplating process

1. Electroplating copper (base layer)

The copper layer, as a base layer, can provide good conductivity and enhance the adhesion of subsequent plating layers. At the same time, it can fill the tiny defects on the surface of the substrate and make the subsequent electroplating more uniform.

The initial voltage is recommended to be set to 0.2V for 30-60 minutes. This stage is mainly to form a dense initial plating layer. Subsequently, the voltage is gradually increased to 0.5V-1V, and the electroplating is continued for about 1 hour to ensure uniform coverage of the plating layer. The longer the immersion time, the thicker the coating.

During the operation, the coating state should be observed: when the surface becomes smooth and shiny, it means that the voltage has reached the ideal value, and electroplating can be continued to increase the thickness. If black spots, bulges or bubbles appear, it may be caused by excessive current or uneven solution composition. The voltage should be appropriately reduced or the solution should be stirred to improve uniformity.

2. Electroplating nickel/chromium (isolation layer)

As an intermediate layer, the nickel layer can improve corrosion resistance, increase the gloss and adhesion of subsequent coatings, and prevent chemical reactions between the bottom layer and the final decorative layer.

The starting voltage of the nickel layer is set to 2V, and the chromium layer is recommended to start from 6V, which can be gradually increased until the surface gloss is uniform. The time for nickel plating and chromium plating is short, usually completed within a few minutes.

3. Electroplating gold (final decorative layer)

Electroplated gold is mainly used for decorative plating, and it also provides excellent anti-oxidation properties.

Soak the electroplating brush head in the gold electrolyte to ensure uniform adsorption of the liquid. Connect the positive pole of the power supply and set the voltage to 7-10V to evenly brush the surface of the workpiece until a complete gold layer is formed. Since the gold coating is thin (usually 0.05-0.1μm), it does not require long electroplating and can be completed within a few minutes.

Source:  https://ameralabs.com/blog/silver-electroplating-resin-3d-prints/

Common problems with electroplating

Plating peeling or poor adhesion: Common in 3D printed plastic parts, it may be due to insufficient activation of the substrate surface or improper pretreatment. Sandblasting or chemical etching can be used to enhance the surface roughness, and conductive coatings can be used to improve adhesion. For metal 3D printed parts, ensure pickling or electrolytic activation before plating to improve bonding.

Uneven coating: It may be caused by uneven current distribution or rough surface of the workpiece. The solution is to optimize the anode position, adjust the current density, and ensure that the workpiece surface is fully polished and cleaned. In addition, the use of auxiliary cathodes or conductive coatings can improve the distribution of coatings.

Black spots or scorching on the surface: Usually caused by too high current or too high plating solution temperature. It is recommended to reduce the current density, control the electrolyte temperature, and check whether the composition of the plating solution is stable. If it is a local black spot, it can be removed by slight polishing and re-electroplating.

Electroplating 3D printed parts can provide higher aesthetics and durability for printed parts. Although the electroplating process is relatively complex and requires precise operation, it is a cost-effective solution that is suitable for many industry needs. Through pre-treatment and precise electroplating process control, the surface quality and performance of 3D printed parts can be effectively improved.