Solvent Welding: Why we use ABS and Acetone for structural joints

Solvent Welding: Why we use ABS and Acetone for structural joints

In 3D printing, the strength of an assembly is often limited by the quality of the bond between individual parts. For our 1/6 scale kits, we prioritize ABS (Acrylonitrile Butadiene Styrene) specifically because of its chemical properties and the ability to be solvent-welded using acetone.

The Chemistry: It’s not a glue, it’s a weld

Unlike CA (superglue) or epoxies, which act as an intermediate layer between two surfaces, acetone works as a solvent. When applied to ABS, it temporarily breaks down the polymer chains and liquefies the surface.

When two such surfaces are pressed together, the polymer chains intermingle. As the acetone evaporates, the material solidifies into a single, continuous piece of plastic. This process is chemically identical to cold welding.

The advantages of solvent welding:

• Structural Integrity: The joint is as strong as the material itself. Under stress, the part will usually break elsewhere rather than at the weld line.
• Gap Filling: By dissolving scrap pieces of filament in acetone, we can create “ABS juice” or slurry, which is perfect for filling seams and sanding them down to a seamless finish.
• No Brittle Residue: Unlike CA glue, which becomes brittle and can “fog” the surrounding surface, an acetone weld remains as durable as the rest of the print.

ABS vs. ASA: Know the difference

While ASA (Acrylonitrile Styrene Acrylate) can also be welded with acetone, it is not a direct substitute for ABS in every application.

• ASA is generally softer and more flexible. It offers superior UV resistance, making it ideal for parts exposed to direct sunlight.
• ABS is more rigid and has higher impact resistance, which is why we use it for the primary structural components of our hulls and chassis.

Mixing these materials or using them interchangeably can lead to unexpected mechanical behavior due to their different flexural modulus. We select each material based on the specific load requirements of the component.

Application in 1/6 Scale Models

For large-scale models, mechanical fasteners (nuts and bolts) are essential for serviceability, but for permanent structural assemblies, solvent welding is the only way to ensure the model behaves like a solid unit rather than a collection of printed blocks.

You can find these material-specific optimizations in our 1/6 scale tank kits. By understanding the chemistry of the materials, we can design kits that are both easy to assemble and extremely durable.