Learning how to accurately measure surface resistance is critical for validating electrostatic discharge (ESD) safe components. While 3D printing with conductive polymers offers immense design freedom, verifying that your final part actually dissipates static electricity requires specific techniques.
Many engineers simply touch a standard multimeter to a part and get a confusing reading. However, to generate data that complies with industry standards, you need to understand the difference between simple point-to-point resistance and true surface resistivity.
Why Your Multimeter Might Be Lying
A standard hardware store multimeter measures resistance in Ohms (Ω). In contrast, material data sheets (TDS) list Surface Resistivity in Ohms per Square (Ω/sq). These are related, but they are not identical.
Specifically, standard multimeter probes have sharp tips. When you press these into a 3D printed part, you often measure the contact resistance of that tiny spot rather than the material’s conductive network. Consequently, your readings might jump wildly depending on how hard you press.
Tools to Measure Surface Resistance Accurately
To get reliable data, you need to increase the surface area of the contact. Therefore, professional labs use a Mega-ohmmeter with “Concentric Ring” probes or heavy weighted electrodes. These apply consistent pressure and measure a defined area.
However, if you only have a standard multimeter, you can still improve your accuracy with a simple trick:
- Use Copper Tape: Stick two pads of conductive copper tape onto your part, spaced 1 cm apart.
- Measure the Tape: Touch your probes to the tape, not the plastic. This creates a stable contact patch.
- Calculate: This gives you a consistent “Point-to-Point” resistance reading.
The Importance of Probe Pressure
Conductive 3D printed parts rely on a network of Carbon Nanotubes (CNTs) touching each other inside the plastic. Furthermore, the surface of a 3D print is naturally rough due to layer lines.
If you press lightly, you only hit the peaks of the layer lines. As a result, the resistance reads High (Insulative). If you press firmly, you flatten the peaks and contact more CNTs. Thus, the resistance reads Low (Conductive). Consistent pressure is key to repeating your results.
Validating Your Print Settings
If your readings are too high, your print settings might be the culprit. For instance, printing too fast can break the conductive pathways. For a deep dive on fixing this, read our guide on 5 Tips for 3D Printing with Conductive Filament.
Ultimately, the ability to properly measure surface resistance ensures your jigs and fixtures are safe for the factory floor. By following standards like ANSI/ESD S20.20, you can verify that your prints sit safely in the static-dissipative range (105 to 109 ohms).
About ABC3D
ABC3D is a Canadian manufacturer of High-Performance & Conductive Polymers. We specialize in functional materials designed for the electronics, automotive, and aerospace sectors. Additionally, we bridge the gap between industrial-grade conductivity and environmental consciousness. Our team engineers materials for industrial applications, large-format printing, and injection molding.
For technical support or material inquiries, please contact:
Nivedita Narayan
Director of Products
info@abc3d.ca