Measuring Filament Diameter

Behind every successful 3D print is a high-quality filament, and the diameter of this filament plays a crucial role. Perhaps you've tried determining the diameter with a caliper. However, here you'll learn why this method leads to inaccurate results. An accurate filament diameter not only reveals a lot about the filament's quality but also about the manufacturer's reliability. Many believe that measuring primarily serves to optimize print results, but in reality, it's an indicator of filament quality. Let's delve deeper into the correct measurement methods and the significance of filament diameter.

A filament that doesn't meet the specified specifications can lead to a variety of printing problems. If the diameter is too small, under-extrusion can occur, where not enough material is extruded. This can result in weak prints with poor layer adhesion. On the other hand, a filament with a diameter larger than specified can clog the nozzle and interrupt the printing process. Therefore, it's crucial to use a filament that meets specifications to achieve optimal print results. It's worth noting that the current industry standard for filament production allows for a tolerance of ±0.05 mm. However, many manufacturers are now adopting tighter tolerances of ±0.03 mm or even ±0.02 mm and promote these more precise tolerances as a quality feature.

In this article, all references specifically relate to DIN standards 862 and 863. Both calipers according to DIN 862 and micrometers according to DIN 863 meet defined requirements and testing procedures. However, it's essential to emphasize that a manufacturer's mere indication that a measuring tool complies with one of these standards doesn't automatically represent a quality feature. Manufacturers can emphasize different aspects of accuracy, be it display accuracy or actual measurement accuracy. High-quality measuring tools usually come with a test certificate that certifies accuracy and conformity.

• Analog Calipers: Use a vernier scale for display. Display accuracy often 0.05 mm or 0.02 mm. Measurement accuracy for high-quality models according to DIN 862 is about ±0.03 mm.
• Digital Calipers: Have an electronic display, often accurate to 0.01 mm. Can switch between different units of measurement. Measurement accuracy typically ±0.02 mm, depending on quality.

• Analog vs. Digital:
  • Analog Micrometers: Use a scale and a vernier or micrometer clock for display.
  • Digital Micrometers: Offer an electronic display with higher resolution and the ability to save or transfer measurements.
• Display Accuracy: Often higher for micrometers than for calipers, with values of 0.001 mm.
• Measurement Accuracy: For high-quality micrometers, often at ±0.002 mm.

• Temperature: Both calipers and micrometers can expand or contract with temperature fluctuations, affecting measurement accuracy.
• Wear and Maintenance: Regular use and lack of maintenance can lead to wear, especially on the measuring surfaces. Regular calibration and maintenance are essential to maintain accuracy.
• User Error: Inaccurate reading, improper handling, or inconsistent pressure, especially with micrometers, can lead to measurement errors.

The diameter of a filament can be influenced by a variety of factors, and understanding these factors helps in assessing its quality and consistency.

• Extrusion Speed: The speed at which the filament is extruded during production can influence the diameter. Too fast or too slow extrusion can lead to inconsistencies.
• Cooling Rate: After extrusion, the filament is cooled. Uneven or too rapid cooling can lead to diameter fluctuations.

• Moisture: Filaments, especially hygroscopic materials like PETG, TPE, Nylon, and PVA, can absorb moisture from the environment. This can cause the filament to swell and change its diameter.
• Temperature: Extreme temperatures, whether cold or hot, can influence filament diameter by causing the material to shrink or expand.

• Time: Over time, some filaments can change their properties, which can also affect the diameter. This is especially the case with filaments that have been stored for a long time or exposed to environmental influences.

• Additives and Fillers: Some filaments contain additives or fillers to enhance certain properties, e.g., increased strength or improved printability. However, these additives can also influence the filament's diameter.
• Mixtures: Filaments made from a mixture of different materials can have different shrinkage or expansion properties that affect the diameter.

Before we carry out the actual measurement process, I'd like to emphasize why the caliper isn't ideal for this task. As an example, consider a filament with a nominal value of 1.75 mm. A digital caliper with a measurement accuracy of ±0.02 mm could theoretically display values between 1.73 mm and 1.77 mm, even if the filament actually measures precisely 1.75 mm. Such a measurement result, of course, doesn't provide a reliable statement regarding the actual quality and consistency of the filament. Therefore, I recommend using a digital micrometer to measure the filament diameter.

• Preparation: Ensure the micrometer is clean and calibrated. Any dirt or wear can distort the result.
• Zeroing: Turn the micrometer so that the two measuring surfaces are in contact. The display should now show “0”. If this isn't the case, the instrument needs to be adjusted.
• Measurement: Take the filament and place it between the micrometer's measuring surfaces. Gently turn the screw until the filament is securely clamped without pressure.
• Reading: Note the displayed value.
• Multiple Measurements: To get an accurate estimate of the diameter, repeat the measurement over a specific length of the filament several times and calculate the average value. This gives you a better overall picture of the filament diameter's consistency.
• Evaluation: Compare the measured values with the manufacturer's specifications. A high-quality filament should be very close to the specified value and be consistent over its length.

If you find that your filament doesn't meet the manufacturer's specifications, there are some steps you can take:

• Contact the Manufacturer: Many manufacturers value customer feedback and may offer you a replacement or refund.
• Adjustments in the Slicer:
  • For Smaller Diameter: If you find that the filament's diameter is smaller than specified, you can specify the actual filament diameter in most slicers under “Filament Diameter” to adjust the extrusion amount and avoid under-extrusion.
  • For Larger Diameter: A larger diameter can lead to over-extrusion or even clog the nozzle. In this case, it's advisable not to use the filament or ask the manufacturer for a solution.
• Check Storage Conditions: If the filament has absorbed moisture or was stored under extreme temperatures, this can influence the diameter. It's always a good idea to store your filament dry and at room temperature.

To ensure your filament diameter measurements are as accurate as possible, here are some tips and pointers to consider:

• Consider Ambient Temperature: The DIN standards for calipers (DIN 862) and micrometers (DIN 863) typically refer to measurements at a standard ambient temperature of 20°C. Deviations from this temperature can affect the accuracy of measurements, especially with metallic measuring tools that can expand or contract with temperature fluctuations. The user's body heat can also influence the measurement result, especially if the measuring tool is held in the hand for an extended period. It's therefore advisable to set the measuring tool aside briefly before measuring and let it adjust to the ambient temperature.
• Clean the Measuring Tool: Before each measurement, ensure your measuring tool is clean. Dirt, dust, or other particles can affect the measuring surfaces and lead to inaccurate measurements. A soft cloth and, if necessary, a special cleaning agent for measuring tools can be helpful.
• Handle the Filament Carefully: When measuring the filament, ensure you don't deform or damage it. Excessive pressure or bending the filament can change its diameter and distort the measurement.
• Regular Calibration: Even the best measuring tool can become inaccurate over time. It's essential to regularly calibrate and check your tool to ensure it provides accurate measurements. Some high-quality measuring tools come with calibration certificates that confirm their accuracy.
• Perform Multiple Measurements: A single measurement can be misleading. It's always a good idea to perform several measurements along the filament and calculate an average value to get an accurate picture of the actual diameter.

Checking the filament diameter provides a solid foundation for assessing a filament's quality and a manufacturer's trustworthiness. But remember: For fine-tuning your print results, you don't need to constantly measure the filament diameter. There are so many variables that can influence your measurement result. Instead of focusing solely on this, consider other approaches, such as calibrating the extrusion factor. With the right tool and an understanding of all the factors at play, you can make informed decisions and further improve your print results.

• Display Accuracy: Refers to the smallest scale division or the smallest value a measuring instrument can display. It indicates how accurately the instrument can display a measurement, but not necessarily how accurately it actually measures.
• Measurement Accuracy: Refers to the actual error that can occur when measuring with an instrument. It indicates how close the measurement is to the actual value.
• Vernier: An auxiliary measuring tool often found in analog measuring instruments like calipers. It helps to read measurements more accurately by dividing the scale into smaller sections.
• Calibration: The process by which the accuracy of a measuring instrument is checked and adjusted if necessary to ensure it provides accurate measurements.
• DIN Standard: A set of standards and specifications developed in Germany to ensure the quality and consistency of products and services.