Are you struggling to print flexible filaments like Ninjaflex on your Prusa Mk3s+? You’re not alone. Many users encounter challenges when venturing into the world of flexible 3D printing materials. However, achieving successful and high-quality flexible prints, or “Ninja Printing” as we like to call it, is absolutely achievable with the right approach. This guide, inspired by expert insights, will walk you through the essential steps to master flexible filament printing on your Prusa Mk3s+ and similar models.
Flexible filaments, known for their elasticity and rubber-like properties, open up a world of possibilities for 3D printing functional parts, wearables, and custom creations. Materials like Ninjaflex, Cheetah, and Armadillo from Ninjatek are popular choices, but their flexibility can make them tricky to handle in Bowden-style extruders. The key to ninja printing lies in understanding the nuances of material settings, printer adjustments, and careful monitoring.
One of the most common misconceptions is that printing flexible filaments requires extensive printer modifications. In reality, Prusa Mk3 and Mk3s printers, even in their stock configurations, are capable of producing excellent results with flexible materials. The secret lies in optimizing your slicer settings and, crucially, adjusting the extruder idler tension.
To begin your ninja printing journey, start by selecting the correct slicer profile. PrusaSlicer offers a pre-configured profile specifically for “Semiflex or Flexfill 98A.” This profile serves as an excellent starting point. Within this profile, make a few key adjustments to optimize for flexible filaments. First, adjust your temperatures. A bed temperature of 40°C is generally sufficient, and in some cases, you might even be able to turn it off completely after the first layer. For the nozzle temperature, 230°C is a recommended starting point, but you may need to fine-tune this based on the specific brand and type of flexible filament you are using. Experimentation within a range of 220°C to 240°C is often necessary to find the sweet spot for your material.
Another critical setting to consider is volumetric speed. The “Semiflex or Flexfill 98A” profile typically sets the maximum volumetric speed to around 1.35 mm³/s (or 1.5 mm³/s in older slicer versions). For successful ninja printing, it’s best to err on the side of caution and avoid pushing for high speeds. Leave the volumetric speed at the default setting and resist the urge to increase print speeds, especially when you are first getting acquainted with flexible filaments. Speed is not your ally in the initial stages of mastering flexible printing.
Now, let’s delve into the physical adjustments required on your Prusa Mk3s+. The most crucial adjustment is the extruder idler tension. For flexible filaments, you’ll need to loosen the idler screws to reduce the pressure on the filament. The goal is to find the sweet spot where the filament is gripped firmly enough to be extruded consistently but not so tightly that it gets deformed or buckles.
Start by loosening the idler screw on the Mk3s (or screws on the Mk3) to the point where you can manually feed the filament into the extruder while gently pressing the idler tension screw. You want just enough space for the filament to pass through without excessive resistance, erring on the side of being too loose rather than too tight initially. Gently feed the filament by hand until you see it extruding from the nozzle. Be patient and feed it slowly, stopping just before you feel the filament starting to bend as you push it in. Keep your Allen wrench handy, as you’ll likely need to make further adjustments. While the Prusa Mk3s+ has an auto-load feature, manual loading is recommended when you are learning to print with flexible filaments, as it gives you more control and feedback.
Once the filament is loaded, allow the nozzle to sit for a minute and purge any excess material until it stops oozing. Prepare a simple test print, such as a 10cm x 10cm square, for your first attempt. Start the print and closely observe the Bondtech gears through the extruder window as the first layer begins to print very slowly. This slow first layer provides an opportunity to fine-tune the idler tension.
Watch for signs of the filament “kicking out” or slipping sideways from the Bondtech gears. If this occurs, it indicates that the idler tension is too high. Loosen the idler screw in small increments, about a quarter turn at a time, and repeat the process until the filament feeds smoothly without slipping.
Conversely, if no filament is extruding at all, gradually tighten the idler screw in quarter-turn increments, waiting a few seconds after each adjustment to see if extrusion starts. It’s generally better to start with the idler too loose and gradually tighten it until extrusion begins, rather than starting too tight and risking filament deformation or gear damage. This is why a large flat square is recommended for initial testing, as it allows for easy observation of the first layer and extruder behavior.
Once you achieve consistent extrusion and a smooth first layer, let the test print complete. Observe the Bondtech gears throughout the print, especially during the initial layers, to ensure consistent filament feeding. Even with careful initial adjustment, it’s possible for back pressure to build up slowly during the print if the tension is still slightly too high. This can eventually lead to the filament slipping out of the side of the gears several layers into the print. If this happens, don’t panic; simply loosen the idler tension slightly.
After successfully printing a few test squares and finding the optimal idler tension for your chosen flexible filament, you should be able to print more complex models reliably. Interestingly, once you’ve dialed in the tension for flexible filaments, you may find that it works well for other materials like PLA, ABS, PETG, and ASA as well. In most cases, only minor adjustments (typically no more than a quarter or half turn of the idler screw) will be needed when switching between different filament types.
Mastering ninja printing with flexible filaments takes practice and patience. Start with filaments that have a higher durometer or Shore hardness, as they are generally easier to handle. Ensure your printer is in good working order, with a clean nozzle and well-tuned mechanics, before attempting flexible filaments. If you are still facing challenges with basic materials like PLA and PETG, it’s advisable to solidify your understanding of those materials before moving on to flexibles.
Finally, if you have experimented with downloaded profiles or custom settings, it’s often beneficial to revert to the standard “Semiflex or Flexfill 98A” profile as a baseline. This ensures you are starting from a known good configuration and making incremental, informed adjustments.
With these tips and a bit of experimentation, you’ll be well on your way to achieving ninja-level flexible printing on your Prusa Mk3s+, unlocking a new dimension of 3D printing possibilities. Happy printing!
