Saturday, 1 August 2015

Huxley #710 - Does NinjaFlex...

NinjaFlex is a flexible filament based on a Thermoplastic polyurethane. Unlike the PLA normally used in Huxley #710 this material has a low hardness of 85A Shore. Making it possible to make soft buttons, bump stops, vibration isolation mounts, stretch covers and shoes (apparently).

Huxley #710 Does NinjaFlex
 I used Talpadk’s Blog and the NinjaFlex website to start configuring Slic3r rev 1.2.9 for Huxley #710.

The short story being, I could not get the higher print speed settings recorded in Talpadk's Blog to run for me. Either the feed would fail or large blobs were evident on the surface of the part. After a DOE, consisting of 20 printed parts. I ended up with a much slower print speed and very short retraction that produced very acceptable results. The NinjaFlex shown is Midnight, which is brightly lit so I can see the state of the print.

The printed part exhibits good tensile strength and elasticity, especially for a part I have printed myself. My eldest son was unable to break the part ~110N! Although it did suffer permanent deformation of ~30%. For an elastomer part this is usual, so the achieved performance was very pleasing. (For scale, the print is 20 mm square, 1.0 mm thick  and 4.9 mm high. Given it's a soft part and I don't have optical measuring equipment, there is large uncertainty in the measurement. However it seems very close to the nominals of the test part, the wall thickness and shrinkage are very acceptable.

Huxley #710 uses a bowden extruder, so the short retraction length surprised me. I suspect this is due to the low feed rate keeping back pressure in the extruder down. Back pressure might arise as a soft filament is somewhat compressible and has a tendency to buckle. Talpadk's higher temperatures will reduce the viscosity, allowing higher feed rates. However, I kept the feed rate low primarily as higher feed rates caused the filament to jump out of the filament feed mechanism too frequently. A tweak to the clamp bracket might reduce this by forming a feed groove. As I am busy designing and printing, the current settings seem like a good compromise.

Nozzle diameter 0.50 mm
Filament print temperature 220 C
Glass bed surface temperature 40 C
Print speed 8 mm/s (all layers currently)
Traverse speed 150 mm/s
Retraction speed 5 mm/s
Retraction distance 0.4 mm
Layer height 0.4 mm
Perimeters 2
Print outer perimeter last

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