Actually usable flexible filament: Polymaker Polyflex!
Flexible materials have changed quite a bit – and are much more easily printable. But still as indestructible as always! This is Polymaker’s offering.
Polymaker’s Polyflex is a good representation of what a typical flexible filament looks like these days – with a shore hardness around 95A, they’re not as crazy soft as some of the earlier materials, which means they’re much more easily printable, even on machines that aren’t super optimized for flexibles, and you can actually adjust how floppy your parts are going to end up by playing with the shell thickness and infill in your slicer.
This Polyflex is quite pricey at 82€ per kilogram and prints at 225°C on the nozzle and optionally 50° on the bed, with the part cooling fan at full speed. I applied a layer of Magigoo on the bed to make part removal easier, and used the Prusa MK2’s default profile for flexibles, which prints at a relaxed 15mm/s. Print quality was surprisingly good for a flexible, of course with a very high tendency of stringing, as retracts are much less effective than with rigid materials, and some noticeable curling with steeper overhangs, leaving Polymaker’s Polyflex at a total 15 out of 20 point, which is respectable for a flexible material.
Strength and rigidity were challenging to measure, as the bend test parts were too soft to be measured. Proportionally scaling the results from the pull tests, Polyflex earns a total combined score of 85kg, which, essentially, means that you’re extremely unlikely to to break a printed part, as it will flex a tremendous amount first. Temperature stability seems ok, as the part will more easily deform, but still, like, mostly flex back into its original shape. So in conclusion, Polymaker’s Polyflex is a material that is rather hard for a flexible, but offers good printability and strength in return.
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