An extruder and hotend made specifically for flexible filaments -- but could it be over-optimized for regular use?
Pwn flexible filaments with the Flexion extruder!
Have you ever been upset by how poorly your 3D printer handles flexible filament? Well, i might just have the solution you’re looking for.
So this is the Flexion extruder and hotend combo. It’s a drop-in replacement for Makerbot-replicator style extruders, which are popular especially with far-east Prusa and Makerbot-derived printers, and unlike what the Flexion page says, it won’t directly fit a real Prusa i3 or a RepRap-style mount -- but i’m sure you can print an adapter for those. Now, the flexion extruder and hotend are specifically made for flexible materials, and in fact, they were developed by the same guy that is making the patented Ninjaflex flexible filament. As such, it has a fully teflon-lined hotend with a single piece of tubing going from the melt zone all the way up to the hobbed gear, giving any filament that might kink, the maximum amount of support while it’s being pushed into the hotend. Also, it does not have any sort of spring-loaded idler mechanism that pushes the filament into the hobbed gear, it uses a very stiff assembly pivoted around the stepper motor’s mounting threads in combination with a four-position cam and a set screw. This lets you compress the filament by a precisely adjustable amount, which is ideal for, again, flexible materials, that might just get squished by a classic spring-loaded extruder.
So the hotend matches pretty closely what the Malyan M150 that i tested this on, came with, just in a much higher quality bracket, and the Flexion uses standard E3D-compatible nozzles, which opens up that entire ecosystem when it comes to swapping in different sizes or abrasion-resistant ones. In fact, the Flexion hotend comes with a set of replacement nozzles with bores in 0.2, 0.3 and 0.5mm, in addition to the installed 0.4mm one. What’s also unique about the extruder part, is that is has this little round brush constantly cleaning out the hobbed gear as it turns. You can tell it’s doing some work as the area around the brush gets pretty dusty pretty quickly. I believe this brush could last a fairly long time before wearing out, but in either case, there’s a replacement included. Now, the thing is, this brush is a bit of a crutch, other high-performance extruders don’t need it to work well since they use a different hob profile for driving the filament. The one on the Flexion extruder is particularly fine and particularly deep and tight. This, of course, give the gear a lot of area around the circumference of the filament to bite into, but it also means that, as the filament engages with the gear, you’re getting a lot of shear on harder plastics. Imagine my right hand is your hobbed drive gear and my left arm is the filament, what you’re seeing as the filament is being pushed is the deeper part of the drive profile actually moving slower than the outside, so especially on retracts, you’re going to see shavings or at least tiny particles come off your filament. With a flatter profile, you’ve got less surface in contact, but also all at mostly the same speed. Now for flexible or even slightly soft filaments, you actually want the larger surface area, because the filament will just flex right along, so that decision of using a finer and tighter profile does make sense here.
Two more things to note, it does not come with a heater cartridge or a thermistor, so i simply reused the ones that the stock hotend used, and because the extruder does not have any quick release, like by pushing down an idler lever or by releasing the springs, you do have to load and unload the filament by actually running the extruder forward or backwards. Not all 3D printers have an preconfigured procedure for this, especially when they originally didn’t require it, so you might end up having to control the extruder manually. Thankfully, though, the mechanical part of the loading process is pretty straightforward thanks to the optional filament guide for keeping the filament aligned as it enters the extruder.
So for testing it, i compared it against the stock setup of the Malyan M150. Some of you have commented under that review that the extruder and hotend used here is practically the same across many low-cost 3D printers, so i guess that would even make it sorta representable. And as much as i hate printing sample or test parts, i had no application that would make proper use of each material i was going to use, so 3D benchies it is. I settled on using standard white PLA, Taulman’s semi-transparent PCTPE, an ever-so-slightly soft material, blue Ninjaflex, obviously, a soft filament, as well as this sample of incredibly flexible orange filament -- if you had handed me that separately, i probably wouldn’t have identified it as a filament at all.
So i started with the stock setup. PLA -- not a problem. PCTPE -- perfectly fine, too, that stuff actually prints very nicely. However, as i tried Ninjaflex, it was pretty much over instantly. I was able to get a few drops out of it, but the filament just started going everywhere and slipped off the driving part of the gear eventually. But i mean, that was exactly what i was expecting, as even on slightly better constrained extruder assemblies Ninjaflex is already tough to print and likes to curl up and wrap around the hobbed gear if you’re trying to print it too quickly. So that’s a good baseline. I swapped in the Flexion extruder and hotend, which were a perfect fit, by the way, and oh, to my surprise, i couldn’t get PLA to print properly. Either the hobbed gear would just spin freely and not drive the filament at all or the motor would end up jamming as i had to put too much pressure on the filament. No matter how much i tried, i just couldn’t find a healthy middle ground where it just worked. I blame this on a few things, one, of course, the extruder, as that is the only thing i changed, and specifically, the lack of a spring-loaded idler. Now, with a hard filament like PLA, there’s nothing that is going to flex and give you fine control over how tight you want the drive gear against the filament other than this grub screw. The other thing in here is the hob profile itself, too, as having that tight wrap-around profile put more stress on the motor from that grinding motion. And the last thing is the motor and its current setting, obviously, this isn’t the most powerful stepper motor, and likely not set to any high-ish current level either, and i fully expect PLA to work with a bit more horsepower, you just need to be aware of that and pay attention to what stepper motor and driver you’re using before diving into the Flexion extruder experience. But, as i started moving towards the softer filament, things were starting to look a lot better. Taulman PCPTE worked perfectly, so did NinjaFlex and even the mind-bogglingly soft sample filament. These were all printed from the exact same gcode, which is 50mm/s with 0.2mm layers, so a decent amount of plastic per second, too. The PCTPE print ended up a bit stringier here, but i think i just hit a spot that had absorbed a bit more moisture as i could really hear it cooking inside the hotend, and the ultrasoft print did require a slight tweak to the extrusion rate, probably because i had set the tension a bit too low for that print. But overall, this has been, quite frankly, an amazing experience with the flexible filaments. And just to double-check how flexible the filament needed to be to work well with this exact setup, i tried some E3D Edge, which is my favorite filament for regular use, and actually quite tough, but not as hard as PLA. And that worked flawlessly, too, but ended up coming off the build platform since this printer doesn’t have a heated bed. Anymore. You know, i was ready to scrap the Malyan or give it away or something -- it just wasn’t an attractive machine for me overall. And while there are still a lot of flaws with it right now, having the Flexion extruder and hotend on here gives it that redeeming quality.
Now, arguably, putting a $149 extruder and hotend on a $280 3D printer might not be the smartest thing to do. You know, you could have just bought a better printer right from the start.
But if you have a better base to work off of or just want that ultimate flexible filament printing experience, then i can totally recommend the Flexion extruder. It’s high-quality and well-built, it works amazingly well for even the softest filaments and the issues i ran into with PLA are easily solved by giving it some more torque from the motor.
So those are my experiences with the Flexion extruder set -- i hope you found them helpful! If you did, i’d appreciate a thumbs, if you didn’t, go ahead, break my heart, give me a thumbs down. If you haven’t done so already, get subscribed, and if you want to support my work on this channel, consider dropping a dollar or two on Patreon. And that’s it for today, see you in the next one.
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