Just to update this, I have a cheap optical comparator but it’s for much bigger gears (race gearboxes) than this so it’s not very accurate down at this level, but my set of helical extruder gears have somewhere less than 100 micron in both profile deviation and runout - I can’t measure less than that at this small scale unfortunately with my setup, not accurately anyway.
The actual tooth profile looks cleaner cut than the OE bambu, but not by much, neither are all that amazing, just acceptable.
The delrin drive gear on the aftermarket set is a little worse in pitch-to-pitch variation - there are hobbing marks on the mating flanks which probably accounts for it, which aren’t there on the OE ones - Bambu’s supplier evidently has a little better finished tooling for that, but I don’t think it’s enough to make any difference.
The aluminium arm is nicely made and the end float on the helical gearset in that arm is much better than the Bambu - it’s less than a tenth of mm, my Bambu one has almost a quarter of a millimeter of slop there.
Whilst a little bit is required, it needs minimising there as both the helical mating gears will shove the gears backwards and forward between the arm sides on extrusion and retracts, so someone put some thought into that - there’s also less end float on the drive side where similar happens with the large helical gear mating the extruder motor too, which is nice to see.
I’m not 100% sure what the nanocoating is but it feels like a polymer fluorocarbon layer, it’s pretty slick, so it should stop buildup of filament fragments (I’d already got a little buildup in my stock gears even after only a few months of printing). It also stops soft filaments like TPU trying to wrap around the gear and distorting at high drive pressures if you do any of that.
That was very important for me I do a lot of TPU so for me it’s worth it for that alone.
The filament drive gears are very nicely hobbed, if anything they’re a little sharper/cleaner than OE, but I don’t think there’s a whole lot in it - both OE and aftermarket will drive filament to the point of the motor skipping all the way to the tension spring backed off to about 2/3rds preload, so there’s not much difference there.
One thing I will note with the aftermarket gears is they don’t have as much root relief as OE - that means the meshing is rough if there’s no filament in the drive path as the teeth bottom out before the hobbed filament drive gears touch.
It’s not really an issue but I guess if you’re using a soft say 60-70A TPU without altering the preload on the extruder* that might compress enough to give contact and inconsistent extrusion.
Or really cheap, very undersized filament, maybe. Does mean the drive gears will touch when loading and unloading filament though, I don’t know if that will be an issue at all so I’ll inspect it regularly and give updates.
One design issue I do have is with the aluminium arm, and helical steel gears, you now have thrust loads taken just by the aluminium face instead of a Delrin/POM arm that’s naturally self lubricating - in my case during installation I tested this for a while, wasn’t entirely happy with it so I greased the contact points there, which should be all that’s needed, but I will keep an eye on it.
I also greased the helical steel gears and the plastic extruder gear during install, I know many don’t but I’m not a big fan of dry gears after many decades in industry, and we’ve seen excessive wear issues on the geartrain on some printers in here, I don’t really think the issue of plastic fume or dust stuck to the gears is anywhere as big an issue as dry sliding surfaces are. But that’s a personal choice - the polymer coating should help there given it’s low friction anyway, but you do as you decide.
I also greased the pivot pin for the arm - for similar reasons.
I won’t expound on the “heat transfer through the aluminium arm” thing as frankly it’s conjecture rooted in nonsense and poor understanding. There’s zero issues. Even with TPU which is terrible for driving with warmth, heat creep is no different to stock.
In terms of actual extrusion quality, I’ve noticed nothing really on stiffer filaments - PLA/ABS/PETG, fibre filled Nylon, no real difference that I can’t put down to usual print-to-print variation.
Softer filaments - Nylon 12, PCTPE, TPU’s, there’s noticeable change, and especially with foaming filaments - retracts especially are cleaner - but there’s definitely less ringing/extrusion variation on sudden direction changes - probably mainly due to the fast speed changes in the extruder with PA’s of 0.1-0.3 for those materials, it’s more noticable when using lower preload on the extruder for soft TPU’s too. At full preload, less so.
I would say for $12-15 shipped, if you need a hardened gear upgrade it’s a fine option but you’re not getting anything out of it vs the OE Bambu gears for most common filaments. Maybe the nanocoating will help with buildup
If you print soft materials, it’s probably worth swapping to it even if you don’t need hardened gears, the wall quality on some NVH vehicle bushes I just prototyped is perfect, they look like they could have been moulded.
- (Not that I would recommend that, even with 95 shore I’d be backing off the preload unless you like it trying to wrap around the gears at any decent drive speed - but that requires putting a hole in your cover and that’s another topic all together. If you’re happy at stock settings and profiles and not trying to push TPU at 15-20mm^3/s, just leave it alone)
