Extruder Design and assembly.
I wanted a nearly lashless geared extruder. I could have downloaded just about any kind of geared extruder around. However they really did not fit my needs.
I had to consider a few things.
1 - Lash: Most of these 3d printed gears have some lash.
2 - Cost: I really didn’t feel like paying for a hobbled bolt, especially since I had a stainless direct drive extruder gear.
3 - Durability. Most of the stuff available to download didn’t seem "Sturdy" to me.
With all that being said, I figured I would design my own with parts I had on hand.
The parts list.
1 - 2x laser printer gears pulled out of a laser printer year’s back. They have very little backlash due to the fine teeth.
2 - 2x 5mm bore bearings pulled from an old hdd.
3 - 1 bearing (608ZZ) roller skate bearing. I bought a pack of 10 when I was building the printer. I am glad I did as I like these bearings and they have come in handy.
4 - 1 3/16th bolt and nuts. Comes very close to 5mm metric.
5 - Misc bolts & nuts hanging around.
6 - 1 GT2-20 pulley used to adapt the smaller gear.
The Extruder, it looks dirty, but that is just grease I put on the gears. The extruder was printed with 100% infill & .3mm layers. I did not need it to be pretty, but I wanted it to be strong.
Well, the extruder worked extremely well first time out the box. No unforeseen issues, and the tension on the bearings is perfect. I don’t need to adjust much of it. It took two uploads of the firmware to get the proper steps per mm so its spot on.
The downside is that the gears are not 100% true, therefore there is some noise. However there is no backlash problem. This thing is printing at faster rates than the direct drive extruder with fewer imperfections due to retraction being much smoother. I am very happy with it.
The other thing is that I calibrated the extruder exactly as I needed it. When asked to push 100mm of filament it pushes exactly 100mm of filament. Measured it 3 times with a caliper. It’s certainly working well. Its retraction speed seems improved due to the 1.77:1 gear ratio and the increased torque it gives. I seem to fail understanding why people use such high numerical value gearboxes, 5:1 and as much as 40:1 I have seen. I doubt I need more than 2:1 or maybe 3:1 gear ratio.