IMG 0969 2I love the prints my Geeetech A20 printers make. I don’t exactly love the printers. I have an A20M (2 color) and an A20T (3 color). Owning both indicates I don’t actually hate them. They are just hard to live with…

The A20M was first. The original mixing extruder hot end had a design flaw. There were two very tiny multi orifice plates in the melted plastic flow path. One for each filament. I assume they were an attempt to mix colors when extruding. What they actually did was constantly plug up.

I ordered a new hot end from China when I discover a new improved A20M hot end was available without the tiny multi orifice plates. But delivery was going to be over a month.

So I purchased the A20T which uses a totally different hot end. Duh! Of course it is different, it has three feeds. But the overall extruder design is totally different and no orifice plates.

Both printers use the same design filament stepper drive. Geeetech calls it the Titian. Borden tubes and remote drives are unavoidable in most single nozzle extruders. No room on the hot end for multiple motor drives.

The Titian has a geared-down drive system to improve feed torque. Don’t know how really necessary that might be, but they like to brag about it.

All five of my drives have worked well for several years and hundreds of prints. 

But I have now discovered a design weakness. The tiny idler wheel that presses the filament (under spring pressure) against the toothed drive wheel has a very tiny ball bearing. The wheel itself is mounted almost totally enclosed in its mount (see first picture) 

titianIn two of my Titian drives, one on each printer, this bearing has seized and the pressure wheel is frozen solid with no rotation. When it fails, weird squeaking and clicking sounds emanate from the drives when trying to feed and the gear quickly grinds a notch in the filament and flow stops.

The first drive (A20M), I got the axel screw out but the bearing and its microscopic balls just fell apart all over my work space (picture 2). With the A20T drive arm, the axel screw will not come out and the wheel is totally locked into the arm and doesn’t rotate. The A20T arm is the one on the box in picture 1.

There has been a small design change in the pressure arm. The Titian drive taken off the A20M has a clearance slot in the arm to let filament “dust” escape. The  arm from the A20T Titian does not have the slot. It was packed with debris. No idea which is the “current” design until my new parts are received. I have five Titan repair kits on order @ $20 ea.

The drives have operated for more than a year with no issues. I do think the tiny ball bearing is inadequate for the task. Certainly not designed and rated to take the spring pressure loads. The bearings are sealed and inaccessible, so no way to lubricate. Certainly a design flaw in bearing choice. Yearly bearing changeout should not be necessary.

I have had no such problem with my five other FDM printer filament drives.

I may get another year or two from the A20’s. Then it’s EOL* for them.

*End Of Life