The filament is jamming on the AMS lite preventing it to get pulled properly from the hotend. Why is this happenning? It seems to be more frequent with matte PLA (although it happened with galaxy PLA also). Maybe the extruder motor is too hot and the heat are smoothing the filament just under the AMS hub and then creating this jam when pushing? Or maybe too resistance from the bowden tubes? It does not seem to be heatcreep as the jam happens way above the cold end.
The color change process have two motors that work to move the filament. The extruder gears retract the filament from the hotend, then when it’s cut, the ams motor pull back the filament. I think the jam happens on the first phase.
PS: I am using the long retraction option but I am pretty sure that already happened before I turned this on.
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I am having the same issue as well. in my case I am using Bambu PETG-HF. we are doing 4 filament color prints. we found that it has only been happening to us in #3 spot.
Hey there, I was looking into online solutions to keep the stepper motor cooler and noticed a lot of people recommend adding an extra fan. I wanted to try a slightly simpler and less invasive approach, so I stuck a few small heatsinks on both sides of the motor. Surprisingly, I haven’t had any failures since then. Coincidence or not? Only time will tell!
Coming back with an update: even with the heatsinks I am still getting some jams (failed to pull back the filament from the toolhead). I did realize that I get this only on slot 4 and mostly with matte PLA.
My hypothesis continue the same, the filament gets deformed when the gears push back the filament. I think there is some resistance on the way back on this specific slot/bowden tube, combined with the softness of matte PLA, the filament gets deformed and gets tucked. I will probably disassemble the AMS hub and check the bowden tube.
I’ve been having this issue for over a year - it ruins my prints. What I see happening is the filament extrudes into the AMS Lite hub then partway, the tip of the filament snags on a hairline seam or ledge, preventing it from going further. I’ve tried a couple of the AMS lite hub braces and they help, but they don’t completely eliminate the problem. I’ve found that before feeding new filament in the AMS lite, snipping it at an angle instead of flat does help … until the Toolhead needs to swap filament and does a straight cut… then it snags about 3/4 down the AMS lite hub chamber. The snag happens after the “X” splitter piece within it.
what worked best for me - but don’t blame me if it doesn’t work for you. I disassembled the hub completely then took a small drill bit and a long dremel grinder bit and worked to smooth out the ledge within the chamber. It’s right where the tunnel leading out connects to the hub. It’s a sharp edge, not a smooth one that helps guide the filament.
so I’ve concluded that this is a defect in the design that you just have to live with. Slicker, glossier filaments will tend to do better because it can slip past that ledge even with a straight cut. Grittier filaments will snag on it much more often.
Other things you can try other than grinding down and hand-smoothing the inside of your dismantled hub : angled cuts (for single color filament prints) swapping the hole the boden tube connects to into the hub completely- this can change the angle or twist the filament slightly to help it overshoot the ledge it was catching on, hub braces and extenders - again you are trying to change the angle of the filament entering the chamber in hope to shoot past the inner ledge.
and you CAN force push the filament from the AMS lite entry until you feel it push past the snag.
But this really is a problem for Bambu to fix in their design and they have moved onto bigger and more lucrative endeavors. If I had a plastic molding system, I’d fix the issue and make a business selling the improved AMS lite hub because it’s a flaw begging to be fixed and I think I could make enough money from the sales to make it worthwhile.
I’m having exactly this problem with my AMS2Pro. I happens frequently on slot 4, once on slot 2. Initial loading of the filament almost always works – especially if the filament is cut diagonally. When called to load by my P2S, slot 4 loads around 50% of the time. If it doesn’t, I can sometimes jam filament through the hub manually, but usually not. Then resetting the AMS (unplugging the 6 pin connector and replugging) usually works. This has been a problem since the AMS was new. Bambu “service” is NOT HELPFUL. Do you think running a filament modified to be particularly abraisive into the hub and then rotating it with a Dremel for a bit would be helpful (or destructive)? Disassembling the AMS2Pro seems daunting.
