I had an idea for a print that required flexible filament. The go-to flexible filament is TPU, but I was going to use the print with food, so I looked around for something that I thought would be safer with food and found Flashforge’s flexible PLA. I was excited to try out this print. Once the filament arrived, I slipped it onto my AMS, got everything set up and… complete disaster. First, the A1 Mini could not load the flexible PLA using the AMS. I tried switching out extruders and loading and re-loading the filament half a dozen times before I realized that the flexible nature of the filament and the friction from the AMS was making it impossible to feed this into the printer using the AMS. I then tried feeding it manually and still ran into problems.
An hour of Googling later, I realized that I was not the first person to run into this problem, though most were running into this printing with TPU and not flexible PLA, but it seemed like the problem was the same – the AMS works with stiff filaments but not flexible ones.
There were two parts to solve this and get a successful print using flexible PLA.
First, you have to use the spool holder and not the AMS to feed the flexible PLA or TPU into the Bambu A1 Mini. To do so, you have to swap out one of the PTFE tubes from the AMS with a PTFE tube that runs from the feeder for the external spool into the back right slot of the AMS feeder (if looking at your A1 Mini directly; it’s possible you could feed it into any of the slots, but that is the one I got to work). This is part of the solution. The second part is finding a way to smoothly and nearly frictionlessly feed the flexible PLA or TPU from the spool into the printer. The filament is so flexible and soft that, if there is any friction, it can cause problems with your print. I managed to successfully print my first item by manually feeding the filament into the A1 Mini, but that isn’t feasible for long prints. There are ways to reduce the friction that primarily focus on better spool holders. The external spool holder that you can get for the Bambu A1 Mini has too much friction. I found a number of solutions online for this (thank you print community). I went with this one. It requires ordering some bearings and screws, but it was worth it for me to be able to print with flexible PLA.
Second, you have to change your slicing settings dramatically. Printing with flexible PLA or TPU requires printing extremely slowly. I changed my print speeds to 20 mm/s for pretty much everything. But you should also set your filament as TPU (there is an option for that in Orca slicer). I also found a forum post that mentioned changing another setting for the filament in your slicer (not a setting for your objects or print plate): Max Volumetric Speed. Changing this from the default of 3.6 to 1.0 made a huge difference. I’m not exactly sure whether it was changing the speeds manually or the Max Volumetric Speed that made this work, but those changes combined worked.
Finally, printing with the spool holder and not the AMS using Orca meant I had to send the sliced file to the device and then print from there. I couldn’t print directly from the slicing software because there isn’t an option to not use the AMS. Not a huge deal, but one more thing for you to be aware of as you try to solve this problem.
In short, it is possible to print TPU or flexible PLA with a Bambu A1 Mini, but it requires a fair amount of preparation work to make this happen: no AMS and a nearly frictionless spool holder, changing the speed settings, and printing from the printer instead of your slicer.
