Hi everyone!
Currently I'm working on a project in which I'm researching material mixes that are suitable for FDM printing, while reducing energy consumption by eliminating the need to heat material and printbed during the print. This means that the material mixes that I'm working with are paste-like and are able to be printed at room temperature and they dry during and after the print until they're solid. I've modified a normal printer and fitted it with a syringe that is slowly pressed by a stepper motor (the extrusion motor). In initial tests I found that the minimal flow rate that Cura supports (5%) is actually too high. With my first design a flow rate of 0.44% was needed. Since then I've fitted some gears, which increased that value for 7.0% and since then I have bought different lead screw which could further increase this value.
Although I've solved the issue, I'm still curious why this lower limit is there in the first place. From a technical standpoint, I feel like a lower flow rate would be easier to deal with for the stepper motors, so why is the limit there? I can understand that it would not be realistic to print PLA or PETG at a 5% flowrate, but still that doesn't explain why it should be possible to choose this lower limit. So my first question is what the arguments would be to install the 5% limit for the flow rate.
My second question is if there is any way to surpass this limit and easily edit the G-code to still be able to use lower flow rates. Using the gears for the modification makes the system a little clunkier, heavier and the center point of gravity is less than ideal. A design that doesn't need gears would result in better print result and makes it easier to place the syringe. As mentioned, with the original lead screw, which had a 8mm lead, I would need a 0.44% flow rate and I've now also got lead screws with a 2 and 1mm lead, which would result into 1.76% and 3.52% flow rates. If you have any suggestions how I could easily make G-codes that allow such low flow rates, I would love to hear. Thanks in advance!