Extruder design question: Mutley's Flex3Drives and a few other extruders I've seen don't use

Extruder design question:

Mutley’s Flex3Drives and a few other extruders I’ve seen don’t use springs on their idlers anymore. They seem to work fine.

Does anyone remember the original design intent of springs on idlers? Was it just a product of the wildly variable filament diameters we used to get? I’m designing a compact little extruder for my new machine, and wondering if there’s any downside to forgoing springs.

The only cases that I can think of is loading becomes easier, and retraction (most filaments deform from the drive hobb, so retraction can be an issue)

Springs do compensate for a lot of things but mainly they are for insertion.

Thanks folks, those are both good points. I guess I’ll keep the springs, not like I don’t have dozens laying around at this point.

Yeah with the Nimble we did a lot of testing and experiments and eventually dropped the spring. We tested with all sorts of filaments even going down to 1.65 mm (yes, was very cheap filament) and we still had more than enough grip. As we have a completely new way of loading the filament ( a breech system) we don’t need the spring for that either. So for us there is no downside.