Is here anyone who knows something about experimenting with a second temperature probe at the heatsink?
I just thought about about the melting curve of plastic and the fact that it’s not linear.
It’s also common practice in injection molding tools from use pellets at a defined temperature. Especially with high temperature plastics.
Maybe it could be an advantage to heat the filament in the “cold zone” but keeping it below the Tg temperature.
This way we could maybe use the hot zone more efficient.
In general a control\comparison between these 2 points would help I guess.
Keeping the cold zone in a constant temperature instead of cooling it as much as we can.
Well it’s quite clear for me that this comes with some risks and additional hardware as well. But that not what I’ve asked for.
I’ve asked if someone knows if there is already knowledge available. In this case I don’t need to start from scratch or reinvent the wheel.
I also don’t say that it works or even makes sense. Entirely possible that someone tried it already and generated knowledge that shows that it simply doesn’t work.
But that’s what I would like to know before I maybe waste time
I get what you’re after, wish I could add something. I really hate how people are so quick to say “that can’t be done” (not saying anyone here is doing that, just talking in general). I think the same way, or at least try to. People are thinking about current limitations based on size and weight of current components, but that stuff will all get smaller. It’s important to do the research into these things now so the technology is ready when the miniaturization that inevitably happens, happens.
I routinely run a thermocouple on the heatsink on some of my printers. A heated build chamber printer with the extruder inside the chamber already preheats incoming filament like this. It’s a big reliability problem. Air-cooled hot ends start to jam when the chamber temp is way below the glass point of the plastic. My experience is ambient temp about 30-35C for PLA and 60-65C for ABS will cause jamming. (Unless you switch to watercooling.)
Injection-molding equipment has to deliver a precise amount of energy to the pellets through conduction and shear friction, or the plastic will get hot spots and burn as the screw violently shears it against the tube walls. About half the heat energy in an injection molding machine comes from this shearing. Controlling the pellet feed temp changes the melting rate, and thus the viscosity profile along the screw, and thus the shear-heating.
In comparison, filament-pushing extruders primarily provide heat via conduction and residence time, not viscous friction. The feed absolutely has to be solid for the filament-pushing mechanism to build pressure and not back-flow molten plastic up the cold zone and jam. So you want a cold feed for reliability, whereas preheating the feed will only provide a marginal increase in print speed.
experimenting with 2nd temp probe, would be to determine minimal heatsink to keep filament out of glass zone…
so you could design smallest hotend for desired filament type?
or to learn general behavior of filament…
regarding pre heating…
ideally you would store filament (palets) in 100% dry place…
because that is not the case, some that are susceptible to moisture get dryed before injection…
not to say that there aren’t particular types that need preheating, specially if mixing is involved…
ideally filament and build chamber would be held just under glass temperature… that would give you the least chance of distortion during printing.
