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Hotend shoot out on Twitter (not my work) and further questions!

Posted by WesBrooks 
Hotend shoot out on Twitter (not my work) and further questions!
December 23, 2019 11:05PM
[twitter.com]

The folk that make the Mosquito are releasing a lower price option, or trying to - it is on kickstarter. I've seen this pending comparison on twitter (not directly by the hotend manufacturer) and it looks interesting.

It has raised a question though. Typically in PID comtrolled heaters don't you want the temp sensor close to the heater? The V6 design has it on the cold end of the heater block after the thermal heat sink of the flowing polymer. This could lead to higher block temps when the hot end is flowing more couldn't it?

Edited 2 time(s). Last edit at 12/23/2019 11:07PM by WesBrooks.
Re: Hotend shoot out on Twitter (not my work) and further questions!
December 24, 2019 06:57AM
Every day, stories on the news demonstrate that social media is a designed to sell bad ideas to gullible/stupid people. Refuse to participate.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Hotend shoot out on Twitter (not my work) and further questions!
December 24, 2019 07:33AM
Yeah, I'm not a huge fan of social media myself either. Forum were the first social media, but at least these have more purpose than posturing and self promotion.

Was that just aimed at Social Media, my comment on the location of the temp sensor, or the product too? If the latter please air your grumbles if they are likely to save me cash!
Re: Hotend shoot out on Twitter (not my work) and further questions!
December 24, 2019 09:19AM
First, what location is the right one to measure the temperature? The temperature of what? The "cold end" of the heater block is probably 2-3C cooler than the molten plastic. I think that locating the temperature sensor a mm or so closer to the molten plastic isn't going to make any practical difference (that's why heater blocks are made of thermally conductive materials). But what do I know, I don't spend vast sums on "fine wine" and loudspeaker cables either.

Why they don't address the real problem- that the outer skin of the noodle of molten plastic coming out of the nozzle is cooler than the inner core? We need a nozzle that mixes the plastic as it extrudes to get a more even temperature profile!


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Hotend shoot out on Twitter (not my work) and further questions!
December 24, 2019 09:39AM
Yeah, I can see why you wouldn't get along well with social media. Nothing I said was a dig at you. Just trying to clarify what you were commenting on.

Regards surface temp of polymer I'd suggest it is likely no one has been able to measure it accurately. I would love a read out of actual melt temp and suspect it would make a huge difference on the portability of process parameter sets between machines. Unfortunately the material volume is just too small.

I know with single screw extruders you can get to the point where the turbulance (/shear) within the polymer can generate enough heat through friction to need very little additional heating, and in somecases cooling on some of the zones. I doubt we're at that stage with ~10-15mm3/sec. With in mind and the polymer being a poor conductor of heat gut instinct would be higher skin temp than core as it exits the hotend, with this inverting after it exits the nozzle.

Mixing tip would ensure a more homogeneous melt, but would increase back pressure and would increase reliance on corrections like preasure advance.

If you've got interesting links on the topic I would appreciate it if you can share them please.

Edited 2 time(s). Last edit at 12/24/2019 09:47AM by WesBrooks.
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