Most soldering and 3D printer hot ends heat a tube from the the outside. What if, by using micro manufacturing techniques, the heating element could be suspended in the centre of the tube.
I am imagining a tube with sharp ended ovoid held in the centre of this tube by wire carrying fins. Given electricity, the resistivity of the ovoid heats to the required temperature and the solder or plastic filament melts and flows around this ovoid to the tip. Diameters could be controlled such that the melted substance just sits at tip as a bubble until use removes it and new cold solder/filament is gravity feed down to replace it.
Having the heating element in the centre means the exterior of the pen tube can be insulated requiring less heating and giving a safe to touch solder pen body. Of course, the tip will still be hot but this pen will have a much reduced hot area compared to the old system.
Writing circuits has never been easier.-- wjt, Jan 31 2020 Concept Sketchup https://www.deviant...Solderpen-848799416Needs better nozzle, thermal break. Possibly a fountain pen nib [wjt, Feb 06 2020, last modified Jul 15 2020] Why not make a ballpoint, using RF induction heating ?
The carrier could be ceramic, therefore only the ball and the solder would be heated by the RF. The heat capacity would be very small (melt volume).-- 8th of 7, Jan 31 2020 I suppose it would depend on the circuit board surface. Ball points don't really write on hard surfaces and don't blob unless damaged.
The ovoid could be RF heated but a straight electrical resistor producing heat is going to be energetically cheaper than high AC current through an electromagnet through the EM field to object's currents to make internal resistance and produce heat.-- wjt, Feb 01 2020 // Ball points don't really write on hard surfaces and don't blob unless damaged. //
That depends on the coefficient of friction between the ball and the surface, and the viscosity and surface tension of the "ink" - plus the susceptibility of the surface to wetting.-- 8th of 7, Feb 01 2020 [+]-- Voice, Feb 01 2020 A moving part has to have a great advantage to be included.
<Imagines a glue gun with a ball nozzle/>
The ball could have cups in the surface to deposit a set quanty of glue per distance travelled. But again, getting the friction right for a multitude of surfaces wouldl be difficult.-- wjt, Feb 01 2020 A squeeze-controlled output would work for that.-- Voice, Feb 01 2020 A peristaltic pen is even more complex.
At least a ball has a physical lock on distance traveled with amount deposited and would be independent of user motion. Else a physical mechanism between application speed and input feed of applied substance is needed.-- wjt, Feb 01 2020 //melted substance just sits at tip as a bubble until use removes it and new cold solder/filament is gravity feed down to replace it//
No. Just plain no. In order to get the replacement feed melted in time to do a continuous bead, you're going to have to have a pretty high heat flux to the tip - however, metallic solder conducts heat really well, and it's going to melt back up the pen; as the melt zone travels, it's going to keep adding the weight of melted solder onto the surface tension holding the solder in the barrel, and it will shortly pee all over your workpiece.
I think, though, that if you take the melting and injection apparatus from an injection molding machine (google terms "injection molding screw barrel" and check images) that you could make a device that would work. (Complex, I grant, but you'd be starting from a known workable solution.) The screws in these rotate as they are withdrawn (enough rotation to Archimedes-fill in the empty space left by the receding tip), and then advance while not rotating when you want to deliver the solder (probably just a button control on the side of the pen). You'd want some kind of heat-rejection a short distance away from the tip to keep a limit on the melt zone, and some hand-protection...-- lurch, Feb 03 2020 // it's going to keep adding the weight of melted solder //
That could be addressed by having the melt pool inside the pen under carefully controlled slight negative pressure, and feeding in make-up solder through a gas-tight orifice. Then, atmospheric pressure on the tip counteracts the weight of the melt.
However, the dynamic control of such a small system - which is presumably subject to lateral and rotational forces on multiple simultaneous vectors - will be non-trivial.-- 8th of 7, Feb 03 2020 [lurch] I grant you it won't solder upside down unless mechanically fed. Well, maybe in space.
The application aperture construction and heating range will have to be played with to get the bubble. I haven't seen yet the solder drop out of a wire solder hole just because it's slightly melted.
Remember the heating element is in the centre of the solder, the temperature has to be more controllable. No heat wastage to fingers.-- wjt, Feb 04 2020 you could squeeze it out between flexi-walls of the pen tube, ) ( where the flexi-walls flex and curve to compress the solder to flow out the tip from electromagnetic patternings on the flexi-sides and windings at pen wall.
)s(-- beanangel, May 07 2021 random, halfbakery