With all the talk of lasers for cuting or polymerising or selective sintering, I had another use for them : Replacement of the heater barrel. Would it be practical to feed the filament as in Darwin, into an insulator barrel with a window in the side just above the nozzle. Use a laser or similar energy source to DIRECTLY heat the polymer to melt. It may even be possible to eliminate anti-ooze valves etc by making the extruder 'heat on demand' THe same wattage will be put in (a few watts currently) as the hot brass system. In fact, less watts will be needed because there wont be any wast heat radiated from the outside of the heater & nozzle. Of course resistive heating is nigh on 100% efficient, and any laser etc isnt going to be, but as we only need a few watts, this wont be important. The whole assembly could be much shorter because there wont be any heat soak back up the current insulator. and no variation in the melt point in the barrel. Ther will be very little thermal mass so the control electronics will need to tightly match the laser heat input to the required plastic flow. It wuld probably need a thermocouple mounted oppersite and just below the 'window' to feed back the melt temperature. My thinking is : why heat a lump of brass in order to melt the filament when we could melt it directly and keep all that heat in the filament by making the barrel/nozzle in a good insulator material. (eg Duratec [uk.rs-online.com]) Edit : I just remembered my other heating idea - Use a utrasonic technique in place of the laser&window. Ultrasonics are used to melt plastic mouldings during product assemly. Usually by 'staking' a small rod which is squashed flat like a rivet head to hold a PCB or case together. Edit2 : Just thought of another idea - add metalic filings to the filament as it is made. Then use an inductive heating system to heat the filament directly in a non metallic barrel. (I say metallic, because eddy currents in aluminium will cause heating) https://reprap.org/forum/read.php?70,14413,14413#msg-14413 Fri, 10 Jul 2026 16:33:08 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?70,14413,14498#msg-14498 https://reprap.org/forum/read.php?70,14413,14498#msg-14498 Kyle Corbitt Plastic Extruder Working Group Thu, 17 Jul 2008 00:45:52 -0400 https://reprap.org/forum/read.php?70,14413,14488#msg-14488 https://reprap.org/forum/read.php?70,14413,14488#msg-14488
Made from material that is optically clear to the laser light in use but rigid enough to withstand the extrusion pressure.]]> Lampbus Plastic Extruder Working Group Wed, 16 Jul 2008 19:03:03 -0400 https://reprap.org/forum/read.php?70,14413,14461#msg-14461 https://reprap.org/forum/read.php?70,14413,14461#msg-14461 Kyle Corbitt Plastic Extruder Working Group Wed, 16 Jul 2008 11:24:30 -0400 https://reprap.org/forum/read.php?70,14413,14451#msg-14451 https://reprap.org/forum/read.php?70,14413,14451#msg-14451
The whole dispense head will be smaller and lighter - higher acceleration & more precision from a lighter, cheaper chassis + motors.

The nozzle will be much closer to the XY assembly so thermal expansion in Z will be insignifcant (currently there is c0.5mm or so variation in Z from hot to cold as I understand it)]]> Lampbus Plastic Extruder Working Group Wed, 16 Jul 2008 06:19:15 -0400 https://reprap.org/forum/read.php?70,14413,14438#msg-14438 https://reprap.org/forum/read.php?70,14413,14438#msg-14438 Kyle Corbitt Plastic Extruder Working Group Tue, 15 Jul 2008 19:10:48 -0400 https://reprap.org/forum/read.php?70,14413,14413#msg-14413 https://reprap.org/forum/read.php?70,14413,14413#msg-14413 Replacement of the heater barrel.

Would it be practical to feed the filament as in Darwin, into an insulator barrel with a window in the side just above the nozzle. Use a laser or similar energy source to DIRECTLY heat the polymer to melt.

It may even be possible to eliminate anti-ooze valves etc by making the extruder 'heat on demand'

THe same wattage will be put in (a few watts currently) as the hot brass system. In fact, less watts will be needed because there wont be any wast heat radiated from the outside of the heater & nozzle. Of course resistive heating is nigh on 100% efficient, and any laser etc isnt going to be, but as we only need a few watts, this wont be important.

The whole assembly could be much shorter because there wont be any heat soak back up the current insulator. and no variation in the melt point in the barrel. Ther will be very little thermal mass so the control electronics will need to tightly match the laser heat input to the required plastic flow. It wuld probably need a thermocouple mounted oppersite and just below the 'window' to feed back the melt temperature.

My thinking is : why heat a lump of brass in order to melt the filament when we could melt it directly and keep all that heat in the filament by making the barrel/nozzle in a good insulator material. (eg Duratec [uk.rs-online.com])


Edit : I just remembered my other heating idea -
Use a utrasonic technique in place of the laser&window. Ultrasonics are used to melt plastic mouldings during product assemly. Usually by 'staking' a small rod which is squashed flat like a rivet head to hold a PCB or case together.

Edit2 : Just thought of another idea - add metalic filings to the filament as it is made. Then use an inductive heating system to heat the filament directly in a non metallic barrel. (I say metallic, because eddy currents in aluminium will cause heating)]]> Lampbus Plastic Extruder Working Group Tue, 15 Jul 2008 09:45:00 -0400