hotends.com. As with the Mk III-B, a cooling fan will be highly recommended for printing with PLA. Printing, with ABS, will not be a problem.
Until more information is available, the shorter version, with the 36.5mm nozzle holder will still be experimental.
A Mk IV, with an aluminum nozzle, will be made; but, will probably not be sold regularly as the available sizes of raw aluminum bar stock require additional machining in order to manufacture the J-Head nozzle. This, of course, would increase the price. In addition, for best results, the aluminum nozzles should be insulated.
Sunday, October 16, 2011
The short Mk IV prototype has been reported to jam when printing long prints with PLA. A cooling fan is going to be tried in the near future. However, due to the number of vents (3) and their locations, this may be difficult.
Tuesday, October 11, 2011
Today, I have received word that the Mk IV prototype, with the 3 grooved 36.5mm nozzle holder, has successfully printed with PLA. This hot-end was equipped with the standard brass nozzle/heater unit.
Sunday, October 9, 2011
The original Mk IV prototype was built with a new, vented, nozzle holder in order to help cool the liner. The goal of the new nozzle holder was to eliminate the heat-sink used in the Mk III-B.
The nozzle/heater unit was made with a 1/2" x 1/2" (13mm x 13mm) piece of 2024 aluminum bar stock as opposed to the 5/8" x 1/2" (16mm x 13mm) brass bar stock that is normally used. Since a 6.8 ohm resistor has a smaller diameter than the 5.6 ohm resistor, the 6.8 ohm resistor was used. The biggest change, however, is that the PTFE sleeve doesn't go all the way to the tip as with the earlier design. Due to the smaller size, there wasn't enough room so a compromise had to be made. The PTFE sleeve now stops slightly above the heater resistor and the filament is in direct contact with the aluminum from there to the tip.
Even though the test results, of the smaller nozzle/heater unit are positive, I am not going to use move to the smaller design at this time. Instead, the Mk IV will use the tried and proven earlier nozzle/heater unit with a vented nozzle holder. I will, however, continue testing and improving the smaller nozzle/heater unit and plan on making it part of the Mk V.
Monday, October 3, 2011
I received some pictures, this morning, from a customer who designed and printed this great cooling system for the J-Head Mk III-B Hot End. The Mk III-B was used to print the fan mount and it was added it to his carriage afterwards. He also uploaded the instructions and .stl file to Thingiverse.
Sunday, October 2, 2011
Initial testing of the short Mk IV prototype, with a 36.5mm nozzle holder, has concluded that PLA only expands 6mm from the tip.