I purchased a few 6.8 ohm resistors to see if I could reduce the size of the J-Head nozzle heater block any further. I managed to reduce the heater block foot print to 13mm x 13mm (1/2" x 1/2"). While I was at it, I added some 0-80 set screws in order to secure the heater resistor and thermistor. The set screws are stacked in the holes in order to lock them in place. This prototype weighs 3.1 grams, without the heater resistor, set screws, and thermistor. If a fluted nozzle holder is used, this may make it possible to make an entire hot-end that weighs around 14 grams. The tip, of the nozzle, needs a little improvement as I need to grind a custom tool to make the smaller tips. But, my real goal was to see if everything could be fit into such a small foot-print. So, I am not concerned about that at this time. I hope to be sending this prototype out for testing within the next 2 weeks. Since I just sent out my fluted nozzle holder, for testing, I'll have to make another one as it wouldn't be right to have such a small, light, nozzle without a light nozzle holder. Regards, Brian https://reprap.org/forum/read.php?70,95778,95778#msg-95778 Tue, 13 Oct 2026 01:08:47 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?70,95778,96019#msg-96019 https://reprap.org/forum/read.php?70,95778,96019#msg-96019
The second test nozzle varied 2-3 degrees, according to the software.

Regards,

Brian


camblonie Wrote:
-------------------------------------------------------
> What is a normal temp range? I'm using a J-Head
> and I simply pushed the resistor into the hole.
> The fit was very snug and some material was
> actually shaved off. Right now I'm seeing
> fluctuations between +-5deg as I print.
> S]]> reifsnyderb Plastic Extruder Working Group Tue, 30 Aug 2011 07:29:06 -0400 https://reprap.org/forum/read.php?70,95778,95981#msg-95981 https://reprap.org/forum/read.php?70,95778,95981#msg-95981
I'll try to find out for you and post it here.

I may be able to tighten up the fit on this as well. The reason it is a little lose on this nozzle may be due to the drill bits. I have a really cheap set of fraction, letter, and number drills that I use for making a prototype. They don't hold their edge very well and are not all that accurate.

The nozzle you have was made with a more expensive and higher-quality drill bit. So, it should have a better fit. I don't use the cheap drill bits for production runs as they are not reliable and don't stay sharp.

Regards,

Brian


camblonie Wrote:
-------------------------------------------------------
> What is a normal temp range? I'm using a J-Head
> and I simply pushed the resistor into the hole.
> The fit was very snug and some material was
> actually shaved off. Right now I'm seeing
> fluctuations between +-5deg as I print.
> S]]> reifsnyderb Plastic Extruder Working Group Tue, 30 Aug 2011 00:38:18 -0400 https://reprap.org/forum/read.php?70,95778,95975#msg-95975 https://reprap.org/forum/read.php?70,95778,95975#msg-95975 S]]> camblonie Plastic Extruder Working Group Mon, 29 Aug 2011 23:14:16 -0400 https://reprap.org/forum/read.php?70,95778,95920#msg-95920 https://reprap.org/forum/read.php?70,95778,95920#msg-95920
The set screw really isn't that tight against the resistor and is kept tight by another set-screw in behind it. But, you do have a really good point regarding the possibility of damage and shorting out. (I didn't think of that.) Maybe a piece of aluminum foil should be placed between the set-screw and the resistor?

Either way, furnace gasket cement, aluminum foil, etc., will need to be added to improve the thermal coupling. Even though the hole is pretty tight, you can still hold it up to the light and see the gap....which is a problem.

Maybe the thermistor set-screws would be more useful than the resistor set-screws?

Regards,

Brian







Andrew Diehl Wrote:
-------------------------------------------------------
> You do not want to secure the resistor with a set
> screw. The enamel coating can easily be
> deformed/damaged at higher temperatures by the set
> screw and short out the resistor. Some high
> temperature furnace gasket cement around the
> resistor works well to keep it in place, as an
> alternative. Also makes for better thermal
> coupling.]]> reifsnyderb Plastic Extruder Working Group Mon, 29 Aug 2011 15:20:16 -0400 https://reprap.org/forum/read.php?70,95778,95911#msg-95911 https://reprap.org/forum/read.php?70,95778,95911#msg-95911 Andrew Diehl Plastic Extruder Working Group Mon, 29 Aug 2011 13:33:44 -0400 https://reprap.org/forum/read.php?70,95778,95778#msg-95778 https://reprap.org/forum/read.php?70,95778,95778#msg-95778 J-Head nozzle heater block any further. I managed to reduce the heater block foot print to 13mm x 13mm (1/2" x 1/2"). While I was at it, I added some 0-80 set screws in order to secure the heater resistor and thermistor. The set screws are stacked in the holes in order to lock them in place.

This prototype weighs 3.1 grams, without the heater resistor, set screws, and thermistor. If a fluted nozzle holder is used, this may make it possible to make an entire hot-end that weighs around 14 grams.

The tip, of the nozzle, needs a little improvement as I need to grind a custom tool to make the smaller tips. But, my real goal was to see if everything could be fit into such a small foot-print. So, I am not concerned about that at this time.

I hope to be sending this prototype out for testing within the next 2 weeks. Since I just sent out my fluted nozzle holder, for testing, I'll have to make another one as it wouldn't be right to have such a small, light, nozzle without a light nozzle holder.

Regards,

Brian]]> reifsnyderb Plastic Extruder Working Group Sun, 28 Aug 2011 14:07:46 -0400