Which nozzle will do better?

I am thinking about a new nozzle for my organ pipe hotend.

Up to now I use this one.



Using my center drill I plan to make this one.



Would it be better?

---

Detlef

Excalibur Hotend

reprapclean32.png

reprapzone.blogspot.de

looks similar in concept to this [www.reprap.org]. try them both and compare. the only issue i have had with my design is it takes a little longer to heat up to temp.

both are still in the hot zone, your second design will allow for more surface area to heat up feedstock faster. the 3mm section should be a little longer if the hot zone will heat that area as well. this is important the 3mm section must heat the pla or abs to where its is easy to push thru. then the smaller sizes of bores will transfer the remaining heat and get it flowing.

Surely the second design has a lower surface area for heat transfer as the radius decreases along the length. Whilst the surface area to volume ratio is imroved in the second design I'm not convinced this is the important parameter as the residence time in the smaller volume will be shorter (assuming the same volumetric flow of plastic) but I'd be interested in knowing for sure as I'm thinking of building a (slightly modified) Detlef design over Christmas!
Would the second design have better ant-ooze performance?

PS is the length of the final (0.5mm) section deliberately longer in the second version (if so why) or is it just how it's drawn?

Edited 2 time(s). Last edit at 12/07/2012 03:36PM by Logrod.

Logrod Wrote:
-------------------------------------------------------

> PS is the length of the final (0.5mm) section
> deliberately longer in the second version (if so
> why) or is it just how it's drawn?

No. That's mere coincidence.

---

Detlef

Excalibur Hotend

reprapclean32.png

reprapzone.blogspot.de

second design also allows faster heating of feedstock, and better control of oozing. the smaller radius actually allows heat to transfer more quickly in the sections that are narrower.

Hi Detlef,

Using a centre drill is an interesting idea for creating that internal profile. I had considered doing something similar for our all-metal stainless insulated hot end nozzles in the brass nozzle portion by using gradually decreasing diameter drill bits, or cutting a custom reamer for the job. But I rejected both ideas due to the amount of labour.

I have recently come into possession of an array of centre drills down to extremely small ones. So I will give this a go and see what effect on performance can be achieved.

Regards,
Sanjay

if you want to get the internal lead up to the orifice a little smoother, theres an interesting trick you can do with a 3mm drill being used like a boring bar, it's the kind of thing you do on a cnc lathe really only by properly skilled programmers/operators, just make sure you use a proper cobalt bit not a HSS one

nice trick but i don't think the precision is worth the time it takes to do the bore.

also one trick i do to ensure drill bits only go as deep as wanted. place tape or a drill stop at the shank of the bit, set it, or place tape by comparing to the side of the part you are drilling. also big concern is your part can only be as long as your smaller bits are long.

perhaps the separate sections will have a capacitive effect on imperfect filament diameter keeping a more constant extrusion?