All metal hotend for recycled plastic

The all metal hotend I use for printing with recycled plastic from my filament extruder (http://forums.reprap.org/read.php?1,205005,205005#msg-205005 )

I used the following:-

A stainless steel hypodermic tube (available at Amazon and Mcmaster's) 0.084" ID
Two m6 brass bolts with holes drilled through
a copper heater block with holes for a 12v/40w stainless steel heater cartridge, a thermistor and for the stainless steel tube and a small hole for a 3 mm bolt to fix the cartridge in the block
a copper round bar with a hole drilled through and 6 groves cut in the copper
6 pieces of flat copper (from 15 mm plumbers copper pipe cut lengthwise and flattened )
a 6 mm brass dome nut for the nozzle with a .5 mm hole drilled in.
6 mm copper washer between the dome nut and the heater block

The first to solder - the heatsink to the stainless steel and at the same time the flat copper to the heatsink.
Once that was done i soldered the heater block to the one brass bolt(head partially filed away) with the stainless steel tube through both and then the other bolt that will be used to fasten the hotend to the mounting plate and the bowden tube.

I used silver solder with a 56% silver content with a handy gas flame and stainless steel flux.The inside of the stainless steel tube and all areas that were not supposed to be soldered were covered with milk of magnesia(one can use tippex as well). The Milk of Magnesia not only keeps the silver solder from flowing beyond the joint, but it seems to protect the stainless from getting that hard black coating from being heated.

After cleaning the hotend the tube was polished with a string and brasso to clear the inside of the tube and the heater cartridge and thermistor installed. I used thermal paste on the cartridge.

Working great with my recycled filament on a delta printer - did not test it with any other plastic.

The first one I made the heater block was insulated with cuttlefish bone held together with silicone. It worked great but you cannot change nozzles without damaging the cuttlefish bone.

Advantages:

One continuous barrel - no gaps for jams
small meltzone
small transition zone
easy to clean - just remove the tube at the top and ram a steel rod down the barrel.
easy to change nozzles
heat up quickly
can be manufactured without any fancy machinery - only need a drill and handy gas.

Edited 2 time(s). Last edit at 05/23/2013 03:14PM by Xabbax.

Nice simple design.

How do you solder the stainless steel tube? I thought lead solder won't stick to stainless steel?
I would put some wood block or a thin metal sheet beneath the heat sink fins to block heat air travelling up from heater block to the fins making the fin hot.

I need to redesign my hot end. The PTFE liner tube is swollen right at the tiny gap between the hot end and the big 16mm PTFE tube.

ThanhTran Wrote:
-------------------------------------------------------
> Nice simple design.
>
> How do you solder the stainless steel tube? I
> thought lead solder won't stick to stainless
> steel?

I use silver solder with a 56% silver content - its melting point(600-800 degrees C) is much higher than ordinary solder and the heat transfer of the silver is better than copper. Use the right flux and temperature for the solder to flow on the stainless.
A bit of practice needed to get it right.


> I would put some wood block or a thin metal sheet
> beneath the heat sink fins to block heat air
> travelling up from heater block to the fins making
> the fin hot.

Thats a good idea to have a shield between the heatsink and the heater block.



>
> I need to redesign my hot end. The PTFE liner tube
> is swollen right at the tiny gap between the hot
> end and the big 16mm PTFE tube.

Thanks for the info. Is it the same solder that is used with copper water pipe?

Xabbax Wrote:

>
> I use silver solder with a 56% silver content -
> its melting point(600-800 degrees C) is much
> higher than ordinary solder and the heat transfer
> of the silver is better than copper. Use the right
> flux and temperature for the solder to flow on the
> stainless.
> A bit of practice needed to get it right.

ThanhTran Wrote:
-------------------------------------------------------
> Thanks for the info. Is it the same solder that is
> used with copper water pipe?

No it is not the same The solder must contain silver - 56% and you must use the right flux with it.

[www.youtube.com]





>
> Xabbax Wrote:
>
> >
> > I use silver solder with a 56% silver content -
> > its melting point(600-800 degrees C) is much
> > higher than ordinary solder and the heat
> transfer
> > of the silver is better than copper. Use the
> right
> > flux and temperature for the solder to flow on
> the
> > stainless.
> > A bit of practice needed to get it right.

Hi Xabbax,

Thanks for the video link. I tried sourcing the SSF 6 solder at HomeDepot, and it had this isntead:

[www.homedepot.com]

Do you think it would work?

I only have a propane torch. Do you think it is hot enough to melt this solder? SSF6 melting temp is 1150*F, and this Stay-Silv 56 solder is melting at 1205*F.

Thank you.

-Thanh

ThanhTran Wrote:
-------------------------------------------------------
> Hi Xabbax,
>
> Thanks for the video link. I tried sourcing the
> SSF 6 solder at HomeDepot, and it had this
> isntead:
>
> [www.homedepot.com]
> 00672839&storeId=10051&langId=-1&catalogId=10053&M
> ERCH=REC-_-product-2-_-100672846-_-100672839-_-N#.
> UaHnIbVtj9U
>
> Do you think it would work?

I do not know the product but it should work - proper cleaning of the parts to be soldered essential and a little practice before doing the real product . Only a little bit of solder is needed for joining - I tended to use to much solder. The solder will flow from the colder section towards the hotter section - If you want the solder to flow just heat the place where you want it a little more than the rest. A propane flame will do the job - the hotend is small enough to heat up. Be carefull not to overheat the stainless - start off with the copper/brass and then the stainless tube - it is very thin. The brass bolt may also melt if you heat it to much.
Practice makes perfect and good luck.




>
> I only have a propane torch. Do you think it is
> hot enough to melt this solder? SSF6 melting temp
> is 1150*F, and this Stay-Silv 56 solder is melting
> at 1205*F.
>
> Thank you.
>
> -Thanh

Reminds me of the Excalibur Hotend.

---

Detlef

Excalibur Hotend

reprapclean32.png

reprapzone.blogspot.de

I just built this hotend following your advice here.

[forums.reprap.org]

It has problem with PLA extrusion, I need help

Thanks

-Thanh