Sunday, July 15, 2012

 

Water-cooled Hot End


At RepRapPro we've been experimenting with a water-cooled head.  Our fan-cooled heads are, we reckon, one of the best designs out there, having a very short melt zone and high-power to respond to changes in load.  But the fan is slightly bulky.
 


This is much lighter and more compact, and the cooling is more efficient.  It consists of a brass block that replaces our normal aluminium cooling block that attaches to the fan.  The brass has water channels drilled in it, and some soft silicone tubing connecting it to a small 12V gear pump.  The inflow and outflow temperatures are only a fraction of a degree different, meaning that multiple heads could be chained in series and all cooled by the same flow.

The CAD file for the cooling block is here on Github.  Though this is work in progress and the design may well change.

Here's a vid:


RepRap water-cooled head from Adrian Bowyer on Vimeo.

Comments:
Crazy ^^
 
Neat!!!
 
Well, this design is not less bulky: the bulky part (the cooler -> the pump) is moved away from the extruder.
Nice design anyway, more efficient for sure! Keep going!
 
I thought about doing this a while back, but at the time my machine was made of mdf and my electronics were at the bottom. A leak would not have been pretty.

I may have to try this again in the future.
 
@marcoalici - I meant less bulky where it matters :-)
 
Do you put anything in the water to prevent pond life developing?
 
Love it! :-)
 
This comment has been removed by the author.
 
With Myles report in mind is it necessary in order to increase energy extraction and reduce the space claim to enable support for multi colour extrusion?

Some reflective tape over the tubes might be considered or perhaps a 90° bend on the metal tubes to help reduce radiant and convected energy from the heater block degrading the silicone tubes?

If the connection can be done from the top, then perhaps it can be a RepRap adaptor part between the tubes and the block?

Perhaps a simpler cavity or no cavity is possible if the RepRap part has channels?
 
Looks great.
Any hints on how far the cooler is way from the hot end?
And what about the feed tube ... is this brass or steel, do you have any PTFE liner (and where does it end) ?

I'm trying to collect as much info as possible - just heard from another builder who tested with water cooling but now the hole thing gets too cold ...
 
i'm also working on a water-cooled hot end, but passive. I'm trying to reduce the heat zone to the very tip, and the water-filled cylinder is used to make sure that the PLA will stay below 60C. I'm waiting some nichrome wire to start testing.
Nice job but even more power consumption?
 
I can not see the detail of the construction so my comment may be in error.
A brass or aluminium block, lined with a PTFE tube and kept at a temperate level will suffice, as it prevents the molten filament from creeping back and blocking the passage when the head is hot, but idle for a while.
We all know that the PTFE insulation block is effective, but, when the centre is overheating and creeping back up the tube the block has no means to cool the centre, in fact, because it is a good insulator it is holding the heat in and allowing it to build back from the hot end.
On this basis the circulating water temperature need only be a few degrees below melting temperature of the filament being used, if it is too cool you are overworking the heater unnecessarily and wasting precious power.
My compliments to the creator of this developement, I shall be following in your footsteps quite soon.
 
It would be great to combine this with a reprap produced peristalic pump http://www.thingiverse.com/thing:8652 , that way you could very acurately control the volume of water delivered to the head, and no impellor assembly etc for leaks or breakages, just a piece of tube and two rollers that will need to be swapped out occasionally.
 
I don't know how the cooling properties compare but you might look at using mineral oil instead of water. It is used in a lot of liquid cooled desktops now and has a couple of advantages. It doesn't conduct electricity in the case of a leak and it will not go stagnant or allow the growth of micro-organisms. Great work, I just lost my extruder because of excess heating high up in the barrel and this would have prevented that failure mode.
 
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