Water cooled all metal hotend
Posted by Xabbax
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Water cooled all metal hotend October 02, 2013 08:41AM |
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 lengthwise
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 hold the cartridge in the block
a copper tube with a hole drilled through
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
I soldered the heater block to the one brass bolt(head partially filed away) with the stainless steel tube through both, then the copper tube to the stainless tube 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.
The heater block insulated on top with cuttlefish bone.
More pictures on the website listed below.
Edited 2 time(s). Last edit at 10/02/2013 08:45AM by Xabbax.
You only learn when you change your mind.
[www.deltaprinter.co.za]
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Re: Water cooled all metal hotend October 02, 2013 04:37PM |
Nice, Xabbax! Thanks for sharing! 
There is a description of a simple way to do this here.
Quote
Jasper1984
Drilling a 0.5mm hole in that domed nut sounds hard
There is a description of a simple way to do this here.
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Re: Water cooled all metal hotend October 04, 2013 03:33PM |
@Xabbax
Well done
Your design looks like a very accessible way to build a DIY water-cooled hot end. Keep up the good work!
@cozmicray
I'll be honest and say that you clearly have no idea what you are talking about.
It can be a good thing to question someone's designs, but do not just jump in and start attacking a person's design if you do not yet understand every aspect of it.
First of all, you claim that the QUBD hot end works very well without water-cooling even though it is known to be one of the most unreliable all metal hot ends on the market. However, the failure of the QUBD extruder is not a result of the fact that it is not water-cooled, but rather due to the lack of internal polishing on the SS heat break, which an essential facet of reliable all metal hot ends.
The hot end is arguably the most complex aspect of 3d printers as it deals with the tricky business of melting and extruding plastic filament. To understand the design features of hot ends, you must have a basic knowledge of the thermal properties of thermoplastics, specifically the way they behave at their glass transition temperature (Tg). At temperatures below Tg, thermoplastics retain their hard, solid consistency (as we see in plastic filament). As the temp rises above the Tg of the thermoplastic, its consistency changes from solid to rubbery and it begins to expand. If you continue to increase the temperature to the melting temperature (Tm) the consistency will change from rubbery to liquid. The plastic filament enters the hot end in its solid state and exits in its liquid state. Within the hot end there is the crucial thermal transition from solid to rubbery to liquid. In its rubbery state, the plastic will expand and grip the inside of the hot end and will resist extrusion/retraction and thus increase the likelihood of the hot end jamming. As a result, the hot end developer makes an effort to mitigate this problem by reducing the area that the rubbery plastic can grip and cause jams (by shortening the transition zone), and by reducing the friction between the rubbery plastic and the interior walls of the hot end (by polishing the internal pathway within the hot end). This rubbery filament problem is more apparent when extruding PLA which has a very low Tg (about 60C).
Ok, RepRap hot end designers may not be professional thermal engineers, but they certainly take into account the basic thermal properties of metals and thermoplastics. Every successful all metal hot end design (regardless of whether it is water-cooled or air-cooled) has a similar set of design features: a short thermal break that is internally polished and machined from a metal with low thermal conductivity (SS is most often the metal of choice), a "hot side" that consists of the heat block which is machined from a metal with high thermal conductivity (brass, copper, aluminium), and a "cold side" which consists of either a heat sink machined from a metal with high thermal conductivity (usually aluminium) with a fan blowing over it or some sort of water-cooled sleeve.
Each of these aspects of reliable all metal hot end design is specifically aimed at regulating the temperature of both the "hot side" and "cold side" and preventing heat flow across the thermal break. Since you claim have worked in designing spacecraft, I will give you the benefit of the doubt and assume that you know all of these basic properties of metals and can now understand the workings of Xabbax's design.
It's ok to not understand how something works, but just don't try to justify your ignorance by putting down a design that you can't fathom.
Eric
Well done
Your design looks like a very accessible way to build a DIY water-cooled hot end. Keep up the good work!
@cozmicray
Quote
cozmicray
No I haven't designed a 3D printer hot end
but
I have been involved in a lot of designs for spacecraft
Keeping hot things from getting cold, keeping cold things from getting hot
Isolation and insolation is the key Preventing heat flow in or out.
Why does a QU-BD type extruder, with hotend 1.5" from mechanics work so well
--- without water cooling
A fan blowing on gear and motor provides good cooling
All these Rep Rap extruders are NOT DESIGNED by Thermal engineers
but kludged together by garage mechanics
I have nothing against Garage inventors
--- but we really need here is some real design, development and testing
of a thermal extruder design.
I'll be honest and say that you clearly have no idea what you are talking about.
It can be a good thing to question someone's designs, but do not just jump in and start attacking a person's design if you do not yet understand every aspect of it.
First of all, you claim that the QUBD hot end works very well without water-cooling even though it is known to be one of the most unreliable all metal hot ends on the market. However, the failure of the QUBD extruder is not a result of the fact that it is not water-cooled, but rather due to the lack of internal polishing on the SS heat break, which an essential facet of reliable all metal hot ends.
The hot end is arguably the most complex aspect of 3d printers as it deals with the tricky business of melting and extruding plastic filament. To understand the design features of hot ends, you must have a basic knowledge of the thermal properties of thermoplastics, specifically the way they behave at their glass transition temperature (Tg). At temperatures below Tg, thermoplastics retain their hard, solid consistency (as we see in plastic filament). As the temp rises above the Tg of the thermoplastic, its consistency changes from solid to rubbery and it begins to expand. If you continue to increase the temperature to the melting temperature (Tm) the consistency will change from rubbery to liquid. The plastic filament enters the hot end in its solid state and exits in its liquid state. Within the hot end there is the crucial thermal transition from solid to rubbery to liquid. In its rubbery state, the plastic will expand and grip the inside of the hot end and will resist extrusion/retraction and thus increase the likelihood of the hot end jamming. As a result, the hot end developer makes an effort to mitigate this problem by reducing the area that the rubbery plastic can grip and cause jams (by shortening the transition zone), and by reducing the friction between the rubbery plastic and the interior walls of the hot end (by polishing the internal pathway within the hot end). This rubbery filament problem is more apparent when extruding PLA which has a very low Tg (about 60C).
Ok, RepRap hot end designers may not be professional thermal engineers, but they certainly take into account the basic thermal properties of metals and thermoplastics. Every successful all metal hot end design (regardless of whether it is water-cooled or air-cooled) has a similar set of design features: a short thermal break that is internally polished and machined from a metal with low thermal conductivity (SS is most often the metal of choice), a "hot side" that consists of the heat block which is machined from a metal with high thermal conductivity (brass, copper, aluminium), and a "cold side" which consists of either a heat sink machined from a metal with high thermal conductivity (usually aluminium) with a fan blowing over it or some sort of water-cooled sleeve.
Each of these aspects of reliable all metal hot end design is specifically aimed at regulating the temperature of both the "hot side" and "cold side" and preventing heat flow across the thermal break. Since you claim have worked in designing spacecraft, I will give you the benefit of the doubt and assume that you know all of these basic properties of metals and can now understand the workings of Xabbax's design.
It's ok to not understand how something works, but just don't try to justify your ignorance by putting down a design that you can't fathom.
Eric
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Re: Water cooled all metal hotend October 04, 2013 06:20PM |
@knowbusiness
No problem
It's best if everyone understands the basics of hot end development so that people can judge designs according to their theoretical functionality rather than aesthetics/hype. This was a huge problem when Jo released his original PrusaNozzle which had some serious design flaws but happened to look beautiful and was of course made by the designer of the Prusa Mendel! Many people ended up buying Jo's hot end based on the aesthetics/hype which unfortunately resulted in a lot of unhappy people and a chip on Jo's reputation. Bad result for all parties involved
Even though the PrusaNozzle MKII design seems to address these flaws, many people are steering clear of it based on the negative experience of MKI users. It's unfortunate, but hopefully people can now use this information to more accurately judge the merits of a design.
I plan on releasing my own all metal hot end design sometime soon and I hope that people in the community will be able to provide constructive feedback, not the kind of ignorant responses that resemble cozmicray's posts.
BTW I am impressed with your work in hot end development. While I have never used an SG2 hot end, I have heard great things about it
Keep up the good work everyone!
Eric
Edited 1 time(s). Last edit at 10/04/2013 06:24PM by RP Iron Man.
No problem
It's best if everyone understands the basics of hot end development so that people can judge designs according to their theoretical functionality rather than aesthetics/hype. This was a huge problem when Jo released his original PrusaNozzle which had some serious design flaws but happened to look beautiful and was of course made by the designer of the Prusa Mendel! Many people ended up buying Jo's hot end based on the aesthetics/hype which unfortunately resulted in a lot of unhappy people and a chip on Jo's reputation. Bad result for all parties involved
Even though the PrusaNozzle MKII design seems to address these flaws, many people are steering clear of it based on the negative experience of MKI users. It's unfortunate, but hopefully people can now use this information to more accurately judge the merits of a design. I plan on releasing my own all metal hot end design sometime soon and I hope that people in the community will be able to provide constructive feedback, not the kind of ignorant responses that resemble cozmicray's posts.
BTW I am impressed with your work in hot end development. While I have never used an SG2 hot end, I have heard great things about it
Keep up the good work everyone!
Eric
Edited 1 time(s). Last edit at 10/04/2013 06:24PM by RP Iron Man.
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