Curious about these recent hot-end failures
Posted by neildarlow
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Curious about these recent hot-end failures December 28, 2013 06:09AM |
Registered: 10 years ago Posts: 541 |
Hi,
A few people have had hot-end failures recently and, apart from those due to known manufacturing problems in the past, I am curious as to what is the cause.
Is it something to do with mechanical loosening of the joint between the hot-end metal and PEEK component or is it a case of convection within the hot-end causing the filament to melt higher-up within the hot-end and cause leakage?
I am looking for causes and ways to avoid these failures. I thought I might attempt auto-tuning the PID parameters but it occurred to me that this might entail heating the hot-end without any extrusion or cooling which might be potentially damaging.
This hot-end design looks interesting being all-metal, not requiring forced cooling, and usable up to 300C. I wonder if this is the way of the future?
Regards,
Neil Darlow
I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.
A few people have had hot-end failures recently and, apart from those due to known manufacturing problems in the past, I am curious as to what is the cause.
Is it something to do with mechanical loosening of the joint between the hot-end metal and PEEK component or is it a case of convection within the hot-end causing the filament to melt higher-up within the hot-end and cause leakage?
I am looking for causes and ways to avoid these failures. I thought I might attempt auto-tuning the PID parameters but it occurred to me that this might entail heating the hot-end without any extrusion or cooling which might be potentially damaging.
This hot-end design looks interesting being all-metal, not requiring forced cooling, and usable up to 300C. I wonder if this is the way of the future?
Regards,
Neil Darlow
I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.
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Re: Curious about these recent hot-end failures December 28, 2013 08:43AM |
Admin Registered: 17 years ago Posts: 7,879 |
When the brass pops out of the PEEK it is the manufacturing fault where the hole in the PEEK was drilled by an off centre drill, so the thread is too shallow. These are all clustered around April dispatch kits and the problem was fixed back then. Typically they fail very quickly but a few have lasted until these holidays it seems.
Leaking is much more rare. I think it is caused by the PTFE tape not being applied correctly. I did repair one for somebody that lives locally and it worked reliably afterwards showing the parts are not faulty but the assembly was somehow.
When they are made correctly they are 100% reliable. I run them contiguously at 250C and they never leak. The only times I have had to replace them is when they get blocked by contaminated filament. I think the massive pressure generated distorts the PTFE liner, so even when they are cleaned out they don't always perform properly.
All metal ones are undoubtedly more robust but are also more expensive to make. Most designs seem problematical with PLA as they don't include the taper that I found to be necessary.
[www.hydraraptor.blogspot.com]
Leaking is much more rare. I think it is caused by the PTFE tape not being applied correctly. I did repair one for somebody that lives locally and it worked reliably afterwards showing the parts are not faulty but the assembly was somehow.
When they are made correctly they are 100% reliable. I run them contiguously at 250C and they never leak. The only times I have had to replace them is when they get blocked by contaminated filament. I think the massive pressure generated distorts the PTFE liner, so even when they are cleaned out they don't always perform properly.
All metal ones are undoubtedly more robust but are also more expensive to make. Most designs seem problematical with PLA as they don't include the taper that I found to be necessary.
[www.hydraraptor.blogspot.com]
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Re: Curious about these recent hot-end failures December 28, 2013 10:58AM |
Registered: 10 years ago Posts: 439 |
It is looking that way. I got an all metal one a few weeks ago and am very happy with it (I just print PLA).Quote
neildarlow
This hot-end design looks interesting being all-metal, not requiring forced cooling, and usable up to 300C. I wonder if this is the way of the future?
Regards,
Neil Darlow
[e3d-online.com] . I use a fan with it but that isn't any problem.
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Re: Curious about these recent hot-end failures December 28, 2013 03:33PM |
Admin Registered: 17 years ago Posts: 7,879 |
Yes the E3D one looks good and most people can print PLA with it but a few say the heat travels up the filament and melts it in the cold section where it them jams as rubbery PLA will grip a straight sided metal tube. I don't know what makes the difference between those that can get it to work and those that can't. I have one myself but have never found the time to try it.
[www.hydraraptor.blogspot.com]
[www.hydraraptor.blogspot.com]
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Re: Curious about these recent hot-end failures December 28, 2013 04:15PM |
Registered: 10 years ago Posts: 541 |
Quote
nophead
I don't know what makes the difference between those that can get it to work and those that can't.
Could long pre-heat times and low extrusion flow rates be a contributing factor? It might be that your standard profiles provide adeqaute safety in these areas and those who depart too far from them run into this problem.
Regards,
Neil Darlow
I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.
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Re: Curious about these recent hot-end failures December 28, 2013 04:18PM |
Registered: 10 years ago Posts: 439 |
While the E3D hotend itself is excellent the fan that I received with it found a new home in the trash can rather quickly. It was noisy and not very strong. I have a 40mm fan fitted with a redesigned mounting: [www.thingiverse.com] . That seems a probable factor to me.
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Re: Curious about these recent hot-end failures December 28, 2013 07:08PM |
Admin Registered: 17 years ago Posts: 7,879 |
You don't need a strong fan to keep a heatsink cool. My all metal hot end only needed to get rid of about 3W.
I don't think the problem is with the heatsink getting too hot. I think the difference probably comes down to the diameter of the PLA. If it is too small then it will have no contact with the cold metal so heat can creep up it. That doesn't matter when you have a PTFE liner as long as it doesn't get to the top. With a metal one it will jam unless it is tapered like a mould.
[www.hydraraptor.blogspot.com]
I don't think the problem is with the heatsink getting too hot. I think the difference probably comes down to the diameter of the PLA. If it is too small then it will have no contact with the cold metal so heat can creep up it. That doesn't matter when you have a PTFE liner as long as it doesn't get to the top. With a metal one it will jam unless it is tapered like a mould.
[www.hydraraptor.blogspot.com]
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Re: Curious about these recent hot-end failures December 31, 2013 10:11AM |
Registered: 11 years ago Posts: 42 |
I had issues with my hot end blocking, so after reading this i decided to replace the liner, and behold, near perfect printsQuote
nophead
The only times I have had to replace them is when they get blocked by contaminated filament. I think the massive pressure generated distorts the PTFE liner, so even when they are cleaned out they don't always perform properly.
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