UM2 print head project

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Neotko
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Re: UM2 print head project

Post by Neotko » September 23rd, 2016, 4:57 am

0.2 layer height 210 - 215 & 225 C.

The heat crawls up on each retraction moving the heat up, is a well know effect and the cause of real clogs while using Wood filaments, wood filament moves the heat really fast (because is a filament that is very easy to 'heat' fast) then with each retraction you move heat to a cold area and when you push filament that heat goes in contact with filament that should stay cool. Basically it 'crawls' up.

I'll try the video and photos of the clogs but I'm freaking flooded with stuff to do. I sent internal photos to Gudo has the photos of what happened the last time so for now is good.

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Re: UM2 print head project

Post by gudo » September 23rd, 2016, 5:19 am

Hi all
Hi Neotko
It's been a long time ! I was busy on other project
This may be why it worked for me :roll: , because I always tested PBI with the Bondtech feeder from the beginning, never with the UM origin one.
Anyway my PBI print head still works fine without any problems yet.
Neotko ,   for PBI couplers, do what you want with it, certainly, you have more contacts than me for giving them to someone else for tests.

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Re: UM2 print head project

Post by Iltacitoduca » September 25th, 2016, 12:59 pm

Neotko wrote:0.2 layer height 210 - 215 & 225 C.

The heat crawls up on each retraction moving the heat up, is a well know effect and the cause of real clogs while using Wood filaments, wood filament moves the heat really fast (because is a filament that is very easy to 'heat' fast) then with each retraction you move heat to a cold area and when you push filament that heat goes in contact with filament that should stay cool. Basically it 'crawls' up.

I'll try the video and photos of the clogs but I'm freaking flooded with stuff to do. I sent internal photos to Gudo has the photos of what happened the last time so for now is good.
Hi Neotko!
Still don't understand your explanation... Seem that you talk about "heat" (caused by IR irradiation) like if it was a fluid... really this doesn't make sense for me ...
would be more probable that part of fused material sticks around the filament that it is retracted and then it sticks around the TFM/PBI/PTFE coupler
So, the coupler doesn't heat up but the thin layer of PLA mantain it's temperature giving the clog you talk about

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Re: UM2 print head project

Post by Iltacitoduca » September 25th, 2016, 1:11 pm

gudo wrote:Hi all
Hi Neotko
It's been a long time ! I was busy on other project
This may be why it worked for me :roll: , because I always tested PBI with the Bondtech feeder from the beginning, never with the UM origin one.
Anyway my PBI print head still works fine without any problems yet.
Neotko ,   for PBI couplers, do what you want with it, certainly, you have more contacts than me for giving them to someone else for tests.

Hi Gudo!
I am pretty sure your print head works fine! I made one for myself more or less similar to your.
What I commented before is that watching at your simple design (but effective) (about the interface with the metal part) PLA or ABS can spill trough the fillet and making difficult to remove the metal part
Of course you can simply heat it up and then unscrew it... but then you have to clean the fillet on the PBI... or screwing it back toghether only heating it

so, the reason you broke the PBI was just the spillage of material through the fillet (but you have just unscrewd it without heating)... right?
This is the reason why I wrote that it is a simple design, don't you?

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Re: UM2 print head project

Post by Amedee » September 26th, 2016, 3:51 am

Iltacitoduca wrote:
Hi Neotko!
Still don't understand your explanation... Seem that you talk about "heat" (caused by IR irradiation) like if it was a fluid... really this doesn't make sense for me ...
The problem is the following: when you retract you bring hot filament higher in the head. If you just retract now and then it is not an issue, but if you repeatedly retract a lot, the head starts to be warmer and warmer with the contact of the filament and the temperature starts to build up higher in the head up to that point that filament will come softer and expand higher in the head. If your extruder is not powerful enough to push it through it will clog...
Phil.

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Re: UM2 print head project

Post by Iltacitoduca » September 26th, 2016, 4:18 am

Amedee wrote:
Iltacitoduca wrote:
Hi Neotko!
Still don't understand your explanation... Seem that you talk about "heat" (caused by IR irradiation) like if it was a fluid... really this doesn't make sense for me ...
The problem is the following: when you retract you bring hot filament higher in the head. If you just retract now and then it is not an issue, but if you repeatedly retract a lot, the head starts to be warmer and warmer with the contact of the filament and the temperature starts to build up higher in the head up to that point that filament will come softer and expand higher in the head. If your extruder is not powerful enough to push it through it will clog...
Hi Amedee,
I will invite you to do some calculation about the linear expansion of a filament of PLA ...
http://www.engineeringtoolbox.com/linea ... -d_95.html

Taking in account that the coefficients of linear thermal expansion even if it was bigger than 200((10-6 m/(m K)) it will give an insignificant change of diameter at a print temperature of 200°C..


I take more in consideration the fact that when retracting the filament part of it will settle On the coupler, reducing the internal diameter of the same...
I will left apart this theory of heating crawling because it's misleading IMO
Cheers

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Re: UM2 print head project

Post by Amedee » September 26th, 2016, 4:51 am

Iltacitoduca wrote: I will invite you to do some calculation about the linear expansion of a filament of PLA ...
http://www.engineeringtoolbox.com/linea ... -d_95.html
Linear expansion is pure thermal expansion -- that is what happens to the filament when it gets hotter, and I agree it is not significant.

But that does not take in account that at higher temperature it gets softer and starts to soften/melt, so it does not expand by the temperature itself, but deforms with the pressure from the extruder (you can even extrude PLA in the 190-200°C range).
So the more you retract, the more you bring softer filament higher in the head which is more prone leave residue the coupler on one side (as you mention), but also combined with and overall warmer and softer filament which will expand due to pressure.
Phil.

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Re: UM2 print head project

Post by Iltacitoduca » September 27th, 2016, 4:23 am

Amedee wrote:
Iltacitoduca wrote: I will invite you to do some calculation about the linear expansion of a filament of PLA ...
http://www.engineeringtoolbox.com/linea ... -d_95.html
Linear expansion is pure thermal expansion -- that is what happens to the filament when it gets hotter, and I agree it is not significant.

But that does not take in account that at higher temperature it gets softer and starts to soften/melt, so it does not expand by the temperature itself, but deforms with the pressure from the extruder (you can even extrude PLA in the 190-200°C range).
So the more you retract, the more you bring softer filament higher in the head which is more prone leave residue the coupler on one side (as you mention), but also combined with and overall warmer and softer filament which will expand due to pressure.

Ok, finally we are "on the same wavelength" ;)
So there is still a problem... Inside the coupler the temperature doesn't reach such high level (talking about PBI of course but even PTFE should not) as it remains practically 20-30°C more hot than ambient temperature .. Perhaps due to its intrinsic characteristics (a bit better coefficient of thermal conduction plus its resistance to high temperature compared to PTFE)
Thermal Properties of Plastic Materials:
http://www.professionalplastics.com/pro ... erials.pdf

And if the problem is the internal diameter of the coupler? I mean, when filament push its "melted side", if there is room to go back, it will!

I have recently made a coupler with internal diameter of 3,1 instead of 3,2 and it seems less predisposed to create the molten material collar due to retraction accumulation (too complicated to explain ... but I think you understand)
(have noticed about it... around the filament I mean... near to the contact between metal and coupler?)

Anyway this is just a part of the problem because the deformation introduced by the feeder on the filament itself complicates things...
(also the curvature of the filament itself helps to create friction problems)

oh! about PLA as you can see its not my preferred material :-D
And I think that printing PLA need in find a tradeoff that then are not useful, and sometimes harmful, with other materials IMO

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Re: UM2 print head project

Post by drayson » October 1st, 2016, 10:48 am

Guys,
I read through the posts here and also at UMForum and I´m really impressed.
I already got a hint from gudo where to source... thank you!

I would be very interesting in the PBI stuff to be used on my UMO and I'd like to ask about your opinion... (Amedee?, LePaul?, anybody else who has experience with the UMO?)
Do you think, just replacing the part (https://github.com/Drayson80/BOM-Ultima ... -Z1P-A.PDF) made from PEEK by PBI would be sufficient? But there is the brass coupler also reaching a few mm into the PEEK...

Another thing is that 305mm of PBI is quite a lot material and € so is anybody having app. 50mm of this stuff laying around and is willing to resell it?

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Re: UM2 print head project

Post by Amedee » October 1st, 2016, 11:20 am

Thinking about that quiet a lot... most new materials are in a printing range just above what the UMO print head can do.

Replacing the peek only is probably not good enough, the coupler won't survive long -- I can print ABS fine at 245°C with the PEEK, but coupler is the week part. I was more thinking of having just the coupler in PBI or making a single part replacing both the PEEK and the coupler...

But I don't have easy access to a lathe and not too much time these days to experiment (I still have plenty of todo's on the firmware side ;) )
Phil.

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Re: UM2 print head project

Post by drayson » October 1st, 2016, 11:43 am

Amedee wrote:Thinking about that quiet a lot... most new materials are in a printing range just above what the UMO print head can do.

Replacing the peek only is probably not good enough, the coupler won't survive long -- I can print ABS fine at 245°C with the PEEK, but coupler is the week part. I was more thinking of having just the coupler in PBI or making a single part replacing both the PEEK and the coupler...

But I don't have easy access to a lathe and not too much time these days to experiment (I still have plenty of todo's on the firmware side ;) )
Right, I forgot the PTFE coupler.
To ave only one piece might be possible. Even with a few ribs on the outer side to enlarge the cooling surface...
I have a micro lathe but I guess it´s too weak to machine PBI so maybe I could find somebody in my company machining it.

The raw piece for 1 pc. needs to be app. 18mm indiameter/30mm lenght to be machined...

Maybe it could also replace the heat insulator tube (brass tube) and be screwed directly into the alu heater block...

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Re: UM2 print head project

Post by drayson » October 1st, 2016, 11:45 am

PS: I hate those drawings released by Ultimaker - those are so unusefull for machining - no tolerances, no propper measures,...

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Re: UM2 print head project

Post by drayson » October 1st, 2016, 12:20 pm

Made a quick sketch how the part could look like... see attched...
Dimensions of
- raw material: diameter 20mm, lenght 40mm, but could be less depending on the skills of the machinist :-)
- machined: diameter 16mm, lenght 35mm
Please note that the lower part has a M6 thread... @gudo: is this possible to be machined with this material??

Would be a 1:1 replacement of 3 parts
PBI_UMO_1.JPG
V2 with cooling ribs...
PBI_UMO_2.JPG

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Re: UM2 print head project

Post by Amedee » October 1st, 2016, 3:20 pm

Nice!

Not sure though that suppressing the brass pipe is a good idea as it it an heat break. Also you would have to screw the nozzle against the PBI each time you change the nozzle...

And it is probably easier to tap a thread inside the PBI than machine one outside ;)

(I am NOT a specialist in thermal conductivity, so this is just gut feeling)
Phil.

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Re: UM2 print head project

Post by Neotko » October 1st, 2016, 8:48 pm

Yeah that barrel is supposed to stay hot, I made a year ago some barrels on titanium (lost good cash there) and had them WS2 coated. It didn't work since the heat conductivity change and allowed pla to stay cold, it didn't clog, but did need a tremendous amount of force to extrude.


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