kris
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Posts posted by kris
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I would unscrew the fans and the metallic bracket that holds them in place. Then you can bend the metallic bracket back to its original shape.
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The same happened to me when changing from PLA to ABS. Clogged the nozzle which led to heavy underextrusion. I had to completely take the extruder apart (carefully!) and soak the nozzle in acetone in order to clean it.
Something happens when the ABS gets mixed with the residual PLA. I am sticking to ABS now.
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Oh wow cool work Kris! Please keep updating whether there's a difference in print quality before and after.
There sure is. Especially for large ABS parts a closed chamber is inevitable, see here http://umforum.ultimaker.com/index.php?/topic/5225-managed-to-overcome-warping/
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That is also a concern I had. But nothing has happened so far. For ABS I even use 110°C for the bed in order to avoid warping.
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Hi all
Here is my version of a closed chamber for the UM2.
The acrylic plates I used are standard sized and glued, hence no cutting required. I spent roughly 35€ on all parts. The rear of the top lid will be covered with cloth.
The door closes with a magnet. I will add a rubber seal to the door and will have to modify and reprint the hinges.
I also have plans to add an IP camera and hock it to the door.
I plan on uploading all plans and material sources if there is any interest.
Cheers Kris
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Did you always have this problem or did it occur suddenly?
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ABS extrudes at 260°C. What happens to residual PLA at that temperature if I switch from PLA to ABS?
Could this potentially clog the nozzle?
Just a thought... :-P
Because I noticed many people experience the problem after changing material, including myself. So maybe there is nothing wrong with the hot end after all.
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Support removal was ok, cleanup and sanding a pain in the butt...
I did the model mainly in Scupltris, with some help from Meshlab.
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Finished this print today (UM2):
ABS white
0.1mm layer thickness
50mm/s
bed @ 110°C in closed chamber
fans off
Sword & horn printed separately
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Wonderful. Also very interested in the results :-)
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Zum bearbeiten von STL Dateien bietet sich auch Meshlab an. Dann einfach mal nach Meshlab und 'join meshes' googeln. Gibt zahlreiche gute Tutorials auch bei Youtube.
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I agree the current heat sink is not helping to cool the PTFE part. It does, however, help in keeping the lower aluminium block relatively cool. I think the cooling of the isolator (the hollow bolt) needs to be improved - for that, another heat sink is needed. My guess is - it's not optimal to combine the two into one. The aluminium block absorbs a lot of heat from the nozzle unit and I'm afraid it will remain quite hot.
You might be correct. Would be interesting to try this out.
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My guess is that the current heat sink is in the wrong place. It is not efficient in preventing heat moving into the PTFE part. It is also too far away.
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I think if the heat sink touches the aluminium block that is not a bad thing. This just increases the cooling area.
Neglecting the rear fan is kind of conservative I guess, since it will improve convection. Now that I think about it, I do not really understand the slotted aluminium block at the back. To me it seems as if it is too far away from the heat source. I think the new heat sink could replace that component completely and reduce temperature in the upper part of the extruder considerably.
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Here are the results. I ran a few different models to test out different ideas to knock down the temperature in the PTFE bushing. I did not take into account forced convection (from the fan). I achieved the best results with a heat sink at the top, as originally proposed. In addition reducing the contact area between the PTFE bushing and the remaining components helps. I managed to reduced the temperature in the bushing from 170°C to 110°C (model ptfe_v2_p). I measured the temperature a few millimetres away from the interface to the nozzle, because here the temperature is pretty much unchanged due to the proximity to the heat source.
I have tried not to alter existing components, in an attempt to create a method that can be retrofitted. Currently the heat sink that I added does not fit into the setup. There is too little space. So it has to be reduced in size somewhat.
Important to note: The TG of ABS is around 104°C. Previously we were well above that in the PTFE bushing which means the ABS will loose most of its mechanical properties before it even enters the nozzle. At the moment the spring pushes the bushing firmly against the nozzle. There will be a certain heat transfer. If we would allow for a little gap between these components the temperature in the PTFE bushing will remain around 100°C. See below. Not sure if that would create other problems. But sure worth a try. The bushing would have to rest against the steel nut.
Feedback is most welcome
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The sketch seems to add heat conductive material between the heater element and the top of the hot end isolator. I would keep the conductive material to its minimum - as i is more or less in the original design. Instead, the added heat dissipation at the top is a good idea - maybe it could continue higher on the sides of the PTFE part? Not front or rear though, as it would likely prevent air flow around the PTFE.
Absolutely. Will show the results here soon.
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Yes, you guys are correct. The idea was basically to pull away heat from the PTFE component. PTFE has two advantages; it has low friction and it can handle high temperatures. A significant drawback is the thermal expansion which might cause under extrusion. My hope is that we can overcome these trouble with minimum effort, i.e. without replacing existing parts.
I have hence added a heat sink in the analysis in an attempt to draw heat away from the PTFE. And it seems to work very well. I will post the calculations here in short while. Have a short business trip tomorrow. That heat sink is just an add on that will not require any changes to the existing components...I hope :???:
I think that ultimaker's initial intention was to use the aluminium structure of the extruder as heat sink. That is the reason for the 3rd fan I guess, in order to improve convection. But apparently it is not efficient enough in doing so.
What do you think, I might be wrong here.
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Maybe if there was a heat sink before the nozzle meets the PTFE fitting. This way the heat could be led away from the fitting. Friction would most likely increase.
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Think it's one of the best hotends on the market. I'm just not that keen on modifying a brand new UM2 -_-
me neither :???:
My hope is that existing parts can me modified and optimized to overcome the problem. Apart from under extrusion I am very happy with the UM2.
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That E3D hotend looks great. There are a few things that stand out:
1.There is very little material connecting the actual hotend with the upper part that meets the bowden tube. Thus heat flow to the upper part will be limited.
2. The upper section has additional large cooling fins
3. All metal means that there is limited and uniform thermal expansion throughout the design
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@3poro: adding additional heat sinks would probably help to reduce the temperature. The effect could easily be measured. Using the space for the second extruder for the heat sink is a good idea. Does anybody know if UM is trying something like this already?
@EldRick: I noticed your post. Do you know if there is a measurable effect?
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I think convection is not doing much to cool the PTFE fitting. A heat sink that leads away heat from the part is far more effective I guess. Maybe using heat transfer paste between the aluminium parts of the extruder helps a bit? Or adding another small heat sink at the front.
Another stupid idea; Could the flow of the middle fan be reversed? At the moment it blows warm air from the heat sink onto the PTFE fitting.
I think the PTFE fitting is getting bigger and bigger because it gets filled with PLA/ABS which will prevent it from contracting back to its original diameter. And it will work its way up through its metal casing. The spring will not be able to push it back. A gap will form between the fitting and the nozzle.
Yes, black anodization might help as well. As so often, a combination of improvements might give us the results we are looking for. The simple things can be tried first.
Any chance the guys from UM could try this? Maybe they already have :-P
Printer stops extruding PLA
in UltiMaker 3D printers
Posted
I had exactly the same problem once. Nothing would help, until I completely took apart the extruder and cleaned it of all residual material. There might be some contamination that travels up and down the nozzle. Actually you only have to clean the nozzle and the PTFE bushing.