Um2 hotend design questions

[Meduza]

The only reason for that the steel coupler is screwed all the way in on all pictures is to compress the spring more and apply higher force to the PTFE+I2K sandwich.

I do not have any cheap source for "trusted" PT100's, but i did use one of these on my UM2 for six months with no problem and no temperature changes needed:
http://www.ebay.com/itm/PT100-0-2-Class ... 635syewU7g

[Neotko]

Thanks Meduza!

Perfect. Then I must just keep a strong constant preassure to avoid anymore leaks.

Nice link! I'll get 3 to have backup!

[Meduza]

Excessive pressure will cause the PTFE to prematurely wear tough, so do not put a crazy amount of force on it.

[Neotko]

That's the problem I see. What's too much preassure? That the steel coupler needs force to rotate or that it can't rotate by using a screwdriver with two fingers? Because with just that I got leaks. So now I'm going with 3 fingers and normal force, not overdoing it won't move.

[Neotko]

Well I think I learned a very important leason. I took out the pt100 from the hotend and did stickit to the center bed glass and raise the temp to 75C. Waited 15mins after reaching the temp and the hotendpt100 was saying 52C and the bed was 73-75C with my thermal camera pointing to a bluetape near the pt100. So I been printing with almost 25C less... Impressive...

Changed the pt100 with my last spare one and well now it's printing just nice... I'll have to run some glossy surface test but so far so good.

[Neotko]

Well today though all was assembled well but clearly it wasn't. There was some material stick to the i2k that at 245C printing carbon moved and left a gap. So I had to take all out again, do a toon of external atomics to clean the threads, inside, steel coupler, as much as I could. Then I tested assembling it this time without the nozzle so I could put some light on the bowden and be able to see the gap between the heater/i2k/ptfe. With the help of a periscope from my son (a toy) and I was looking while rotating the steel coupler and clearly the force to set all without cisible gaps it's more than 3 fingers pushing. So now all seems perfect. The first print was beautiful, really really nice and clear print, now totally glossy since the new pt100 it's spot-on.

The only think bugging me it's the bigger and totally visible ringing. But that it's just me looking too much. So next think to do its install the igus linear bearings and hopefully I will finally enjoy this hotend. Btw clearly um2 hotend it's quite superior to umo on:

- It can be fully clean inside/outside without much disassembly. (Compared to a hotbarrel leak or trying to clean a peek)
- It does better second top layers, but there's no real improvement on the third/fourth vs umo.
- It drips less.
- I actually can print at lower temps than umo since now that I found the non-glissy temp was 190ish at that temp (same feeder motor/mk7) on umo it skips but um2 can actually print (ofc at that temp quality suffers but it's an option for overhangs).
- The hotend cools down quite faster (but almost the same for me since my umo's have fan pointing at the peek/coupler).
- Weights less, should do less ringing but I get toons more so I don't know so far about that.
- With i2k I should have a really really long coupler life.

And the best think about um2 olsson hotend, the change nozzle speed it's light years from the umo weak aluminium. I always thought that it was no biggie but well it' really it's.

Oh also, when you get use to it it's really easy/fast to do repairs. Yesterday when I changed the sensor, well that was just much easier compared to umo because when you change stuff on umo you have to worry about not touching the barrel, nozzle, and specially there's more room to adjust stuff (specially if you don't use the metal fancap).

[Neotko]

Well this pst weeks I have learn quite abit about the um2 hotend.

First. It needs more heat, definitely. Today I move a pt100 from a printer to the other and not only I can extrude 10C less, also the filament suffers less preassure. Ao yo keep the 'shinny' look on um2 I must print 10-15C vs umo temperature.

The good think also it's that since I use i2k on um2 (anyone knows if that affects the extrusion/speed?) I can easily keep printing at high temps without the worries of lossing a coupler fast. Today I did some coupler/i2k inspection on the um2 hotend that already has 30-50h print time with carbon/ngen/pla and the coupler it's in perfect shape and dimensions.

The only weird think I found was a brown oil/goo near the i2k, that curiously it smells and fells just like the goo that forms on umo coupler vs barrel area. So I suppose that's a side effect of pla residue finding even the smallest atom to rest. Cleaned and reassembled all. And it's printing like a dream.

Other thing I just got use too, contrary to my first posts. The coupler/assembly/disassembly it just take a few minutes. Specially as soon I got rit of the metal fancap. With my printed fancap I don't have anymore issues.

Last think. The Anders olsson adjustable spacer works amazingly well. Today I broke it by mistake but when I took it out even when it was pla printed it didn't show any deformation at all.

Ofc I think the weak point are the fans (my 40x40x20 fans clearly are superior by far) but also the um2+
Fancap it's actually quite good, but it isn't symmetrical, so I will change it quite soon.

So. My next todo will be to do propper test with the um2+
Feeder & 1.75mm filament, Install heatsinks on the feeder motors since the heat it's starting to be a issue here in spain and plug my little stepper chips heat sinks on all my boards to keep it cold.

Summer it's coming!

[Dim3nsioneer]

...The Anders olsson adjustable spacer works amazingly well. ...

Did I miss a genius' design? Link?

[Neotko]

...The Anders olsson adjustable spacer works amazingly well. ...

Did I miss a genius' design? Link?

Indeed.

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[Dim3nsioneer]

Ah...thanks!
You know... page 2 is much too far away from page 3 not to speak of page 1...

[Izzy]

I printed a set with a 0.4 nozzle, file layers, and it's great.
Just need to print one in transparent.

[Neotko]

I solved that think about knowing when the ptfe it's in by printing a bottom hotend part with a hole on a side. But indeed transparent it's a much better sollution.

[Anders Olsson]

Last think. The Anders olsson adjustable spacer works amazingly well. Today I broke it by mistake but when I took it out even when it was pla printed it didn't show any deformation at all.

I did not expect you to use that thing to this extent, it was just design challenge for me which resulted in that prototype
I have used it myself since I designed it though, maybe I should upload it on youmagine if it appears to work well for people.

If you are using the adjustable spacer by the way, check every now and then that it is still properly tightened.
You can do this by putting the socked on the nozzle as when changing nozzle and rock it side to side.
If the whole heater block can tilt side to side you need to tighten the spacer, or you might get lower precision than expected when printing.

[Dim3nsioneer]

@Anders: Get familiar with the fact your designs are far more used than initially expected... that's a sign of quality!
The adjustable spacer is indeed very nice. I printed it in NGen.

[Neotko]

Thanks anders! I had that tilt on one of the hotends for a week and wasn't sure what was. One half turn and all fixed. Weird enough the print quality remain the same (very good).

Today printed pla-tec versions (110-120C max temp) to replace the normal pla. Anyhow pla version works. Superb design men. Enjoy the little one! They really grow up fast and become even more amazing.