Um2 hotend design questions

[Neotko]

I never used an um2 hotend until today so bear with me.

First of all... Why it sucks so much? (well it doesn't but it also kinda does).

I mean. Umo hotend solved most of the errors long ago.

Ptfe spring it's just bad bad bad bad bad design. Why using a spring to compensate the area that suffers more preassure? On umo+ with the wood vs ptfe coupler it's all stable and it can't move. If it dies you only get leak inside the barrel, and that's (if you get it on time) quite easy to clean. But here the black goo expands up and down the steel coupler.

More stuff. The steel coupler. Why? Oh my oh why? Why it doesn't have a clamp system like pushfit connectors. That stuff it's designed to hold preassure, but steel vs ptfe, ofc the smallest change in preassure will make the coupler to splip since nothing graps them together. And the spring... I can't stand even looking at it.

If they already fixed this on umo with a flat wood preasing down the ptfe, why they went for a spring? To have an adjustable height? And if that's true, why the ptfe/steel coupler gap must be 1mm? If you can adjust the height you can't have 1mm gap. Or it's that 1mm gap something that can be as much as I want? Seems quite contradictory.

Anyone knows the perfect height for the spring replacement. I seen a design with 11mm but the step files I see 9.5mm or 10.5mm height to have all perfectly fit.

Omg. Also, the um2 standard fans (got a couple from ultimaker distributor) they SUCk sooo badlyyy. The airflow it's horrible vs the umo+ fan. Ofc, they are 2... My 40x40x20 fans do muuuch more air than this fans BY faaar.

Even my 40x40x10 fans work better. And they are the less amps... My 40x40x20 fans are 70mA...

Ok I suppose the advantage of this head it's the weight so have more aceleration. But so far, I need to clean the coupler from goo and print a static holder to avoid springs.

Well so far I can't see any advantage on the um2 hotend except weight, tfm/tft couplers and... That's all.

Also omg to change the ptfe you need to disassemble everything!? On umo I can change it by unscrewing the 4 long screws... A very easy redesign would fix all this issues! And noone saw this?

I'm just very surprised with the um2 hotend. It's quite a stepback on some areas from a umo hotend.

Sorry the semi rant. But woa it's quite the shock to see this after reading so much praise about it.

[Izzy]

I think the UM2+ has better fans.
I think the reason for the spring was that it was going to be dual head and so would need some adjustment to get the nozzles at the same height, so rather than a solid spacer that would not allow for adjustment there is a spring that would keep the pressure and allow for adjustment.
If set correctly, then you only need to strip the head apart if you want to change the PTFE or the I2K, mine doesn't leak.
By the way my design of fan ducts allow for single or dual printing heads, can swivel out of the way to allow easy access to the nozzle, & are height adjustable , OK advert over

Upgrade the head to an Olsson block and a 35W heater and it's going a good one,

[reibuehl]

Not sure what you did with that poor UM2 hotend in the apparently short time that you had it... Mine has printed well over 1000 hrs without ever having something come out where it shouldn't. Sometimes nothing came out, but that was usually a worn out PTFE. I never had any leakages.

The spring is a remainder of the planed but never implemented dual extrusion. The 1mm as far as I understand is just the default setting that gives you a default spring pressure. If your spring is a little on the loose side, I don't think that you couldn't adjust it to something else if that works better.

[Neotko]

Well I used a china hotend and fixed the parts

But it's basically (now after good cash spend) a good hotend. OFC my spring it's pure crap quality ! Anyhow... If the gap should be 1mm, it doesn't make sense to use springs when you could just have a flat alu part pressing down at a fixed height. Also, even with a spacer you can't have equally distributed pressure I suppose...

[Neotko]

Just to add info. I got the crappiest um2 clone ever and updated with real stuff bough to 3dsolex (real olsson, tfm coupler, steel coupler, real um2 fans bough to ultimaker distributor and 35w heater from 3dsolex). So far it works quite ok, I got a leak on the first test because the spring sucks (my fault because I should have wait to print a carbon fixed replacement). Anyhow I have a box of high quality springs from a my magnetic head changer project.

But anyhow... Well, it's quite the pain in the ass to just change a ptfe... Compared to umo/umo+

[Meduza]

The reason for the spring is that the UM2 was supposed to be a dual extrusion machine and the spring made it possible to change the height of the induvidual heater blocks in a easy way. The 1mm distance is just a recommendation to be sure that people do not adjust it way too far down and get too low spring tension and also do not ram the steel coupler into the block. You really should replace it with a rigid spacer, especially if you have a crappy china spring. The length of the spacer are only important to set the block the right height inside the fanshroud.

I have never ever had a leak of filament out in the coupler, so that risk is overstated.

That you have to screw the head apart to replace the PTFE does suck, even if i can do it in pretty few minutes now after doing it quite a lot of times, not as fast as IRobertI does it tough...

[Neotko]

The length of the spacer are only important to set the block the right height inside the fanshroud.

I have never ever had a leak of filament out in the coupler, so that risk is overstated.

That you have to screw the head apart to replace the PTFE does suck, even if i can do it in pretty few minutes now after doing it quite a lot of times, not as fast as IRobertI does it tough...

Thanks, perfect I'll do the spacer. But would PLA work for that area for at least a few prints time? I need to make it on carbon and I don't want to install the ruby nozzle on other machines since they work perfect atm.

Yes it's quite a mess compared to umo, now I get why people get angry when their coupler dies. On umo it's so easy to check it.

So the system just needs some room below and tight but not overtight to the spacer so it doesn't move when retracts. Sounds perfectly logical. Thanks!!

[Meduza]

The spacer will probably work just fine in PLA for a while, it is not particularly hot up there, i had one in regular XT on my printer for about 5 months without a problem.

[Neotko]

Oh btw Meduza!! Your top um2 for umo+ works like a charm. And it prints so beautiful!

Thanks again!

[Anders Olsson]

Regarding the spring, it does surprise me that Ultimaker selected to use it from the beginning.
If going for dual extrusion, you would only need to adjust the height of one of the hotends.
So they could as well have used a solid spacer from start and kept the spring to the dual setup that eventually was cancelled.

If you really dislike the spring so much, I can send you the STL-files for my adjustable spacer:

Not sure you like that one better though

Hmm, maybe I should print it on the Form 2 by the way, would be nice if it had better surface quality and was transparent.

[Meduza]

There is a distinct advantage of the spring vs the solid spacer in large scale production, the spacer is very sensitive to correct positioning and the spring only requires you to eyeball the approximate position since it is self adjusting. Also the plan was probably to have identical hotends so only one set of parts to stock.

I also like that you can see that you have seated the bowden correctly after a atomic pull wich is not possible with the aluminium spacer. I have actually been thinking of milling a slot in mine for that purpose

[Neotko]

If you really dislike the spring so much, I can send you the STL-files for my adjustable spacer:

2016-03-02-6848.jpg

Not sure you like that one better though

Yes pls! I have your bowden clip, your block, I would love to have a full olsson set !

Transparent makes sense go see the bowden indeed.

[Meduza]

Anders adjustable spacer is a quite nice design, i have seen it in person and it works better than you would expect

[Neotko]

Anders adjustable spacer is a quite nice design, i have seen it in person and it works better than you would expect

They printed flawlessly with my perfectrobot settings simulating a 0.28nozzle with my umo+

[Neotko]

One think um2 I can't think will surpass it's my fan cap. It's so good can't wait for everyone to use it.