3poro

There's quite little space for anything extra behind the print head - unless you adjust the home location by tweaking the micro switches. I would advise you to remove the white metal sheet which is covering the feeder stepper motor and one of gantry stepper motors. It's good riddance anyway - without it the stepper motors get better ventilated I think the idea of the decouples is good. It might even help to improve the cooling of the print head, because the original mounting of the fan wastes some of the fan's capacity (by having aluminium blocks actually blocking the air flow).

Yes - and your draft seems to tackle that really well - it looks great! Here, I don't see the situation so black/white. There is obviously room (and need) to improve the original design. At the same time, I wouldn't turn down help offered by different materials. Keeping the current PTFE isolator "as is" by its shape and just changing its material doesn't seem to be easy. Attempts to use ceramic materials or aluminium have failed. Until proven wrong, I still believe in the washer approach. If the washer is thin enough, the negative properties of its material (like added friction) will be manageable - but it can reduce the temperature at the tip of the actual isolator. About the simulations - there's one factor which is tricky to simulate but might also have an impact: retraction. When 260C filament is pulled up and pushed back (in some cases almost immediately after), it certainly warms up the inner surface of the isolator. Maybe retraction settings need to be tried, hmm... Maybe the solution will be a combination of new materials, new design and new isolator pricing by Ultimaker

I have taken the white sheet metal thingy out and I'm not planning to put it back. In my opinion it's too close to the print head rear fan and the nozzle block wiring when the head is parked. Also, it causes the 2 stepper motors to heat up even more than they do without the metal wrap. The good thing about it is - it's easy to remove

I'm very interested to hear how your tests will turn out - best of luck with them! Regarding the idea of different spacers... I'm referring to the discussion over here: http://umforum.ultimaker.com/index.php?/topic/3803-ultimaker-2-dual-extrusion/ I would accept the idea of using two different spacer materials - but preferably on different extruders, at least as long as they aren't made very simple to change.

I don't think it's obvious a complete redesign is needed. We'll see, one day For me the cost of Teflon isolators is not the biggest issue. The bigger problem is - I don't know when it needs to be changed - or even checked for its condition. What's contributing to its failure and how much? Printing temperature? Filament being used? Printing speed? Number of retractions? Also, it's difficult to inspect the Teflon part accurately enough to know whether problems are likely to appear or not. When problems appear, they are nasty to track and they tend to ruin prints when you are least in the mood for debugging. Another aspect; if the print head was more tolerant for high temperatures, it might help to sort some of the problems now facing dual extrusion. Also, this would allow us to use broader range of materials - see for instance this thread: http://umforum.ultimaker.com/index.php?/topic/6867-is-there-some-way-hack-to-print-at-270c/ Of course, some people would use the better temperature tolerance to decrease noise level by using less noisy (rear) fan in the print head.

It's not a strange way of thinking, but the cases are not quite analogue. First, you can't easily check whether the Teflon isolator is worn out or not. In order to check it, you'll have to take the print head into parts - which is not fun. Second, if you decided to just change the consumable once a week to be on the safe side, changing of it is not fun.

If I understand the heat dispersion in the nozzle unit correctly - and referring to simulations made by Kris - I think the temperature of the Teflon isolator drops pretty quickly (vertically, from bottom upwards). In other words, only the first couple of millimeters are really vulnerable. Two ideas for brainstorming: What if the isolator's filament hole was drilled a bit bigger for the first 4mm from the bottom - and there was a very thin-walled tube inside it? If its walls were thin enough, it wouldn't act as a strong enough transport for heat to cause problems for the upper parts of the Teflon isolator. As the weight of the tube (3.2/3.8mm(?) in diameter, 4mm? in length) would be minimal, it could be made out of almost any material (like gold) from cost perspective. There could be a thin isolator ring between the brass nozzle unit and the Teflon isolator - just thick enough to reduce temperature transfer by a bit. If the ring was thin enough, maybe it wouldn't be a catastrophe even if PLA would stick to it? Ceramics? PEEK? http://www.extreme-bolt.com/Products-PI-Washers.html ? The latter would naturally be a very easy solution - even a failed PTFE isolator could be used as a basis after cutting off the malformed bit of it.

What can I say - lucky you. I'm now having my 3rd temperature sensor and with all the sensors the ABS behavior has been similar - so I don't think my nozzle temperature reading is somehow off. Given the problems the high temperatures are causing, I really wouldn't mind using lower temperatures. Every time I have made any bigger changes to my system, I have tried using temperatures around 235C..245C with ABS - and every time I have been thrown back to use higher temperatures. In my opinion UM2's default temperature of 260C (for ABS) makes sense.

I think this is the problem. The new Teflon piece has stayed in shape from outside perfectly - it still has very good fit with the stainless steel isolator. However, the ridge is more distinct and sharper in shape than in my original (old type) Teflon piece - even if the old one got slightly malformed and wouldn't fit inside the stainless steel isolator without using a lot of force.

In case you are planning to print ABS, I would pay a lot of attention on closing gaps in the enclosure. At first I didn't close the holes of the original filament spool holder and some other smaller holes, as I felt I had already managed to get rid of most of the smells. Some weeks back I took the time to close them - and it really did make a nice difference. I haven't yet added any air purifier into my enclosure, but I'm thinking of doing it to get rid of whatever is left of the fumes - but I'll keep the air circulation closed. Here's my implementation: http://umforum.ultimaker.com/index.php?/topic/5921-um2-greenhouse-edition/ Regarding the front door, I would recommend Kris's solution: http://umforum.ultimaker.com/index.php?/topic/6612-another-green-house/

I guess you have 255 N. There is also 252 N, but that uses higher voltage. The 255 N is pretty quiet (16dB), but its air flow is also a third lower than that of the original UM2 Sunon fan. But - if it works, great!

The description of the problem seems identical to what I faced with my (2nd) temperature sensor. You might want to read about my experiences here: http://umforum.ultimaker.com/index.php?/topic/5431-thermocouple-failure/

OK, I figure the detailed specifications for the Ultimaker's original temperature sensor are not available. I don't think it's good for 260C and the reference to 400C is a joke of some sort. I made my own temperature sensor out of these parts: http://www.tme.eu/en/details/pt106054/resistive-temperature-sensors/ http://octopart.com/mm01006-multicore-1013894 Kapton tape (as insulator for electrical connections) cord from broken UM2 temperature sensor After installing I don't have to rely on adhesion characteristics of the Kapton tape, so the solder is setting the maximum temperature - at 301C. Already by now this self-made sensor has lasted longer than the two Ultimaker original sensors.

Which model did you choose? I can't find anything nearly as powerful from ebm-papst, normally I use their fans whenever possible.

On Ultimaker's ABS filament spools the temperature is indicated as "<265C" and 260C is the UM2's default nozzle temperature for ABS. If I use anything below 255C, I don't get very good layer-to-layer adhesion and also the risk for under-extrusion grows.

Yes, heating takes longer - which is actually a good sign - the cooling gets more efficient. Of course, in the design of the print head there should be better insulation between the nozzle/heating block and the aluminium structure. What comes to temperature oscillation, see the last messages over here: http://umforum.ultimaker.com/index.php?/topic/6307-um2-twin-tornadoes/ ...so it looks like there's some problem with the fan output, if even a single Tornado causes such a problem.

Here's my 2nd PTFE isolator, the new glass-infused type: ...after some weeks of use. Can anyone quote a price for 10pcs?

It looks like some UM2 feeders take a tighter grip of the filament than the others. In my case, the feeder was biting the filament way too hard - even when adjusted to be as gentle as possible. However, I agree with you - the UM2 stock feeder is not _that_ bad. The overall filament path just has many problems... It works better for full spools than for half empty ones. The grinded side of the filament gets to the "outer track" in the Bowden tube. There's too much friction in spool rotation - and if you add bearings, the filament may jump off the spool. Most of my problems were solved by changing the filament path - although I also needed another feeder: Stepper motors are not very sensitive for high temperatures. Mine are running around 80C, no problems I'm using 1.5A current for the feeder stepper motor - and the others are inside my closed chamber where I normally have my print bed at 110C.

I would think twice before trying to reduce the noise level of UM2 by changing the fans. The fact is that in such small size the noise level and airflow go pretty much hand in hand. With larger diameter fans you can reduce noise by design and number of the blades, materials etc - with very small ones there's much less room for such smart noise mitigation. Of course the side fans can be replaced with a different type of ventilation design altogether, that's another story. But replacing fans with ones of similar size will not help a lot - the ones used by Ultimaker are of high quality. If you win in noise level, you'll lose in airflow. If lower airflow is acceptable for the side fans, why not just reduce their speed? Cura has good options for that. What comes to the rear fan, I really wouldn't lower its capacity. Using weaker fan will raise temperature of the print head - and the airflow towards the PTFE isolator will be even warmer than it already is. If the noise level of UM2 is not acceptable, you need to either take into use a different print head or to build some sort of enclosure for the printer.

I haven't tried, but please allow me to speculate Rubber coated wheel would require quite different feeder design. The wheel itself would need to have quite big diameter - also, there would need to be some guides to keep the filament touching the wheel for more than a millimeter or two. Even if friction can be excellent between rubber and filament, it gets much worse when either of the surfaces gets dusty or dirty. The only way to overcome this problem is to have a lengthier touching area between the two. With a large diameter wheel - or your belt design - that would be possible. However, I'm not sure whether the original stepper motor would be strong enough to handle a much bigger diameter wheel without some sort of a gear system.

This part is clear and well described in your posts. Forgive me for insisting, but there's something I don't fully understand... There are a few design flaws in the original UM2 print head which certainly contribute to the problem: There is no heat insulation at all between the nozzle block and the lowest aluminium block. The heat is radiated pretty efficiently over the couple of millimeters gap. The rear fan - not the strongest one - blows forward. Its airflow gets heated by the heat sink before it hits the PTFE isolator. Surfaces which are supposed to radiate heat are not black anodized - and they are smooth. Fixing points #2 and #3 help to convey the heat away from the parts that should be kept cool - but fixing point #1 would actually reduce the need for heating. There are insulator materials which could be placed between the nozzle block(s) and the lowest aluminium block - which would reduce heat transmission from the nozzle unit to the print head significantly. There is also physical connection through the stainless steel isolator, yes, but the radiation component is not insignificant. What am I trying to say is - if the temperature goes "slightly" above the glass transition temperature using 2 hot ends, I find it strange that particular problem couldn't be fixed without making major changes. I personally would be ready to accept "known issues" for the first release of dual extrusion.

LIKE I WROTE IN MY ORIGINAL MESSAGE: "IF I WOULDN'T HAVE THE DOME AROUND MY PRINTER, THE NOISE FROM THE NEW FANS WOULD DRIVE ME NUTS." YOU CAN TRY TO REDUCE THEIR VOLTAGE BY 10% OR 20%. I HAVE 2 OF THE TORNADO FANS, SO I NEED TO SHOUT TO HEAR MY OWN VOICE

Yes, I'm using a similar power source for the fans now. However, as the Tornado fans use 5VDC as their operating voltage (and up to 7DC), I also use one of these for regulating the voltage: http://www.ebay.co.uk/itm/331125688871 Very good combo, in my opinion.

Good point about the upper temperature limit. However, the temperature limit is not set by Kapton but by the adhesive. As it's written on that website: "Kapton ® Tapes are made from Kapton ® HN film with Silicone adhesive" Kapton itself can take temperatures higher than that: http://en.wikipedia.org/wiki/Kapton - so if you don't rely on the adhesive too much, you should be OK. When you order Kapton tape, it's not uncommon to receive some Chinese version with name Koptan or Kopton on it. You can test the tape quite easily with soldering iron (if it has a thermostat). If the material looks Kapton but isn't Kapton, it will melt at temperatures much below 300C.

It is naturally your decision whether the compromise is made on schedule, functionality - or both. Now at least the schedule is compromised. Don't get me wrong - I'm also eager to get some of the more advanced possibilities of dual extrusion into use. Solvable support material would be fantastic. Two-color prints, meh...