foehnsturm

Time to share some experience: You might consider throwing away your printhead fans ... I'm using this setup for some weeks now and never experienced corners lifting of or parts warping. Seems to work for bigger parts and smaller parts like the robot or bridging as it addresses both, the warping and the cooling problem, fairly well. The current setup is basically a kind of topless convection oven. Just Nick's minimum printhead with nothing attached, except a thermal insulation for the heater block. All 3 three open sidewalls covered and a heated bed with the wood glue mix. A crossflow fan with huge 130 m3/h air volume blows at z height 0 +/- 10 mm and acts like an air curtain as well. I bought an anemometer, so the 20% and 80% are quite accurate. The fan is always on. For printing PLA, bed is set to 40-50°C. Air temperature within the printer is typically two or three degrees lower. So even without a covered top, most of the heat energy stays within the printer. The "cooling" air is some degrees warmer compared to a normal setup but it seems, that the huge air flow covering the whole printing area outweighs this by far. Which might also be true for the luff and lee issue.

Hi, nur damit andere nicht genauso Geld versenken wie ich: Standard Pulleys sind aus 3 Teilen zusammengepresst (Mittelteil mit Zahnung und die beiden Seitenteile) und fallen bei einem bestimmten Bohrungsdurchmesser auseinander weil dann innen keine Wandstärke mehr da ist. 20er MXL Pulleys (ich hab damals die von Maedler gekauft) kann man praktisch nicht auf eine 8mm Bohrung aufbohren. Die GT2 haben einen etwas größeren Durchmesser, da wird es wohl gehen. Tatsächlich haben die originalen MXL Pulleys auf dem Zahnriemen minimal Umkehrspiel, das hat sich im Vergleich mit den von mir produzierten herausgestellt. Warum die kein spürbares zeigten, weiss ich nicht wirklich. Wahrscheinlich ist, dass das Zahnprofil des stranggepressten Rohmaterials der billigen Massenware leicht anders (rundere Kanten) ausfällt als das mit einem 2mm Schaftfräser CNC-gefräste Profil.

Just my 2 cents, I don't own an UM2 right now. The pulley-spacer design is a smart one. It is self-aligning and makes end caps obsolete. Set screws provide a frictional locking, dependent on their tightening torque, which is limited by their (tiny) size. The rotational torque won't be a problem, there is only some frictional resistance to overcome. However, any longitudinal movement of the rods and pulleys is like banging into a wall. So, with everything in place and no play, things should be fine. If there is some play which allows the rods to move and build up inertia, shit will happen sooner or later. My recommendation would be like gr5's: Just slide the pulley against the spacer and then against the outer wall. But don't care about centering the pulley to the rod above. Ultimaker should have designed the length of the spacers to do so automatically. Any play is bad.

Seems to depend on machine and / or material. With 100 mm/s and UM silver PLA (195°) I'm loosing strings right when laying them down, at 50 mm/s everything is perfect. However I don't loose any strings thereafter when passing nearby, which should be related to the heavy cooling. Yellow colorFab PLA/PHA is a mess so far quite similar to Zernyu Chou's picture. Even at 20° below recommended printing temp.

Here you go. Perimeter 50 mm/s, infill 100 mm/s The long infill lines of the fist bridge layer are mostly lost, revealing the diagonal pattern of the second layer. The reason might be a combination of (excess) infill speed and unsteady extrusion. The perimeter lines start with a 90° turn and may establish steady extrusion while passing the 5 mm wide strut. In contrast, the infill starts with a 180° turn and there is just 0.8 mm (wall thickness) to settle for constant conditions.

I just tried thing 12925 with Cura 31.11. While the fan is set to 100% while printing the struts, Cura sets it to minimum when starting the bridging (based on longer path and calculated layer time I suppose). So at least, having min and max fan set to 100% is a must. Besides this it works well (on UM1 with enhanced cooling) . First bridge layer perimeter lines are perfect, infill not (printed too fast). Simple question: If Cura knows that there is only thin air beneath a certain path, why not always print this path with perimeter speed only?

Nevertheless, a difference in quality, which caused Ultimaking to inquire whether I could produce the pulleys for UM2 But no way for me to meet their price target - what was to be expected.

Congratulations! As far as I know, coloring is done by putting some additives into the plastics blend. Besides their color, those additives differ in various other properties as well. An unwanted side effect, which manufacturers try to minimize.

Here is an update on my evaluations: I stopped using a printhead-attached device for cooling. Instead I went for a cross flow fan like http://www.conrad.de/ce/de/product/560546/X-Fan-Querstromluefter-Motor-rechts-DF43198-R-12-V-400-mA and mounted it to one side of the housing. What you get is: - a (- well almost -) laminar air flow covering the whole print area at nozzle height +/- 1-2 cm. - lots of air volume (138 m3/h) - silence ... compared to many other fans - no issues with luff and lee so far (can even be improved with an adapted print head design which directs some air downwards) - an opportunity for a kind of air curtain for realizing a heated chamber without covering the top - ... Of course you need a thermal insulation for the hot end like MadOverlord's. It's working very well so far and might be a building block for a modified printer design I started thinking about.

... perhaps also temporarily increase the flow rate when the bottom is almost finished and the shell starts. Or even increase layer height: the lower the layer height, the lower the "reserves" to even out any ripples beneath (just a theory so far). Generally speaking, it looks like the problem has to do with the viscosity of the filament and its gap-filling properties. For instance, yellow and green PLA/PHA works fine while XT drives me nuts (despite producing a very good looking surface).

Hi, To me there are three main reasons for leaking: - leaking through bottom: infill is not dense enough / bottom thickness to low - leaking shell: underextrusion / bad layer adhesion - leaks between bottom and shell, which I find is the most difficult issue First and second are relatively easy to fix. Actually, if settings are fine even shells with a single outline are watertight. But I am frequently fighting the third issue. My suspicion is that even the lightest ripple in the top-most layer of the bottom impedes a watertight fusion with the perimeter lines on top of it. Recently I played two days with slicer settings and even two nozzles (0.4mm and 0.7 mm) to get double-walled espresso cups watertight with Coforfabb XT filament - and failed. If the bottom/shell detail is under your control, adding a fillet and using more perimeter lines might help. But there should be some expert advice available here ... Markus

Does "welded" refer to leaking PLA/ABS creeping between brass and aluminum thread?

BTW, is there any reason why Ultimaker uses a screw instead of a nut as nozzle? Using a nut would also remove the somewhat critical brass pipe to brass pipe joint within the heater block. Looks like changing a nut should be easier than changing the screw-type nozzle.

PWM signals seem to have different effects on different motors. My voltmeter showed irritating 7 V all the time but with fan settings beyond 100 current raised to 0.6 A and more Amp and the fan blew way more than when connected to a stabilized 12V supply. 255 should be mapped to a full-on duty cycle, so you are right, with the overvolting.

Thanks! Works fine - and doesn't scream. I only had to set cura max fan settings to 40%. Otherwise the PWM driver seems to operate the fan (8-15 V, 0.4 Amp @ 12V) way beyond its specs.

Hi guys, Accidentally, just an hour after my post in the already too long "Fixing Pulley..." thread I had a conversation with the guys who are machining them. Taking both things together, upcoming batches would require a modified pricing. So, regarding the quality (difference to other pulleys), what do you think would be an acceptable price? Markus

Is there any new information about the max. current, the fan drive can handle? I want to test a fan with 0.4 Amp.

@ji11 I still have 2 pre-ordered sets left. If nothing happens until Friday one is yours.

Well, I'm somewhat irritated by Ultimaking's pricing policy. Currently, they sell 10 pulleys for 49.95 + tax. I don't know if the quality is still as low / varying as it used to be. But as far as I know they should be buying close to 1$ or 1€ / pulley. Following the same policy I would have to ask for 150 € a set. I won't do that, but I don't want to sell immaculate precision mechanics quality for almost the same price tag as Chinese bulk ware, either. I feel some responsibility for my supplier and the value of his work.

I love it.

@drayson I used 2 40 mm fans quite similar to the UM2. Worked fine, but (PLA) ducts desintegrated over time and I wanted to get rid of the bulky parts moving with the print head. @MSURunner Those pumps would be fine but they draw considerable current (additional power supply). As far as I know, most compresor-like systems can only be switched on and off. Unfortunately, there are only a few 12 V, low amp, speed-controllable fans /pumps, which provide sufficient air flow and static pressure. There will be a possibility to order pulleys in the future. I just will have to switch to a kind of webshop in order to reduce the efforts for messaging and waiting for answers.

Left me a little underwhelmed after the first look, too. But they might have improved a number of important things regarding speed and precision: new hot end, new sliding blocks (with GT2 belts), new extruder ... But I still don't like those short belts ...

That's why I use a radial fan vs. axial. Radial fans can build up more static pressure. But given the original 12 V fan supply it is a compromise of course. But you are right with the tubes. I already designed 2 high-volume downdraft hoods for my wok cooking stations and I know, flow resistance of (low diameter) flex hoses can be a nightmare. I tested the setup with fan, adaptors, various tubes (30, 40, 50 mm and without tube at all for comparison) and print head before mounting. That's how I came to that guesstimate. If it had been inferior to my normal setup with 2 axial fans and ducts, I wouldn't have mounted it.

BTW: Nice responsive web design.

Oh, we don't have to wait any longer! The new print head looks interesting.