Taz replacement 25mm hotend Fan Duct

by KillaCycle Apr 3, 2016
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Hey there, thank you for the design. I just printed this duct in PETG and attached the 5v 25mm Sunon fan you linked in a previous comment. After installation, I tried another print in PETG (target temp 237C) and it started out okay but soon the hotend temp was falling way under target (217C). Any ideas? I tried turning the target hot end temp way up to 265 to reach 230 and get semi-okay extrusion and adhesion. Certainly this is not a great solution long-term... Do you think if I modify the shape of the duct I wouldn't be getting the fan fighting against the heater so much? Any suggestions would be awesome!

Perhaps your print cooling fan is set a bit too high. Turn down your print cooling fan a bit. (Alternatively, install a 40 watt heating element, but you shouldn't need to do this, actually.)

The print cooling fan often blows a bit on the nozzle, so you may have to turn it down a bit as you have a bit extra nozzle cooling from the heat sink fan than the tiny blower gave you before..

It seems odd that you could turn up the target cooling setpoint on your hot end, and get more heating. The PID controller in the program should be giving the heater 100% of the available power when the temperature fell to 217 when the set point was 237. Turning up the heater setpoint should not raise the nozzle temp. If it does, then this suggests that you have monkeyed with the PID settings in the firmware, (or someone has.)

Didn't have any time to test the past couple days, so I'm just starting today.

First test: Raising the temperature and holding at 245 without printing for 15ish minutes — hotend fan on, part cooling fan off — went fine, so the hotend fan alone is not an issue.
Second test: Printing — both fans on — was not good. Once the part fan went on, the temp started dropping, so I dialed the fan back to 50% to get the right hotend temp.

So that's an issue. I've never had problems with the part fan overpowering the ability of the thermistor the keep temperature up when I was using the tiny squirrel cage fan—but I did get some heat creep occasionally—so apparently having both is causing a problem... somehow. Turning the temperature up was just a red herring (that'll teach me to isolate my variables)., so you're right to dismiss that.

I'm using the stock print cooling fan but a modified duct that splits the airflow to hit both sides of the print. https://www.thingiverse.com/thing:1349016 I believe the shape of the right side duct is still the same as the stock duct, but maybe I'll need to try to modify it to point the flow down a bit. Perhaps I will ask the dual duct designer.

P.S. I'm using a slightly modified version of your overhead spool holder, and it's awesome! No more goofy side-spool shenanigans.

Dual duct with single fan for TAZ 5

Yeah, I ended up turning down the part cooling fan to about 60-some percent of full speed and decreasing the print speed to 2/3 what I'd initially set (so 50mm/s to around 30). So it's possible that turning down the other fan helped. But that doesn't quite add up, either, because I'd think if the part fan were the issue I'd have seen something similar before, right? Hmm. I don't think I've done anything with the PID (I hope I would remember that!) I'll have to look at the fan again in the morning; maybe I have the new one pointing somehow too far down so it's not directing the air properly.

Where are you guys finding 2mm screws? Not of the hardware stores in my area carry anything that small (no 4-40 screws either).
Are you using something like a wood screw or a machine screw?

The oridginal Taz blower is held on with a 2mm screw. This duct is meant to directly replace the little blower, so you just reuse the 2mm screw from the blower.

I bought a nice selection of 2mm screws from Ebay,
You can also buy them from McMaster Carr:

Thanks for the links. I think the fan on the Mini where I'm installing this is only held on with one screw. I was planning on using more than one for this.

Number 4-40 screws are pretty common. A pair of 4-40 screws are used to hold VGA monitor connector in place, for example. Your hardware store probably keeps these small screws in a multi-compartment metal drawer/case. Look for the pull-out metal compartment drawers and you will find the small screws.

I looked when I saw that size in your notes. 3 hardware stores, for all of them the smallest they stocked was #6. I finally went online and ordered some assortment packs of 2, 2.5, and 3mm stainless screws. I figured it wouldn't hurt to have some hardware around for the elementary school class I'm volunteering with, and they already have some metric stuff in the classroom anyway. (One of the kids has been reading up: he just asked if we have any heat-set inserts. He wouldn't say what he's planning yet. This is getting fun!)

I appreciate all your help, and the time you took to design the shroud and make it available.

One additional note. The 12V fans move a lot of air compared to the TAZ5 stock 5v fan. Plus the air is pushed directly at the heat break. This can cause the TAZ to detect a heat failure because of the heater struggling to heat the hot end while the upper part is being cooled. I found it is best to dial back the voltage to about 9V to prevent this from happening. The pot on the buck converter allows you to set the voltage you want. That amount of air movement is plenty to cool the filament tunnel, but allow the hotend to stay at temp.

This works great. Most fans you can buy are 12v however. A cheap buck converter (https://www.amazon.com/gp/product/B014Y3OT6Y/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1) can be used to convert the TAZ's 24V to 12V. http://www.thingiverse.com/thing:1703682 is a holder for the converter inside the TAZ cabinet.

Buck Converter Holder
by eussrh

The small blower that you are replacing on the Taz5 runs on 5 volts. Thus, for a direct replacement a 5 volt 25mm fan is used/needed.
You can rewire your RAMBO board to feed 24 volts, or 12 volts or whatever you wish, but 5 volts is what is standard on the Taz5.

This is just an alternative. The fan is on as long as the TAZ is powered, so it doesn't need to be switched.

Thank you for the design! Works great - coupled it with the addition of "seasoning" the head with oil, and completely solved the grinding issue with PLA.

FYI - I'm using a beefier 25mm fan - 12V 2A. Had to wire it externally to the printer, but seems to work even better.

I'm glad it works for you as well as it has worked for us. Thanks for posting pictures of your "make". :-)
It appears that you made yours from the same purple color Innova that I made the original. ;-)

Its actually purple HIPS (what I had lying around that I could still print in the printer while PLA was out of commission).

Its been going for about 1 week now, pretty much consistently printing PLA without warping the HIPS fan. Am thinking the higher melting point for HIPS will work well here.

Maxxra - I'm curious how your HIPS fan duct is holding up. I'm printing one of these for a Mini at an elementary school where I volunteer occasionally. All they have is PLA and HIPS. The PLA is out due to it's low melting point. I'm hoping I can use the HIPS, but concerned about it melting, since most of their printing is done with HIPS (they may switch to something else some day, but they have 5 1 kg rolls of HIPS to get through first).

Will a duct made from HIPS hold up to printing with HIPS temperatures? Do I need to just buy a spool of something else to make this part from?

Its still going! I dont print above 240 (HIPS), so the shroud never gets to more than apx 200 radiating from the hot end - combined withe constant air flow, it has yet to warp.

Recommend investment in a good fan though - since its running 24/7, you dont want to replace it every 2 weeks.

Also - cant recommend "seasoning" the hot end enough. Its goofy, but it really really works. I print production quantities of PLA on our Taz 5 and mini, and seasoning has gotten us up to something like 95% uptime,

Cheap 25mm muffin fans tend not to last. They will last maybe six months under normal use, and much less under continuous use. You definitely want to buy a "ball bearing" or "vapo-bearing" name-brand fan versus a fan with sleeve bearings. (Sleeve bearing fans are the cheapest and thus they often don't list the bearing type.)

Here is a $10 Sunon "Vapo-bearing" fan that is quiet and seems to hold up nicely:

This fixed the heat creep with PLA on the TAZ 5 like a Champ! Thank you!!!

I can't tell you how frustrating it was having PLA fail, and hang up in the nozzle.

I'm glad this duct worked for you as well as it has worked for me.
Indeed, it is very frustrating to figure out why your prints are randomly failing.

You should print my overhead spool holder next:
I really don't know why Lulzbot uses the side spool holder and the tubing to feed the filament. The overhead spool holder saves space and feeds much much smoother.
Bill D.

Overhead Filament Spool Holder (Lulzbot Taz)


What brand of PLA are you using? I'm still having issues with esun. It takes longer for the heat creep to happen, but it will eventually seize up. If I stop and cut the material, everything is back to normal.

Thank you;

Before you fix blame on the brand (which could well be the cause) is the extruder servo motor getting hot? Like too hot to hold your hand on? Sometimes, the servo current is set too high, the servo gets too hot, and then the servo can't produce the torque it needs and stalls.

Also, the different brands of filament, as well as different colors of the same brand, require different extruder temperatures. The temperature range is 195 to 230 Celsius, so try a lower and a higher temperature within that range and see if that helps. Folks say that esun pla prints better at a sightly higher temperature setting (like 5 degrees) than other brands of pla.

Hi Bill

The issue with the PLA is it carves out a notch in the filament. It will run great at the beginning of the print than when it seems things are too hot it will begin to start choking off, and dig a notch out of the filiment. I only have the issue with PLA. I'm simply blown away. I have tried 180-205 deg C, and all ended up failing. The upgrade bought me some time before the problem starts. As always if I cut the material and feed it back through all is normal again till it heats up. The higher the heat the quicker the problem occurs.

This is called "grinding" the filament. You might be running the other cooling fan at too high a percentage.
The main cooling fan can overcool the hotend tip and reduce its' temperature. The hotend heater can only put out so much wattage and can be overwhelmed by the main cooling fan. The main fan normally ramps percentage from zero (off) at the beginning, to 100% later in the print. Try limiting it to ~ 50%.
Also, check the hotend temperature and the main cooling fan percentage just as the print fails. You my find that the hotend has cooled a bit below the set point just as the print fails.
I watched the hotend temperature and ramped the main fan manually while just sitting, not printing. Discovered that with the particular duct and fan I had chosen, the max cooling fan percentage was ~60%. If I ramped the fan rapidly, like from zero to 50%, the hotend temp would dip and then take several minutes to recover

Also, reducing the filament withdrawals might also help with grinding. The length and speed can be reduced.


I'm working through your suggestions currently. Thank you for taking the time to help. I did limit the fan speed and cut the withdraw to 1/3. This has helped the performance. Do you have any tips on hotend aliments.and how to correct it? When I perform my cold pulls I notice the alignment seems to be eccentric.

You have been more than helpful. Thank you;

Yeah - I saw that. I'm sure your setup will be the easiest. I actually found a 4-40 tap around and will use the same you did and will work just fine based on your design! Thanks again

Cool! I appreciate your quick response. I was starting to really get fed up with this great machine. Even a complete kit I built years ago is more reliable right now :( I'll get on ordering up the fan(s) for my multiple extruders and change them all over. Does Lulzbot actually sell a complete setup like the 6 to retrofit onto or are you just saying to contact and ask???

Thanks again for the breath of fresh air!!

They have published the parts on their server site, so you can download and print whatever Taz 6 parts you like. They have officially launched the Taz 6, like yesterday. So you can simply buy the Taz 6 complete extruder head if you like.

I have had the Taz 5 and am on extruder 2 now - one with them and one with me. I can't print with a 0.35mm nozzle anymore (could all day long) and realized it's stripping the filament mainly on longer prints.... So do you suspect since I'm on a brand new extruder @ 0.5mm and still can't print something past 2 hrs that this is the issue?? I have a warranty that extends a couple years so I'd be interested to see what their response is.... to save time and $$$ on both ends w/o having to send extruders back and forth across the country. I get more consistent printing from a $850 thing right now which is unnerving :)

The tiny blower has been updated to a 40mm fan with a duct similar to my duct on the Taz6. Thus, the Lutzbot folks have figured out that the tiny blower was inadequate for some filaments. I personally think that the 40mm fan is overkill.

Everyone that has tried a 25mm fan and my duct says that it cured grinding a jamming when printing PLA. A few hours work and about $10 for the fan. Just make the modification (or buy the 40mm Taz6 set up from Lulzbot.) and get on with happy PLA 3D printing. :-)

Folks have made smaller ducts for smaller 20mm fans for the dual extruder. (25mm fans won't quite fit.) You can look up those on the Lutzbot forum (filament section, PLA printing SOLVED thread.)

Updated STL file to proper metric scale

I should scale the stl so that it prints without the user scaling having it from inches to mm.
My CAD uses inches as the default unit. All 3D printers assume that mm is the standard unit, however.
I'll fix it tonight when I get home.

Sorry about that.

It's not a big deal. Once I switched it, it was good. Looks like it's printing well. Thanks for the cool upgrade!

If you like it, please post an "I made one" photo when you have it installed and working.

Made and installed. Works great, thanks!

When I opened this in MatterControl, it is super tiny. What size should it be?

I think I figured it out. Switched from IN to MM.