A single fan blade broke off...should I stop using it?

[Steve Gong]

While changing the filament, I snipped the end of it which fell into the fan and broke off a single fan blade.  (This is the front fan that cools the extruder)

I figured I probably should order a new fan anyway, but in the interim, should I...

1.  Keep using it as is?

2.  Glue the fan blade back on using krazy glue?

3.  Not use it at all?

I'm on a replicator 2

[Kobus du Toit]

Break off the opposite side.  I stuck an Allen key into my fan the first day, we broke off the opposite side to stabilize it.  It has been fine since then, except for the normal 2X fan issues

[Steve Gong]

That's a great idea.  I forgot to specify initially, but I'm on a Replicator 2.  I'm guessing it's the same kind of fan?

[Kobus du Toit]

Yep the little one that is infront of the extruder.  The little one that if you tighten the screws to make sure it is tight against the extruder then it can't turn because the plastic buckles

[Steve Gong]

I just realized this is a 9 bladed fan, so odd number of blades.  Just break off one of the two sort of opposite blades you say?

[Kobus du Toit]

I can take a photo for you tonight, in about 8 hours, how we fixed mine

[lassi kinnunen]

break off half of the opposing. if you can :).

seriously though, if it doesn't vibrate too badly, try to order a replacement and in the meanwhile keep using as is. if it's not vibrating too badly then trying to balance it by breaking off more can be a losing game where in the end you'll have no blades at all..

-lassi

[Ryan Carlyle]

9 blades, break off every third to balance it.

Or just buy a new fan...

[Jetguy]

I see you implemented the "Emergency Fan Self Destruct Mechanism".

 

User Eighty kindly made this sticker for Carl's aluminum carriage upgrade. https://groups.google.com/d/msg/makerbot/KYpKaSjLhlo/0dU7DmkUThgJ

 

On Tuesday, October 14, 2014 10:40:45 PM UTC-4, Steve Gong wrote:

While changing the filament, I snipped the end of it which fell into the fan and broke off a single fan blade.  (This is the front fan that cools the extruder)

I figured I probably should order a new fan anyway, but in the interim, should I...

1.  Keep using it as is?

2.  Glue the fan blade back on using krazy glue?

3.  Not use it at all?

[Kobus du Toit]

Lol yep and that was day 1 after spending more than $3k.  You can imagine I was not happy.  At that point in time I still thought if you spend $3k on a machine it is supposed to work

[Jetguy]

In real response, it will never be right. You pretty much should replace the fan. Most of use buy in bulk at this point.

 

You can break every 3rd blade but it's still never right. What then happens is less blades is less drag, it spins faster but is still out of balance. That in turn shakes the head and you can see it in the prints.

[Steve Gong]

Haha, Eighty's sticker is hilarious.  I guess breaking your fan is like an initiation thing.  Glad to be in the club finally.

I did some research, and found this fan:  http://www.ebay.com/itm/170764030269?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

This is the right fan, yes?

Someone mentioned it's not the right connector.  Can I just snip the wires from both the old and new fans, and just twist them together and tape with electrical tape?

Thanks

[Ryan Carlyle]

You can use any 40x10mm 24v brushless DC fan, with something like >6cfm for all-metal hot ends or >3cfm for PTFE-lined hot ends.

How you wire it is up to you, but remember that the fan wiring flexes a lot during printing, and if the join fails you may melt your carriage.

[lassi kinnunen]

I ended up rigging mine (after breaking both from dual rep1) with 12v in series on extruder 1. because 12v fans were easily available(from my box). not proper, but works ok(and I was using just one extruder -  and I think my bro is still running with that..).

-lassi

[Jetguy]

I need to give  you an important warning here. There is a MASSIVE difference between a Replicator 1 AKA Replicator Dual mightyboard rev E and any Makerbot Replicator 2 or 2X mainboard (AKA rev g and h).

That is that any 2 series mainboard has EXTREMELY fragile MOSFET outputs for the fans compared to a rep-1 AKA rev E.

Putting 12 volt fans in series, rigging up a resistor, or any of the other improper workarounds can result in not just the fan failing, but also you blowing the mainboard on A 2 series.

Don't play around with this. Again, if the fan fails, it likely fails drawing excessive current. When that happens, you now blow the mainboard.

Again, a Replicator 1 based machine has a HUGE MOSFET for each and every output that is the same that can drive a heated bed or extruder heater.

A Replicator 2 based board has maybe on it's best day 100-150mA for the fan outputs and that's pushing the MOSFET to the edge of destruction.

It's NOT WORTH DAMAGING the board to rig up a less than $10 fan because somebody said it will work and blow your board because you were too impatient to get the right fan. ONLY replace the fan with a like rated 24V fan.

[Jetguy]

I found the specifics here:

Dan Newman posted in the Tips and Tricks group in reference to a user with a 2X obviously a Rev G or H board https://groups.google.com/d/msg/3dprintertipstricksreviews/Vgq2z2_x1zc/9PfZqflsbBIJ

"The MOSFET they use for the cooling fan is a 2N7002K which is good for 60V but
only 0.3 A.  So make sure that the two fans combined use do not exceed that
current rating @ 24V. "

A mightyboard Rev E or clone in a Replicator 1 (AKA Replicator Dual, AKA Any Flash Forge, Wanhao, or CTC)

They use a PSMN7R0-30YL rated at 30V but a huge 76A!!! Now proper derating for driving with 5V gate and conservative cooling still says they should be good well north of maybe 20 Amps as the board, traces, connectors are likely to fail before the MOSFET goes. This is night and day difference from any 2 series board.

Factors we need to take into effect that seriously de-rate from maximum:

We use direct 5 volt logic driven from the processor.

Most of the MAX ratings on these data sheets are for a gate voltage of 10V not 5V

The board may not provide effective or adequate heatsinking to the FET.

The 5V gate drive means ON resistance is slightly higher meaning the FET gets hotter than normal (not fully saturated thus higher RDS ON), that in turn puts us further in the de-rating.

That's why I said at best, safely assume 100-150ma for safe reliable operation. AKA that means the max rating on the fan is 0.1 to 0.15A and that assumes 24 V rating. If you take a 12V fan on 24V and it's rated at 0.1A@12V, on 24V it likely draws a peak nearer to 0.2A AKA 200mA which is on the verge of smoking that FET. If the fan begins to fail, it could draw 300-400 mA and worst case is a total failure- maybe dead short.

[lassi kinnunen]

I don't really see how it would blow it up if it's two similar 100-150ma fans in _series_ vs. one 100-150ma 24v fan.

of course, you could just use another psu for the fans to be on the safe side, you want them running pretty much all the time anyways. thats how I ran all the other fans I had rigged to the rep1(for part cooling).

-lassi

[Jetguy]

Series is never a safe assumption. If one fan spins slower due to drag, broken blade, something caught in the fan, etc, now the other fan likely sees a higher voltage. It then blows and now we have a dead short.

Do you really want to risk the cascading failure? Electronics don't tolerate assumptions. They have hard limits. A 12 volt fan is rated at 12V for a reason. Further, the current rating of the fan is measured at 12V. If you double voltage, it's safe assumption current at least doubles if not more. Again, talking two passive devices, say a heater or a light bulb, current and power are generally the limits. You can put them in series and since they are relatively simple and even in failure, the device has sufficient capacity to not blow sky high. As soon as you get into electronics, now we have voltage, current, total power, and heat limitations. Exceeding any one factor is usually enough for total failure. Just because on paper, series makes it look like both fans only see 12V, that is not a safe long term all condition assumption. You have to plan for worst case and even then, have some safety margin beyond worst case.

In your case, you can go nuts on Replicator 1 because you have insanely high margin of overhead current capacity in the MOSFET. You blow a fan, one shorts, etc, no big deal, it burns the wires before it damages the board. Again, you will smoke the wiring long before the board goes.

The question is about a Replicator 2.

#1 there is only one fan.

#2 it has a known weak MOSFET.

Couple that with really bad information that "sure a 12V fan works fine for me" and now we aren't just talking about burning up the fan, now we are killing the poor owners mainboard too.

[lassi kinnunen]

well, a fan never broke for me so that it would act just as a conductor straight through and I don't see how it normally would. besides, if they broke like that, then you would burn the psu's QUITE often with broken fans if you think about it.

I'm just saying that I don't see the failure mode going like you describe, since no pc or any other device of mine has blown fuses because of someone holding the fan in place or fan bearings going bad or whatever - they have never shorted.

sure, the 12volt fan will break if you push 24volts through it. it's just that I don't see it happening here, the other fan would need to short or malfunction in a way that would blow any psu(or wires).

I would still say not to run different kind of fans.. and I haven't heard from anyone blowing their rep's whilst doing this(and it's quite common to do it in the series way, 24v fans are hard to come by locally almost everywhere).

and it did concern me initially that they're brushless dc motors. not for too long though.

as long as they're identical spec fans the voltage drop over each will be about equal. this is very common in pc modding circles, too.

-lassi

[Scott Booker]

When my original fan failed on my R2X it had a "melt down" and went dern near dead-short.  That popped the (fragile, as noted by Jetguy) FET on the Mightyboard.  MBI replaced the Mightyboard free of charge.  But that was "back in the day".... before MBI completely sucked.

[MacGyver]

I broke off a blade over a year ago, then I went on thingiverse and printed one of the replacement things broke the rest of the blades off and slipped on the replacement.  It's been working fine ever since.

Here's the one I used:

http://www.thingiverse.com/thing:186979

[Ryan Carlyle]

Putting brushless DC fans in series is questionable. There's some weird current chopping going on and you can't say for sure that there isn't any inductive kick or anything feeding from one fan to the other. 

A PC power supply is a HELL OF A LOT more robust than the Mightyboard, so stuff you can "get away with" on a PC can be a lot riskier on a 3d printer.

On Wednesday, October 15, 2014 4:33:54 AM UTC-5, lassi kinnunen wrote: