Need exhaust fan

The -S99 is not in stock at Digi - 1 month lead time - and Mouser doesn’t stock it. I’ve checked eBay and Amazon.

Does anyone have a used fan to spare? :slight_smile:

(also will need some 1744423-1 terminals, if I can’t find a former GF-deployed unit…)

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… or should I just leave it out, and rely on an external fan in the ducting - the unit seems to operate just fine without the built-in exhaust fan, and it sure is a lot quieter!

As per usual, it appears that a Glowforge design decision has pigeonholed everyone.

Barring your external fan solution, and focusing on replacing the factory fan, the issue is matching the designed airflow balance with a fan that works with the control system. The intake and exhaust fans are balanced in a way to create a negative airflow inside the unit. This reduces the amount of noxious gasses that will leak out of the non-airtight seams. The gaps are all over the Glowforge, not just the door.

There are several required specifications for the fan:

  1. Airflow: >= 182.4 CFM @ 13,000 RPM
    This is required to maintain the negative interior pressure. The airflow can be higher that this, but the RPM must be exactly this (see below).

  2. Physical Size: 92mm x 92mm x <= 38mm
    This is the mounting size for the existing fan. I don’t have a Pro, so I am assuming if it is thicker than 38mm it may not fit with thermoelectric cooler heatsink.

  3. Electrical: 12 VDC, PWM speed control, x2 tachometer output
    These are required as they match the existing electrical and control interfaces. Note that currently the GF control system simply sets the PWM input to the fan at 100% (full speed).

  4. RPM: 13,000
    The Glowforge control system will set the fan at maximum speed, and will expect to see the tachometer output a ~26 kHz square wave. They are definitely monitoring this and sending this value as part of their telemetry, but I don’t know if they currently alert the user or halt printing if there is a problem*.

The reason why I say they pigeonholed everyone is because there is exactly one manufacturer (at least the only one I can find) with exactly one part number that matches these specifications, and that is the Sunon PF92381BX-000U-S99 (datasheet). Which, as you have noticed, doesn’t currently seem to be stocked any place where it can be purchased in single quantities. A single source with a single product doesn’t exactly give you a lot of choices when it comes to availability of alternatives.

*Since you are running without the fan in place, makes me think they are not halting prints on exhaust fan failures. I haven’t been keeping up on the product announcements or the updates to the firmware (I haven’t worked on this project in quite some time), so I may have missed a notice about fan alarms (other than this one). And, of course, because it works for you now doesn’t mean they won’t release a firmware update (without advance notice, of course) that will stop it from working and leave you dead in the water.

Thanks, Scott. After a lot of research, I’m thinking of going in a different direction.

Side note - I’ve found another fan (Sanyo Denki America Inc. 9GV0912P1G03) that appears to match the specs. I just don’t think I’m going that way now for multiple reasons.

90mm Fans are hugely inefficient for these kinds of air volumes. I already have a cheap external AC-powered fan (240CFM rated), as I have about 20’ of ducting. The fan unit itself has a larger impeller, just necks down to 4". I’ve had no smoke/odor issues, and it’s also very quiet. I’ve made a few cuts since removing my internal exhaust fan without issue.

I think I’m going to build an enclosure for a grid of cheap, commonly available fans, large enough to throw a standard HVAC filter in front of. Probably AC powered, as that increases efficiency - and building a simple PWM->relay to turn them on when the GD “demands”. If the firmware changes to “detect” fan speed, I can easily add functionality to send the appropriate signal back (I’m an EE…)

I’ll add, removing the provided fan with the pro heatsink is a major PIA! I’ll be glad to never have to repeat that process again!

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There’s an option to disable the fan entirely (for people using the Compact Filter) so one could always use that.

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Mouser has it, I just had one overnighted.

Also, as far as disabling the fan altogether, when I do glass, I use wet paper on top of the glass and I turn on compact filter even though I don’t have one, just so it won’t blow air on the glass and dry out my paper and get it flapping in the wind and mess up my engrave. Anyway just a little for what it’s worth info there.


Unless you know of a different supplier, doesn’t stock it or have an assigned part number for it.

They DO have the -A99, which is not the same part. It does not have PWM controller or tach output - so it will be running at full speed the entire time the machine is powered on.

Edit - I am assuming you’re in the USA. They may carry it outside of the USA…

It already runs at full speed during normal operation. As long as they are not alarming on the tach output, it will probably be ok. Just annoying. You could put a switch on it.

Hey, I posted this in the other thread too but I got my 6" 390CFM fan today and put it in the exhaust line. Even on high I’m getting a pretty smoky smell in the room with it. It was never like this when my GF exhaust fan was working. Any thoughts?

I’m currently removing an apparently dead fan from my pro, so will get the pics loaded later today.
Now I can see how it’s constructed, I think I’ll post what may be an easier way to release the tabs, ie from the outside, not from the inside.
The bottom bolts of the fan, as all have observed are a PITA, but I’ve cut down an allen key to have a 1/4" side arm, and that worked.
I say apparently dead fan, as its lack of movement yesterday made the decision to go ahead on my out-of-warranty unit for me.

Should I be able to hook up a 12v supply, and to which of the four leads - I’d guess black/red ?

Yup. Without a PWM signal, it runs at full speed.

Just put a multimeter across red/black, but appears to be open circuit, rather than about 3 ohms that I would expect ?

I had this issue. I tested my exhaust. Carefully I sprayed a light mist of water over the exhaust hose to check for leaks. Turned out the glow forge was sucking some of it back in through the top of the window.

I did not want to seal the window so I ended up just going through a wall with the exhaust vent .

Then I added an closable inlet vent (No Hose) for fresh air from a different wall and positioned it right behind the glowforge and lined it up with the bottom so it gets sucked right into the bottom of the glowforge.

Hope thats helpful.

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No used fan, I’m afraid.

I bought this as a booster fan. If I turn it on before I turn on the GF, it spins the original fan up to what sounds like a higher speed than original. I like that I could have it half-way through my duct run, and that mounting it to the table top was a matter of two clamps, so it’s moveable. I bought an external on/off switch, too.

I’ve now put a 9v battery across the red/black leads, and discovered that, in two starting positions it will run, but in the other two it doesn’t move. This leads me to suspect a fault in the switching electronics.
Bit hazy about the details, but my next move will be to re-install the fan, but on the outside of the exhaust exit, so that I can see if it behaves in the same way once connected.
I could then build in simpler cleaning access, and possible further work on the fan.

Curious to see how this has progressed.

My inline duct fan has been fine for what little I’ve done with the machine since my exhaust fan failed, but I’ve been idly investigating other options. I’m leaning towards an enclosure similar to cheap window fans, with a number of fans drawing thru a cheap (low resistance) HVAC filter.

I’ll be doing the construction work this afternoon, But I have to work out how to get at the fan blades to poke them into the working ‘start’ position, yet keep the exhaust contained.
I need to be able to see the blades ( small acrylic window, perhaps) and have a rod to move them, mounted through a rubber grommet in the wall of the pipe.
I’m still trying to find some sort of circuit diagram for the electronics inside the fan housing, but quite prepared to take it apart and take a look see!
John :upside_down_face:

Having thought about this for 24 hours, with advice from swmbo, I decided to go ahead and order a replacement from Digi-Key.
With taxes and carriage, the total cost is about $40.
I’ve opened the fan, ie removed the circlip and slid the rotor off, but complete acess to the pcb is prevented by the construction. I brushed off all the crud that was on the face of the board that I could see, but re-assembled, the fan was still behaving the same.
So nothing possible there then.
John :upside_down_face:

All credit to Digi-Key for a 3 day delivery over the weekend.
The new fan has been installed, and tested in place, and works perfectly.
In fact, I suspect that with the removal of the grid, it now produces a more uniform flow.
The installation was a nightmare, to be honest.
It would seem to me that the fan was mounted on the back plate of the internals before the whole lot was lowered into the case. Thus having the case lugs for the heat sink to bolt onto made no difference ! However, it does. If they had had the lugs and bolt holes even 1/4" nearer to the front (1/2" would be doable, and better), re-assembly would have been perfectly straight forward.
It took me about an hour, great patience and some luck, along with a sawn-off allen key, to get the fan bolted on.
John :upside_down_face:

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