ajmadison wrote:I had the exact same warping problem (you have no idea how many bad/almost unacceptable prints I went through) you've experienced. I have installed this duct and have not worried about backpressure issues, AND solved my issues with over-cooling on the front. The below duct reduces maintenance access to the extruder nozzle. As that my routine involves doing the pre-extrusion and wiping the excess off before starting up the print, with its own pre-extrusion segment. The lack of access makes the pre-print extrusion process awkward. Not impossible, just more annoying than a "naked" nozzle.
I've looked into the fan/blower issue. I started by trying to track down the specs on the fan MakerGear supplies, which is a Sunon KDE2405PFV1 fan. The fan says 2.3W, but the only specs I could find are for a 1.4W power version:
https://www.gmelectronic.com/data/attac ... -173.1.pdf
This is an old fan, and is discontinued. I'm guessing that MakerGear got a good deal on a big supply, and that the 1.4W version is a newer one with a more efficient motor. Hopefully it has the same general airflow & noise specs.
Rather than trying to save a few bucks by getting an unknown fan off of eBay, I went to Digikey to look for a similar sized fan or blower that had similar specs but could handle more back pressure. I came up with:
https://www.digikey.com/products/en?key ... 70-1034-ND
This is a 50 mm x 50 mm x 15 mm regular fan. Specs are here: http://www.delta-fan.com/Download/Spec/AFB0524HHB.pdf
https://www.digikey.com/products/en?key ... 1282-ND%20
This is a 50 mm blower, 15 mm thick. Specs are here: http://www.mechatronics.com/pdf/B5015.pdf
https://www.digikey.com/products/en?key ... 1036-ND%20
This is a much quieter 50 mm blower. Specs are here: http://www.mechatronics.com/pdf/B5020.pdf
The critical specs are tabulated below. I had to assume that the original fan specs are the same as the lower power version:
The battle is largely between the middle pair. The quieter blower can handle only slightly better back pressure than the original fan, at half the CFM.
The 15mm thick fan draws less power than the original, and produces 30% boost in CFM and at a 66% increase in back pressure. The only downside is the extra weight, but that will probably get swapped by the shroud. The existing fan is supported by only one screw, so going to two should fix that.
The blower is 10 dB louder than the original fan, and produces less than 1/3rd the CFM at only a modest increase in back pressure. It also draws almost twice the DC power.
The trick is to compare the CFM vs back pressure curves. The one on the left is the 15 mm thick fan, and the one on the right is the blower (Digikey sells the "E" version):
Just as an initial data point, the fan can deliver the same 5 CFM as the free-air rating of the blower at a back pressure of 5 mm. However, at a back pressure of 5 mm, the blower can only deliver ~ 4 CFM. At least in that back pressure regime, the fan wins on CFM by 20%. At a back pressure of 6mm, the fan is at ~ 3 CFM, while the blower has barely noticed, and is still putting out close to 4 CFM. I'm not sure how I could quantify the back pressure of a shroud, but 5 to 6 mm sounds like a lot.
I've ordered one of the fans, and the appropriate connector & pins to plug it into the existing harness block. With the possible exception of the added weight it should just bolt right on in place of the old one.
As for shrouds, I've looked at both of ajmadison's designs, and will probably use one as a starting point. The ring is nice, but I also like to be able to clean my nozzle easily. The single nozzle still has a bit of a problem that it will tend to cool the front of things more than the rear, but the affected area is much smaller. There are a couple of designs where the nozzles are split, and feed in from each side. That gives more uniform cooling, and still has reasonable access to the nozzle. I thought I found one that looked like a good starting point, but I can't locate it now. Here's a design using that concept with a fan, but for a different printer:
https://cdn.thingiverse.com/renders/4e/ ... atured.jpg
For those who want to dig into this swamp further, I also found a couple detailed studies of the effectiveness of different fan, blower & duct combinations: