Replicator MightyBoard Airflow Rework
by garyacrowellsr, published
The standard fan positioned to cool the MightyBoard can be reworked to greatly improve the cooling. Maybe we can avoid a few popped voltage regulators. Very little here is original; I've simply appropriated and combined several fine things.
As it originally sits, the fan is positioned to draw air mostly from the heated build chamber. What's more, free standing as it is, it also largely just recirculates the warm air under the base plate; there is little cooling airflow.
This thing re-routes the airflow of the original fan, and adds a location for a second fan.
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The first thing we've got to do is close off the base from the heated build chamber. Fortunately, this is well handled with things 29858 and 29862 by DDStarkey; I recommend them highly. The only change is that the cover that goes in the right rear corner needs to be cut off so it does not extend into the bottom chamber. As-is it will interfere with the duct I'm going to put there. I just sliced it off with a scroll saw.
The next thing I did was print the new fan plate from Dave Randolph's thing 24066. It's not totally necessary to print it; you could just take the existing plate and cut and drill it to add a new fan mounting location. Dave's plate does have a smaller cable opening which helps keep the air flowing where you want it, but you could just tape off the hole on the existing plate. If you print Dave's plate, you might want to make it about 50% thicker, but it works fine as is.
The new fan that will be mounted on the plate needs to have an air intake. Dave suggests some cutouts on his thing, but I just took a hole saw to the existing bottom plate near where the fan will mount, as shown. Note also that I cut off the corner of the bottom plate so that it could be removed without removing the foot on that corner.
Now, the original fan is positioned well to blow directly over the hot voltage regulator, but I wanted it to draw air in from outside the box. That meant sawing a hole in the side panel. First remove the fan and standoffs, and set the fan on the outside of the box, and drop the bolts through the original holes. Then mark positions for the other two holes. (A transfer punch is the ideal tool for marking stuff like this, really cheap at HF: http://www.harborfreight.com/28-piece-transfer-punch-set-3577.html You'll be surprised at how often you use it.) Drill out those two new holes, and mark the center point from them. A 1.5" hole saw takes care of the hole, but be careful to avoid any of the wires inside, and cover the MightyBoard to keep the sawdust off.
Print up the duct and fan guard. The fan duct is thing 18273 by doommeister. He made the thing parametric so it was easy to set it to an 18mm length to place the fan where I wanted. The fan mounts to the duct, and I added a pair of rubber grommets for a bit of vibration damping. Be sure you get the fan direction correct; you want the fan blowing into the Replicator. Then mount the fan guard and duct to the side panel. The fan guard extends outward from the side a bit, so you can't lay something flat against it and cut off the airflow. (2) M3x25mm screws on the fan side, and (4) M3x10mm screws on the outside.
Finally, I really recommend some better fans. All of the fans in my Replicator are making noise. I was going to just get some cheap replacements off of ebay, but then I decided that I'd really rather only do this once. So I've got some new ones on order that I think will work well and probably outlast the life of the Replicator. 40mm ball bearing fans in 10mm thickness aren't all that common. I ordered Orion fans from Allied Electronics www.alliedelec.com
70103494 OD4010-24MB $9.63 ea. Fan; DC; 24V; Plastic; 6 CFM; 4800 RPM; 20dB; 0.04A; Ball; Leads; 40x10mm
70103497 OD4020-24HB $9.64 ea. Fan; DC; 24V; Plastic; 9 CFM; 7800 RPM; 32dB; 0.07A; Ball; Leads; 40x20mm
I ordered two of each. The 20mm thick fans will go in the bottom where the thickness doesn't matter, and the 10mm fans will replace those on the extruders. I will report on how those work out when I get them installed.
Finally, someone on the forum suggested insulating the bottom of the build chamber, and coincidentally I had just received a package with some foil insulated bubble wrap. Maybe overkill, but it doesn't hurt anything and easy to cut to fit. A bit of double-sided tape holds it in place just fine. Looks cool too. (If you didn't happen to receive a foil package, the same stuff appears to be called Reflectix, available at Home Depot. http://www.homedepot.com/h_d1/N-5yc1v/R-100318552/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=foil+insulation&storeId=10051#.UL03KIPEbaM )
After installing the two Orion 40x20mm 24V fans in the base, well, it had great airflow, but it was frankly much too loud. I wound up putting them in series, and that tamed things down nicely. There's now just a nice hum, and I could probably get rid of that with some more insulation on the mounting. If I were doing this again, I wouldn't bother with getting the 20mm thick fans, and just get four of the 10mm.
As someone pointed out on the MakerBot Group, the Orion fans are not countersunk for socket head bolts like the original fans were. No difference on the bottom fans, but this is a problem for the extruder fans. It might be necessary to get new bolts, but I tried drilling them out first. It turned out that a step drill on a small drill press worked perfectly! Practice first on one of the upper fan holes that is not used, then carefully, and with frequent checking bore out the bottom holes. The result was perfect and they mounted up with the original bolts with no problem.
The extruder fans are now utterly silent. I have to look to see if they are on.
(In the picture of splicing the extruder fan wires, yes, it's ugly, but I left the extra wire length because I'm doing the XL upgrade soon.)
I notice that the same Orion 10mm fan is available for slightly less from Digi-Key. Also for the same price there is a choice of different RPM and airflow (5, 6, or 7 CFM). The -MB model I chose is the 6 CFM model. Used in the extruders, using an airflow different from the original MBI fans might have an effect on the cooling of the filament feed. Too much cooling and it might jam if the heater can't keep up; too little, and it might jam if the filament softens in the feeder. I haven't noticed any issues with the -MB model. The three Digi-Key numbers are: OD4010-24LB .. 1053-1211-ND .. 4200 RPM .. 5.0 CFM OD4010-24MB .. 1053-1212-ND .. 4800 RPM .. 6.0 CFM OD4010-24HB .. 1053-1208-ND .. 6000 RPM .. 7.0 CFM