This is an "as is where is" design.
I quickly designed this part to help with a problem I was having in reliably printing large structural parts. These are parts that fill the print area and have been up to 80+mm high, also printed with a high fill (>60%).
There were many failed attempts to print these types of parts with the unmodified machine. It seemed to me that there is a good reason industrial machines have heated print chambers etc.
So as an attempt to get an improvement I covered the sides, front and top of the machine and these modifications produced better results but still not usable parts. This prompted me try adding this duct and was rewarded with my sanity and good parts.
WARNING: I used this duct with no problems until I updated the Replicator to V6.2, this caused a small problem when a job is started. The machine with this version moves to the far front left corner before printing, this caused the duct to collide with the top rim of the Replicator. This was fixed (like other things in my life) by taking a saw to the top rim of the machine (see attached image). If the M3 bolt heads used are high they can also collide with the left end of the front panel of the machine, further sawing can fix this as well. If these mods put you off do not bother employing this design.
The Duct has one inlet tube that splits in two internally in front of the fans and two outlet tubes, one on each side of the head. It was designed (before V6.2) to fit inside of the machine without colliding with anything (unfortunately V6.2 spoiled the party and a mod was needed). On the right of the duct is a thin section that sticks out over the position where the home micro switch hits (this was a fix as the right outlet tube was a little thick stopping the switch from working, I have added it to the design so I did not have to change the tube).
No real design was done on the flow of air in and out, it was design as it is as a guess as to what was needed, keeping in mind that sometimes only one fan runs. My machine has been working without fault for about 9 months with good result for the problems I aimed to fix.
There are six parts to make and assemble, I glued the parts with Acetone. There are two holes in the front top corners that two 31mm (cut longer bolts if needed) M3 bolts go though, these need a couple spacers (~2mm) on them before guiding them thought the holes in the fans and a nut added to secure them. I added a small bit of tape under the front to stop any leakage of air down on to the job though the gap.
It was printed on a MakerBot Replicator with the following setup:
Object infill = 30% (parts are very thin so anything will do)
Layer Thickness = 0.333mm
Number of shells = 0
Feed rate = 30mm/sec
Note: A saw could be used in the fitting of this part to your machine.... 1) Do not destroy your guitar career by modifying your fingers..... 2) do not turn your Replicator in to art.
Note: There is no guarantee this will make any difference or improvement to anything you print. I have convinced myself it works and that's the story I'm sticking to.
Note: Fit and use this part at your own risk!!!!!