I had the circuit board fan in my CR-10 fail after about 2 months of use. I took the unit apart and replaced the fan, but while I was in there I was unimpressed with the units overall cooling, especially given the amount of time its on per day. So of course the maker side of me decided to fix the problem with the machine with the machine!
I printed these as two separate parts that interlock so they would fit on the machine print bed easily. They exactly fit 120mm fans and have the mounting holes as well. I've notched out the area for the 3 wire to come out the back. In my case, I got a small CPU power supply and juice them up from a toggle switch. I placed the front fan blowing up and the rear fan blowing down to maximize air flow thru the unit. You'll need to remove the bottom plate from the unit to allow the air flow from this base design.
The result: MUCH better cooling, which should lead to longer component life.
I've uploaded the STL files, but let me know if you're interested in another file format. I own Solidworks and can export to nearly any file type.
You can print with or without the raft, just need to make sure it stays stuck down, as the lowest surface is holding the unit level. You'll need supports but just at the build platform. I used PLA at 100mm speeds with no issues. I'm sure you can print out of PETG as well.
Solidworks, a tape measure and a pair of digital calipers
I just measured the Cr-10 unit and gave the base clearance. Measured two standard 120mm fans to ensure their fit. Carved out an area for the wires, then drafted and filleted for looks. Finally, I split the model into two pieces and created interlocking tab/slots to snap it together.