The main goal is getting the inside of my new computer as dust free as possible.
All of my previous computers needed to be regularly opened and the dust blown out, the earlier ones I even had to take them apart to do this and they had no dust filters. None.
Yes, you can buy filtered cases for industrial use but they are big, ugly and probably sound like a jet engine while my design needs to be very quiet and small – well, small enough to fit behind the monitor on my desk which has specific size limits since it is in a corner.
As you can guess, I don't want glass doors, RGB or any bling at all either.
The new computer will be built in a case that comes with dust filters – but these filters are thin fabric mesh, only effective for larger bits of dust like hair – the fine stuff just goes straight through and there is a reason for that: the better the filtration, the harder the fans have to work to suck air through them.
None of the cases I have seen met my needs so I settled for the Fractal Define 7 Compact knowing that I would have to modify it to get what I wanted.
I found a review that suggested that there is not enough front air intake area in the Define 7 Compact case as supplied. Nobody mentioned the total lack of positive pressure though: it seems that other people don't care if there are gaps between the fans or if parts of the case block fan intakes. Some areas of the case have vent holes in places that make it look like the airflow can easily become circular! I am not going to have any of that though. The filter box will leave a gap at the bottom where air from the bottom of the case can be drawn in.
My mods will not show outside the finished case and they should give positive pressure.
Please note that I am not complaining about the case: I am sure that Fractal made a good case, it is just that my needs are apparently a bit unusual.
THE CASE MODS
The design uses automotive air filters (the type used for cabin air, not the engine ones) which will be sucked on by three 120mm Noctua fans. Finding the right filters was a bit tedious since the measurements need to be close but I found something that will do. They are listed as “ Ryco Cabin Air Pollen Filter RCA294P fits Great Wall X200 2.0DT 4x4” and cost $45.90 AU for two.
Stage 1
To make sure the filtered air all goes into the case and provides positive pressure I worked out the places where the case needed to be sealed off and made patterns for the parts. I did this with cardboard and used sticky tape to hold them in place.
There is the filter box, the lower air box which seals off the bottom of the case from the insides and two blanking plates, one to close the hole at the bottom of the door and one for the inside bottom of the case.
Stage 2
Next I got some ABS sheet off Ebay – this was not cheap but it is well worth it.
Since it was black I put masking tape over the sheets where I wanted to draw lines and then marked out the parts from the patterns I had made on the tape.
The back of the filter box was made of 5mm thick sheet , most of the rest were 2mm and the blanking parts were 1mm sheet.
To cut the back of the filter box I first drilled out the fan holes with a 115mm hole saw. This is best done first since if they are off or you get the plastic too hot it could ruin it. In a bigger sheet it will be more stable and easier to handle. Then I cut the outside shape with a saw.
The thinner parts were cut with a heavy craft knife – clamp a metal ruler over the line you want then cut repeatedly until it gets thin or the groove gets deep enough that you can crack it off. Sand and file everything to exact size and you are done. Note that cut edges will have a raised edge and a V shaped profile which is why you need to file and sand.
Stage 3
I taped all of the filter box parts together with masking tape on the outside and checked that they all fit together nicely at the joins. Then it was a simple matter of running superglue ( I used Zap-a-gap) along inside the seams to stick them together. You don't need a lot of glue and it should run along the seams by itself, with a little help from gravity.
Once the glue was set I took off the tape and ran more glue on the outside seams now exposed.
Stage 4
While the glue was drying I got out my dremel- like device and suitably covered in mask, earmuffs, safety glasses and gloves, chopped the front of the case to fit the filter box.
Before I did this I took everything removable off the case as the metal and paint dust is the type of gunk that you do NOT want in a PC case. It took an hour or two and three saw blades but I kept at it and chopped the front out as well as a small part of the inside so that the filter box would go behind the case front plate.
After that I filed all of the metal edges as smooth as possible and then washed the whole case in lots of water and a cleaning rag to get all of the metal dust off.
This is crucial and I washed it twice as I missed some corners the first time.
Stage 5
I sanded the filter box to get rid of the glue lumps on the outside and taped it into the case and started fitting the parts of the lower air box to the case with more sticky tape, adjusting the part shapes until they all fitted neatly together.
Then it was a simple task to take the assembled lower air box parts out and glue them together as previously described. While that dried I worked on the filter box. I needed to add some supports for the filters and I had already drilled holes for some coathanger wire rods across the box for this purpose. I wanted to make sure the spot in the middle where the two filters met did not leak and I found an offcut of 5mm that fitted nicely there. I also made three small blocks of 5mm on the side of the box where it could be screwed into the case.
By using screws to attach it I could modify it later and it just looked neater.
Stage 6
The lower filter box needed finishing and a bit of reinforcement but once that was done and filed down neatly it all looked good. The bottom screw holding the filter box also holds on the lower air box. Originally I thought of gluing it all into the case but in the end I got some heavy black tape and used that to seal the air gaps and fix the lower air box to the case.
Stage 7
The door blanker was glued in, the big plate stuck inside the case with double side tape and then there was one last thing to do: The knobs that clip the door on needed to be shaved a little to avoid hitting the filter box.
Once everything was installed it looked good. I did not paint the cut areas of the case as it was more trouble that it was worth – this is not a display case. I don't expect the metal to rust as it should not get wet.
After finishing the installation of everything and testing, it all works just fine, no overheating anywhere - but then I credit that to AMD making an excellent CPU with a nice big heat spreader and Noctua making a good cooler to match it. The new PC has an AMD 3970 CPU and an Nvidia RTX 3090 GPU and it really is a big improvement over the old one.
