PoorMan’s Fan Filter

Like it says – Gene Hardesty aka “MoFoQ”

How To Make a Cheap Fan Filter

Here are the materials:


  • Used dryer sheets ($free)
  • Clear plastic packaging ($free)

And the necessary tools:


  • Scissors
  • Ruler (preferably a metal one)
  • Xacto knife and cutting mat
  • Super glue
  • The target fan
  • Sharpie
  • Zippo lighter fluid (naphtha)

By the way, my Xacto knife looks a tad different from the pic above. It’s the X2000, here:


Let’s Begin!


First, find enough space on the clear plastic and roughly cut it with scissors.


Using the target fan as a guide, make the necessary outlines on the plastic with the Sharpie.
If you make a mistake, just use a tissue or cloth with the lighter fluid to wipe it clean.



Using a ruler, measure 5mm (0.5cm) from the edge of the outline and make two marks per side and connect them. Where the lines intersect, that’s where the holes are (roughly), and basically we want to avoid cutting too close to the intersections.

PII Case Diagram

PII Case Diagram

Use the fan and make diagonal lines accordingly,
and mark half way (in this case, since it’s an 80mm case fan, that would be 40mm) on both orientations and make the lines. The lines don’t need to be perfect.


Make two sets of marks per line, 2mm from the center lines and draw them.
Mark the holes and, if you wish, scribble in the area that will be removed (using a different color is best).



Use the Xacto (or equivalent) and score the inside areas to be removed.
You don’t need to cut all the way through as it’s easier to score and peel.

PII Case Diagram

To make it easier to “peel,” cut through one corner of each area and simply apply pressure. The scoring will help guide how it splits.
In fact, once it gets going with the help of the corner cuts, it comes out as if it were peeled.

Next, we need to clean it up and trim away the unnecessary parts of the plastic.
To do that, you’ll need to make an incision in the corner as shown, score, then bend.
One of the sides is not marked, that part well, because of the way the plastic is formed, it is thin enough to cut easily without the need to score it.


Now the tough part (though this is a little different in the improved version as it will be discussed later).
One way is to outline the circles with hexagonal scoring and then score cross lines, after which, poking through and peeling back the unneeded parts can be done.
Make any final adjustments (such as hole enlarging) if needed.


Finally, score the two halves (or whatever you may have) and make them into two.

PII Case Diagram


Next, let’s clean off the Sharpie marks, though you can skip this step.


Now onto the gluing of the “filter.”

To start, glue just one corner. Avoid plugging the hole up by gluing only one side of the hole. Spread the blob of glue if need be and use a scrap piece of plastic to hold down to avoid getting too “attached” to the filter.


Wait for the corner to dry, as this is necessary to hold the “filter” in place.
Once it’s dry, proceed to glue two of the squares. Remember – the inner areas need more glue than the outer areas as you don’t want to cover the holes up (see the “Glue map” on the right).
Stretch the filter over it and use the scrap plastic to secure it down. This is why gluing one corner first is important – so you can securely stretch it.



Do the rest once dry.


Trim the filter.

Final Cut

Here’s the completed fan filter pic:


Improved Version

Afterwards, I improved the original design, as cutting out the holes can be a pain (using a hole puncher is possible but the hole might be too big for typical fan screws).
So, I decided to notch it out. This allows for one more added benefit – the filter can be removed and replaced without the need to unscrew the fan. Perfect for quick changing filters, especially “disposable” filters like these.


Gene Hardesty – aka “MoFoQ”

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