carbon pellet filter box

For the line filter I wanted to use carbon charcoal pellets. This filter box keeps those pellets inside and in place. I used pellets with 4mm diameter.

The original design is great, just not for pellets. It falls apart if you disassemble the line filter, makin quite a mess - see picture. Also the pellets fall through the mesh holder.

The lid fits all sizes

There are different sizes, the size defines the free space inside for the carbon pellets

With pellets alone the size of 20-25 mm seems to work ok for me. This all depens on your type of fan of course.

It is also possible to add a carbon mesh filter, then you could use a larger size.

Print the lid and the box of your liking.

assembly

For assembly you will need 9 M4 bolts and hex nuts. I did not use washers

Test the fit of the lid first.

Add some pellets and shake the box, so that the smaller pellets get sorted out. With my batch there were quite some pellets smaller than 4mm diameter.

Insert the Bolts from the bottom of the box.
Fill the box with pellets.
You will need to overfill a little bit, the pellets seem to be fall into place and take less space.
Add the lid and hex nuts.
Be careful when tightening the nuts.
Shake the box, so the pellets fall into place.
Finally tighten the bolts carefully, do not apply to much force, or the corners of the lid will be raised. 

There should be enough pellets inside, so that they dont move if you move the box around.

Mount together with the line filter parts

If the air flow is too low, print a smaller box height.

added a box to hold the carbon pellets in place