Width 6mm to 17mm Self-adhesive EPDM Foaming Strips Self-adhesive Flat Square Strip Glued EPDM Foaming Sealing Strips (WHL #118)
Slot covers. Slot covers for aluminium extrusions. That’s the topic for today.
Just the other day I was thinking about sealing against a 2020 extrusion slot. In a sort-of air-tight way. And after tinkering and ordering a bunch of samples of things that could work, I had a second look into one of the options: This could work for pure looks as well.
You see, the classic 40×40 (or larger, like 40×80, 40×160 if you like it beefy) aluminium profiles have readily available sealing strips against dust. Depending on exact slot type (since there are a couple of manufacturers/specifications), the typical slot to cover is like 8mm wide and goes 14ish millimeters deep. And the most economical and prevalent way to do so is by one of these strips:
They’re made from polypropylene, cost like one Euro per meter, sometimes come in 1m strips for easy shipping (looks cheap when your slot to cover is longer than that and you have several pieces slotted in there), or in 2m pieces which usually bend in storage. Can be mounted basically flush with the extrusion, and can be inserted later on, but shoving them in beforehand is much easier – which also means they’re not sealing properly, they just occupy 98% of the space. Not perfect, but it works and is cheap.
On the 20×20 (“2020”) ones, this isn’t offered as far as I know. Maybe the smaller dimensions make it difficult for regular PP to bend and then snap snugly into place and not get damaged in the process, and other materials make it seem excessively expensive for what these things actually do. Or maybe nobody cares to cover these slots, although I have personally printed covers, but more for albedo reasons, I needed black extrusions to be as white as possible. Anyway, 30×30 / “3030” profiles are also not really covered (ha!) by those stiff slot strips.
There are flexible solutions, though, attached is one of the advertising images from some Aliexpress seller. These covers all have a closed O shape, but do not fit the extrusions perfectly, as can even be seen in the photo below. So they don’t seal on top, neither do they squeeze against the sides or the bottom, and they do protrude on the top, so the seal sits higher than the aluminium piece. Maybe they’re trying to emulate the 4040 covers and are therefore slightly undersized, despite being a flexible PVC material that would work well in an oversized fashion? I don’t know, seems odd to me. They do come in quite a variety of colors, though, so even with the limited anodizing colors of the aluminium (typically natural-silvery and black, but I have seen some golden ones as well), the combination with a slot cover can really make a contraption pop visually.
And here’s the thing: Why not use foam? With the stuff that I ordered for actual sealing purposes, I do get a very nice fill of the 2020 slots, because 9mm x 4mm is technically oversized. And since it is foam and not a block of rubber (those do exist as well, different application!), it is easy to compress them a little to get them in from the top, and it’s relatively easy to get them back out. Here’s an example with the last bit on the left hanging in there, this is how the stuff is pushed in:
But unless it ages and decays, it’s pressing against all surfaces. So slotting it in from the front is basically impossible due to friction.
This is sold as EPDM foam – I don’t know if it really is ethylene propylene diene monomer rubber, but unlike other rubbery products from Aliexpress, this one doesn’t reek of an entire chemical plant. The surface is somewhat delicate, it does survive multiple insertions and removals just fine, but scraping over the strip when in place can ruin the pretty surface structure and leave permanent marks. Shoutout to my second WHL post from January 2016 (jeez!) with the prying tools – this, moved slowly across after installation, is the perfect tool for a smooth surface
If this works out for the sealing application I’ll likely feature this again, but even if it does not, I probably will order a bunch more of these for dust-proofing all the existing 2020 profiles with open slots facing up or sideways.
This was a somewhat “special order” via Aliexpress from seller “SHININGHAIDER RUBBER AND PLASTIC PRODUCTS“, because this exact size is hard to find, and they were the only ones that clearly sell foam and not solid EPDM/rubber (some sellers are strangely secretive about that in their product photos and description). One however cannot order directly, their only 9×4 offer has a glue backing and I figured this would make a worse seal with the backing paper still in place, or a terrible thing to get right with the glue side activated. So I texted them and asked for no glue backing – which they happily offered to me, although I suspect they specifically made that for me. And they didn’t even charge me for it – instead, they threw in one meter (= 10%) extra for free. That’s customer service 
(hence my direct link to their offer, which I typically don’t do as all of those offers might vanish tomorrow). In terms of pricing, I paid 13.49€ for those 11 meters, or 1.23€/m, shipping was free via the choice shipping option.
Stores easily, doesn’t bend out of shape, seals properly and has a nice matte finish where exposed – I like it.
