Encasing the Monocle without breaking the bank

I’ve looked at the prices for acrylic sheet as case material for the Monocle and my heart shrank. If I’m paying that much for acrylic, I want to be shooting it with a laser to make something useful or beautiful. Heavy-duty aluminum sheet isn’t cheap either. But it needs to be encased to be safe, of course.

What can I do?

A CO2 laser won’t cut through aluminum even when it’s focused, at least at the power range that could possibly be installed in this machine. It won’t even cut through aluminum foil.

It turns out that aluminum flashing isn’t terribly expensive, and is widely available in a variety of widths. But (as @Eclsnowman pointed out ot me) alone it would oil-can and sound a terrible racket, as he discovered with 3d printers and 1/8" acrylic long ago.

That led me to think about Aluminum Composite Material (ACM), an aluminum/plastic/aluminum sandwich often used for making signs. It’s easy to cut, the aluminum would not burn from the laser, and it looks nice enough to use as a sign. But it turns out it’s not particularly cheap either.

So for a large-format laser, it starts to look like the box could cost more than the laser.

But you know what else is cheap? Masonite and contact cement are really not very expensive.

I could make my own “ACM” that’s an aluminum/masonite/aluminum composite sandwich, held together with contact cement. Masonite doesn’t burn that easily, and since it’s made of just wood I would expect that if were to catch fire somehow and be extinguished, it would probably (a) be easier to extinguish than the plastic in normal ACM and (b) be less likely to give off noxious fumes.

A 4’ x 8’ masonite panel is less than $10 in 1/8" nominal thickness; it’s available in 1/4" as well. A 20" x 50’ of aluminum flashing costs $43. 20" is 508mm, plenty for the largest likely useful depth for a Monocle, though you can get it 24" wide for $60 if you need over 600mm. $15 will get a quart of contact cement which is more than you’d need here anyway.

I would imagine cutting the masonite to size, gluing a very slightly undersized piece of aluminum to the inside face, and then gluing a ~4cm oversized piece centered on the outside face. Trim out the corners with shears, then fold it over and file the corners smooth. Glue those folded edges to the inside surface with more contact cement and clamp them in place.

It might even look nice. Brushed aluminum is classic, right?

Am I nuts?

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You can also use Faced Polystyrene Foam Board Insulation. It is used as outdoor siding underlayment. This would dampen the noise too.

If there were a fire inside the cutter, it could easily melt the polystyrene before I could put it out. Burning styrene gets very hot, and burning styrene fumes aren’t great to breathe. Of foam products, faced polyisocyanurate would probably be better. I used it to build my filament drying oven because of its flame resistance.


The masonite alu dibond sounds like a reasonable idea to me.


As tempting as it is to tape aluminum to the sides and use the laser cutter to cut out its own masonite side panels, I think I’ll use the router to cut the side panels. :slight_smile:


I ordered the aluminum flashing today. Projected to get here within the week. Hopefully by the time it gets here I have the CNC router functional again and can use it to cut masonite for the underside panel to stiffen the Monocle while I’m working on it.

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Actually, the underside panel will be too big for the CNC router. The other panels should fit, but the underside panel I’ll have to cut by hand…

It turns out that water-based contact cement does not bond well to aluminum, and I’m not super interested in using lots of the high-VOC organic solvent contact cement here. Also, it might be a challenge to bond aluminum sheet to the rough side of the masonite. I’ve been reading up on what people have done to bond metal to wood, and they point out that flexible adhesives are a good idea. I’m now thinking about a thin-spread coat of elastomeric caulk, like 3M 5200 or DAP Dynaflex 920. I don’t need much mechanical strength, just enough to keep the aluminum from making oil-canning noises…

I ended up with a construction adhesive instead. I chose gorilla because it was lower VOC (2% vs I think 6-8%) than other construction adhesives that bond to metal; it was also the least expensive of the ones that bonds to metal. Lots of construction adhesives specifically say that they don’t bond well to metal. I’m thinking of making the panels, and then putting aluminum only on the inside against the rough side of the masonite, and just lean into the DIY vibe with unfinished masonite on the outside. I can always add aluminum on top of that if I want later.

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