[Published 21 Aug, 16:16]

As I said in the previous log, unlike most cheap laser engravers and 3D printers with attachments, the Suspense has nearly everything for safe and effective laser cutting use. I'm not interested in engraving, and Klipper doesn't support it either, though at the time of writing, it sounds like it's in the pipeline. 

I did a quick scan of modules, and since they were <= 40mm square by some Z height, I quickly thought of a solution that could fit in the Placement Block (the thing that houses things like the silver paste dispenser and fibre).

Still though, while it's technically an afterthought, I still have to treat it like a first rate citizen. I don't want some "Jack of all trades, master of none" review, but "It's just BetterTM". So I spent all of yesterday researching lasers, both for the SecSavr and so that I'm finally somewhat informed in this traditional manufacturing method.

Laser Types

This page from XTool helped a lot in my research. The TLDR is that:

• Fibre lasers have max watts, max lifespan
• Diode lasers have min watts, medium lifespan
• CO2 lasers have good watts, min lifespan.

The lifespan of the CO2 actually suprised me. I thought CO2 was a complete upgrade over the cheap diode laser modules, but allegedly, there's quite expensive recurring maintenance costs.

Cheap-ish diode lasers max out at around 5.5W of light power. The best efficiency I've seen is 27.5%, or 20W of input power. Unfortunately, the diode laser industry likes to advertise the input power. To get more light power, multple diodes go through optics to merge the beams.

The above is from Snapmaker's AliExpress listing. I saw it right at the start of the day and it's what got me thinking of lasers in the first place. It's >£400 at the time of writing and they advertised 10W, so I was wondering why. Other than getting the impression that Snapmaker is like the engineering version of Dyson, I eventually deduced that it was because of the optics and dual diodes. For the rest of the log, I'm just going to refer to lasers in their output power (unless talking about specific lasers on AliExpress).

Looking at options

The only 405nm laser I could find had 1W of output power; the vast majority are 450nm with some being 445nm. I couldn't seem to find any remotely affordable and high powered UV lasers either.

I found a black heatsink, 5.5W diode for £32 on the same listing as a 5W, gold heatsink diode for £80. Obviousy I'm confused, but it's because of optics again. As you can see from the snapmaker image above, Fast-Axis Collimating lenses decrease the laser dot, allowing for 100% faster cutting speeds. It's only when I went onto another listing that had this handy table that I found out.

Air assist, where pressurised air blows burnt debris away from the cutting area, is also an important feature to have:

Shortlisted Options

A few minutes later, I found the bottom two lasers:

I've been wondering why the 80W version is cheaper than the other 80W version on their same store, but while they look identical, only at this present moment that I'm writing this log that I see that the codenames are different so obviously there's got to be some change I don't know about. I just didn't want to pick a laser that was going to spontaneously bump in price, even if AliTools said that £132 is some of the highest seen in recent months.

There are other "80W" lasers that have the same 10W output power, but the TwoTrees has a larger 69x157um dot, the gold one doesn't say and the orange one has a bold claim of 10um, though I suspect it's 100um.

Neither of these had air assist out of the box and TwoTrees was the only other laser to support 24V input. Additionally, the C40 is one of the cheapest modules with FAC lenses and the exact same outter dimensions as the C80. I would have to ask about 24V input since they only mention 24V once and 12V everywhere else.

Safety

I'm planning on putting a switch in an area of the door hinge that cannot be reached from outside (like a fridge light door switch) so that the laser only has power when both doors are closed. 

An e-stop should be easy to add to the front of the machine, but I'd also need to have some way to mount it to the back of the machine if it's more favourable to use the machine in that way (closer access to the Placement Block, printer can be placed right next to a wall...).

The laser input power will be connected to one of the onboard mosfets.

Due to the toxic fumes of resin printing already, I'm planning on electronic locks on the doors that only unlocks when VOCs have returned to a safe level. These locks will also be on when the laser is in use. 

Unfortunately, I don't think there'd be any suitable amount of space for fire suppression in the SuspenseSlim and SuspenseSmall. The expected laser cutting area is also not large, and the BOM suggests that the price between the Small and the Squared is going to be slim, so I'd recommend the Suspense and Suspense^2 if a laser is to be installed in the Placement Block. From my basic knowledge of fire, I assume that it would eventually run out of oxygen in an enclosed volume and self extinguish.

Considering there's not much safety precausions for 1mW laser pointers, I'm assuming that the laser power has to be reduced to this level when talking about safetly glass. The OD rating has the formula ResultantP

ResultantPower = LaserPower * 10 ^ (-1 * OD)

 So an OD rating of => 4 is needed to reduce a 10W laser to 1mW. For glasses, that's straightforward to obtain. For an A3 sized window... no. Therefore, a dark and heavily frosted material is required instead of the dark grey lexan window. The laser focus is fixed, a 3DTouch will be included on the Placement Block and there's a scanner inside, so there shouldn't be any requirement to see the dot of the laser. Heavily frosted is preferred over opaque as light from the laser or the start of a fire can still be visible from outside, but I cannot confirm if the laser dot will be diffused enough to be safe. Considering that the 108W UV LED is now being used to cure the 3d printed part, it's likely that I'd opt for an opaque door regardless.

Comparisons with other budget laser cutters on the market

The first thing I was concerned about is the cutting area. The "Ender3 of the laser cutting world" K40 CO2 laser cutter only comes in at 300x200mm, and the Suspense is expected to be 360x320mm without replacing the bed for a larger one that doesn't move in Y. If this bed is replaced, the area becomes an expected 360x480mm.

XTool uses 30L/min for their laser cutter in a £120+shipping kit, but I just found this £25 compressor that does 45L/min, thought it only does 15kpa. For reference from Zibatiu:

Watching this video (timestamped), it's probably fine to have any airflow at all. Actually scratch that as I just found this writeup and a 24V fan actually looks worse than no air at all, but the compressor that looks very similar to the one I just found is where the good cuts start (and it seems that David, the author of the writeup, also questioned adding a laser to his project). I found the pump on Amazon for £28 and most of the reviewers use it on laser engravers fine, though a PC fan on the heatsink would help with keeping the compressor cool. 

Other than CO2 lasers, I can't seem to find lasers with enclosures. The most similar I've seen is this:

It seems that the market for both buy and DIY is:

• Large, cheap and open laser cutters, which may be part of a cheap CNC mill or 3D printer,
• The ultra rare DIY diode build with an enclosure and filtration,
• The K40's for £400,
• DIY enclosures for the open laser cutters, and
• The >£1,000 CO2, enclosed-diode and fibre laser machines.

Thus, it seems that a laser in the Suspense would fufill a gap in the market.