Best pratice to engrave mirror acrylic?

[justginbg (Gary Rowlands)]

There’s such a lot of great advice here To add a little something to the mix is trying a slight de-focus. You can maintain power and speed settings, just take the focus off perfect especially with a shorter focal length lens.

Everything else is also relevant and especially the acrylic type. The cast is slightly more expensive but returns consistency in buckets.

[Bonjour (Bo)]

@Hank

Just recently I’ve been playing with plain paper (like printer paper) and School Glue.
School Glue?, I hear you ask… what the heck is School Glue?

The world outside the Elmer glue company calls that PVA glue

[Bonjour (Bo)]

@Stroonzo

@simocyz

I am engraving (without masking tape) at 400 mm/sec,15% power, 0.055 mm interval, roughly 640 lines per inch

You have a W4, so about 100 watts correct? 400mm is too fast for unmasked. And your line interval is outside of rational parameters. The max you will achieve is upward of 0.0635mm (400 lines per inch). Run the engraving slower. Try 190mm / sec @ 10% power.

And again, if you can do this without air assist (keeping the smallest amount of of air flowing in the cone), you will not need to bother with the masking. I personally do not like how the paper masking affects the engraving.

Another very big consideration here is your acrylic type. Are you using extruded or cast acrylic?

I’m with Jeff on this - masking causes more issues than it solves

Not just the acrylic type but the brand can have the biggest effect

I have two sheets of extruded ‘acrylic’ of the same thickness and they behave completely differently - one is pmma, the other is a mystery - probably pmma, but a very different composition

The branded, known one, I bought from the sign supplies in NZ is consistent, the one I bought in Asia from a plastics warehouse is incapable of a decent engraving and I keep it for cutting only. I have one sheet left which will be gone soon

[simocyz (Simone)]

Thank you so much everyone for good advices, I’m amazed, really.
I am working on sheets of extruded acrylic, that’s for sure, as it seems quite impossible to source cast mirror acrylic (I’m in Italy, by the way). I will try all your very precious advices this weekend, as I have the machine at my parent’s house.
And yes, I confirm, I’m with a Reci W4 tube. About this, I have a doubt: I’m not running it above 60% power, manual says to keep it under 24-26mA to extend its life.
At first use, I started at 5% power and increased until mA gauge reached that limit (at 60% power). am I doing it right?
I also noticed that tube won’t fire if power is set less than 9-10%.

[Stroonzo (Jeff)]

You need to calibrate your laser PSU before any of the percentage of power settings make any sense.

Could this be a sign of a bad laser tube?

I am beginning to think you need to tune your laser PSU (as if the PSU is set too low). To do this, you need to know the highest mA draw specification for the laser tube longevity. A guess for an 80w tube may be somewhere in the upper 26 - 28 mA range (but you need to check to be sure). With this number in mind and with a mA meter on the machine (if you don’t already have an ammeter installled on the machine, they’re a pretty easy retro fit down stream of the laser tube) you can properly tune…