Cutting speeds and depth

[technomupet67]

Hello all,

I have a 6840 with a 60w laser fitted.
I am very happy with the machine and am learning the software flow required to get to my finished cuts.
I make mostly hobby stuff (acrylic cases for electronics etc) and some jigs for my wood working.

I have been cutting 3.5mm plywood mostly so far.
I have tried a whole range a speeds and power but nothing seems to provide a consistent all the way through cut.

For example I will do 12 speed and 100 power and not get full through cut.
Then I will do 8 speed 100 power and get a lot of burning
I sort of settled on 8 and 70 power but quite often will not get all the way through which then need a lot of final adjustments.

One thing I do not do is multiple passes. Would this help ?


I am sort of disappointed that it seems I am struggling to go through 3.5mm ply with a 60w laser...
I have tried 9mm mdf and it requires 4 speed and 100 power? Is this right ?

I have checked the alignment and all is good on that front. I get a nice spot in the middle of each mirror and laser is focused on correct height. Any idea if anything is wrong or this is just right ?

Thanks
Olivier

[Spooky]

Hi Oli,

Seems kind of high, I'm running a 6840 with a 40watt tube and I run at:

3mm Ply Speed 16 Power 80
3.2mm MDF Speed 12 Power 70
4.2mm MDF Speed 8 Power 75
4mm Ply Speed 10 Power 75

Double runs can help but not as much as you may hope for as on the second run the beam is trying to burn carbon deposits from the first run.

Are you using laser ply and Medite MDF? B&Q stuff is no real use for laser cutting sadly

best wishes

Dave

[technomupet67]

Dave,
Thanks for the response, great to have some reference point from other users.
I use b and q plywood and mdf so far.
I might try the other sources to see if it changes anything.
Will report back here.
Olivier

[Spooky]

Hi Oli,

A LOT will change, B&Q ply is bonded with an oil based resin, it will give off some quite nasty (read: toxic) fumes when cut as well as leaving a nasty black edge.

Laser ply is bonded with a water based resin and gives off less fumes, less edge burning, it cuts better (read: deeper at any given power) and has no inclusions in it (areas where the ply has been patched with wood filler)

It actually works out a LOT cheaper as well, B&Q commercial ply varies a lot in width (starting at 2.8 going to 3.6) and quality, laser ply is 3mm width and holds to that size very well.

Same situation for MDF but a bit more serious, commercial MDF is bonded using a Formaldehyde resin, this when burned gives off VERY toxic fumes and can cause a lot of long term exposure illness.

Grab a sample piece of laser ply from Chris, (the sheets are very cheap) and see how you get on, I'm sure you will be surprised by how much easier things get

best wishes

Dave