Working with a large format laser

Very Large Laser Beds
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Gene Uselman
Posts: 2161
Joined: Thu Jul 07, 2016 3:18 pm
Location: Suburban Minneapolis, Minnesota, US
Country: USA
Nickname: Gene
Laser Machine Make or Type: QC
Laser Power: 130W
Laser Bed Size: 900x1300
Home Position: TR
Control Software: LIGHTBURN
RDWorks Version: RDw .19 & Lightburn
LightBurn Version: Latest
Ruida Controller: RDC6442
Windows Version: Win 10 Pro
Accessories: I have a combining lenses, pin tables [homebuilt], honeycomb tables , wireless remote, Modifed Ultimate Air Assist, home built non-powered rotary device, PrusaMK4 and Mini Prusa printers.

I just got a Private message from a gentleman wondering why his new 3x4 foot 130w laser does not engrave as well as his K40 laser and I will publish my answer in case someone might have the same situation:

I have been impressed with how well high powered tubes will cut and engrave- the problem I think is more the size of the bed... it is a lot harder to get a large machine dialed in. My current machine is 1800x1300 and for maximum quality the left rear quadrant will always engrave better than the right front [ laser tube fires to the left]. Larger machines have longer rails and heavier gantries of course which makes alignment harder - I would suggest spending more time aligning the mirrors/laser beam. It is aggravating but it helps me to quit and work on it the next day sometimes. I also have three Reci tubes that have substandard beam patterns which is becoming more common I am afraid- they cannot be adjusted on a large machine as the beams diverge too much over the long distances. These are tubes that fail to pass for first quality and used to be scrapped but are now sold out the back door.

He also wondered about the lenses he should be using- a 1.5" versus a 2.0:

The 38mm [1.5"] lens is more for engraving- longer FL lenses are better for cutting- so yes for making rubber stamps it would be worth a try. I use a 2inch lens for most everything but have a GaAs 2.5" lens for thick/hard to cut media. This hobby/business is very much experimental- try everything you can think of and use what works the best. Each machine is a combination of totally different components and there are no real ground rules to follow. Good Luck. Gene

It would be wonderful if there were cleancut answers to all the possible questions... put there are not. If you do not like to tinker and experiment you are not likely to end up with a machine that does what you expect it to. I have five + years of trying different combinations of hardware and techniques to be 'fairly' comfortable with everything I make/do.
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BT48 Alpha Shopbot and 1300x1800 130W Laser

The days that I keep my gratitude higher than
my expectations, Well, I have really good days.

Ray Wylie Hubbard
Philipp Pap
Posts: 80
Joined: Wed Mar 15, 2017 5:45 am
Location: Innsbruck
Country: Austria
Laser Machine Make or Type: rdc6445
Laser Power: 55W
Laser Bed Size: 50x30cm
Home Position: TL
Control Software: LIGHTBURN
RDWorks Version: lightburn
Ruida Controller: RDC6445
Windows Version: 10

On my lasercutter (a small one), I put two wooden boards under the metal construction, that holds the mechanic. So the plastic feed that are attached to the thin metal frame in the corners don't even touch the table. I think that helps with stability.
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