[ron0909]

Hi everyone,

I'm a real newbie with a 2 week old 60 watt G Weike LG500 'Desk' model. I must say I am pleased as can be with my laser other than the width of the cut when cutting 1mm grey board. I make 3 dimensional paper models and use the 1mm board for ribs, formers etc. With these models there is very little room for error and loosing .3mm or more from a cut is not good. Unfortunately, Tina my excellent sales manager says that my lens cannot be changed to another because of the size of the machine. I see that many folks here are changing out their lenses on smaller machines and I'm really messed if I can't get a finer cut. My specs are f50 focus lens with f20 mirrors. I believe (from measuring with calipers) that it uses a 20 mm lens. The nozzle itself from top to bottom is roughly 41 mm. The mirror is roughly 25 mm

Please, I realize this is a crappy intro but I could use some advice

Best regards
Ron

[Awardmasters]

First, make sure that your lens is in near perfect focus. If you are cutting while out of focus, the beam width will be larger. I would suggest that you manually set the focus to be sure it is correct. The machine settings could be off a few mm. Search the forum for info on establishing the optimum focal length (this may vary somewhat from one lens to another) so your auto focus could be a little off.

Second, you can change to a 1.5" ( it sounds like you now have a 2") focal lens. This lens will create a slightly smaller beam, but not by much. These lens are available on eBay in the $25 to $40 price range.

[wascallywabbit]

Hi Ron,

You should be able to compensate for your kerf in your design program, just expand your borders by the kerf-width. If you can't do that for some reason:

1) The next size of lens that you'll get from China is 1.5in focal length (~38mm)--which is inside your nozzle. Depending on which model and sub-version you have, you ought to be able to machine down the tip of the cone, but you'll lose air flow.

2) What really kills you though, is just the nature of a CO2 laser and organic materials themselves. I've never seen a glass tube laser cut a kerf less than 0.010in (any tube power, 1.5/2in lenses and any output power). A more realistic number for kerf is 0.012-0.014--I've tested this extensively on 40W-90W glass tubes on everything from paper through plywood. Acrylic and plastics I haven't tested as thoroughly.

This may or may not have been helpful :/. Good luck!

[ron0909]

Thanks guys for the educational responses! This place is a blessing as I can only imagine what one would go through without this resource. I might have over reacted to the limitations on my machine. I make paper models which use the 1mm board as formers, ribs etc. These models are as detailed as any plastic or wooden kit and I was concerned with the loss of material taken by the beam. Someone mentioned to me that LaserCut has an option for cutting on the outside of the line. Anyone know how to do this? I am open to almost anything in regard to fiddling with the machine however, machining the nozzle is probably beyond me. I would if possible change out the entire nozzle/head assembly if it was viable. Has anyone any opinions on the new fangled nozzle assemblies available on ebay?

Thanks again for filling my brain
Ron

[epilotdk]

There is an offset function in Lasercut but it's much easier to just draw the parts a bit larger in CAD. When I cut greyboard on my GW laser the kerf is very small - about 0.1-0.2mm. Are you sure you have the focus set correctly?

[ron0909]

Well..we have success! Tina of G Weike did in fact send me out 2 38mm lenses, 2 50's, 3 mirrors and 2 additional mirror/nozzle combos (both different). I ended up taking the advice here and had one of the nozzles milled down by a centimeter. Thankfully the nozzle's internal 'cone' shape didn't actually extend down to the bottom. Now I can easily use both lenses and still have a bit of room to manipulate stock. The 38mm lens gives a beautiful cut but I had problems at the top and bottom of the sheets I was cutting. For the life of me I couldn't figure out what I was doing wrong as the kerf became larger and the cut uglier! For giggles I threw a straight edge on my z table. Well, that was a disappointment. I'm assuming the sheet aluminum that it is made out of was originally a rolled product later cut on a sheer brake as it was bowed in both directions (high in the center, low on all edges). I read somewhere here that someone else ran into the same problem and fixed it with a piece of 1/4 inch plate. I have a piece of 1/4 inch tooling plate aluminum coming in the morning. A little nibbling, a little drilling and a bit of filing should do the job...oh...and 60 bucks later for the aluminum
All the best!
Ron

PS. I just wanted to say how I wish every company we all come across in the future acts with the business ethic and commitment to their customers as G Weike. I have never been one to spout praises to the sky but lately, I have been troubled by arrogance, rudeness, plain old look down their nose contempt etc.. Some folks could do a lot better by following G Weike's example