[eeboy]

I am very close to pulling the trigger on a G.Weike LG900N machine primarily based on the positive posts that I read here as well as the G. Weike staff's willingness to help resolve any issues that come up. The price seems quite reasonable given my budget is right around $5k. There are a few things I am struggling with so I thought I'd ask the community...

The difference between 60W and 80W is fairly significant relative to my budget (~$600). How much will I regret not having this extra 20W if I plan to use the machine for cutting acrylic (1/2" max), hardwood (1/4"), acetal (1/4") and various other thin material (gasket, mylar, kapton, etc). I don't plan on doing a lot of engraving with this machine.

I have decided on a few add-ons such as red dot positioning, auto focus and a chiller. However, I've read in a few posts that the auto focus feature is easily broken. Is it worth the money to add this feature or is manually focusing the beam tolerable? Note, this machine is more of a R&D toy and not something that will be running 100% of the time. So, extra setup time (if it's minimal) would not be so painful.

They sell a filter for the system at $500 which seems very pricey. I am pretty resourceful and I am guessing that I could easily make something to serve this purpose for roughly 10% of that cost.

Finally, it is extra for the USB option. Can anybody comment on the differences between USB and the PCI card? I'd love to eventually run this from Linux using EMC2 and it seems like the PCI card would actually be beneficial in this case (or maybe not).

[GWEIKE-LASER]

1. Actually the 80w tube is much powerful and can reach power more than 90W.
Anyway, even 60w tube can cut acrylic (1/2" max), when it coming with long focus, and special cutting system of machine.
2. The new type auto focus feature is much better now. And after two years testing. no angent complain it's fragile. so it not broken easily now.

3. Filter is filled with carbon and filter layer. you are right, it's easy to make by your self.
4. I suggest your choose USB feature，Because USB feature coming with the newest version software. and the related software support output through CorelDraw x4, AutoCAD output directly.
PCI some times cause problem by the transfer data cable. because the cable end is needle. any bent or cutoff will cause problem.

This is our suggestions, hope give you some info for choosing

JENNY from GWEIKE laser
([email protected])

[gfacer]

Based on your requirements, I would definately go for the 80w, even I'd you have to ditch the autofocus. Autofocus is more handy the more you are changing the thickness of the material regularly and it's "neato" and convenient. However the cutting improvement on the 80w should make up for the extra set up time, if you have to choose. 1/2 on an 80w will be slooooow, as I saw some 3/8 demoed on an 80w and it was only 7-8mm per second.

Anyways, my suggestion if your goal is cutting.

[rcpilot82]

If it were me, I would buy the 80 watt, USB, chiller, and red dot. wouldn't waste the $$ on the autofocus. If you are handy you can make your own red-dot pointer for about $20 and a trip to radio-shack.

If you haven't already, check out Rabbit Laser USA for the RL-9060. Call or E-mail Ray or Carol for best results. this would save you the import hassles and any fees you didn't expect. They have a bunch in stock as well.

Just another option for ya.

[RossMosh]

If all you plan on doing is cutting, power and table size should be your primary objective. I wouldn't expect 60W to cut 1/2" acrylic well. Even 80W probably won't do the job well. You should look into getting over 100W if you're serious about cutting 1/2" acrylic.

As for the chiller, buy the CW5000. It's not an option unless you plan on building one yourself. You need coolant flowing through the tube at the proper temperature or you're going to be constantly changing out tubes, which are not the cheapest things in the world.

Auto-focus is 100% optional and its a feature you can easily dump. It can be convenient at times but you can cut your own little gauges and manually focus in less than 30 seconds. Big picture, auto focus is not that big of a deal.

The red dot is cheap so I have no idea why you wouldn't want it. It shouldn't cost more than $100 and it can make lining up parts and jigs a lot easier.

The filter is 100% something you could build yourself or not at all. Lots and lots of people exhaust their fumes outside with no filter. Building an activated carbon filter is not that difficult otherwise. Especially if you have a big laser to cut the parts for you.

One last thing: Don't underestimate shipping costs. Expect around $1000-2000 when all said and done. Seeing you are a hobbiest, you probably don't need to stock up on parts, but it's not the worst idea either. An 80W tube is probably about $300-350 now. To buy it in a year it will cost $900 if you buy it from someone in the US. Drivers, steppers, mirrors, lenses, and control boards are all significantly more expensive from local distributors as well an might only cost you $300 now.

[eeboy]

Thank you all for your inputs. Much appreciated!

If all you plan on doing is cutting, power and table size should be your primary objective. I wouldn't expect 60W to cut 1/2" acrylic well. Even 80W probably won't do the job well. You should look into getting over 100W if you're serious about cutting 1/2" acrylic.

So how can I gauge the benefit of say 100W over 80W or 80W over 60W? Let's continue to use 1/2 acrylic as my benchmark. When you say it won't cut well are we simply talking slow cuts? I would assume the more time that laser dwells in one location the more the heat affects the material. Do you start to see a taper? Or???

[gweikelaser]

Lets take 1/2 acrylic for example, use 100% power the speed for 60w usally 1-2mm/s,80w 2-3mm/s and 100w 3-4mm/s

Best Wishes
Lucy Lee
G.WEIKE LASER
[email protected]

[Asynchronism]

I'm 100% in agreement with the others, but I strongly recommend the chiller. You can't build anything better yourself, and it's set up to shut the tube down in the event of an stop in water flow or overtemp. I like that a lot.

You stated that you don't plan on engraving. All of the larger tubes are a trade off between engraving quality and cutting power - for cutting, power is king. Get the biggest tube you can afford.

Can you cut 1/2" acrylic at 80 watts? Sure (I've done it at 50) - but slowly. The slower you go, the higher the chance of the material catching on fire. You'll be laying more heat into the material, and getting a wider kerf... more thermal stress, less detail, more taper. Basically, you're correct in your assumptions.

The bigger tubes will also allow you to run longer focal length lenses - the longer the lens, the larger the focused spot, so the lower the power intensity. More power overcomes that, and you get a longer area of focused beam to cut with... and perform better in thicker materials.

I will disagree with the idea about running the 80w tube maxed out at 90w - yes, you can do that, but not for very long. Reci is very specific about that. If you run it a little under the rated power (say, 75w), the tube should 10,000 hours. I'm run mine about 10% under spec'd power.

Dave

[eeboy]

Thanks! Everything that has been said here is quite logical and I see myself stretching to get into a higher power machine. I've certainly talked myself into 80W. Now, I am trying to figure out where to stop.

Can you cut 1/2" acrylic at 80 watts? Sure (I've done it at 50) - but slowly. The slower you go, the higher the chance of the material catching on fire. You'll be laying more heat into the material, and getting a wider kerf... more thermal stress, less detail, more taper. Basically, you're correct in your assumptions.
Dave

Sorry for harping on this one point... does anyone have pictures of thick acrylic done at slow speeds? If not, can anyone offer up some values for kerf and taper?

[Rodney Gold]

1/2" acrylic will not cut that well on these lasers , you will struggle to get a nice edge , 8mm and 6mm are a snap, If you want to cut thicker , you need more power , a longish lens (60-80mm) and a LOT of air assist.

[lucylucky]

Hi eeboy,

If choose Dual Red Dot Pointer, no need choose auto focus, Dual Red Dot Pointer has function to adjust focus distance.

Ms. Lucy
Jinan Quanxing Mechanical Equipment Co.,Ltd-CNC Router Machine,Woodworking Machine
MSN: [email protected]
Email: [email protected]

[eeboy]

The bigger tubes will also allow you to run longer focal length lenses - the longer the lens, the larger the focused spot, so the lower the power intensity. More power overcomes that, and you get a longer area of focused beam to cut with... and perform better in thicker materials.

Can you elaborate on the lens? The beam is focused to the surface of the material correct? Beyond the surface that beam diverges. Isn't the angle of divergence inversely proportional to the focal length of the lens? So, a larger focal length gives a tighter beam (greater intensity - less divergence)?

[Asynchronism]

Sure... basically, there's no free lunch.

The key to all of it is power density - the diameter of the spot size vs. the total wattage of the beam. Only when the beam reaches a certain density does it have the ability to vaporize the material, instead of just setting it on fire. That density is usually achieved at the focal point, or close to it... both above and below.

As the focal length gets longer, the hourglass shape gets narrower, and the area of useful density exists farther from the actual focal point... so you can cut thicker things with the beam still focused. However, the diameter of the spot at the focal point gets larger with the longer lenses, so your effective power is actually reduced. It's the reason they use the really short focal length lenses for engraving... you can get the most detail that way.

Basically, the longer the lens, the larger the focused spot and the lower the power density, but the trade-off is that the beam is more useful in thicker materials. The solution, as always, is more power!

I actually did some 1/2" acrylic cutting this afternoon... seems to run about 4mm/sec at 150w with a decent edge.

[eeboy]

Sure... basically, there's no free lunch.

The key to all of it is power density - the diameter of the spot size vs. the total wattage of the beam. Only when the beam reaches a certain density does it have the ability to vaporize the material, instead of just setting it on fire. That density is usually achieved at the focal point, or close to it... both above and below.

As the focal length gets longer, the hourglass shape gets narrower, and the area of useful density exists farther from the actual focal point... so you can cut thicker things with the beam still focused. However, the diameter of the spot at the focal point gets larger with the longer lenses, so your effective power is actually reduced. It's the reason they use the really short focal length lenses for engraving... you can get the most detail that way.

Basically, the longer the lens, the larger the focused spot and the lower the power density, but the trade-off is that the beam is more useful in thicker materials. The solution, as always, is more power!

I actually did some 1/2" acrylic cutting this afternoon... seems to run about 4mm/sec at 150w with a decent edge.

Thanks! I have a clear understanding now. IF I wanted to do some engraving it would probably be wise to get the smaller focal length lens eh?

From all that I am reading and seeing it sounds like even if I stretch to 100W the edge on the 1/2" acrylic will not be desirable. 150W is definitely out of my range (I can stretch but not that far). So, I should simply order the biggest tube I can afford and manage my expectations.

10,000 hours is about a factor of 10 over what I have been reading for the life time. Can anybody else confirm this? Most of the failures I read about are related to the chiller failing.

[Rodney Gold]

Acrylic acts as a wave guide of sorts , so the beam divergence isnt a big a factor in other materials - the issue really is heat affected zones , if you have to go slow , you are actually gonna heat the material up and this can cause some issues like resolidification of the melt , bad melts, melt splattering , highly stressed workpieces , distortion etc. The issue with long lenses is 2 fold , 1 , they will have much wider kerfs (cuts) and 2, your power density on the increased spot size might be too low to start vaporisation.

The RECI tubes have the 10 000 hour figures , whether that is true or not is debateable. The glass tubes are still dirt cheap compared to a metal tubed RF laser source , about 1/10th the price , they are consumables
Reci 100-120w is about $700. The cheaper laser tubes with the 1000 hour life expectancy are in the $200 mark , an 80w RF source can cost $10k!!!!
You NEVER get a perfect edge on any acrylic -- the laser mnfgrs might show a 1" piece cut , with great edges , but you will NEVER get it. If you are looking for seriously good edges without striations etc , then you need to flame polish.

[eeboy]

I appreciate the feedback!

How does the air assist affect the heat? I assume it helps to carry some away from the work piece? Is the compressor that comes with the Chinese units adequate or am I going to need to hook up my shop air to this?

[Rodney Gold]

Air assist is VITAL for acrylic cutting , it regulates temperature (you need enough heat to flame polish but not too much that you get flaming) and it blows away the melt that occurs.
Ideally you want a blast of air strong enought to expel all the melt and not so strong as to cause frosting on the cut edge.

[GWEIKE-LASER]

TO CUT THICK MATERIALS, SUGGEST CHOOSE 100MM FOCUS LENS TO UPGRADE THE CUTTING EFFECTION.
ALSO THE AUTO CHILLER SHOULD BE CHOOSED.
Attachment is picture for 2cm acrylic cutted by our 100w laser cutter.