Shenhui G2515 or Goldenlaser CJG150250, or even something third?

[Vahidin Goga]

Hi everyone,

My name is Vahidin. I am from Bosnia, and employed in a company which is doing sign making, acrylic processing, printing, advertisement industry generally...
I am operating Goldenlaser JGSH 12560, mostly used for acrylic processing. Now we are looking for new, bigger machine which will also be used in 99% of cases for acrylic cutting.
I found out that Shenhui is really popular around here, and i contacted guy so he recommended me Shenhui G2515, 100W Reci laser. It costs 6850 USD FOB China.
Other solution, since we already purchased Goldenlaser, and we were quite satisfied with it, was CJG 150250. This machine seems to be more sophisticated, it has servo motor, seams to be much more robust (weight 1700 kg), and advanced cooling system which keeps water always at constant temperature, but it costs 16800 USD.

So, my question would be, which one to choose? Obviously, price difference is huge, and i doubt quality is that much different. Shenhui seems to be reliable machine, but i never saw it or experienced how it works, so i am looking for a help from you guys. Could someone help me and recommend what to buy? It does not have to be any of these lasers, if you have even better option. As i said, we will mainly cut acrylic, very rarely wood, plywood, or other plastic or wood materials. We cut acrylic up to 20mm thick, so machine should be quite strong to cut this thick acrylic, not to compensate it too much on speed.

At the moment , our JGSH 12560 cuts 20mm acrylic in speed 1mm/s, and generally when cutting edge has vertical lines (like steps) so it is a problem which i can't figure out why is happening. Other problem is that cut edge is always bended, not straight vertically...

If you need more info i would be glad to provide it to you. Any help or suggestion is highly appreciated.

[Dan Hintz]

At the moment , our JGSH 12560 cuts 20mm acrylic in speed 1mm/s, and generally when cutting edge has vertical lines (like steps) so it is a problem which i can't figure out why is happening. Other problem is that cut edge is always bended, not straight vertically...

The "bent" edge is the kerf due to the laser's hourglass-shaped beam. 20mm is pretty thick stuff, so it shows off the kerf more readily. What focal length lens are you using, 4"? If not, change to one (or try something a bit longer, if you can get it)... that should help with the kerf angle.

The striations (steps) are due to the repeated heating/cooling of the kerf as you eject the melted plastic. What frequency are you cutting at? Select the highest frequency you can. You'll also want to spend some time tweaking the air pressure... too much and you cool too quickly, too little and you will get a "pulsing" ejection of material.

[Dave Sheldrake]

Hi Vahidin,

Check the Z axis movement on the Shenhui as it may not have enough adjustment to use long focal length lens's. Most flatbeds (mine included) focus by moving the lens barrel up and down by hand on a side lock screw (horrible method) Have a look at the HX KingRabbit machines, the 2515 is a good piece of kit if you can stand the limitations of very little bed adjustment. I'd probably go for the Shenhui but fitted with a 150 - 180 watt EFR tube rather than a 100 watt RECI.

DC Glassers don't have adjustable frequency in most machines Dan :(

cheers

Dave

[Rodne Gold]

I wouldnt spend $10 000 more on a machine that cuts acrylic for signage , you dont need precision and the machine does not have to be fast either , even cutting 3mm you would not go at any speeds that would require precision and motors capable of serious acceleration etc.
I would rather spend on a potent source - 150-180w as Dave suggests
Most important thing will be your bed flatness compared to the laser head
I don't like tube focus , IMO it is not good once you set alignment at a particular point , moving the lens up and down *could* throw it out...
However , I would also be real hesitant to get a machine of that size with a motorised up/down bed.

[Dan Hintz]

DC Glassers don't have adjustable frequency in most machines Dan :(

Yeah, kind of forgot the type of machine we were talking about... maybe I'm getting spoiled? ;)

[Vahidin Goga]

Thanks everybody, your advices are really helpful. Let's go one by one:

Dan: This is lens we use. It is standard which came equipped to JGSH 12560 as we bought. I don't understand marks u use, guess inches, but still i don't know if this right one What do you think about lenses for new machine i am looking for (250 x 150 cm). Which one to use considering we will mostly cut acrylic?

277236

Dave: Shenhui 2515 has no Z axis movement. I think it would be suicide to go with machine which moves table that size and weight. It would cause so many troubles. So, this machine has no movable table, and maximum depth is 50 mm (which is i think enough). I will follow your advice for tube. By the way, when we talk about focus, what is the optimum distance between lens and material you are cutting? How do you test or measure that? I noticed this distance is affecting cutting quality, but i never figured out what is the best distance for best focus.

Rodne: I agree about the price. I don't think Goldenlaser can offer me that much more for the price difference of 10 000 USD. I believe Goldenlaser is more sophisticated laser, but do i really need it, and is it that much better? I don't think so... Regarding speed and precision: I need speed because we also charge by time used for cutting. So, faster is cheaper, and more competitive in the market. Precision is also important, i have to take care about it, but i believe this machine is precise enough. My fear is exactly what you are saying: flatness of table. This size can have a lot of problems, especially by the time, since we will load heavy sheets on it. One 20mm acrylic 1x1 m sheet is 24 kg, we will sometimes load sheets up to 100 kg or more... I already have problems with much smaller table (125 x 60) and it is bended after 3 years of use. I think is should definitely ask for bar table instead of honeycomb, to avoid problems. What do you think?

One more question: The cooler he offered me is CW 5000. Is it OK?

Is there anything else i should take care of? I would really appreciate your help, since you are far more experienced then i am...

[Dan Hintz]

That's a 3" lens (inches)... better than a typical 2", but you may still want to consider a 4" (100mm, give or take). Focus into the acrylic about 5mm.

[Dave Sheldrake]

Hi Vahidin,

The lens in the picture is good to very good quality, II-VI are highly respected manufacturers of Laser optics. The focal length (distance between the back of lens and the surface of the material) is shown on the package as 76.2mm FL (ie:3 inches) and the lens diameter is 19.05mm (3/4 inch).(The ET figures are of no real consequence for us)

The only issue I would raise is that it's a Plano Convex not a Meniscus, if possible ask for a meniscus when you come to purchase lens's.

As Rod said, I also don't like tube focus and have made a micro adjuster for mine that uses non rotating slides from Thorlabs, it allows me to focus to the nth degree and not have to loosen any tubes. Not cheap (around $400 in total) but well worth the modification.

Go for a CW5200 if possible, the 5000 has some occasional problems that on an import can mean waiting for a new chiller if yours fails. The 5200 is rated to 300 watts (2 x 150watt tubes) so will do a good job of keeping temperatures stable.

For the big tube go with the EFR ZX series, they are more stable than RECI and give better beam quality.

cheers

Dave

[Vahidin Goga]

One more question, regarding table: I think to go for 'bar table' or 'knife' as they call it, instead of honeycomb. Honeycomb always caused me many problems when cutting acrylic, since the beam which goes through the acrylic, hits the honeycomb, and reverse damages acrylic. So, i think bar table would be better for acrylic cutting.

Does anyone have any suggestions how to avoid bended side when cutting acrylic, and those marks i always had (vertical lines, on the cut side of acrylic)?

[Dan Hintz]

If the laser hits anything other than air when it exits the substrate, you're going to get some amount of flashback. The perfect solution (for flashback, that is... it's not ideal as far as setup goes) is a pin table with the pins only in areas where the beam will not be. Also try beam-absorbant material under the substrate, like acrylic scraps.

[Jerome Stanek]

I had a big job that I made a jig out of corian so the flashback didn't hit the acrylic