PDA

View Full Version : Laser Cutting Speeds Chinese Machines Vs High End (Kern, Trotec)



Robert Bonenfant
08-31-2017, 3:25 PM
We have been looking into upgrading our laser machines in the near future and have heard that a 150 watt Chinese machine will cut just as fast as say a 150 Watt kern Laser or Trotec. This just doesn't seem to make sense to me, a $15,000 - $25,000 metal laser tube is gonna preform the same as a $1200 glass tube ?? Why would kern and trotec use metal and ceramic tubes then ??

Im pretty sure Glass tubes loss power gradually over the life of the tube and metal tubes do not ?? (Might be wrong) If this is true than day one the assumption might be true but a month later there would be a clear difference. My current machines make me think this is true when the tubes were new we could cut at 14 mm/s - Now we are at about 9 mm/s. For a hobbyist this would be fine but for our production shop this just means higher labor cost and more time per item.

We have been looking at Kerns DHS (Dual Head Laser Cutter) and if the above statement is true why would they even sell this model of machine ??

We really just want to make sure we are moving in the right direction because its a large investment. We could buy 17 of our current machine for the same price, all we use our lasers for is cutting 1/4" Wood and acrylic parts. We have been happy with our imported machines (For the price) but we can see a clear issue with quality of the machines .
Thanks for the Help

Robert Bonenfant
08-31-2017, 5:31 PM
Dave provided a great explanation below

"RF tubes produce very high quality single mode beams, cheaper glass tubes don't, there are some glass tubes that easily match or out perform metal tubes but they usually cost the same as metal tubes anyhows.

In general a 30 watt RF will perform as well as a 50 watt DC laser (cut wise), as you get further up the power range refinement makes more difference than raw power

To beat a 150 watt RF you would need a 220 to 250watt DC tube (of the usual Chinese type)

There are new types of DC tube due to be released soon that use closed loop air cooling but they are still about 3 months off.

It is possible to build a long lasting DC ceramic tube, the problem is it would then cost the same as a normal Metal RF does so no real benefit (other than being refillable)"

John Lifer
08-31-2017, 7:12 PM
150w is a 150w :) If they are both equally rated....

you are paying for US machine, US labor, and US software. THIS is where the difference lies.... $50 per hour labor vs $50 a MONTH labor, Not really power difference.

Scott Shepherd
09-01-2017, 8:47 AM
I'd disagree with the statement that all machines vector cut at the same speed. Years ago, I did a youtube video of our Trotec vectoring the same shape as our Universal. The Trotec crushed the Universal. Crushed it. The move speed between vectors is so fast that you can't see the machine even move a lot of the time. The time spent in the cut might be the same, but the time moving around the cut is far less. Is it 17 machines worth faster? Of course not, but there is certainly a huge difference in speed when vectoring a lot of work. Don't be fooled into thinking there isn't.

Dave Sheldrake
09-01-2017, 11:18 AM
RF tubes produce very high quality single mode beams, cheaper glass tubes don't, there are some glass tubes that easily match or out perform metal tubes but they usually cost the same as metal tubes anyhows.

In general a 30 watt RF will perform as well as a 50 watt DC laser (cut wise), as you get further up the power range refinement makes more difference than raw power

To beat a 150 watt RF you would need a 220 to 250watt DC tube (of the usual Chinese type)

There are new types of DC tube due to be released soon that use closed loop air cooling but they are still about 3 months off.

It is possible to build a long lasting DC ceramic tube, the problem is it would then cost the same as a normal Metal RF does so no real benefit (other than being refillable)

Robert Bonenfant
09-01-2017, 12:18 PM
Thanks Dave and Scott for your input and for explaining this a little better. Im gonna edit my comment above and looks like I will be sticking to the plan of upgrading to a kern laser.

We produce alot of the same parts for companies that order every month - The next three days all of my machines will be making 10,000 of the same bracket so speed and quality will be key in increasing my profit margins and work load. We dont expect the increase cost of the machine to pay for itself on day one but over the life of the machine we expect to see better results and overall making every production run more profitable.

This is the reason I bring my questions to Sawmillcreek ;-)

Kev Williams
09-01-2017, 3:30 PM
Universals are notoriously slow machines. And for vector cutting, so is my LS900, in my opinion... My Gravo rep explained to me that the factory decided to limit vector speed of my machine around 10% of it's 72ips advertised speed-- I just ran a simple stopwatch test of it vectoring 200", and it came out to 7.17" per second, which is only 182mm/second. But my machine is 13 years old and 40 watts, so not sure if any faster would help. The newer LS machines with more power may go faster, I'm not sure. The GCC will vector up to it's full speed, but it's pointless because (a) with 30 watts nothing much happens, and (b) it takes half the 38" table space to even reach full speed in vector mode, and by then it has to slow down. To get nice cuts, very much slower is the norm. It has a 'precision cut' mode, that basically just cuts the machine's speed by like 70%. And it does help, especially with cutting decent looking curves and circles. But- it's slower!

My point is, even if the machine has the hardware to make it very capable of cutting fast, you can only cut as fast as the material, power, and cut quality will allow. You won't get $25,000 worth of additional CUTTING speed with a Trotec or any other RF laser. RASTER speed, yes, in spades. :)

Michael Henriksen
09-01-2017, 3:49 PM
It's not just tube power that plays a part. How you move the gantry is also important. There´s a big difference in the speeds you can achieve with servo motors compared to steppers.

On my 100W machine I can't go fast enough to utilize the full power of the tube when cutting 3mm poplar plywood. Once the speed goes above 40mm/s it starts to shake a fair bit. At this point I'm only using 40% power.

Dave Sheldrake
09-01-2017, 9:16 PM
Once the speed goes above 40mm/s it starts to shake a fair bit. At this point I'm only using 40% power.

Then you have a fault somewhere Mike :) my Rabbit machines routinely run 75mm per second without problems cutting :) and 175mm per second line marking in vector mode

Michael Henriksen
09-01-2017, 9:34 PM
I think I have to play around with the settings in RDWorks.367106

On a previous machine running LaserCut 5.3 I changed some values - I think it was called corner acceleration - which quited things down. The settings in the pic are as they came with the machine except for the idle speed. I've not played around much with RDWorks to date.

John Lifer
09-04-2017, 11:10 AM
my 1300x900 has these, not too much different.
367224

Robert Bonenfant
09-04-2017, 10:51 PM
Kev that might be true on a low powered machine but I think Trotec and Kern machines are more than capable of matching there power output with there machine capabilities. Just seen a Kern HSE 400 Watt this weekend at a shop in Columbus OH and that thing flew when cutting 1/4" Plywood (This sealed the deal for us). Once we get the new machine Ill post a few videos with our current lasers next to it (Wont be a fair challenge but it might help others with the same questions)

Scott do you have a link to the video you posted ?

Scott Shepherd
09-05-2017, 8:52 AM
Scott do you have a link to the video you posted ?

Sure, but be warned, it's painful to watch :) You can fast forward to the last few seconds where I post the results.

This was done 5 1/2 years ago.


https://www.youtube.com/watch?v=mUHY5Km8Ekk