Laser beam too big

[simonsk]

Hi to all
I'm new on this forum.
I buy cheap china 40W CO2 laser cutter. I need to cut 0.1mm mylar foil.
Problem nr.1: SW witch come with laser is unused. Controller have no speed controll. Well this is not problem. I'll use Pokeys system.
Problem nr.2: I need laser beam max 0.2mm. With original lens I got smallest dot 0.3mm. Can you suggest me witch lens to use ? Meby witch material is better for cutting?

Regards
Simon

[herby08]

Hi simon
which 40WCO2 laser did you buy is this a laser who has a moshi ssytem??
look inside on the controller board ther should be somewhere the name or number of the system.
the speed is by all conroller to be set before you finish the job for up loading to the machine on the computer. it is in the same settings where you set the power.
for a small laser beam you need a focuslense what has a low focal lenght like 38.1mm or even a 25mm and you have to buy them seperatly because the most manufacturer have just a 58.1mm focal lense put in it is a price question. one of this low focal lenght lense cost about $ 40 to 70.
but the focal lenght is the hight from you lense to the material means if you got a 25mm lense the material needs to be at 25mm from the laser head lense to the material.
greetings
walt

Hi to all
I'm new on this forum.
I buy cheap china 40W CO2 laser cutter. I need to cut 0.1mm mylar foil.
Problem nr.1: SW witch come with laser is unused. Controller have no speed controll. Well this is not problem. I'll use Pokeys system.
Problem nr.2: I need laser beam max 0.2mm. With original lens I got smallest dot 0.3mm. Can you suggest me witch lens to use ? Meby witch material is better for cutting?

Regards
Simon

[simonsk]

TNX for your fast replay.
I have SH-K40-40W. Speed is controlabile by SW only in SCAN mode only ... from 1-10
I hate this DSP, becouse you cannot chancel job. (turn OFF/ON not chancel job) So I'll made my own (I'm good in electronic)
So you suggest me lens with smaller focus. I go to buy 25mm. Do I must look for some special one, or are all same (ebay)
Material is mylar OK? I need to do high precise stencil, witch are used for PCBs
regards
Simon

[herby08]

Hi simon,
you need something like this

18mm ZnSe Focus Lens for CO2 10600nm 10.6?m Laser Engraver 25.4mm Focal Length | eBay
but you need to check first what diameter your original lense has and then find the right diameter here in the sample is 18mm.
what kind of DSP do you have?? dont you have a LCD panel with the DSP?
can you make a picture of the machine and one from inside the controler
greetings
walt

TNX for your fast replay.
I have SH-K40-40W. Speed is controlabile by SW only in SCAN mode only ... from 1-10
I hate this DSP, becouse you cannot chancel job. (turn OFF/ON not chancel job) So I'll made my own (I'm good in electronic)
So you suggest me lens with smaller focus. I go to buy 25mm. Do I must look for some special one, or are all same (ebay)
Material is mylar OK? I need to do high precise stencil, witch are used for PCBs
regards
Simon

[simonsk]

Hi Walt
I'm not at home, to make foto. My laser is like this: Laser Cutter
Here is 12mm lens. But if it better 18mm lens I can do new nozzle (I working on CNC mill machine)
Regards
Simon

[gweikelaser]

Dear Simon,
after checking your machine piture ,we think you should use 12mm or 15mm lens and focal length is f=50mm.then will be the best distance for machine working.

hope we can help you
Lucy Lee
G.WEIKE LASER
EMail:han@wklaser.com
MSN:gweikecnc@live.cn

[simonsk]

Dear Simon,
after checking your machine piture ,we think you should use 12mm or 15mm lens and focal length is f=50mm.then will be the best distance for machine working.

hope we can help you
Lucy Lee
G.WEIKE LASER
EMail:han@wklaser.com
MSN:gweikecnc@live.cn

Correct!
But with this lens is laser beam is too big. I try to use lens with focus 25mm

[herby08]

Hi simon
I had the 12mm lense original but i switched over to 18mm because it is easier and mor affordable to find the right focal lenght in this diameter.
the main advantage from a shorter focal lense is that it gives a more precise and finer beam but you have to adjust the worktable hight to the distance ( 25 or 38mm )
greetings
walt

Hi Walt
I'm not at home, to make foto. My laser is like this: Laser Cutter
Here is 12mm lens. But if it better 18mm lens I can do new nozzle (I working on CNC mill machine)
Regards
Simon

[Exsecratio]

Power Density Explained HERE

Focal Length Explained HERE

Short focal length lens systems have a much smaller depth of field so will not cut thick material very well although will have a small spot size. Long focal length lens's have a better depth of field but lower power density and a bigger spot size.

Best wishes

Dave

[herby08]

Hi dave
thats absolut correct just one little opinion from my experience I do a lot of engraving on all kinds of material and need a very fine details especially for picture and there is the best way to go with a short focal lenght lense.
as far as I understood simon he need to cut cut 0.1 mm mylar but very precise and for this purpose is a short lenght lense the best option.
I mean I personly have three sizes anyway ( 25mm, 38mm, and 50mm) this way I am independent for all material.
greetings
walt

Power Density Explained HERE

Focal Length Explained HERE

Short focal length lens systems have a much smaller depth of field so will not cut thick material very well although will have a small spot size. Long focal length lens's have a better depth of field but lower power density and a bigger spot size.

Best wishes

Dave

[Exsecratio]

Exactly right Walt, short focal length = better engraving as the spot is smaller and the power per sq mm is higher

best wishes

Dave