LASER CUTTER BASICS

[fnp]

Hi I am a real novice in this field so i am hoping some can help. Also I hope I am in the right forum.
Can some one tell me the basics of laser cutting. some of my questions are as follows.
1. If the laser cuts by cutting through the material then what prevents it from cutting through the board the material is on.
2. Is there a focussing mechanism. If so does it focus on the top surface or the base plate.
3. in 3D Laser cutting how dpes the laser only burn out the right depth and not burn through.
4. it seems that most Laser Cutters move around 1000mm/s. What mechanism is used i.e a lead screw style or what as that is a fast speed compared to CNC.

Regards fnp

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[Litografa]

Welcome on board! You will love lasers!
1) Usually laser can cut SOME materials only. And CAN NOT cut other materials. So if you have chinese laser with CO2 tube - you will be able cut wood, plastic, paper and some other materials BUT you can not cut metals - steel, aluminium and etc. So usually table in laser engraver/cutter is made from aluminium.
2) Focus is setting based on top of material. Be careful with cutting of thick materials. Usually you will cut this materials in few passes. And if for the first pass you must set focus on top of material, for all other passes you must set focus to the top of material BUT AFTER setting focus manually move table slightly up (depend from how deeply was cut during previous pass/passes)
3) You couldn't do real 3D on laser (especially on Chinese with glass tube). You will have (I name it) pseudo-3D. Gray scale image will be engraved based on machine's settings POWER/SPEED for each level of grey color. Together with problem that all materials are not homogen final result (depth of engraving in certain place) is difficult to predict.
4) I am very familar with GCC laser engravers and they have stepper/servo motors and belts for moving laser head.

[fnp]

Thanks a lot mate, that really helps. but I have a few more questions.
1. What if the laser cuts through metal then what do you use for a base.
2.Say I am cutting balsa wood say .5" thick does one pass suffice.
3.Is the focussing of the laser manual or automatic.
4.is the laser focussed by moving a lens apparatus or moving it along the z axis.
5.If lasers dont do 3D then what do these 5axis machines do.
6.Also say if you are looking to make wood mold would you then suggest a cnc router for that and a laser for cutting. are there cnc machines where you can change the cutting head betweena router and a laser.

Regards,

fnp

[Litografa]

1. What if the laser cuts through metal then what do you use for a base.
In this case manufacturers use steel and make special cutting tables - looks like honeycombs or like set of linears. During cutting some parts of this table will be damaged. Best way to prevent damaging is try to move parts of table from focus of laser.

2.Say I am cutting balsa wood say .5" thick does one pass suffice.
Will be enough 80 Wt chinese glass tube or 40 Wt SYNRAD. But keep in mind that cut area will be burned.

3.Is the focussing of the laser manual or automatic.
Depends from laser manufacturer. Europe/Taiwan/USA - automatic, China - mostly manual

4.is the laser focussed by moving a lens apparatus or moving it along the z axis.
Usually moving table on Z

5.If lasers dont do 3D then what do these 5axis machines do.
5axis machines do REAL 3D with high precision. Laser honestly speaking DO NOT produce 3D at all.

6.Also say if you are looking to make wood mold would you then suggest a cnc router for that and a laser for cutting. are there cnc machines where you can change the cutting head betweena router and a laser.
For mould - no doubt - only router. There is no combined router/laser models on market and I think will not be as tasks for each technology is really different.

[oneeye]

Hi, i have been looking for a table with the co2 laser power, how thick it can cut and which speed. i need only aproximate, i need only to mdf or plywood and acrylic for ex.:
co2 400w can cut mdf ......thick at ....in/seg
acrylic...........................
co2 200w can cut mdf ......thick at ....in/seg
acrylic...........................
co2 100w can cut mdf ......thick at ....in/seg
acrylic...........................
co2 80w can cut mdf ......thick at ....in/seg
acrylic...........................
60W......
40w........
thank you

[Litografa]

Do you want figures for glass tube or for RF tube? I will provide figures for RF tube later today when will be at home. But can't help you if you are looking for glass tube laser.

[oneeye]

Do you want figures for glass tube or for RF tube? I will provide figures for RF tube later today when will be at home. But can't help you if you are looking for glass tube laser.

It is to glass tube.... well, if u find some reference about .....
thank you 4 ya attention

[Litografa]

Here is information from one of my customers. He have two chinese lasers with glass tubes - 60 and 30 Wt.

[fnp]

Hi,
Well the picture is surely getting clearer so thanks a lot. Just a few more questions.
1. How is the laser focussed as would it not burn a hole will trying to do so also do you just move ot up or down z axis for the smallest dot.
2. How dp suto focus machines focus the laser?
3. Why cant I replace the router in my cnc machine with a laser head what are the issues.
4. do you determine the cutting speed by trial and error or is there a some system to do so.

Best regards,
fnp

[Litografa]

1) In each laser you have lens which focus laser light. Each lens have FOCAL DISTANCE - usually in inches 1", 2", 4"
Generally speaking FOCAL DISTANCE is distance between centre of lens and surface of material. If you have 2" lens, MAXIMUM POWER OF LASER will be on material's surface when distance between centre of lens and material's surface will be 2"
Auto focus - once you input in laser memory type of your lens and laser automatically set distance from material.
Manual focus - you just measure this distance with ruler and try to reach proper distance.
2) Do not understand question
3) Because they have different controllers, different software nad etc - it's practically impossible for you.
4) For example we give to all our customer special manual which indicate APPROXIMATE speed/power settings for cutting/engraving of different materials. When we have start sales of lasers in 1998, this manual was half of page, now it is over 5 pages, because we collect different settings for different materials. So our customers start with settings from this table and after +\- depend from result

[fnp]

Thanks mate. If a laser cutter uses different software and controller then does it not operate on G-code. What does it operate on? What software is required? Can you name a few. Can the cut files be edited in a text editor or are they more complex.
Regards fnp.

[Litografa]

You ask me too much Command codes and etc it's not my area of responsibility - sorry, can't provide you information

[LOLO80]

hello,
I am sorry, i need know if it is posible to make a laser line to 2 or 3 tenth width millimeter , with chinese laser co2!

[Litografa]

From the Physics and Optics view - possible but everything depends from quality of laser

[LOLO80]

hi litografa,
how make for optening a laser line extra fine, I have 2 laser machine the first is redsail 6090 with laser 60W, and one machine ruijie 1290 with laser tube 80W, with redsail I have a laser line of 2 tenth millimeters, but on the laser machine 1290 I have a laser line of 4,5 tenth millimeter, i do not understand because the light laser it is midle mirror!, the lenght focus is good, what to do!!

[Litografa]

I think it's not possible have same line thickness on 60x90 cm table and on 120x90 cm table Also keep in mind that on 80 Wt tube laser dot ALWAYS will be bigger than on 60 Wt tube.
As I understood on redsail 6090 laser tube is fixed, but on ruijie 1290 tube is moving with portal? Is it true?

[LOLO80]

Hi litografa,
no, the laser tube on the laser machine ruijie is fixed, may be ,I have to change a lens focus...

[Litografa]

First of all - do you have possibility install lens with smaller focus?

[LOLO80]

no, I have not an other focus lens, you know which lens focus i need for optening for small laser line?

[Litografa]

What is focal lenght of your current lens? Ask you supplier - did they have different lenses? For example we sell 1", 1,5", 2", 4" lenses. Unfortunately our lenses are expensive and do not fit your laser.
As you have 120x90 table I think you have 4" lens for cutting, but to have thin line you need 2" lens.