Focus Focus Focus

[Terry Wade]

Hey Guy's I have finally got my laser running and one thing I'm not sure about is the focus. The laser came with a little tool that is about 2" long X 3/8" wide X 1/8" thick. Which dimension do I use to focus with? I've tried the 2" and 3/8" dimensions and I don't get the greatest cut with either one. I took an anodized aluminum tag that I've been using with the diamond drag and tried engraving it with 30% power from a shen 350d laser and it showed no affect. So I don't think that the laser is focused correctly. Also how can I go about checking the focus and know when I have it right?

Thanks....Terry Wade

[John Noell]

Might be a good idea to share what kind of machine you have so we know which kind of tool you are holding. :) You will see a lot of tips to check focus, but one of the best is to put a piece of something flat like anodized aluminum on the table, with one end raised a bit. Engrave a line. Where the line is thinnest is where you have the best focus. Move the head to that spot and check the distance from the lens to that spot. If it is a Chinese machine it will probably be about the 3/8" width from the lens tube to the best focus spot. The focal length of the lens will determine the best distance from lens to spot.

[Ross Moshinsky]

2" lens will focus 2" from the actual lens. Now when I say 2", that is a very close, but approximate value. Sometimes you'll find focus being better at 1.92" vs 2.0". With cutting, the more infocus you are, the better the results. With "normal" engraving, you can be a bit out of focus and not have a problem. For fine engraving, you really want to be spot on.

[Clark Pace]

Might be a good idea to share what kind of machine you have so we know which kind of tool you are holding. :) You will see a lot of tips to check focus, but one of the best is to put a piece of something flat like anodized aluminum on the table, with one end raised a bit. Engrave a line. Where the line is thinnest is where you have the best focus. Move the head to that spot and check the distance from the lens to that spot. If it is a Chinese machine it will probably be about the 3/8" width from the lens tube to the best focus spot. The focal length of the lens will determine the best distance from lens to spot.

My focus tool was a simple piece of acrylic, and it really didn't work well either. I ended up making a new one by trial and error. Made the laser cut a vector line, and see if sharp it was. Then moved the laser head a bit and do the same thing again until I go the correct height. I think the tool they sent me was for a different lens.

Also test cut depths.

[Terry Wade]

Sorry, The laser is a Shenhui 350 50 watts, So far the best cutting has come from the 3/8" dimension, cutting a piece of wood at 30% power, however when I tried to engrave the anodized aluminum tag it shows no affect. The focus tool that I have is also a piece of acrylic. Ican very easily make a new one if I need to once I get the right focal length. I guess I need to find me a piece of anodized aluminum long enough to try to cut a line on and see what I get.

Thanks.........Terry Wade

[Gary Hair]

There are several threads on how to check focus but the general idea is to have a slanted piece of anodized aluminum so you can laser along it and see where it is sharpest. That will give you the optimal focus and you can make a focus tool to match. Don't use wood or acrylic, neither will give you the fine line that anodized aluminum will give and your focus won't be as precise.

[Dave Sheldrake]

Use a bit of plywood Terry, anything you can hold at an angle and burn will do.

A few words from the Master Himself Tweakie


If you ever have occasion to change a lens then one way of measuring the correct focal distance or checking the existing gauge is to set up a small piece of black anodized aluminium or wood as shown in the diagram below then laser a line across the metal plate.
The correct focal distance can be measured between the point at which the line is thinnest and a suitable point on the lens assembly. If a new acrylic gauge is now made to this dimension it can then be used to set the correct focal distance for any thickness of work material.

I added the "or wood" bit

300078

cheers

Dave

cross posted with Gary, Gary is right, anodised will work best but whatever you have will be a good starting point if no ally sheet is available

[Gary Hair]

Looks like I added the picture about the same time you posted... at least we are both telling him to do the same thing!

[Dave Sheldrake]

Thats always good Gary :)

[Tony Lenkic]

Terry,

When you say "anodized aluminum" are you using colored or clear one? Clear anodized will not render contrast you require.

[Rich Harman]

You can get perfectly good results using wood (anything that marks well). I've tried both and I don't really see any advantage to using anodized aluminum. All you are looking for is the narrowest part of the line. I use a pencil to mark off the beginning and end of where the line looks the sharpest. Right in the middle of those two marks is the best focus distance. Wood or MDF makes a nice dark, easy to see line - it is cheap and readily available too.

[Keith Colson]

Before focusing you should check to make sure your bed is level with the laser head. e.g. measure the head to the bed with some calipers at 4 points. You want that pretty good first. I just did mine last night. After that I found perfect focus. I adjusted my focus tool and bed setting to match. I used a measurement microscope to find the best focus on the test cut. I just looked for the skinniest cut result.

Cheers
Keith

[Clark Pace]

Before focusing you should check to make sure your bed is level with the laser head. e.g. measure the head to the bed with some calipers at 4 points. You want that pretty good first. I just did mine last night. After that I found perfect focus. I adjusted my focus tool and bed setting to match. I used a measurement microscope to find the best focus on the test cut. I just looked for the skinniest cut result.

Cheers
Keith

My Shenhui 350 was really good at 3/4 of an inch . 75"

[Shannon Bruce]

I may be missing something, but I think it's more a setting issue than a focus issue. We have a ULS M-300 50 watt and I have to use 50 Power and 50 Speed to get any kind of marking on anodized aluminum, sometimes having to do 2 passes. Are you playing with your settings at all?

[Bert Kemp]

I use 30% pwr and 325 mms and have no problem marking AA

I may be missing something, but I think it's more a setting issue than a focus issue. We have a ULS M-300 50 watt and I have to use 50 Power and 50 Speed to get any kind of marking on anodized aluminum, sometimes having to do 2 passes. Are you playing with your settings at all?

[Shannon Bruce]

I use 30% pwr and 325 mms and have no problem marking AA

As sad as I am to admit this, I have no idea how the 325 mms compares to our % of speed on our settings. As much as I love what I do and the machines I talk to every day, I am clueless as to how any other makes/models work. Don't hold it against me though! LOL

[Brian Leavitt]

I use 20% Power and 100% Speed on all of our laser machines for anodized aluminum, with good results.

[Ross Moshinsky]

As sad as I am to admit this, I have no idea how the 325 mms compares to our % of speed on our settings. As much as I love what I do and the machines I talk to every day, I am clueless as to how any other makes/models work. Don't hold it against me though! LOL

You should be able to mark anodized aluminum at 100 speed and about 15W. Sometimes you can get away with less and sometimes you need a bit more power. You should always run at 100% speed or very close to it.

[Shannon Bruce]

I use 20% Power and 100% Speed on all of our laser machines for anodized aluminum, with good results.

I haven't tried adjusting the speed to 100%, that's a good idea. Thanks!

[Eric j Allen]

You can do the focus test cut line just on paper. Is doesn't need to be on the anodized aluminum. What kind of settings you're running (dpi-speed-power)should determine why you aren't marking.

[Dan Hintz]

You can do the focus test cut line just on paper. Is doesn't need to be on the anodized aluminum. What kind of settings you're running (dpi-speed-power)should determine why you aren't marking.

It will get you in the ballpark, but if you really want to know where the focal point is (especially for fine-detail work), you need a durable, high-resolution substrate such as anodized aluminum. Paper simply isn't going to cut it.

[Terry Wade]

Thanks for all tips. I didn't have any aluminum around to use but I did use a piece of hardwood that I had and I found the sweet spot appears to be around the 3/4" zone. I took a piece of acrylic and made a new measuring tool and it seems to work pretty well at the moment. I'm using the software that came with the laser at the moment and it's OK I guess but I'm sure there are some better. I would like to find one that I can fill in the fonts instead of just cutting the outline.

Thanks Guys,.......Terry Wade

[Bert Kemp]

Terry List your machine and software in your signature so were better able to give advice. I'm assuming your using lasercut 5.3 that came with the machine YES? Most of us here use Coreldraw to do the design work and them import to lasercut to do the engraving or cutting. If you want to engrave in lasercut the box on the right side were it says cut, if you clic the arrow it opens and give the the option to engrave. any thing thats total enclosed can be engraved. try a setting of 30% pwr and 350mms for wood to start.

[Khalid Nazim]

Terry, select "scan" as the mode option for the font color and the laser will engrave the area between the lines. You can preview this in RDCAM before you actually run the laser operation.

Regards
Khalid

[Terry Wade]

I looked for the text color mode options and I'm not finding that in the RDWorksV8 software. It would be fantastic if I can fill in the body of my text instead of just cutting the outline.

Thanks.......Terry Wade

[Keith Colson]

You can focus your laser with paper but you need a microscope or some way to measure the line width. I just focused my laser cutter like this 2 days ago. The cutting table height was wrong and the focusing stick was wrong too. It works much better now.

What I did was cut small star shapes into paper with the lowest power and highest speed. I cut Z heights in 0.5mm increments. With a good microscope I could see one graticule of difference (~40um) between in focus and 0.5mm out of focus. All I did was pick the cut that had the thinnest line width. The star shaped corners were good to see how defined they came out for gross calibration.

Cheers
Keith

[Jerome Stanek]

I looked for the text color mode options and I'm not finding that in the RDWorksV8 software. It would be fantastic if I can fill in the body of my text instead of just cutting the outline.

Thanks.......Terry Wade

In RDworks 6 you click on the color and the properties comes up change it to scan and that should be what you want