View Full Version : Laser focus

Adrian Hill
03-24-2011, 1:32 PM
I am running a 70W Chinese laser and the machine is working very well. But I do have a couple of questions:

1. The laser is fitted with a red dot pointer that is pointed at the job from a 45 degrees angled mounting on the side of the head - would it not be better to shine the red dot through the laser optics?
1.1 This would mean that one would need to put the pointer directly in the path of the main laser - any ideas? how do other manufacturers do this?
2. What is the most effective way to focus the laser? I did quite a bit of testwork to determine the point by firing the laser at the same intensity and duration at differnt heights off a test sheet and I got to what I think is the best focus. But isn't there a more scientific way?
3. I find that the spot size is still a bit large for my liking. I would say that the spot diameter is about 0.3mm. I deduce this from the fact that a square of 50mm comes out to be 49.7mm which of course is 0.15mm lost on ether side of the job. Is this size acceptable?
4. Does a lower power laser i.e. 30w have a smaller diameter spot or is the spot size determined purely by the quality of the optics and the correct focal length?

BTW: I must say, I think that the machine software and the machine controller suck bigtime. The software includes some Chinglish which doesn't always make sense (I won't talk about the manual). It also forgets its settings all the time. I would love to be able to save a job and the machine settings in one file. The machine uses Coreldraw with an additional toolbar. I would have though that there would be a bit more integration. with regard to the controller - the thing that erks me the most (probably because I am used to CNC machines) is that I do not have a handheld controller, XYZ DROs and a mechanism to change the jog speed on the fly. I set up jobs on jigs all the time. I set the positioning using a high jog speed at first but as the position becomes more accurate I lower the speed right down. It would be so nice, as in Mach 3, to type G0 X0.01 Y0.2 and know that that is where the laser head is going to go.

Larry Bratton
03-24-2011, 2:29 PM
Dude, you gave up some of the things your speaking of when you opted for the lower priced Chinese machine. It's a trade off. Is your CNC machine Chinese?

Rodne Gold
03-24-2011, 2:32 PM
Hiya Adrian

You need a "BEAM COMBINE WITH HALF REFLECTOR MIRROR " to position the red dot coincident with the laser on the chinese machines , you can get a replacement head with that included for about $55.

Best way to get focus is what you have done, otherwise you can measure the focal length from the lens to the surface of the material , ie a lens with a 40mm focal point needs to be 40mm from the work , dunno if you measure from the top side , middle or bottom exit side of the lens.

Cant do much about the spot size , other than changing the lens to shorter focal length , the glass tubes have a large spot size to begin with, maybe adding a beam expander/collimator would help?

The lower power tubes do seem to have a smaller spot size and can fire more "delicately"

You could probably change your mother board to a later version and use "better" software , would maybe be a mission
What machine do you have and what software you running?

Adrian Hill
03-24-2011, 3:26 PM
The CNC is a Turret mill with Mach3 retrofit. I'm quite happy with the CNC.

Rod, the laser runs a RDLC-430-A controller. The software is caller Laserwork but I think it is also called RDCAD. The controller drives standard Gecko-like stepper drives so I suppose tossing the motherboard and replacing it with another wouldn't be too hard - I've done it before on the CNC.

I haven't been able to find any more information on the controller or software. It seems to be a generic setup that is branded for each supplier.

I'm not unhappy with the machine, I know how to work around its niggles, but it would be good if I were able to enhance its functionality.

Dan Hintz
03-24-2011, 5:10 PM
I would say that the spot diameter is about 0.3mm. I deduce this from the fact that a square of 50mm comes out to be 49.7mm which of course is 0.15mm lost on ether side of the job. Is this size acceptable?
A 12mil spot size is not out of bounds for a glass tube, assuming the typical 2-2.5" focal length lens... with a metal tube, waist size is typically 5mil with a 2" lens, 1mil with a collimator.

Rodne Gold
03-25-2011, 12:18 AM
What version of laserwork/rdcam ? Ive seen the latest laserworks in action and it seems ok

Adrian Hill
03-25-2011, 1:32 AM
As far as I can make out it seems to be

Rodne Gold
03-25-2011, 2:11 AM
I can give you a later version with Usb drivers - the controller I think its for is a leetro - not sure of the version , you may be able to kludge it
the Version I have seems to be 3.0 something

Adrian Hill
03-25-2011, 3:27 AM
Hi Rod,

Its worth a try. The software that i have refuses torun from Cordeldraw (anything higher than version 12) so the later software might help. I'll also contact the supplier and see if they have any more information about the controler (I'm not holding my breath though)