View Full Version : Calibrating table

Eric Seest
11-23-2008, 6:22 PM
How often should I expect to have to calibrate the table? I switch between the cutting table and regular table a lot and I have noticed that I have to re-calibrate the table quiet often. At first I thought it was because I have been through several drivers since receiving my laser (five drivers in 7 months). Today the cutting table was good but when I checked the table it was off by about .040. I have a ULS PLS6.60 with ULS cutting table. Just a little concerned with some of the other problems I have had.

Darren Null
11-24-2008, 11:04 AM
You should calibrate every job. Let's assume that your laser beam is absolutely perfectly aligned from the laser onwards, and your beam is perfectly vertical. Movement of the head is going to knock the mirrors slightly out of true, as well as expansion, dust on lasers/mirrors and many other factors. And that's if your lens is perfect and all your mirrors are too.

Once your beam is slightly off vertical; you're going to get different offsets for different parts of the table as the beam wanders around the lens.

You can't calibrate for (say) the top-left-hand corner of your table and expect it to be right for other parts of the table. Lasering just doesn't work that way because there's too many variables. There's 4 (in my case) mirrors and 1 lens that the beam passes through over a distance of approx. 0.8-2m. The distance varies, the lens isn't perfect, the mirrors -even if they were perfect, which they aren't- could be put out of true by your tightening of the adjusting screws too much or too little.

So. Don't expect the dot to be where you left it.

Mike Mackenzie
11-24-2008, 12:15 PM

The problem might be that when you install a different driver you are not removing the older version completely. What version are you using now?

When you install the driver you should calibrate the Z to the solid table first then re home Z put the cutting table in and calibrate the cutting table. Be sure to have the proper lens selected.

Richard Rumancik
11-24-2008, 12:16 PM
Eric, I was trying to figure out what you meant by "calibrate". Now from what Darren says I assume you mean setting the 0,0 point on the table. I agree with Darren that there are many sources of error.

If this is what you mean, I will give you my take on it. I do things a little differently - I set my zero approximately (within .010") but don't worry too much if it is not spot on. The reason is that the red beam pointer is not 100% aligned with the co2 beam anyway, so using it as a reference is prone to error. In order to get the 0,0 aligned to the co2 beam, you need to make a physical mark at (say) 1,1 and then find out where it really landed. (You can't make a mark at 0,0 or at negative values on my laser). Then you can determine the errors delta-x and delta-y and then set 0,0 relative to the co2 beam. But measuring is prone to error as well. But if you change lenses, or focus, do an alignment, clean a mirror, or work in another area of the table you may find it is different again.

It is not quite like a machine tool where it is relatively easy to set the "home" position and know exactly where the cutter is. The center of a cutter is known to a precise degree (the center of the focal point is not.) As well, you know the tool is straight. (Whereas the beam may hit the table at a slight angle.) In comparison, laser engravers are "loose".

Thus I don't really use the rulers for much other than a rough approximation (within .030" maybe) of where the co2 beam is. Basically I use them as a hard stop for fixtures. If I am marking items, such as a plaque or plate, I would plot the outline of the item using the laser on a piece of spoilboard (rigidly attached to the table)and then use that as my reference. If I ran it again I would not use the old spoilboard as it would likely be wrong. I would move the image or use a new piece.

When cutting parts out of sheet having an accurate 0,0 is not that critical. It is critical when marking existing parts, but since it is time consuming and prone to error to set it, I decided it was faster to go a different way.

I also like having the item a little closer to the middle of the left side of the laser when I mark it rather than in the top left corner where it is harder to view and inspect.


Okay, Mike thinks you mean something different regarding calibration - if you were talking about setting the z axis then what I said here is irrelevant to your problem . . .

Eric Seest
11-24-2008, 8:00 PM
Thanks for the information, I was talking about calibrating the Z direction because it keeps changing on me. I am using 2.19.39 and I have tried to the best of my ability to unistall the old drivers. The information about the beam alignment is very good information and I will take a look at that. I do notice a difference between the alum. table and the cutting table. Thank you.

Scott Shepherd
11-24-2008, 8:24 PM
Just to clear up the calibration issue so other's who aren't familiar with the ULS systems, the PLS systems (and others) work off of a Z height. You calibrate the machine to the table top, and then from that point on, you just enter the thickness of your material. Since the machine knows where the table is in Z, and it knows how thick your workpiece is, it knows where the focal point is and it moves there when the job starts.

It's the way CNC machines work. Instead of setting the machine to every single job, you set the machine to itself and then enter one offset.

It doesn't have a plunger, and it doesn't focus on every part, so in that respect, it's quite different than what some of you are used to using.

I too have checked the calibration after a couple of months and found it to be off as well. Now any time I see things not acting like I'm used to them acting, I immediately check the calibration of the table and the cutting grid.

Mike Mackenzie
11-24-2008, 9:07 PM

2.19.39 is a good version it should hold the calibration. By completely removing the driver would mean to UN-install then search for ULS and delete the two folders. This is not something you would always do however with the amount of driver versions you have gone through it may help to completely do a fresh install. There should be two folders (ULS, and ULSdb) Before you delete these folders save any permanent job to a different folder. (open the UCP and go into the jobs folder and copy the ones you want to keep into a different folder on the desktop) If you delete these folder you will delete all of the previously printed jobs if you need them save them.

Once you delete these folders restart your computer and then re load the software 2.19.39. Once all the software is loaded re start the computer again.

Now open the UPC and make sure you have a connection click on the re home Z button in the UCP. Now bring the table up and use the focus tool in the center of the solid table and calibrate it.

Now re home Z again put the cutting table in and calibrate it to the center of the cutting table.

This should be all thats necessary our pls has not lost its calibration in over six months and we switch to different lens and take the cutting table in and out all the time.

Eric Seest
11-24-2008, 9:25 PM
I will give that a try; I have never deleted the two files you mentioned, I didn't know there was more to unistall. I was told just to run the unistall and it would take care of itself. Do you happen to have a copy of the 2.19.39 that you would be able to email me, the exe. copy I had got deleted. Thanks to all for the help.

Mike Mackenzie
11-25-2008, 12:07 PM

You can get that driver here http://www.cemlasers.com/pg--17--Drivers.aspx

Eric Seest
11-25-2008, 9:16 PM
Thanks for the information. Nice web site, the samples are nice. Do you happen to know when the new driver is coming out that is supposed to help with pictures? Once again thank you very much for the information.

Mike Mackenzie
11-26-2008, 3:41 PM

Sept, Oct., Nov.,Now Dec. I think they want to be absolutely sure everything is working correctly before they release it.

Andrey Anfimov
11-26-2008, 8:39 PM
To remove completely all parts of ULS driver you should make following steps.
1) remove folders ULS and ULSdb from directory C:\Program Files
In folder ULSdb there is a user base of materials! Make a backup copy!
2) from directory C:\Windows\inf remove files oem*.inf in which you will find records about ULS drivers.
3) remove a folder with the name of your laser from a directory "C:\WINDOWS\system32\spool\drivers\w32x86". For Versalaser 3.50 it is folder with name "vl3_50".
4) REGISTRY CLEANOUT. For Versalaser you should remove keys from the register that begin with that VID_10c3. Find all keys that start with VID_10c3 and remove them.