Laser spot shape? what does yours look like? mine has square halo

So I’ve got an open ticket regarding the X-galvo being off-kilter, but I’ve been trying to get one last final print done before returning the printer - and suddenly all of my prints have started failing. They got dramatically worse over the course of about four/five prints from simple tearing, through to just a base with only droopy soft support stumps, through to nothing adhering to the build platform at all.

I’ve been trying everything to figure out what might be wrong,  fresh resin tank, fresh stirred resin, fresh build platform - checked and cleaned both mirrors. I checked and even tried adjusting the tank-frame self-levelling springs. Nothing helped - so I began to wonder about the laser and the galvo mirrors.

Replacing the resin tank with a sheet of white paper, using a magnet to “print” with the case open, and removing the build platform. I had a look at the shape of the laser spot - and it doesn’t seem right to me. I was expecting a well defined simple dot - but instead there is a lot of scattered light around the central dot in a rounded square shape. See attached picture (shows a line+halo because the shutter is too slow) and video here

I raised a ticket with formlabs yesterday asking if this is normal - but it’s the friday before xmas and I imagine they’re enjoying the season - as they should, they deserve it. But in the meantime I’m still really keen to resolve or find out more about this new much more serious issue before sending my printer back.

What does your laser spot look like?



thats mine - and I really want to know what it should look like

All my latest prints failed



@Klaus - have you got a little magnet? you can use it to trick the form1 into thinking the cover is closed. I found that the halo was not easily visible with the case closed. Also how badly have your prints been failing? mine won’t even get as far as the base now.

I’ve made a form1 file with face-planted cylinders that are 0.3mm thick - so that the laser path is just the spot - I duplicated the cylinders lots of times to get a better chance at taking a photo - unfortunately I still wasn’t able to time my shot right to capture one of the dots - but I was able to using my camera film mode.

see here :

So the resolution is low - but it still shows the spot and halo. Wierdly I can now see two different types of spot - one with the halo and one without - so now I am very concerned about my laser spot - and I’m becoming convinced it’s why my prints fail so completely.

The spots being with an without halo’s is not an artifact of my ancient camera - it was clearly visible to the naked eye that sometimes the spot was haloed and sometimes not. The video here is dim, but faithful to what I actually saw.

The two attached images are still from the video - and the fact that the spot without the halo is a lot dimmer than the spot with the halo may or may not be an artifact of my camera film.  Unfortunately the spots were flickering too fast for me to be certain the unhaloed spot was dimmer.



One  of my failed prints you can see here:

Sorry but the video link does not work for me.

My picture of the spot:

I tried to focus on the spots shape and used a manual exposure and aperture time and a macro lens.

I didn´t focus on the halo. Maybe I try this today or tomorrow.



@klaus looks like you might have a different issue - my prints are failing without even printing a base. Sorry for linking the wrong you-tube link, this one should be the right one

I can’t see a picture on your most recent post?




Thank you - the link worked. wow - thats a halo!!

Sorry for the misunderstanding. There was no picture in my most recent post. I talked about the picture posted in my first comment.




I used your file and took some pictures.

I have no halo. but the spot is very seldom really round and the lightness is too very different. (but this may have other reasons)


@Klaus - Thanks very much! that’s really helpful, I think that shows definitively that I have a really bad issue with my laser.

It’s true yours dont often look very round -  and yes it could be due to other issues - although some of them do look quite stretched - more than I could explain  for example by diffusion in the paper, or some kind of artefact of the Form1 toolpath, or from the camera.

I take it you’ve inspected and cleaned your mirrors? I learned the hard way that you have to be careful with them (I scratched the bottom of my large mirror -  just the bottom and after my issues) - they are “front surface” mirrors - meaning the delicate reflective surface is on top of the glass not on the back. You’ll need a microfibre (lens) cloth. To clean the first mirror at the base of the z-axis column I first removed the second large mirror and  then used a cotton bud wrapped in lens cloth to reach in and wipe it.

For variation in spot brightness in the pictures - I think that could perhaps be explained by variance in time window overlap of the camera shutter with the duration of the laser spot.

The variance in shape is perhaps a concern for your failed prints though. There was another thread on the topic of the shape of the laser spot - and Formlabs provided a Form file to check the spot shape, unfortunately that was for a previous version of Preform and doesn’t work in current versions, in any case I can’t find it now - but it would be great if Formlabs would weigh in with another such file - I’ll update my ticket with that request, and if you end up raising a ticket perhaps you could ask for it too.

In the meantime I made another Form file - with 0.1mm diameter cylinders this time and actually it does seem to make a difference to the toolpath - in spite the laser spot supposedly being 0.3mm in diameter, I found my spots had smaller halos on this file - and also oddly there were no spots without halos like there were with the previous file.

thanks again!




Hi Kevin

Here is the file I got a while ago.



@Klaus - I think that’s the same file I was referring to, when opening in Prefom it doesn’t show a spot - it shows a small wall. Interestingly though when I try to “print” that - I get no laser spot at all - with or without a halo. I take it you get a spot like the picture in your zip?

thanks again,


Hi Kevin

You are right it is just a wall 5 x 5 mm and very small.

When I click form it took some time to calculate and to load it up.  I think it took more then one or two minutes till I saw the spot after I pressed the button on the form1 (file already loaded up).

The spot can be seen for a while and disappeared then again for one or two minutes. Then the spot is here again and so on. So you have a lot of time to take pictures.

If that does not work for you, you have a big problem with your printer.



Hi Klaus - ah many thanks again. So yes that just confirms my laser halo issue. See attached - it’s off centre because of my other issue with the skewed X-galvo.

Hi Kevin

that looks really strange.

My spot is also not in the center.



I might say munted, foobared, all gone a bit pete-tong - rather than just strange :slight_smile: - it’s not a camera artefact either. It is a bit blurred cause I can’t control the exposure much on my phone - but it’s pretty much what I see.



So it’s definately the laser - I didn’t know lasers could break like this, being solid-state and all…

I was searching for info on the laser test and this thread was the most relevant.

But my prints are all failing now, supports not fully forming etc.

As everything was working fine & no variables such as updates all I could guess was laser power diminished.

I’m doing the email back n forth with support but I wondered if anyone knew exactly what the laser test is supposed to look like?

But here’s a couple pics of mine:

Unfortunately, I never did the official spot test on a functional laser or the bad lasers I have gone through.  I just saw the aftermath in my failed prints as well as looking at the shape on the top cover as it danced around.  Just based on your description I believe your laser is bad.  Looking at the pictures I would think something was wrong as well.  My understanding is you should have a really bright center dot that is circular and a small much duller halo around it.  Looking at yours, you have a funny shaped bright dot with a very oddly shaped hallo with a second halo around that.  If yo tell me how to get the test feature to show up, and I can find a camera that will take the picture, (and I do not forget this weekend) I will post up what my laser spot looks like.

Sure and thanks, here’s how:

To access the diagnostic test, please make sure your computer is connected to your Form 1 and open the Windows command line prompt by searching “cmd” in the Windows 7 start menu, or pressing Windows Key+R and searching “cmd”. In the command line prompt, type the following:

For Windows XP:
“C:\Program Files\Formlabs\PreForm\PreForm.exe” -diagnostic

For Windows 7 and above:
“C:\Program Files (X86)\Formlabs\PreForm\PreForm.exe” -diagnostic

Wow I guess copy and paste from outlook express is bad! sorry bout that

editability would be nice!

Hi, Does anyone think my Form1 laser beam spot looks right?

I got 6 consecutive printing failure which looks like mushroom with extra extrude from main part. The detail can be found in this post:

I hope it can be fixed and do not require lengthy replacement process. Any hint?

Thanks a lot!