Form1+ laser flare issues illustrated - pics and video

Hi Kevin,

Thanks for the detailed reply. I hope you don’t mind but I’ve made a video response as its just quicker for me. The links for the files for the original parts are below -

Thanks again,


@EvanFoss what happens is that the air bubble “travels” through the part and can leave liquid resin behind it, hence you can get tunnels filled with liquid resin (that are invisible until you break the part open) - and airbubbles at the end of the tunnels just under the surface of the part. I saw this when I printed some glasses arms - there was a “trapped-air-cell” near the lowest (first printed) point of the part - an air bubble formed, broke the surface of the part, then “tunnelled” it’s way through almost the entire length of the arm - leaving a pit and a bubble under the surface near the end (last printed) of the arm.

I was initially completely baffled as to how it happened - until I broke it apart and saw the liquid resin tunnel reaching all the way back to the “trapped air cell”.


@KevinHolmes Thanks for the explanation. I probably never would have figured that out.

The following is my test. I was not happy with the quality of my photos taken through the printers cover so I took a different method. Our lab used to have a dark room and I saved some of the supplies. I took a sheet of Kodak photograph paper and taped it flat to a sheet of acrylic. I then put that in the printer face down. Yes it is sitting on top of the resin tray fixture and not in it but the point is that it should still be level. If people (in ether the user group or formlabs) want it done better I can find a better scheme to get the paper flat in the printer but for now I think this proves the point.

Never to be accused of a safety violation.

How it was mounted.

How it was setup.

What I saw.

@Steve_Johnstone - as I comment in reply to @EvanFoss - trapped cell bubbles travel - and actually the effects of a trapped air cell are not typically obvious where the bubble enters - but at a completely different location in the part.

To rule out the potential trapped air cell you highlighted, you’ll need to break your part in pieces and wash it in IPA to see if there are any liquid resin filled hollows/tunnels.

As for the lower area pits/porosity - I can only theorise that perhaps you have bubbles travelling up through your base and through your supports - it does sound unlikely I know - but it’s easy to check if you still have the supports and the part - break open all the supports and see if there are any liquid tunnels in them.

This is really interesting stuff. I just wanted to add some context to the discussion, here, regardless of what has been heard.

No laser spot is a perfect circle. Creating a laser module with a spot that captures most of the energy within a specified diameter with tolerances both reliably and repeatedly is a classic engineering and product development challenge. Some amount of light outside of that diameter (whether in the form of a “tail” or a uniform gaussian spread “galaxy”) is inherent in the process. This is something that we’ve been aware of for some time, and we’ve run tests not so different from your own. In our QA, we actively attempt to minimize it to within our specification.

If we find a laser module that doesn’t meet our specification, it doesn’t ship with a Form 1+. In our tests, the power in our “tails” is a small fraction of the overall energy deposited. For most prints, that’s not a problem. For taller pieces, where the layer profile is the same over and over, you may start to see an effect from this “tail”. Cured bits can accumulate on the part or in the tank. Most of the time, they’re undercured, so you can just wipe them away, and your part looks fine. What I’m seeing here, though, indicates that this is still a critical question, and we’re going to continue to take a hard look at it.

Things like running the laser spot test twice and then showing the cured bit, while a good way to get an profile of the entire laser spot, isn’t how our resin curing process works in vivo. Our raster cures only a circle (where the vast majority of the power is), because it moves so fast, and it takes more energy than is available in the tail to cure at those speeds. That doesn’t mean there isn’t some residual curing, but we work hard to keep it negligible.

With our current laser specification, we think we’ve hit a sweet spot between quality and manufacturability. We’re always looking to see if we can make it better, and welcome suggestions, but lasers are a tricky beast.

As always, if you’re seeing persistent part failures, you should get in touch with our support team.


Now to me the interesting thing is not only the fact that the laser point is not a dot but that there is another smaller diagonal line above it. I could be convinced that this line is too low in intensity to be an issue but the others intersecting the beam are sketchy.

@CraigBroady - I can certainly appreciate the points you’ve made, but I think it’s easy to sum up the problem with the laser spot quality and hence part quality in the Form1+ : it’s not as good as the original Form1 laser was.

Note that’s laser spot quality - not which laser is better. On balance I’d much rather have the Form1+ laser with it’s limitations than the failure prone laser in the original Form1.

However - I have to say it, while it was working - I never saw anything like the amount of flaking and jello, or any surface corrugation at all, from the original Form1 laser that I’m seeing with the Form1+ laser.

Moreover the issue is not limited to flaking that just washes off - take note of the small parts in my OP. Yes the tall parts are perhaps slightly specialised examples. However the op small parts are not - and what it means is that effectively a large chunk of my build platform is ruled out for printing,

This means I can’t make parts the size that I used to - which is a very serious issue for me. I was printing dental moulds that took up nearly the entire build platform - and orientation was extremely sensitive. Reducing my effective build volume makes me wonder if I’ll be able to print the same pieces again…

Flakes/Jello can find it’s way into crevices from which they’re very difficult to wash out, and the tougher larger flakes than can occur during long prints can make parts with complex features a bit of a lottery.

That said - it is good to hear that you are taking a renewed look at the Form1+ laser.


I agree with Kevin. The laser in the form1 I had before I sent the machine back to be exchange for a refurbished form1+ was perfect. My laser spot was perfect. The form1+ is a much better machine, but it’s possible the source for this new more powerful laser is not great.

I wonder how much the laser module in the form1+ costs. I’m searching online and I can see some from china going for $5-20 and some bluray lasers going for around $40 and then I see some professional quality ones going for a whopping $1500.

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@CraigBroady While nothing you say is technically incorrect the severity of flare that you guys allow is clearly in some cases far too much. Also the blacklight laser pointer I bought to cure resin while not having a perfect circle doesn’t have a ridiculous amount of flare and a far from round shape like the one in my printer does. The fact that perfection is impossible or cost prohibitive doesn’t mean sloppy and awful is acceptable. If your quality standards where closer to those my laser pointer was held to I imagine we would be in a much better position.


@CraigBroady It would be unfair to you and your companies work for me to suggest that the problems I have had are attributable to imperfections of the laser in my unit at this time. I have more testing to do and it will be a while before I can really get into it.

Since you opened the floor to suggestions I would like to add something. Laser printers do more or less what your product does only with out any user apparent signs of this kind of issue. I know that is a bit of an over simplification but bear with me here. As far as I can tell the secret to their sucess is the use of an F-Theta Lense. If you had one between the main mirror and the underside of the resin tank it might improve things. If that sounds to expenive just try curving the underside of the resin tank to form an f-theta lense. I favor the former because it means less disposable plastic and people would no longer be able to spill resin or what ever else onto the main mirror.

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Hi There

Many thanks for the testprint. My upgraded form1 to + has not this problems.

Best regards


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That’s really interesting @SachaGloor - they look great. Thankyou very much for posting your results.

One note of caution however, those test pieces are probably only going to show issues for people who’s laser flare is oriented closely to one of the four points of the compass - if your laser flare is at 45 degress to X or Y dimensions instead - then I’m not sure if those test pieces are good indicators. I haven’t tried my laser in that orientation.

If you could provide a picture indicating your laser spot orientation like mine or @KjellNilsson’s or @Steve_Johnstone that would be a great help.

If you have trouble getting a clear photo of your laser spot - you could run the simple test I’ve shown above in post 12. Use a clear sheet of perspex, or perhaps just a clean tank, or even a transparency sheet in a clean tank - run the spot test - note where the spot is, and put a drop of resin there - preferably black. Then run the spot test again - perhaps twice - and then rinse off the uncured resin with IPA. You will then have a cured blob of resin in the shape of your laser spot.

I’m really keen to see your laser spot orientation - because those pieces looks so good - and it would very interesting to know for sure that the Form1+ laser quality is that variable.

Hi Kevin

Will try it this weekend. How do i run a laserspot test ? Is it a special .form file ?



Here it is:

On post #1 explain all for Mac

On post #73 there is a capture from Windows

In fact it did used to be a special form file, but now when you start Preform with the command line option “-diagnostic” it gives you an extra menu called “diagnostic” and the one entry there is “laser spot test”.

If you’re on windows and have preform in your shortcut bar you can just edit the shortcut properties to look like this:

edit: alternatively see @Jose_Ignacio_Vicente’s link above :slight_smile:

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at the same time… :smile:

@KevinHolmes, I’ve just reread the Cluster or Bubbles of Cured Resin and @KenCitron comment ready struck a cord -

What is it’s this jello caused by the lenses flare that’s causing the problems on my parts?

There is more surface area being cures in these areas and a greater chance on the jello causing problems.

I had a think about what you said reference trapped air bubbles. I’m pretty sure that the print surface of the print remains submerged during the whole print process so cant see how air could be introduce unless the resin level was too low. I may be wrong but will pay a bit more attention with my next print.

I’m going to print a solid version of Test Exhaust v2 to see what happens.

@SachaGloor, +1 on @KevinHolmes comment.

I would love to see what your laser spot test looks like.

@KevinHolmes - Awesome tip!

Having to type the whole command line into the cmd window, exactly as shown in the FormLabs instructions is a PITA.

Your way is so much easier. Even better is having the diagnostic tab available when ever I start up preform from now on :smile: