Form1+ laser flare issues illustrated - pics and video

@JoshK there’s nothing mounted in the threads on the F1+ laser - are you looking at shots of the original F1 laser?

There’s a visible fixed rectangular lens in the F1+ laser.

No the laser like I have in my picture. That’s an upgraded (Form1+) laser. It seems the threads go all the way back to the lens inside. Of course trying to reach inside risks getting dust on a lens you can not clean.

This is why I can print just fine at the far edge of the build platform, ok in the center and it looks like a mess on the hinge side. The laser profile changes dramatically because of the flare shape.

No collimating lens?! Is it possible that the lens is there and it is just poorly calibrated/aligned?

I wonder if the collimating lens is what was dying on the form1 lasers, and if they decided to use a non-collimated laser for the form1+ to avoid the problem all together.

Now I have two questions. Are there any form1+ printers in existence that have a clean enough laser spot profile to print without noticeable artifacts due to flare, or noticeable loss of detail due to loss of focus, across the entire build platform, and at all resolutions? If there are not, could the same laser be made with adequate quality to allow one to do so?

If the answer to the first question is yes then this problem seems like a QA problem, all they need to do is do a more thorough check of their lasers so printers don’t go out with inadequate lasers. If the answer to the first question is no but the second is yes then the problem is a parts sourcing, or supplier problem, they just need to get their supplier to make them better quality lasers, or find someone who will. If the answer to both questions is no, then the problem is a fairly major design flaw, they made a bad design decision that prevents their printer from being able to do what they intended for it to do. This last conclusion assumes they did not intend or expect noticeable artifacts due to flare, or noticeable loss of detail due to loss of focus.

@RocusHalbasch - I think the contrast of @SachaGloor’s results with mine shows that the answer to the first question is pretty much yes, and that there is a QA problem.

@Ante_Vukorepa et al - I’ve tried and tried to take decent shots of the spot convergence and then divergence over distance, but it’s just not feasible with my nexus 5 camera (I did try “manual camera” app which is awesome, but even at v fast shutter and adjusting ISO, shots still blown out)

So I went back to the UV sensitive paper I used back in the day for tuning my replacement galvos on the original F1 - and I think it’s worked out ok - I think the spot convergence and then divergence over distance is shown well - see below


first run (two pic composite):

second run all spots shown

second run close up - first spots missing

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I’m inclined to agree with you however @SachaGloor’s results on one test are far from conclusive evidence that he has a clean enough laser spot profile to print without noticeable artifacts due to flare, or noticeable loss of detail due to loss of focus, across the entire build platform, and at all resolutions. I wish I had access to his machine so I could put it through it’s paces.

Sorry to back things up, but I just realized @RocusHalbasch asked for before and after pics for the laser choke on the post following the laser choke designs. I updated it with the pictures.

@JoshK I actually meant prints before vs prints after.

So I’m looking at Kevin’s tests and wondering what the distance of the laser path is in a Form1+. And Ante and other are wondering how much it changes across the build platform. Could someone take a few measurements please?

my very rough measurements gave an approximate distance from laser to pdms surface of 30cm say plus or minus 3cm.

Here’s one Rocus. It is a large 1/2 tube shape. As you can see, where my flare reached out from the model the farthest the resin would cure to the bottom of the tank and start tearing into my new layers. What I did was check on the print every so many minutes, and when I saw the model failing, I lifted the lid and scraped off (and removed) the huge, round, cured area on the bottom. The print would heal and continue, until it happened again. And again. Now I’m getting pissed off again…

This object printed perfect with the Laser Choke in place.

Sorry @JoshK didn’t mean to make wounds fresh. So as for the difference in distance. If you measure the shortest distance from the laser to the tray, which would be from the laser to the center of the first galvo, to the center of the second galvo, to the center of the small mirror, to the center of the large mirror, to the center of the platform at height 0, and call that shortest distance in mm s, then the longest distance in mm l can be roughly approximated as:

So if the shortest distance is 300mm as @KevinHolmes approximates the longest distance should only be about 312.75mm.

For those who want to verify my work or know how I came up with that. The distance from one corner of the platform to the farthest corner is sqrt(125^2+125^2) which is equal to 125sqrt(2). The distance from the center to a corner is then half that 125sqrt(2)/2 which is equal to 125/sqrt(2). To approximate the longest distance I just then treated the system as if it where a straight line with no mirrors, and as if the spread started at the laser instead of at each galvo. The result will actually be slightly longer than the real path. However calculating it correctly would require the additional use of shortest distance from the center of the y galvo and shortest distance from the center of the x galvo, and calculating the x and y components separately then adding them for the correct result.

No worries :smiley:
Sorry to question your math, but I got a different answer.
Using 30cm to center I came up with a difference of 6.44mm, about half your number. Did you divide by 2 to adjust for only half the platform distance from center to edge?

@JoshK your calculations give you the distance from the laser to the center of an edge of the build area. However the greatest distance is from the laser to a corner of the build area. So instead of 125 which is the length of one side of the build area you should use 125*sqrt(2) which is the distance from one corner to the farthest corner of the build area.

Ah, you’re right. Thanks for the explanation.

@JoshK, @RocusHalbasch I think you’re both a bit off, I think the right angle triangle math is too simplistic.

I modelled the path of the laser in Solidworks with mates to trace the path of the spot. Dimensions in the model are only vaguely approximate to the F1+ but summing just the two largest laser path component dimensions with the spot in the center vs at the corners I get a variation in path length of just over 2cm.

Which may or may not be enough to affect spot focus at the edges of the build area - my feeling though is that it won’t be a very significant effect.

solidworks 2015 files here :


Maybe, but are your objects positioned correctly relative to each other? Maybe we are all wrong.

Things just don’t look placed right in the picture. I guess I can’t say without a printer to look at.