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 donāt 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 @SachaGloorās 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 - Iāve tried and tried to take decent shots of the spot convergence and then divergence over distance, but itās just not feasible with my nexus 5 camera (I did try āmanual cameraā 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 itās worked out ok - I think the spot convergence and then divergence over distance is shown well - see below
setup:
first run (two pic composite):
second run all spots shown
second run close up - first spots missing
1 Like
Iām inclined to agree with you however @SachaGloorās 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 itās 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.
So Iām looking at Kevinās 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.
Hereās 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 Iām getting pissed off againā¦
This object printed perfect with the Laser Choke in place.
Sorry @JoshK didnāt 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 
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, youāre right. Thanks for the explanation.
@JoshK, @RocusHalbasch I think youāre 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 wonāt be a very significant effect.
solidworks 2015 files here :
https://drive.google.com/file/d/0Bxi9QnsGaF7EOVdRVE5pbzFma3c/view?usp=sharing
2 Likes
Maybe, but are your objects positioned correctly relative to each other? Maybe we are all wrong.
Things just donāt look placed right in the picture. I guess I canāt say without a printer to look at.
oh - well of course the components are only approximately positioned - but it doesnāt matter, itās enough to show that right angle triangle math is not sufficient for the problem
and youāre interpreting the perspective view wrong - heres the same model side on:
No it is not. Redesign your model so the following constraints are true, which Iām fairly certain they are on the form1+. The large mirror is exactly 45 degrees different from the tray. The center of the large mirror is directly below the center of the tray. The small mirror is exactly 90 degrees different from the large mirror. The center of the small mirror is at exactly the same height as the center of the large mirror. The center of the x galvo is directly above the center of the small mirror. The center of the y galvo is at exactly the same height as the center of the x galvo. The center of the y galvo is directly on the path of the laser. The length of the path from the laser to each consecutive center totals 300mm.
If my assertion that the above constraints are true is correct, Iām confident your new model meeting them will consistently yield a value less than 312.75mm for any path to any position in the build area. I did my rough calculation based on all the assumptions listed above, but like I said I am pretty confident that is how the form1+ is laid out.