I really wish they would give us at least enough information about the updates, that getting a decent print didn’t require multiple people on a forum having to order $300 of tanks and resin, just to test and see if an improvement in a particular resin is real, or just a rumor.
Having to keep printing the same parts in different resolutions, in different resins, just to see if there has actually been any improvement, is getting very old, and a little on the expensive side.
So, finally I got around to make another test-print - the results of which I will use to flesh out my theory of why the prints turn out like they do.
So in this “episode” we’re gonna take a look at the specific issue of “overcured resin” or missing detail and lack of sharpness on the support-side of prints printed with Gray v4 resin on the Form 3. I’m also gonna give a bit of an explanation as to why I think this is happening.
Introduction
First off, I’m gonna give a bit of summary on the test-prints that I’ve done, as well as some print of actual models that I had intended for sale, before I became aware of the printers “defects”.
As of this writing, I have done three test-prints, for the specific purpose of finding out exactly how the printer is misbehaving and why it does that. The prints were made up of small “centicubes” that was supposed to act as “simple” geometry. The reason that it had to be “simple” geometry, is that it makes it a lot easier to see and measure the difference between how the model was supposed to be, and how it actually turned out. Now of course a cube is not gonna expose every single type of flaw that the printer might have, and it might not indicate some issues that would occour at odd angles and the like, but it does give a good indication of whether the issues we are facing are related to errors within coding/math expressions and calculations of the actual machine or preform - or if the issues are related to a physical error in concept, design or construction of the machine itself.
The specs of the three prints are as follows;
Print 1:
Print 2:
Print 3:
Print 1 was my initial test-print, and my first post in this forum was based on the subsequent analysis of the printed parts from that print. Two issues were identified from that print;
1: Overcured resin of support-side of model
and
2: Artifacting/displacement on/of parts of model
As Print 1 was printed long before the post on this forum was made, new software and firmware had been released at the time of posting. The next two prints (Prints 2 & 3) were done after the printer and Preform had been updated to the (at that time) most current version of the soft/firmware.
Print 2 was a follow-up print to the discoveries with Print 1, and to see whether the new soft/firmware had done any difference in the outcome of the print. It could be concluded (which was also documented in a another post of mine in this thread) that issue 2 had been significantly reduced, but issue 1 had slightly worsened or was stagnant.
Print 3 is the first print that was supposed to try and test whether or not my theory - which I will get into at the end of this post - could have any merit. In the meantime between the actual printing of Print 2 and Print 3, new soft/firmware had once again been released. I did not update anything - as it would be changing to many “parameters” for my tests to be conclusive about anthing. So I had to keep Print 3 the same soft/firmware as Print 2 - otherwise improvements or new errors to the soft/firmware might change the outcome of the test and thus give a distorted view of what is really happening.
Print 3
Now for the actual review of my third print - which I have yet to show:
The print itself has turned out really great. Issue nr 2 is completely gone at this layer height - and even under the microscope I can’t seem to find any signs of this issue.
Issue nr 1 however is still present. The deviation is though significantly less at 100 micron than what the same test showed for 25 micron in Print 2. Now we’re down to rougly 0,35mm in deviation instead of the 0,55mm that we saw in Print 2. This is a good development and also ties into my theory about why this is happening at all. The hole and notch of the cube has also decreased in the amount og deviation. This is down to about 0,25mm from approximately 0,32mm in Print 2.
Take a look at the attached pictures and see for yourselves.
It can clearly be seen that the cube from Print 2 is higher than the one from Print 3. If you look closely, you can also see that the notch is “higher” on the support side on the cube from Print 2 than it is on the cube from Print 3.
Same goes for the hole on the other side of the model. You can clearly see that the hole is more rectangular on the cube from Print 2 than the one from Print 3. Contrary to what some may believe; it is not the “top” of the hole that “sags” down due to lack of support. The part of the hole that is too narrow is the bottom-side, which is taller than it should be - once again a good indication for my theory.
The Theory
Now then, what is this theory of mine? Well, it’s a theory inspired by people within this thread. I can’t be bothered to sift through the thread to find everyone who has ever mentioned “light control” as a possible issue, but nevertheless, if you have once theorized that “light control” might be the issue then I’ve probably taken some inspiration from you 
“Light control” is a very broad term though, so it would help us to narrow down the amount of possible issues that migth lie within the umbrella term of “light control”. When looking back at Print 1, 2 & 3, a pattern of issues and non-issues start to emerge.
First of all, what elements of the print went as expected? Well, apart from some artifacting - and maybe some displacement (which was not consistant across all models) the models turned out fine on all sides. That is, the sides were within spec. The biggest deviation on any vertical side was 0,01-0,02mm, which I would classify as being within what one can expect from a printer of this quality and price range. What about horizontal sides then? Well here there were two different outcomes;
Out of these two outcomes, only outcome number two is interesting to continue investigating, as it is the only outcome that produces something different than what we expect.
Now all horizontal sides are not affected by this issue, so we must try to understand what leads to some being affected while others aren’t. A common denominator of the sides being affected, is that it is always the top-side of any geometry that seems to have the issue. Contrary to the top-side, the bottom-side of any geometry always seems to be within spec. What do I mean when I say “top-side”? “The top” can be many different things when talking about prints, models etc. Well, when I say that it’s the “top-side” being affected, what I mean is that it is the side facing the buildplate or the “top” of the printer. It is the side facing away from the tank, and facing the support structure.
As only top-facing surfaces of prints are affected by this issue, then we must ask; why is that? Well, this is where my theory comes into play.
When I first started to print on my Form 3, way back in November / December 2019, I printed some models that I’ve designed for the purpose of selling via my company. One thing I noticed at the time was that there was always a “bad” and a “good” side of a print. Usually when I printed I used the “auto-orient” function of Preform, and the only thing I ever adjusted was the supports and touchpoints. As I printed more models, I noticed that it was always the same side that was “wavy” undetailed in its finish - the top-side of the print. All other sides were usually nice and crisp - except of course for the artifacts and displacements that so many other people have already documented at length.
If one takes a moment to think about the way the Form 3 works, one realizes that the printer uses a laser, guided by mirrors (Front/back) and steppermotors (side/side) to direct the laser light onto the right point in the 2D-plane that a layer represents. The buildplate controls which layer is currently being worked on, and this is also facilitated with steppermotors, like the side/side travel of the LPU, though in this case it controls up/down movement of the buildplate.
When printing the first many layers of any model or geometry - this is done directly onto the buildplate. Whether it’s the model put directly on the buildplate itself (Formlabs doesn’t recommend this) or either full/mini-rafts for the model + support-structure. The laser will hit the resin immediately infront of the buildplate - travel through it to some degree and will afterwards be stopped by the buildplate itself. However, when the printer works on layers further down the model, the buildplate doesn’t act as an endpoint for the laser, and the laser will (as much as it is able to) penetrate through the current working layer, and into either previous layers or residual/uncured resin of the tank. Just as lightsabers doesn’t work in real life, due to the fact that you can’t just tell a laser when to stop, the laser in the Form 3 will keep on going until all its energy has been absorbed and/or reflected by other material/objects. While printing directly onto the buildplate the top surface turns out excelent, as the energy of the laser is completely absorbed and/or reflected by the buildplate. But as the buildplate moves further away, and the current active layer finds itself deep within the tank of resin, the laser is only going to be stopped by the surrounding resin. If your model has a top-facing surface, that isn’t directly on the buildplate, the only thing that lies on top of that surface is uncured resin. (As the working layer + a bunch more of the model is always submerged in resin).
Illustration 1
Illustration 2
Why does this happen then? Well, this takes us back to what my theory actually is; Laser-power control being mismanaged, thus causing the laser to penetrate too far beyond the currently inteded working layer, and as a consequence of this, resin occupiyng this space will be cured to some extend.
This theory seems to be supported by the fact that this issue - of overcured resin on the top-surfaces on any model - seems to get worse as layer height decreases. As the only difference between Print 2 & Print 3 was the layer height, the correlation seems to be quite obvious. at 25micron the deviation on the top-surfaces was around 0,55mm while at 100micron the deviation was only around 0,35mm.
Now why would this difference occur? Well, I have tried to illustrate what I believe the issue to be;
Illustration 3
If you take a look at illustration nr 3 above, you’ll see an illustration of the laser’s layer penetration. The image is to scale with the real deviation, so you can see just how much resin the laser actually overcures, when printing the top-surface of any geometry. It is important to know that this illustration is for the 25micron layer height. The red area of the illustration, is to show the resin that is within the zone where resin would be cured, if it stays in place. Although as you all probably know, the buildplate moves up/down between each layer, and thus the resin that is too close to the edge, will fall of or be mixed around between layers. This is what I think is the reason for the “curvy” nature of the top-surfaces in my test-prints.
Although I don’t know how much energy is disapated in a cured 0,025mm layer of resin contrary to a uncured layer of resin at 0,025mm - This illustration tries to show how much resin the laser has to pass through, before so much of the laser energy is absorbed, that the laser can’t cure any further resin.
Now back to the question; Why is there a difference between 25micron and 100micron? Well, for this we’ll take a look at illustration nr 4:
Illustration 4
On illustration 4, we see how the laser layer penetration looks, when the printer prints at 100micron. This illustration is also to scale, and you can see that the amount of overcured resin is much less than that of illustration 3 - especially compared to the layer height. First of all, much more of the lasers energy is needed to cure the full 100micron layer as opposed to the 25micron. This will mean that the energy-level of the laserbeam, that makes it all the way through the layer, is much lower than that of 25micron. Only after the layer-thickness of 100micron, will the laser start to go into unwanted territory and cure resin that is not supposed to be cured. As the laser has already used up alot of its energy, it doesn’t have to go through as much uncured resin before it is depleted of energy. Also it is worth noting, that since every layer is 100micron, the laser will be moved 100micron further away each layer and get less energy overall wasted on resin that is not supposed to be cured, and thus the amount of unwanted cured resin is less. On illustration 4 it is seen that the laser moves out of the “overcured resin”-zone much faster than on illustration 3 - supporting this idea.
Conclusion -
In conclusion to this mess of a theory, I woundn’t 100% say that it’s proven and that no other explanation might be valid or possible. This theory however seems to be describing what is seen across a bunch of different models posted on here. Especially the recent test done by @lmlloyd shows very clearly how the top/support side of the “wheel-thingy” is unsharp and undetailed, while being nice and fine on the bottom.
Why is this issue less pronounced with Black resin? Well, I don’t know, but I would suspect it has got something to do with Formlabs maybe trying to dial in one resin to perfection, before they begin on all the other resins - or maybe black resin just requires more energy to cure, and thus the issue will not be as pronounced. As far as I can tell, from pictures on this thread, it seems that black resin also has this issue - it’s just a lot less than with Grey.
If I get around to do it, I might try printing at an even bigger layer-height than 100micron, just to see if the issue gets even less then. According to this theory, it atleast should Looking forward to seing the further developments on this thread.
Thanks for all the testing. A user named @Dxxxx goes into some great detail about the chemistry of the resin in this post:
He explains some of why black works better.
Hope the team of Formlabs would care out thoughts.
It’s really terrible that i bought Form3 for all over 7 month that can’t printer a usable part of my anime figure.
I still use my old form2 to print my works。
Really hope that our Form3 can be our useful printer，not just set to collect dust！
Thanks for the fantastic analysis and explanation. This is entirely consistent w/ my own observations on my Form 3, and your logic seems sound to me.
I think that it might be helpful to have this post here as it helps explain some of the reasons for “bad prints” Those reasons are something that we address on a daily basis as part of our work…
Earlier post:
Welcome to our working world - at work we spend a lot of time configuring resins to operate with different printers (often directly for the printer manufacturers). Those include Masked LCD, DLP and other printers that use a laser as the light source. The reality is that most resins (in fact almost all) are chemically configurable to work very well with different printer types. The base formulation for the resin remains consistent, its simply the components that alter how it cures (speed and depth of cure) that are varied between different types of printer.
In general terms a resin can be adopted to almost all printer types chemically. However the process is time consuming and lengthy. Utopia for us is when we can also alter the printer settings for time of exposure and the power is variable. Formlabs certainly is able to do that inhouse.
If we look at the resin cure then two things influence it, the first is how reactive it is, the second is how well it allows the UV energy to penetrate through the cured / uncured material (at a certain wavelength).
If the energy penetrates too far then different chemicals can be used to stop the penetration (we know these as light blockers) There are also available things known as light “absorbers”,
Light “blockers” and “absorbers” work in very different ways, generally the absorber takes the UV energy and changes it to heat (Remember the principle established by Émilie du Châtelet in about 1730, that energy cannot be destroyed or created, it can only be transformed or transferred from one form to another) The transfer from UV energy to heat energy is an undesirable effect for us as it leads to the warping of prints and effects the adhesion of the print to the build platform.
Light "blockers work in a very different way, that relies upon the fact that different photoinitiators work at different rates of efficiency dependent on the amount of energy at a set wavelength (in the case of the Form 2 and 3 around 405nm)
If that light was at a wavelength of say 450nm then the resin would not really cure.
Light blockers work by taking the energy that remains after the cure (polymerisation) has been effected at a certain depth of penetration and they fluoresce That takes the form of taking the 405nm energy and then transferring it form a visible glow at a different wavelength (in this case around 435 to 460nm) which is beyond the range for the photoinitiator to work efficiently.
Unfortunately the chemicals used to create colours (the pigments) are made up of materials that show very different characteristics (some absorb UV, some fluoresce, some do a little of both)…In practical terms this generates unique problems for each colour (and often varies dramatically from one pigment manufacturer to another - due to factors such as particle size, suspension or material used for the pigment) .
The chart below gives a little insight into just how complex this is:
The reality is that black is a particularly difficult colour (as is white - but for slightly different reasons), black generates a lot of heat when exposed to the UV energy source (due to the black pigment) and the depth of UV light energy penetration is much less than say a clear resin (or a blue pigmented resin). Its good to see that black now works well, that demonstrates that mechanically the Form 3 is a sound design (accurate).
I realise that the Form 3 uses a different laser (higher power) than the Form 2 and wonder about Formlabs intention to make all resins cross platform compatible (so they can be used on either Form 2 or Form 3) in reality thats unlikely to achieve best performance from the Form 3 (you would need to run the more powerful laser at lower speeds and power - which results in longer print times)
Hopefully Formlabs will see the light and optimise both the resin formulation AND the Form 3 profiles to take maximum advantage from its higher power laser… Rather than simply trying to match the Form 3 to Form 2 performance to suit the existing amounts of photoinitiators, light blockers / absorbers used in their resins for the Form2.
So to summarise:
To fully optimise a resin requires both alterations to the laser settings (and thus the amount of energy entering the resin at a point per unit of time) and also chemical optimisation. (pigment, photoinitiator and also the use of various light blockers.
For correct optimisation of the resin for maximum performance, the light blockers are a very important part, and a very small alteration (normally in the range of a few hundred parts per million of the actual light blocker chemical) can make huge differences in how the material cures. Of equal importance is the correct amount of photoinitiator, too much and the material becomes brittle and may suffer with uncontrollable light bleed (the overgrowth, especially in the Z plane), Too little photoinitiator and the print is soft and often with very poor adhesion to the build plate. Both have an interaction dependent on timings and speed at which the UV is applied (at a certain wavelength or range of wave lengths). (think units of UV power x area applied to times the length of time the energy is applied - we normally measure that as (mw/cm2) x time to achieve desired cure )
Not being able to get good quality out of the Gray V4 at 50/m and 25/m a few days ago I finally broke, went out and bought Black V4 and a new tank. Today I see there is a new software update which, besides other things is good for Gray V4 to be run at 50 and 25/m… of course…
If you guys do some test can you post them here…
Thanks
An update for Preform dropped yesterday:
Grey Resin: Improved print quality at 100, 50, and 25 microns
Anyone try one of the problematic Grey prints on that version yet? I’m hoping this is the refinement we’ve been waiting for to do for Grey what they did for Black.
Can you go into explicit detail (or show pictures) of the symptoms? I have an early rev Form 3 and I experienced a lot of issues that might be similar.
Are these rings angled at all off-axis to the build platform? Why do you print them with this orientation?
Hi
They are not angled , Formlabs support recommended (to me at least) not to angle rings - but I suppose that it’s all about the design, so different structures will need different adjustments . Mine were pretty simple
Is the layer shifting now a problem of early form3 printer or have this issue the complete serie??? I have a early form 3 and also the problem with the layers??
What did the support mean to this problem?? can they fix the problem with the many updates in last time??
Thank you for your answers!!
The problems that were present that got me to start this thread in the first place are still present an o updates to date have fixed it. It seems the updates to the black resin have eliminated most of the original issue but all other resins still suffer the same problems.
Hi everybody!
I looked at my first print and… saw all my grids are look damaged. Which reason can it be?
The second question. I reduced walls thickness to 0,3 mm. Is it too thin? Shall I choose lower temperature for Form Cure? I have selected 60 degree.
May be I have washed too long (13 minutes 70% concentrated IPA in the Form Wash… )
Or wrong placed on the platform… I don´t know…
Thank you for your answer
Looks like damage from too-long IPA exposure. IPA is very hard on features that are long and very thin, like your grills.
Recommend trying 7 minute wash in 90% IPA.
Hope this helps.
Form 3 black V4 at 50 microns is working much better for me than Form 3 gray V4 at any resolution including 100 microns.
Form 3 print quality with black V4 at 50 microns is as good as Form 2 print quality in gray V4 at 50 microns. Form 3 black models are sellable in this quality.
But will my customers buy black models? So far, customers prefer gray for easier painting.
Still hoping for a fix to gray V4.
Today new version of preform/firmware was released noting grey resin improvements. Can you check it on your models?
Thank you Stephen
Ok. I will try 7 minutes wash in 90% IPA.
I thought if a take 70% IPA, I can wash little bit longer as by Formlabs recommended… (10 minutes for black V4, 90% IPA). But it looks having not the same result…
Another phenomenon: there are very fine accuracy details on the roof. The handle on the picture has a diameter only 0,3 mm. It is much more accuracy than in Z-direction…
I was having a lot of failures (around a 72% success rate), and on most of those failures the raft would either incompletely adhere to the platform, or the first several layers of the raft would be on the platform, but then about where the lip of the raft would start, it would just cut off, and all subsequent layers would be stuck to the bottom of the tank.I eventually had a set of parts that just wouldn’t print at all, no matter what I did. I was talking about it on the forum, and someone from Formlabs urged me to call support. When I did, they swapped out my machine.
My original machine was from the first batch of orders, pretty much ordered as soon as they announced the machine. The new machine is not having the same problem, and is so far running at an 85% success rate, with most of those failures coming from one difficult part I finally got printing correctly with some work.
There’s not much to see, but this is what one of my failures would look like in clear resin.
I just finished a test of rings with new firmware and update form software- grey V4 looks MUCH MUCH better then any other result I got in the past.
Just printed off a WW2 Russian howitzer with the latest PreForm software upgrade. Printer is the Form 3, with Gray v4 resin at 25um layers setting. Here is the user-visible surface of the model. The base is 30mm x 30mm, just to give you a sense of scale for this 1/285 model. The details are excellent, bearing in mind that a standing figure is only 6-7mm tall:
Here is the top surface, nearest the build platform. You can see the scalloping effect of extra curing between the support connection points. Not an issue for my models but would still be an issue for others:
Robert
