Form 3, at last some light at the end of the tunnel

We use a Form 2 printer here at work on an almost daily basis and find it very good (often using it to produce prototype parts or to prove / develop different resin formulations). The company I work for helps design printers / formulate and or refine materials for many printer manufacturers, as such we perhaps have a good skill set (Engineers / Chemists – working together) . We tend to only work directly for manufacturers, and operate a series of precautionary measures which are controlled under contract and by Non Disclosure Agreements, to prevent the secrets of different manufacturers being shared by their rivals.

Our own thoughts remain that the Form 2 is impressive, that comes about due to the exceptional performance of its laser galvanometer (which we understand was designed by Formlabs) and its software, which in our experience produces prints that are hard to rival in terms of degree of repeatability and accuracy (linear and geometric accuracy) against the capital cost of the printer.

It was a sad day when Formlabs decided to stop production of the Form 2, and replaced it with the Form 3 before the Form 3 was really finished.

We have a lot of experience of configuring printers from scratch and in the formulation / tweaking of the resin materials to get the best performance possible from a printing system (and that goes right across the range of 3D printing techniques and materials).

For best results (Fastest speeds possible / best print quality) we need to be able to alter both the printer parameters (exposure timing and power) AND also the formulation of the materials (in particular the additives needed to get the best quality print from a specific resin))

Our hands have always been tied with the Form 2, despite the “open” mode (which in reality is not that open) we have been forced to adjust the resin formulations to suit the profiles provided by Formlabs (for that very reason we tend to go for either “Clear V4” or “Grey V4” profiles – the quickest profiles) The settings defined in Preform of course set the laser power, the laser transit speed and thus the exposure levels to the UV energy.

The Preform profiles also alter the amount of UV exposure at different stages of the print – generally, you need greater exposure for the first few layers to ensure adhesion to the build plate.

We have avoided yet buying a Form 3 to replace the Form 2 for two reasons, first and foremost – the Form 2 works great. Secondly, the feedback with regards the Form 3 has not been great.

However an extra printer is needed so its a hard call to know what way to go for a budget of less than £5k for that additional printer.

During the last ten days we have been lucky enough to be able to borrow a Form 3 Printer in order to evaluate its performance.

Overall we are quietly impressed, however we notice that whilst it uses exactly the same resins as the Form 2, with most of the resins The Form 3 is generally slower and is prone to produce artifacts in the prints. However the black profile and resin appears to work brilliantly. It prints faster than the black profile on the Form 2 and it produces really nice prints.

Based on this, we decided to chemically configure Formlabs grey and clear resins by the addition of various additives but using the Black profile.

We also decided to try the Clear profile

The results are outstanding (once the resin was tweaked)!! However we feel the Form 3 can be even better with tweaks also in the print profiles.

We can conclude that its unlikely Formlabs will ever reach the true potential of the Form 3 WITHOUT producing the resins in versions specially chemically optimised to use the speed and power of the Form 3.

To try to keep the resins standard between the Form 2 and 3 was a nice try by Formlabs, but why limit the Form 3 printer performance by doing that…

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After reading your earlier post on resin additives, it occurred to me that Formlabs is probably waiting some unspecified, but probably already determined internally, amount of time after they stopped selling the Form 2, before reformulating the resins. They probably want to wait long enough that people who bought Form 2s near the end of its lifecycle won’t feel like they were ripped off, and then they’ll start reformulating the resins with a more Form 3-centric mix.

The irony is that to optimise the resin would not require a complete change in the formulation. Its simply the photoinitiator / light blocker that changes to get the best performance from a given resin.

If we talk of a hypothetical formulation of a 3D print resin and assume its derived from 4 basic components, known as chemical a, b, c and d, and take a starting point of 100 gms of that resin as one unit.

Lets say the resin is going to produce a grey print (see RAL colour 7015) for arguments sake.

To print with optimal cure USING THE CLEAR V4 profile in the FORM 2 we need to add the following to 100gms of the base mixture

0.65gm Photo initiator
0.4gm Grey pigment
1.25gm Light blocker

Result is a highly defined print, good linear accuracy with minimum shrinkage and NO overgrowth (light bleed in z plane) with good adhesion to the build plate

To achieve the same result using the Form 3, using the CLEAR V4 profile for the FORM3 we simply need to add the following to the base resin.

0.9 gm Photoinitiator
0.4 gm grey pigment
and 1.3 gm Light blocker

From that we can see that taking the formulation for the Form 2 and adding some extra photo initiator and light blocker we can equal the results in the Form 2.

The advantage is that we can use smaller supports due to the LFS yet still achieve the same performance in terms of print quality and accuracy.

Interestingly the above formulation works well with the Form 2 for 100, 50, and 25um layer heights, which shows that the Clear V4 profile has optimised timings for the three different layer thicknesses, yet with the Form 3 only works well at 100um, which shows that the profiles for the other layer hights need work to adjust the timings (laser transit speed and power) We cannot alter those as Formlabs do not allow access to those settings.