In the interest of giving back a little in return for all that I have learned on this forum over the last year and half, I would like to share some results from my most recent experimentation. My primary interest is very small scale ship models. I am not casting, so my focus is on wringing out every last bit of detail in the final prints, particularly with regard to small/slender details, in a consistent fashion.
I have been experimenting with B9 Black resin for a while now, and I really like its overall sharpness and hard cure properties. However, it does suffer from some z-bleed, particularly when using 25 micron layers. In order to quantify the amount of bleed, I created a square test model 0.5 mm thick. Z-bleed is more pronounced over larger surfaces, so I included two narrow 0.5 x 0.5 mm bottom rails along the length of the model. This results are shown below (the diagram shows a cross section of the test piece):
I began experimenting with introducing additional pigment to reduce z-bleed with Black resin. I initially started with Spot-A pigment I had on hand, which worked well, but switched to Maker Juice due to the cost of shipping. I selected grey as it seemed the obvious choice for my subject matter. A custom material profile was developed from the generic black profile for each pigment concentration. The more pigment added, the better the results, but more pigment also means longer print times and an increasing tendency of pigment to settle out when not in use. I was ultimately satisfied with a concentration of 20g pigment added per kg of stock resin. This has resulted in a significant reduction in bleed:
Below is an example of an actual print, though the photo does not really do justice to the level of detail that is possible with this resin/pigment combination. I am still amazed at what the B9 is capable of. This model includes cross braces as small as 0.12 mm in diameter. The turrets do actually rotate, and are another feature where controlling z-bleed is critical. I did cheat a bit on the aft (right hand) mast for the sake of durability; it is actually a length of steel wire slipped through from below. Consistently achieving this level of results requires very careful projector focus and a relatively fresh PDMS. I also use a reduced shutter open speed and increased settle time.
There is one very important additional thing to note here. The model above was printed using version 1.8.0 of the B9 software. Later versions include an “enhancement” designed to reduce z-bleed. While it appears to work for larger items, it can have a detrimental effect on very small/thin elements (Mike is aware of this). I was hoping that this latest release of the software (1.8.4) would include a switch to allow users to selectively disable this feature, but no such luck. Perhaps next update.