07-08-2022, 01:17 PM
This problem seems difficult to solve in a budget printer.
I have been researching it for about a week now.
The consesus seems to be that the capillary flow resistance of the resin getting squished to the sides, holds the build plate away from the FEP. If the Z axis assembly was infinitely stiff then the LCD screen would get pushed down into the printer by this capillary action. So it would need more support and protection. All this is possible, but not at the Elegoo prices.
The main fix for solving this on the mars is to use UVTools to set high "wait before cure" times for the initial layers.
But the issue remains how to get the build plate to land at the correct Z height after pushing the resin out of the way during the wait before cure
time.https://blog.honzamrazek.cz/2022/02/a-step-by-step-guide-for-the-perfect-bed-adhesion-and-removing-elephant-foot-on-a-resin-3d-printer/
To do this the Z axis would need to provide consistent force all the way down to the correct Z height, and then stop applying force while the curing commences. Obviously this is technically very difficult as it would require somehow closing the control loop on the Z axis with force sensors or encoders.
The Mars 3 Pro is solving this by adding some springinness into the Z axis. In the Mars 3 it was the whole Z tower that flexed. In the Mars 3 Pro it seems to be the leadscrew that is spring loaded into the stepper motor with a rubber damping plate and a spring washer. This can provide a force that drops off as the spring decompresses and the build plate approaches the target z height.
This is solved in high end printers wih a few features:
The Z zero point doesn't really come into play here. The first challenge of getting the build plate to push through the resin and arrive at the Z zero point, within the rest and cure time, must be solved. The Z zero just ensures that the full model z dimension ends up correct and the final layer is cured at the correct distance from the build plate.
I have been researching it for about a week now.
The consesus seems to be that the capillary flow resistance of the resin getting squished to the sides, holds the build plate away from the FEP. If the Z axis assembly was infinitely stiff then the LCD screen would get pushed down into the printer by this capillary action. So it would need more support and protection. All this is possible, but not at the Elegoo prices.
The main fix for solving this on the mars is to use UVTools to set high "wait before cure" times for the initial layers.
But the issue remains how to get the build plate to land at the correct Z height after pushing the resin out of the way during the wait before cure
time.https://blog.honzamrazek.cz/2022/02/a-step-by-step-guide-for-the-perfect-bed-adhesion-and-removing-elephant-foot-on-a-resin-3d-printer/
To do this the Z axis would need to provide consistent force all the way down to the correct Z height, and then stop applying force while the curing commences. Obviously this is technically very difficult as it would require somehow closing the control loop on the Z axis with force sensors or encoders.
The Mars 3 Pro is solving this by adding some springinness into the Z axis. In the Mars 3 it was the whole Z tower that flexed. In the Mars 3 Pro it seems to be the leadscrew that is spring loaded into the stepper motor with a rubber damping plate and a spring washer. This can provide a force that drops off as the spring decompresses and the build plate approaches the target z height.
This is solved in high end printers wih a few features:
- Heating the resin to reduce it's viscosity
- Wiping the resin vat
- Setting Z zero correctly
- Using a closed resin ecosystem and calibrating their printers wait and cure times to match the resin and the force required to squish the resin into a certain space
The Z zero point doesn't really come into play here. The first challenge of getting the build plate to push through the resin and arrive at the Z zero point, within the rest and cure time, must be solved. The Z zero just ensures that the full model z dimension ends up correct and the final layer is cured at the correct distance from the build plate.