Z Reset Protocol

#1

Hey everyone,

I’ve spent a good couple of hours trying to track down this information so I have to resort to asking.

When calibrating the z reset position every guide I can find states to set it at 1877 for PDMS and then print out the DIY test to measure the 4 cylinders. Let’s say the cylinders are uniformly short at 10.5mm with an easy-level-plate. I go into the settings, click to reduce the z reset to 1875 to increase the cylinder height, the build plate lowers into the vat, I turn off the machine, turn it back on, the arm raises to the top, and I select the DIY test again to print another set of cylinders.

The pieces of this protocol that are missing for me, or are some concerns: when I change the z reset after printing out the cylinders, can I have resin in the vat when the build plate lowers and raises after power reset or do I have to drain the resin out every time I make a change to the z reset setting? No guide specifically states if leaving resin in the vat when the build plate lowers and raises would be damaging to the PDMS or FEP.

Secondly, after changing the z reset and the arm successfully lowers down into the vat and the power is turned off, when I turn it back on there is a rather loud low pitched grind/rapid clicking of once every 10th of a second that lasts for maybe 2.5 seconds total with no perceptible arm movement or strain to the vat, then the arm raises up to the top with the normal soft sounding high pitched hum of the arm moving. Is that a normal sound to hear after changing the z reset? Perhaps it’s just the sound of the arm reindexing to the new z reset setting before raising the arm up? I’ve done only a couple of prints and it works absolutely perfectly with no suction popping, tilt clanking, or any other sounds as others have reported, but when the z reset is changed, it throws a mini fit for me after turning the power back on to raise the plate. I should also add, changing the z reset is successful in changing the cylinder height, so the clicking does not keep the z reset from functioning mechanically.

Lastly, what is the normal visual wear and tear on a PDMS vat? How will I visually know it will need to be replaced outside of catastrophic chunks coming off the vat? Is a single 5 inch horizontal line/crack of bubbles normal wear and tear for little more than 10 small prints? Should I expect to see more and more lines and cracks as I print more? Do the layers of silicone just gradually get used up without any visual change? If not, the above information may have something to do with my situation. The lowest my DIY cylinders have ever been when leveling is 10.5mm for little more than 3 (out of the 10 total) very small prints.

Thank you any help or clarification you can send my way.

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#2
  • It is ok to have resin in the vat.
  • The sound you hear is the PM motor zeroing out under the vat. This is done every time you start the printer and is 100% ok.
  • The fogging of the vat can be described as a white layer on the PDMS that you can not scrape off with your rubber squeege.
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#3

I’ve only been successful leveling vats when they were empty. The ez-level build plate makes leveling a LOT easier, as does the fep vat since tolerance is much looser with that vat.

Edit: actually, the very first time I leveled a PDMS vat with the old build plate, I did it with resin in the vat. It took me like 14 tries to get it right. In part because I had the corners mixed up and was turning the wrong screws. Since I switched to fep and ez-level I’ve had success only with an empty vat.

The stepper motors they used don’t provide positional feedback. Therefore the best way to get the motor to a known location is to run it until it hits a physical stop, and keep running it some just in case it wasn’t there yet. The motor running while hitting the stop is what makes the funky noise. It doesn’t hurt the motor at all.

Someone else will have to answer about pdms wear. I only used the pdms vat for about a week as a stop-gap since the fep vat was on backorder at matterhackers when I ordered my printer.

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#4

the wear on pdms is dependent on

1 resin type
2 exposure (correct exposure improves liftspan, overcuring reduces liftspan)
3 leveling (10.7mm or higher improve lifespan )

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