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problem with uniform horizontal lines
#1
Hi,

Lately I got a some lines in my print and I'm not sure what could cause them. Especially because they are so uniform.

   
   

They are not very pronounced but big enough that you can feel them when you run your fingers over it.

   

Both models are printed with 2.5 sec exposure time and 60/210 mm/min lift/retract on an Elegoo Mars 2 Pro.
The female is printed with Elegoo standard grey resin and the male in eSun water washable grey resin.

Has anybody an idea what could cause such lines?
Could this be a lubrication issue of the Z-Axis? 
I would re-grease the spindle to test it but I don't have grease at home. Due to the corona situation I could not buy some in a local store but have to order it online, so it will take a few days to arrive.

thanks in advance for the help!
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#2
This looks very similar to, but less pronounced than, the effect I'm getting in my prints. I'd follow the advice Cliff gave in the "Wavy Prints" thread.
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#3
I've checked Cliffs linked video.
Unfortunately it shows a standard mars. The "pro" models and the standard mars 2 have a different linear rail which should not or cannot be adjusted (not sure).
As soon as the grease arrives I will clean and re-grease the rail and let you know if it fixes the problem.
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#4
I also have a Pro, and now I'm also waiting on grease to arrive for the same procedure. Good luck to you - I hope this fixes it.
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#5
A great grease, Super Lube's PTFE grease is usually in stock at Home Depot. Walmart stores often have it as well.

I use it on all my precision equipment.

The Pro 2 uses the same commercially available recirculating ball linear bearing as my longer Orange-10 and -30 printers, and the Jackson upgrade mast for the Mars.

They can be disassembled however getting all the balls back in without special jigs is a real PITA--damned near impossible. The good news is that they are not subject to mus-adjustment like the plain ol' Mars tri-pulley and cylindrical rail mast (they cannot be, and do not need, adjustment) .
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#6
Meanwhile the grease arrived and after removing the old one I relubricated the spindle. Unfortunately that doesn't help.
After some more research I've read of a guy who had problems with jerky movement of the linear bearings caused by the factory grease.
Just to be safe, I disassembled the bearings, cleaned everything in IPA and relubricated them, but the problem still persists.
I played with the print settings, tried different resins, reinstalled the firmware and used a different slicer, but still no success.

Eventually i found the cause: my stupidity! and temperature fluctuation (but mainly the former)

Since I don't have a suitable place for the printer in the house, I have set up a corner for it in the garage. The garage is unheated, so I have installed a small 12V PTC heater to keep ~25° C in the build room. I kept the hysteresis at their default value of 2 degrees and since the heating element is not very powerful and need some time to heat up, the temperature drops even lower before it starts to rise again. It works flawlessly in the first few weeks, therefore I excluded it as cause of the problem.
But then the temperature outside drops about 10-15 degrees to ~0° C. At the same time the lines start to appear.
I guess as the temperature delta between inside and outside the build room is much higher now, the frequency of fluctuations inside increased and the effects became more visible.

To verify this theory I made a few test prints without the heating, but 2 of 4 prints failed (probably ~3-4° C garage the garage are a little too cold Tongue ).
Then I adjusted the hysteresis of the thermostat to 0.1 degrees and finally: the lines are gone!
I've printed 4 pieces since then, all without problems  Smile

Here are some pics of the same model before and after the adjustment:
   
   
   
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