I’ve been talking back and forth with Formlabs for quite a while now about my prints coming out crooked / my tank not being parallel to my platform. I have had two machine replacements trying to get my platform parallel to my bed. I want this so prints printed directly to the platform with no supports come out correctly. However they told me:
the platform and tank are intended to be positioned at a slight angle to each other, and that angle is accommodated in the machine’s calibration processes.
I tried to get an answer to what “accommodated” means explaining that the angle to which it is not parallel translates directly to my prints, resulting in a variance in thickness and a lean. With a lot of back and forth and a lot of non-committal answers on their part I finally asked:
I’m just trying to figure out if my machine is behaving as designed or not. If it is I’ll figure out something. So could you please ask the engineering people if it is considered correct behaviour that when the Eiffel Tower is printed directly to the bed at 100um it prints leaning to one side by 0.4 degrees and with the pads on the bottom varying in thickness by 0.85mm? If they say that is expected behaviour then my printer is fine. If not then something is wrong with it.
And they answered:
From everything I’ve heard from our engineers, yes, your machine is performing as it’s designed to.
So now I am curious just how far off it is supposed to be and how far off most machines are. Particularly I would like to know just how much the angle varies. I have a simple technique for measuring the difference in angle.
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Get a digital surface level app for your phone that allows you to calibrate it.
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Remove your platform and tank from your printer.
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Set the phone on the aluminum bracket for the platform so the phone is square to the bracket.
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Calibrate the level so it thinks of this as zero.
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Place the phone square to the plate the resin tray slides in to.
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Read the numbers for X, and Y
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Rotate the phone some so you can figure out which way the lean is oriented.
My current printer has a 0.5 degree drop toward the back and an 0.2 degree drop toward the hinge. So I’d be really interested to see how crooked other peoples printers are, and if this is consistent or varies a lot from machine to machine.
Do you have a recommendation for which iPhone app to get?
Looks like Handy Tools - Surface Level by ofijo is a good app and it’s free.
@Rocus
I’m going to assume from your description, your Eiffel Tower prints with a lean like the Tower of Pisa, not a banana with increasing curvature.
If you print with base and supports, the base “absorbs” the errors of calibration, non-planar surfaces, etc. As you prefer to print without base+supports, a printer calibrated using my method will print as closely to straight as one can get but I can tell you the build platforms are not uniformly flat (+/- 0.15mm concavity from edge to center on mine) so factor that in as well.
After calibration, a 2mm, small foot print base prints uniformly 1.98 - 2mm thick. Calibrating your printer this way will help when printing directly to the platform (no base) and void your warranty if they see finger prints inside the case! I’m working on a write up for the process and hope to post it to the Unofficial Wiki this week.
Also, leveling the silver case to the Form 1 is not useful to this issue however parallelising the build platform to the peel tray (the black metal frame under the vat) is critical.
@Korben
The issue here is I would prefer not to void my warranty and formlabs claims the platform and tank are intended to be positioned at a slight angle to each other. What I want to know is how much that angle varies and about what it is on most machines. If the angle is consistent then it is simple to explain a good uniform technique for printing to the bed if they are not consistent then more work needs to be done to find how crooked any given machine is before attempting to compensate.
So all in all I’m just trying to get data on what degree and direction of “misalignment” is normal on the average Form 1.
As an update I’ve asked in an ongoing conversation with customer support if they can tell me the specific desired angle and tolerance. We’ll see if they tell me or not. If they do I’ll pass it on.
@Korben Dallas: In fact the Leaning Tower of Pisa is EXACTLY shaped like a banana with increasing curvature. But we all know what you meant. 
Are you saying I’m overcompensating for something? Because I’m not. I"M NOT!!! Do you even lift, bro?
Formlabs replied:
The angle between the build platform and the resin tank can vary from printer to printer. The build platform compresses against the tank, thus the gap is irrelevant.
Still nothing specific but it sounds less like it is supposed to be at different angles and more like they don’t care. I wish I could get a straight answer about what the specific desired orientation is.