I’ll just pass along what Edwin told me. But the tolerance of the webbed carriage, not the build platform, is 0.15mm, see below for the full details.
Email 1
Thank you for reaching out to us.
On our end, the heated bed PCBA board is flexible and needs to be fixed on the platform. But it is tough to make the platform completely flat because it is not a consistent plate but a Gridded platform.
You can also try to loosen some screws on the heated bed, which may cause the uneven working area. If the issue cannot be solved by adjusting the screws, you may need a new platform instead of the heated bed.
We recommend you to loosen those screws at the edges of the heated bed, which may be lower than the central area.
You can turn off the auto levelling feature and calibrate the print sheet manually.
If you have any other questions, please feel free to contact us.
Email 2
You can put the platform on a desk or something flat and big enough, you can check if all the screws are close to the plate.
Here are some pictures for your reference.
Email 3
In order to exclude the linear modules’ impact, I would like to ask you to measure the platform separately when it is not on the Y axes sliders.
The machining tolerance of this part is less than 0.15mm