Error z line in my models

Hello good afternoon.
I have a form 1+ with its latest software version.
Apparently it prints correctly but when I have made a technical piece I find some problems.

My model “cube” 1cm square … does not print exactly.

On the X & Y axes the measurement is precise and perfect.

But on the Z axis I was 1 mm short.

I have solved this with the fine tuning Z offset … but the value I had to set is the last and fair of -1mm is this normal? If tomorrow I must increase I have no possibility :frowning:

On the other hand I notice that my cube at a certain height of Z makes me some unwanted lines.

Impression without supports, “for calibration”

Is this normal? can you help me?

Thank you very much, best regards.

This is normal and why FL suggests not printing directly on the build platform.

The XY band running up the Z axis by about 5mm is the over exposure double passes designed into the printing process. The only way to remove it is by creating a custom OpenFL ini file.

The Z discrepancy is caused by the over compression designed into the print process to ensure proper model adhesion to the build platform. Fine tuning the Z axis to remove this is a bad idea.


If you watch the machine carefully, when the build platform descends in to the resin tank for the first layers, it pushes down on the resin tank. The tank physically moves down on a set of springs in the machine’s frame. The amount of compression can vary from machine to machine and I suspect tank to tank and build platform to build platform. There are a lot of tolerances. The machine has a “Z Axis” fine tuning adjustment because of this. At some point in the life of your machine you may need to compensate for the mechanics by moving the 0 reference up or down slightly. Besides allowing the machine to operate with some tolerance variations, FormLabs does this intentionally to compress the first few layers to make sure the base sticks and so the base is stronger. If you print directly on the build platform without a base, the object you’re printing is compressed in Z for the first few layers the same as if you were printing a base. You might be able to fine-tune Z to minimize this effect, but you cannot eliminate it. Without the compression your print probably won’t stick to the build platform.

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Without supports, the part will be short due to compression of the build platform, and will have a line on it. (Early layers get double exposure.)

Hi again,

first, thanks for your answers.

Second, I have seen that all the parts of my pieces that are looking down have very poor quality. It seems as if they have not been properly cured or they were melted. Reading through the forum, I could see that I had to do a laser spot test and the result is the following.

It is right? Should I reconfigure my laser? How can I do it?


Lets start at the beginning, can you post up pictures of the poor print quality you are seeing.

Have you opened a support ticket?

We tend to err away from using the laser spot test for troubleshooting and if you’re running into issues, it’s best to open a ticket with our support team. As @DavidRosenfeld mentioned, can you post up pictures of your prints? It’s possible that this has to do with the orientation of the part rather than being an issue with the printer itself.

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The bottom of the print will always not be as sharp as the rest of the print due to the laser curing resin beyond the current laser–that’s because you can’t make the laser cure at only the current layer thickness.
It’s going to be especially an issue on areas around supports where the resin will accumulate.

True but the new resin versions and improvements to preform are doing a great job at getting closer and closer to “perfect” parts… besides the support dots.

Sure, but ultimately it is impossible to avoid with this printing method, as long as the print is submerged in the resin there will be extra resin cured onto the underside. You can make some chemical adjustments and change exposures but everything you do to reduce the effect will also make it less effective at curing the layer that you’re printing and then you get issues with the layer not curing enough and being damaged during layer separation.

I have almost the same problem with my form 2 in z-axis. I made a bigger base into 3d models ( 0.60 mm thickness) and put support structures with 5 mm height. after 5 mm it started to print main model.
but it has between 0.10 mm to 0.25 mm error. for example as you see in the photo I printed 101010 cubes and repeat them in different areas of the build platform & with orientation & without orientation. but I still have errors in Z-axis. thickness in z-axis isn’t totally 10 mm. it is about 10.2 mm.
can I solve this problem? I should say I print the models in open-mode & with blue-cast resin.
I wanna repeat this print again with clear v2 resin & check the results.

Unsupported overhangs like you get with an axis-aligned brick are challenging to get precisely. If you want to verify z accuracy, I’d recommend printing a stair step or a vertical wall with very shallow tick marks on it.

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