Z Axis Fine Tuning - Gap Test

At the start of each print, the build platform moves down and compresses against the tank membrane. This is a critical step that allows the printer to expose light in a way that ensures proper part adhesion to the platform. 

Sometimes, the springs that hold the tank frame in place can shift during shipping or through wear over time from the printing process. If this happens, it can affect this process by changing the amount of pressure that the build platform applies to the tank. 

If this balance is upset and there isn’t enough compression,, parts may not attach to the platform. If there is too much compression, tanks may break prematurely, parts pulled off the platform mid print, or layers near the base of the model may be lost.

SprintRay 3D Printers have a setting called Z-Offset, which is used to adjust the starting position of the platform to compensate for any changes from when SprintRay locked in this setting at the factory. This is a very sensitive setting and we do not recommend making changes unless you've been instructed to do so by the SprintRay support teams. Changes in Z-Offset settings can cause catastrophic damage to your printer if performed without proper guidance.

If your prints are falling from your platform, peeling around the edges, or simply printing to the tank instead of the metal platform your support technician may instruct you to run the Gap Test. 

What you'll need:

  • Paper towels
  • Platform Scraper
  • Digital Calipers
  • Gloves


To begin, ensure that your printer's tank has resin to at least the minimum fill line.

Note: The gap test is traditionally performed with model, or die and model resin. If you do not have access to one of these SprintRay resins, contact your support tech.


Open RayWare, and go to Print > Fine Tuning > Z-Axis Fine Tuning


Press Continue


Next, select Print Gap Test


RayWare will show an example of the test we are about to print. Press Start Print


The print arm will now lower into the resin, and your printer will cure a single 100-micron layer. This process should only take about 1 minute. Once the build platform has returned to its full height, the test is complete.

Note: Because only a single layer has been printed, it can appear as though nothing has printed at first glance. 


Gap test should always be performed to guide and validate any changes made to the Z-Offset settings. Only use Die & Model resins when printing gap tests - other resins may damage your tank if printing gap tests from this screen. The gap test should print a very thin layer, less than .25mm thick in each corner; due to its thinness, the scraper will be required to remove it from the platform. Once the gap test is completed, use digital calipers to measure the thickness of this printed test in each corner. 

If the test is too thick, peeling away from the platform, or failed to attach to the platform at all, that means there is not enough pressure against the tank and the Z Offset must be lower to ensure that there is sufficient pressure against the tank. 

If the test makes a loud popping noise during printing, has extremely uneven results, or is thinner than .1mm across the entire test that means there is too much compression and a higher Z Offset value is needed.. 

When calibrating Z Offset, the goal is to use the highest Z-Offset value that yields a test wherein the part still attached to the platform and is thinner than .25mm in each corner. Do not change Z-Offset in increments greater than 100 without printing gap tests to confirm your results. Making extreme changes to this setting can break your tank and cause resin spills. 

Do not hesitate to reach out to our support team at 800-914-8004 or support@sprintray.com if you are unsure whether you have issues with your Z-Offset setting or have any questions about this process. 

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