# What are the critical machine tolerances / measurements **URL:** \ **Category:** Support & Troubleshooting\ **Created:** [January 23, 2014, 7:10pm UTC](https://forum.formlabs.com/t/what-are-the-critical-machine-tolerances-measurements/809 "2014-01-23T19:10:09Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![JeffreyAlexande](https://avatars.discourse-cdn.com/v4/letter/j/da6949/32.png) [@JeffreyAlexande](https://forum.formlabs.com/u/JeffreyAlexande)\ **Post date:** [January 23, 2014, 7:10pm UTC](https://forum.formlabs.com/t/what-are-the-critical-machine-tolerances-measurements/809/1 "2014-01-23T19:10:09Z")
Howdy- I saw in another post regarding leveling that the exact level of the machine is not critical.  I understand how that is true, but can you confirm what the important tolerances are (what should we look out for). For example I would suspect that aside from the laser accuracy one of the critical tolerances would be the spacing/flatness between the resin tank bottom and the build platform.  If the tank is not level with the build platform then the slices would end up “wedge shaped”.  As I look at my tank it appears to be lower in the back but that could be an optical illusion. ---
**Author:** ![KevinHolmes](https://avatars.discourse-cdn.com/v4/letter/k/3ec8ea/32.png) [@KevinHolmes](https://forum.formlabs.com/u/KevinHolmes)\ **Post date:** [January 23, 2014, 9:31pm UTC](https://forum.formlabs.com/t/what-are-the-critical-machine-tolerances-measurements/809/2 "2014-01-23T21:31:36Z")
Hi Jeffrey, The way the form1 overcome this is by mounting the resin tank on springs - so when the build platform is raised, the resin tank is actually slightly higher than the build platform surface at it’s lowest point. When the build platform descends then - it squishes the resin tank down on it’s springs. Which is why the first few layers are compressed.  The springs are tensioned and adjustable via lock nuts that you can access when you remove the upper casing. It’s also why on machines which have a resin tank with a PDMS layer that’s too thick, or which have incorrectly tensioned springs - the print base can come out too thin - see here : [https://support.formlabs.com/entries/38561208-Testfile-didn-t-print-succesfully-Base-plate-too-thin](https://support.formlabs.com/entries/38561208-Testfile-didn-t-print-succesfully-Base-plate-too-thin) Basically this sprung platform means that prints even themselves out as soon at the build platform entirely loses contact with the base of the resin tank - up to that point yes, your part base may be uneven or wedge shaped - but after that everything will be printed exactly level to the base of the resin tank. So as long as your bases are slightly thinner than specified all around - eg about 1.6mm when print base in Preform was set to 2mm - then you don’t need to worry. kevin. ---
**Author:** ![JeffreyAlexande](https://avatars.discourse-cdn.com/v4/letter/j/da6949/32.png) [@JeffreyAlexande](https://forum.formlabs.com/u/JeffreyAlexande)\ **Post date:** [January 23, 2014, 9:44pm UTC](https://forum.formlabs.com/t/what-are-the-critical-machine-tolerances-measurements/809/3 "2014-01-23T21:44:50Z")
HI Kevin- Thanks for the in depth response - Form1 Support continues to impress ---
**Author:** ![KevinHolmes](https://avatars.discourse-cdn.com/v4/letter/k/3ec8ea/32.png) [@KevinHolmes](https://forum.formlabs.com/u/KevinHolmes)\ **Post date:** [January 23, 2014, 9:51pm UTC](https://forum.formlabs.com/t/what-are-the-critical-machine-tolerances-measurements/809/4 "2014-01-23T21:51:49Z")
Um - hope you didn’t mistake me for Formlabs support!! far from it, just another Form1 user with some hard-won experience… ---
**Author:** ![MongerDesigns](https://avatars.discourse-cdn.com/v4/letter/m/a87d85/32.png) [@MongerDesigns](https://forum.formlabs.com/u/MongerDesigns)\ **Post date:** [January 23, 2014, 10:16pm UTC](https://forum.formlabs.com/t/what-are-the-critical-machine-tolerances-measurements/809/5 "2014-01-23T22:16:05Z")
Jeffrey, I don’t think that’s an optical illusion. I’m thinking the entire tank assembly is a little tilted in the back right corner. This makes sense, because during the peel process you would then start from a corner and peel away, instead of peeling from one side. Less stress forces on the printed part during the peel process. It’s like peeling a sticker off from a corner instead of from the side. Kevin would know better since he has disassembled the machine. I’m just guesstimating.