# Most Critical Measured Dimensions

**URL:** <https://forums.maslowcnc.com/t/most-critical-measured-dimensions/4263>\
**Category:** Technical Details\
**Created:** [June 7, 2018, 12:01am UTC](https://forums.maslowcnc.com/t/most-critical-measured-dimensions/4263 "2018-06-07T00:01:03Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![c0depr1sm](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/c0depr1sm/32/9614_2.png) [@c0depr1sm](https://forums.maslowcnc.com/u/c0depr1sm)\
**Post date:** [January 19, 2019, 2:42am UTC](https://forums.maslowcnc.com/t/most-critical-measured-dimensions/4263/3 "2019-01-19T02:42:50Z")

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To achieve the [Zipper Tree Challenge](https://forums.maslowcnc.com/t/the-zipper-tree-challenge-because/8455), I analysed extensively the [list of sources of errors](https://forums.maslowcnc.com/t/list-of-sources-of-error/7523), found some missing parameters, then searched [ways to set parameters right](https://forums.maslowcnc.com/t/accurate-maslowcnc-manual-calibration-how-to/8458).

Below I summarize my findings about chain length calculation for accurate sled positioning

- the most critical machine parameters,
- the missing parameter in the current official firmware (items 4 and 7),
- the target accuracy needed for each parameter,
- and my advice about parameters quite impractical to measure directly and requiring a “calibration routine” help :

 ![ChainCalculation-Parameter-accuracy-measurability](https://canada1.discourse-cdn.com/flex031/uploads/maslowcnc/original/2X/8/8a002c583d4d9d84e3467acf82fb6ca03dd53cb2.png)

Now, either the firmware uses the actual sag correction value , or gets improved with accurate catenary correction using weights, but either way weights are missing and necessary in the firmware to identify chain stretch.

(edit) I invite you to look at the Wiki page showing the [sled position accuracy vs precision](https://forums.maslowcnc.com/t/accuracy-issues/5855) where the sled position and chain properties are highlighted.

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