Tronxy X5SA Z Synchronization with Belt Tensioner by Toto-42

Last crawled date: 2 years, 10 months ago

The iterations of my Z axis lead screws synchronization:
Z sync (kit from Tronxy) initially installed above lead screw couplershttps://www.aliexpress.com/item/1005001659453055.html
Z sync moved from above to below lead screw couplers to get additional Z range (2x GT2 24T 5B timing pulleys required)https://www.aliexpress.com/item/32659887427
Z sync belt tension idler pulleys designed and installed (2x F623ZZ or 623ZZ bearings, M3x12/14mm screw, and M3 nut required per idler pulley)https://www.amazon.de/gp/product/B0859ZD1NQhttps://www.amazon.de/gp/product/B07H5GQ6X9
Because the 1068mm/534T closed belt is quite slackly with only those two 24T pulleys from the kit (or my latter replacements) I wanted to enhance tension.
The M3 mount holes at the Nema 17 Z stepper motors seemed a practical choice for positioning some idler pulleys.
After some testing with different radii and heights I came to the current design for the idler pulleys:
The bore is 10mm to hold two 623ZZ or F623ZZ bearings.
The outer diameter is 23mm - the maximum without touching the 24T pulley.
Intentionally it has no additional flange because that would limit its useful diameter.
The height is 8mm to cover the full height of toothed section of the 24T pulley.
You can use up to 4 of these idler pulleys: at one or both Nema Z steppers, each with one or two idlers. The more idler pulley - the more belt tension you will get.
With all 4 idler pulleys installed I get a belt tension equivalent to 67Hz (measured with Gates Carbon Drive App, see screenshot).
Preparation prior to installation:
Place the two bearings in the 10mm borehole.
Use a M3 screw as a shaft for the bearings.
Place a M3 nut underneath the idler pulley as spacer and bed for the lower bearing.
Installation:
Screw the prepared unit into the Nema stepper M3 mounting hole.
Fix the to M3 nut against the Nema stepper to lock the screw against it.
Videos on how it is working can be found in the Videos section below or in this Youtube playlist. All show an Auto-Bed-Levelling tour with obviosly some Z movements.