Double_GEAR_ratio_Z by zzp8202 (#1052)

* Publish ‘Double_GEAR_ratio_Z’

* add photo

* Add Assemble Instructions，Resize photo

* Update Z_Belt_Clamp_Upper_x8.STL

* edit read me and YAML file

* fix Voron LOGO for stl， change description in readme

* Update README.md

printer_mods/ZZP8202/Double_GEAR_ratio_Z/.metadata.yml

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+title: Double_GEAR_ratio_Z
+description: "Double_GEAR_ratio_Z_belt_assembly_with_spherical_bearing_connection"
+mod_version: 1
+discord_username: ZZP8202
+cad:
+- 3D/Double_GEAR_ratio_Z_belt_assembly_with_Spherical_Bearing_connection.STEP
+stl:
+- STL/Adapter_x4.STL
+- STL/Pulley_Holder_x4.STL
+- STL/XY_Cable_Chain_Brdge_x1.STL
+- STL/Z_Bearing_Block_Bottom_With_Pulley_Left_A_x2.STL
+- STL/Z_Bearing_Block_Bottom_With_Pulley_Left_B_X2.STL
+- STL/Z_Bearing_Block_Bottom_With_Pulley_Right_A_x2.STL
+- STL/Z_Bearing_Block_Bottom_With_Pulley_Right_B_X2.STL
+- STL/Z_Bearing_Block_Top_X4.STL
+- STL/Z_Belt_Clamp_Bottom_x8.STL
+- STL/Z_Belt_Clamp_Upper_x8.STL
+images:
+- Images/CAD_Detal_view1.png
+- Images/CAD_Detal_view2.png
+- Images/CAD_front_view.png
+- Images/CAD_side_view.png
+- Images/Photo.jpg
+- Other/Assemble_Instructions/Pulley_Holder.gif
+- Other/Assemble_Instructions/Z_Bearing_Block_Bottom_With_Pulley.gif
+- Other/Assemble_Instructions/BOM/Pulley_Holder_X4_BOM.png
+- Other/Assemble_Instructions/BOM/Z_Bearing_Block_Bottom_With_Pulley_BOM.png
+Other:
+- Other/Assemble_Instructions/BOM/Pulley_Holder_X4_BOM.pdf
+- Other/Assemble_Instructions/BOM/Z_Bearing_Block_Bottom_With_Pulley_BOM.pdf
+
+printer_compatibility:
+- V2.4
+

printer_mods/ZZP8202/Double_GEAR_ratio_Z/README.md

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+# Double_GEAR_ratio_Z
+
+## Description: 
+#### Utilizing the characteristics of a movable pulley system, the original Z belt structure's 4:1 gear ratio has been changed to 8:1, amplifying the stepper motor's static torque. This ensures that the gantry can resist gravity even in the event of a power outage. Additionally, using spherical bearings to connect the linear rails and the gantry makes the connection more reliable.
+
+## Objectives：
+#### Reject Sagging
+##### Enabling the Voron 2.4 Gantry to Defy Gravity
+
+Voron 2.4 uses a belt-driven Z gantry structure. Voron 2.4 theoretically can achieve smaller layer lines compared to most 3D printers that use lead screw structures Due to the linearity of the lead screw affecting the stability of the horizontal position. However, with the original design's 4:1 gear ratio, the static torque of the stepper motor is insufficient to support the heavy gantry in the event of a power outage, especially when mods such as nozzle cleaner and klicky are added to the gantry, further increasing its weight. Since the rear weight of the gantry is significantly greater than the front, the gantry tilt is inevitable, requiring multiple calibrations before each print to achieve an acceptable parallelism with the print bed. To prevent the print head from hitting the platform during leveling, a higher leveling height is also necessary. In my opinion, a bigger issue is that in a power-off state, the gantry and the main frame might stretch, posing unknown deformation risks.
+
+Previously, I modified the original G-code M84 to never turn off the Z motors unless an emergency stop or power cut occurs, to prevent significant gantry tilt.
+
+Additionally, in the current setup, the connection between the gantry and the linear rails is in a 'semi-connected' state, requiring high calibration efforts and even risking disconnection during printing.
+
+In my modification, I used GE5C spherical bearings to connect the gantry and the linear rails, which should provide a more stable structure. I also used a pulley system to increase the gear ratio to 8:1, allowing the gantry to maintain its position without external forces after a power outage. Practical tests show that only one leveling attempt is needed after a power outage without external influences, compared to the previous 3-4 attempts needed to complete the leveling.
+
+
+## Image:
+![front](Images/CAD_front_view.png)
+![side](Images/CAD_side_view.png)
+![Detal2](Images/CAD_Detal_view2.png)
+![Detal1](Images/CAD_Detal_view1.png)
+
+
+## Assemble Instructions:
+You can replace Z0~Z3 one by one. 
+
+When installing the pulleys, threading the belt in advance will make the process easier.
+
+1. Secure the gantry.you can use this MOD https://mods.vorondesign.com/details/p80KEQX34UKwVvovF0ig
+2. Remove the existing Bearing Block and related modules.
+3. Loosen the belt tensioning structure.
+4. Install the bottom belt clamp.
+5. Assemble the Bearing Block Bottom With Pulley module.
+6. Assemble the Pulley Holder module.
+7. Install the top belt clamp.
+8. Restore the belt tensioning structure.
+9. Adjust the belt tension.
+10. Replace the XY drag chain bracket.
+
+#### Pulley_Holder
+![Pulley_Holder_BOM](Other/Assemble_Instructions/BOM/Pulley_Holder_X4_BOM.png)
+![Pulley_Holder_Assemble Instructions](Other/Assemble_Instructions/Pulley_Holder.gif)
+
+
+#### Bearing_Block_Bottom_With_Pulley
+![Z_Bearing_Block_Bottom_With_Pulley_BOM](Other/Assemble_Instructions/BOM/Z_Bearing_Block_Bottom_With_Pulley_BOM.png)
+![Bearing_Block_Bottom_With_Pulley_Assemble Instructions](Other/Assemble_Instructions/Z_Bearing_Block_Bottom_With_Pulley.gif)
+
+
+## Configuration Change:
+
+Find the 'gear_ratio' parameter in 'stepper_z', 'stepper_z1',' stepper_z2', and ' stepper_z3':
+Change from 4:1 to 8:1.
+
+### Optional Configuration Change:
+
+You may adjust the 'horizontal_move_z' parameter in '[quad_gantry_level] 'and '[bed_mesh]' to reduce the Z-axis lift height during operations, thereby increasing speed. I have change it to '10'.
+
+
+## Bill of Materials (BOM)：
+|NO.	|Category	|Part Name						|Qty				|Remark
+|--|--|--|--|--|
+|1	|Fasteners	|M3x15 SHCS 							|4				|		|
+|2	|Fasteners	|M3x20 SHCS 							|16	                  	|	  |
+|3	|Fasteners	|M5X25 BHCS 						|12				|M5X27 BHCS Better|
+|4	|Fasteners	|M5x15 BHCS 							|24				|		|
+|5	|Fasteners	|M5x15 SHCS 							|8				|		|
+|6	|Fasteners	|M5xNUT								|8				|		|
+|7	|Fasteners	|M5x12x8 NUT 						|4				|LEN:12mm,Out DIA:8mm	|
+|8	|Fasteners	|M5X1x8 washer 						|8				|		|
+|9	|Fasteners	|M5 T-nut HNTAJ5-5					|16				|		|
+|10	|Motion		|F605zz  Bearing 						|16				|		|
+|11	|Motion		|GE5C Spherical Bearing 				|4				|		|
+|12	|Motion		|GT2 Open Belt LL-2GT-9 (9mm wide)		|Increase 50%		|		|