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ERCP Buffer Cross with enlarged wheel inset to reduce friction #155

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ERCP Buffer Cross with enlarged wheel inset to reduce friction #155

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NameOfTheDragon Sep 21, 2022
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NameOfTheDragon Sep 21, 2022
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Added a diagram of the modified area in ReadMe.
NameOfTheDragon Sep 21, 2022
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21 changes: 21 additions & 0 deletions usermods/ERCP_Cross_Arm_With_Enlarged_Wheel_Inset/ReadMe.md
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# ERCP Buffer Cross With Enlarged Wheel Inset

![Modified area in blue](Diagram-showing-modified-area.png)

This mod enlarges the circular inset on the inside of the buffer cross so that the filament wheel fits completely inside it. The original design has this inset a little smaller than the wheel. I believe the design intent is to prevent filament from falling between the wheel and the cross by pressing the wheel up close. I have found this to be problematic due to the resulting friction between the wheel and the cross, which undermines the point of having the wheel mounted on a bearing. Even with a smooth wheel printed on smooth PEI, I've found that the friction generated is enough to occasionally break filament in the bowden tube or to cause the extruder to grind away the filament and stop feeding. I have even tried applying silicone grease to the outside of the wheel and it still causes printing issues.

Any amount of tension in the filament within the buffer causes increased friction along the entire feed path, as the filament pulls tight against edges and curves. In my opinion, it is critical to eliminate all sources of friction within the buffer.

In this mod, the wheel inset diameter has been increased to 71mm which is just large enough to clear the wheel. The fit is still close and there is not a large enough gap to allow any filament to fall between the wheel and the cross, so this should not be a problem (I have never had this happen in a year of use, even on the older V1.0 design).

The modified cross-arm allows the wheel to spin freely on the bearing and (for me at least) this has significantly reduced printing issues on the unit I've tested.

## What's Included

- The buffer cross as a .3MF file (like an STL but better).
- A Fusion 360 CAD model with the modified part.

## License

This mod is released under the MIT license, which essentially means
"anyone can do anything at all with this project, but you can't come after me if it breaks". Full license details are at https://tigra.mit-license.org/