Placement of the rails, stage 2

[TheRealGennie]

This mod looks very interesting, and Im planning to go this way. I do have a question (or probably a lot ;)

Why not put both rails on the outside of the frame?

My thinking is that it would increase the possible gantry travel by 50 mm. My plan is to add dual z (stage 4;) ) move the existing z axis back, either to the main frame, which would give 20 mm, (or maybe even to the outside of the frame) and the standard hotend assembly have another 12 mm clearance to the front extrusion, This would allow for a larger bed.

[endorphin3d]

@TheRealGennie Thanks for your interest in the project. I'll paste my answer to the same question from another user on Reddit (I need to add this answer to the docs, as obviously it's a common question)

The reason the rails are like that is because of the asymmetrical tension the belt puts on the bearing blocks. A CoreXY has two belts, each pulling in opposite directions, so this isn't an issue. But on the Endorphin I wanted the belt tension to be pulling the bearing blocks toward the rail rather than away from it. If you look at a bearing block up close, I don't think it would take too much strength to rip it off a rail.

Maybe I should make a version of the right rail mount for users who want to put both rails on the outside. Personally, I would be curious to see how well a rail block stands up to the tension pulling it away from the rail. I may be fretting over nothing.

By the way I'm really hoping to find some time over the holidays to work on stage 4. Still open to suggestions on stage 4 if you'd like to weigh in here: https://github.com/endorphin3d/endorphin/issues/4

[TheRealGennie]

Thanks for the answer. I really like this project!! Im not an engineer, but I did study to be one for a year a LONG timer ago, so I remember a bit about forces. Anyway, (to me anyway) tension is the exact reason to put the rails on the outside. Belts cant push, only pull!! As they cross the middle of the printer, they can never push a bearing block away from the outside of the frame, only pull towards it, or towards the steppermotor. Hope it makes sense!! I tried to draw/speak through my thoughts in Explain Everything (https://expl.ai/3MFKKQV) if you are interested

[endorphin3d]

Hey @TheRealGennie, thanks for the explainer video. The tension I was talking about actually wasn't due to the stepper moving the belt, but the tension that's on the belt 24/7 due to the belt feeding around the tensioner on the left side. See the yellow arrow:

But like I said, while the tension is there (you can pluck on the belts to feel it) it may not be near enough to matter. I am a big fan of making the print area larger, so this may be worth doing.

[tryptech]

Adding 2 cents, rail on the outside is exactly what is needed for Stage 2 on Ender 5 Plus as described in #5

[endorphin3d]

Anyone interested in beta testing the outside-mounted right-y-rail? It's no work of art--it's just the rail block piece mirrored to the other side--but we can pretty it up if it works.

I haven't tested yet myself as I need to get my printer back in working order, but feel free to give me your feedback.

STL

[endorphin3d]

And here's an STL for a Y limit switch holder that mounts in any of the rail's screw holes (with a T nut on the inside, same as all the other T nuts that mount the rail to the frame)

[tryptech]

I'll give it a go this weekend and report back.

EDIT: On first glance, i'm not sure what the optimal printing angle could be for this part, but I'll proceed with this orientation and report back.

[tryptech]

Two issues of note with the outside-mounted right-y-rail:

1. Using the M5 bolt to mount extrusion to the part does not account for the space the head of the bolt takes up. The rail carriage is right up against the underside of the part, but the head of the bolt prevents it from sitting flush with the underside and making it impossible to screw in. I worked around this for now by installing an m5 heat set insert on the part and using a an M5x25 bolt from the top.

2. The vertical alignment of the belt ends up hitting the rail with or without the bottom part. I will print the part at half height which should account for it.

[sgayol]

" Using the M5 bolt to mount extrusion to the part does not account for the space the head of the bolt takes up. The rail carriage is right up against the underside of the part, but the head of the bolt prevents it from sitting flush with the underside and making it impossible to screw in. I worked around this for now by installing an m5 heat set insert on the part and using a an M5x25 bolt from the top." And now I know why my AliExpress rail kit ended up lifting the X gantry about 6mm.

[endorphin3d]

Yep, I see the issue now. Thanks to both of you for testing. I'll try to design a fixed version this evening.

[endorphin3d]

Okay @sgayol and @tryptech, let's see if this one works better. It now uses the inner M5 screw hole to mount to the X rail.

[sgayol]

Okay @sgayol and @tryptech, let's see if this one works better. It now uses the inner M5 screw hole to mount to the X rail.

Printed and installed. Fit is excellent. The only pending issue with the mod as a whole is that the tensioner I had for the x axis belt needed to be modified. Do you have one that's definitely compatible? It's incredibly helpful having one, especially with the longer belt path.

[endorphin3d]

@sgayol What do you need to modify about the X tensioner?