An "hardware" advice for linear rails

zapta

@gixxerfast said in An "hardware" advice for linear rails:

As you probably already know the Voron 2 still has (it's changing) two MGN9H rails.

A data point regarding the Voron new single MGN12 design. The recommendation is to get a rail that has 'medium preload'. That's slightly tighter than the standard ones.

Has for the two MGN9 design, people complained that it creates a twist or distortion with temperature changes. I can't confirm that from personal experience.

Gixxerfast

@zapta Yes, on my V2.4 I have the single Hiwin MGN12H with Z1 preload which I feel was a big improvement. My Z-offset movement and bed mesh caused by heat was significantly improved.

I now also have the Ti-backers but they are mostly bling IMHO.

However, many still have the dual MGN9H setup and seem to be happy with that.

deckingman

@achrn A perfect personification of why I don't send much time helping others out on these forums any more..........Bye

zapta

@gixxerfast said in An "hardware" advice for linear rails:

However, many still have the dual MGN9H setup and seem to be happy with that.

Titanium backers, wow! https://www.fabreeko.com/products/v2-4-trident-titanium-extrusion-backers

I think that the direction is to move to a single MGN12. The Trident (latest design) uses it and IIRC the upcoming ClockWorks 2 extruder will required it. It also simplifies the design, single rail and no seesaw underneath.

BTW, on the Voron, the extruder stepper (heaviest part) is located above the rail, rather than hanging on its side as the picture in the OP here suggests. May provide extra stability, though not sure how it handles Y acceleration as dc42 mentioned above.

zapta

@achrn said in An "hardware" advice for linear rails:

Deflection os a simply supported beam with point load at mid span is proportional to cube of span

One more reason for not building a 3D printer larger than one actually needs.

A Former User

Guys thanks to everybody for the very precious advices! At the end I want to be more cautios as I can so I've decided to add another linear rail in the back of the 2020 extrusion. I'll loose about 2,5cm of Y space but for me is not a problem.

Thanks again!

deckingman

@thedragonlord said in An "hardware" advice for linear rails:

Guys thanks to everybody for the very precious advices! At the end I want to be more cautios as I can so I've decided to add another linear rail in the back of the 2020 extrusion. I'll loose about 2,5cm of Y space but for me is not a problem.

Thanks again!

If the extra rail is just to increase stiffness, you could use a piece of flat steel or some such, which would save you some money. BTW, I never claimed that your rail would deflect by any amount because you didn't specify a length. I merely used a 1 metre length to keep the maths simple and illustrate the importance of doing the maths. I hope you saw through the pedantic criticism of my effort to help you.

A Former User

@deckingman said in An "hardware" advice for linear rails:

@thedragonlord said in An "hardware" advice for linear rails:

Guys thanks to everybody for the very precious advices! At the end I want to be more cautios as I can so I've decided to add another linear rail in the back of the 2020 extrusion. I'll loose about 2,5cm of Y space but for me is not a problem.

Thanks again!

If the extra rail is just to increase stiffness, you could use a piece of flat steel or some such, which would save you some money. BTW, I never claimed that your rail would deflect by any amount because you didn't specify a length. I merely used a 1 metre length to keep the maths simple and illustrate the importance of doing the maths. I hope you saw through the pedantic criticism of my effort to help you.

I did! I really appreciated your help!

A Former User

Here's the mod!

How about it?

Thanks!

o_lampe

@thedragonlord
The yellow tongue could be much thicker for my liking or have vertical struts (like an U-shape)

A Former User

@o_lampe said in An "hardware" advice for linear rails:

@thedragonlord
The yellow tongue could be much thicker for my liking or have vertical struts (like an U-shape)

mmmmhh....I think you're right! I thing I'm going to take of tthe middle row of screws and add an u shape vertical "fin" in their palce...the thickness is already at 5,2mm....thanks!

A Former User

@o_lampe said in An "hardware" advice for linear rails:

@thedragonlord
The yellow tongue could be much thicker for my liking or have vertical struts (like an U-shape)

better like this?:

zapta

@thedragonlord, now that you have two rails, you may want stepping back and rethinking the position of the parts and the load distribution. For example, moving the two motors (heave) on top of the rails. Just a thought.

A Former User

@zapta said in An "hardware" advice for linear rails:

@thedragonlord, now that you have two rails, you may want stepping back and rethinking the position of the parts and the load distribution. For example, moving the two motors (heave) on top of the rails. Just a thought.

It's impossible, the X2 is a single piece

zapta

@thedragonlord said in An "hardware" advice for linear rails:

It's impossible, the X2 is a single piece

You can also rethink the x2 choice.

A Former User

@zapta said in An "hardware" advice for linear rails:

@thedragonlord said in An "hardware" advice for linear rails:

It's impossible, the X2 is a single piece

You can also rethink the x2 choice.

no, I've already bought it

Phaedrux

@thedragonlord said in An "hardware" advice for linear rails:

@zapta said in An "hardware" advice for linear rails:

@thedragonlord said in An "hardware" advice for linear rails:

It's impossible, the X2 is a single piece

You can also rethink the x2 choice.

no, I've already bought it

Sunken Cost Fallacy.

fcwilt

@phaedrux said in An "hardware" advice for linear rails:

Sunken Cost Fallacy.

Does that apply if he is happy with the X2 and wants to use it?

Frederick

A Former User

@phaedrux said in An "hardware" advice for linear rails:

@thedragonlord said in An "hardware" advice for linear rails:

@zapta said in An "hardware" advice for linear rails:

@thedragonlord said in An "hardware" advice for linear rails:

It's impossible, the X2 is a single piece

You can also rethink the x2 choice.

no, I've already bought it

Sunken Cost Fallacy.

I'm not English so maybe I don't understand your humor....I was just asking for advices....

zapta

@fcwilt said in An "hardware" advice for linear rails:

Does that apply if he is happy with the X2 and wants to use it?

My understanding in mechanical engineering is almost none but looking at the final design, that small piece of support at the back looks to me as an afterthought. From my experience, when new data is presented (e.g. a single guide can't support well the dual head), it's useful to revisit the entire design to see what other aspects are affected by that change, a wholistic approach if you may.

I am not suggesting that @TheDragonLord is doing anything wrong, especially if this is a hobby project, or that I could do anything better (I can't), just suggesting to step back and revisit the entire design in light of that change. it's easier to make changes now while it's still on paper.

My 2c.