Linear Rails Load Rating

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Septeract7
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Linear Rails Load Rating

Post by Septeract7 »

Hi

I was wondering why those Hiwin rails (MGN12H/C) are so popular in the 3D printing communities.

Sure, they are high precision. But they also have dynamic load ratings of around 3000N. Isn't that completely overkill for a 3D printer?
Assuming that the printhead (Extruder+Hotend) weighs around 0.5 kg, this would result in a force of 0.5*9.81 kg*m*s^(-2) ~= 5 N on the x-carriage.
Further guestimating a weight of 2 kg (this is really just a guess, please correct me) of the total x-axis results in 2*9.81 kg*m*s^(-2) ~= 20 N on both y-carriages --> ~10 N per y-carriage.
Of course this is static load and it might increase with acceleration/deceleration of the printhead but even with a safetyfactor of 100 (!!!) we are ~1000-2000 N above what is really necessairy.

So would it not make more sense to go for cheaper, lighter load rails that still have the high precision? Do such products even exist?

Am i totally missing sth. here?

Looking forward to some enlightenment :) :idea:

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Re: Linear Rails Load Rating

Post by Jhonno »

I suspect it is down to stability too, longevity also. And being able to print fixings that are stiff enough/work/cant be easily printed. Packaging.

Some are running MGN9 on the X axis.

I'd say that if smaller rails were also fully suited then they would be being used by manufacturers!

Septeract7
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Re: Linear Rails Load Rating

Post by Septeract7 »

Thank you Johonno
After some digging I also think that rails with the same size and precision but with lower load capabilities just don't exist. My guess is that when a rail is precisely manufactured it can also automatically bear such high loads...

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Aure3D
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Re: Linear Rails Load Rating

Post by Aure3D »

Hello,

Hiwin guides are very accurate and very well finished.
An official dealer showed me the Hiwin range at my office when I am doing research for my printer, and it is incomparable with non-branded models.
All the Hiwin guides you find on Aliexpress marked with 100% original are fake.
Hiwin company don't use this distributor for sold.

The reason why the mgn12 is so popular is because it fits the groove size of the aluminium profile.
In order to reduce the price of the guides, it is possible to use MGN5 guides, which will be more than sufficient, but you will have to adapt the fixing system to the width of the groove.
I think it would save weight on the X axis
For exemple with mgn5:

Image

hiwin datasheet, dynamic load in the second column and static load in the third column:
(Source page 93: http://outils.marlin.free.fr/Hiwin.pdf )

Image

It is not the precision that allows a high load to be carried, but the size of the rail.

Here is the price for mgn 12 Hiwin in Euro just for the X and Y axis, if you find it cheaper there is a reason:

Image

I find it too expensive for a DIY 3D printer. The mgn rail of the RDC store that I have been advised on this forum are sufficient to start. If I can give some advice, your editing is not necessarily final, so nothing prevents you from starting with cheap material and improving in the future.

https://fr.aliexpress.com/store/3719012 ... 6c376fFEPt

Sorry for my english I use a online traductor.

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