Bearing play

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Trhuster
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Re: Bearing play

Postby Trhuster » Tue May 17, 2016 1:07 pm

GoffyOne wrote:Is this kind of bearing play something that should be requested to get fixed. I have same play on mine N2 as was posted in
viewtopic.php?f=4&t=239
I checked it and the play is betwen the rod and bearing not the bearing and housing as Jetguy mentioned might be the problem.


If you are happy with your prints don't bother. It is a real pain to replace the bearings in the housing imo. :shock:

GoffyOne
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Re: Bearing play

Postby GoffyOne » Tue May 17, 2016 1:15 pm

well not realy pleased with the prints. what problems does the bearing play make?
I get variatains in layer, when a line is printed in x direction there is variations in the Y direction.
thinking of doing the bondtech change to one direct and one bowden extruder to lower the mass so do get rid of some of the rinnging.
but I still also feel that the bearing play can make the rinning worse.

Ps waiting for a micrometer to arive to be able to better mesure the rods.

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Trhuster
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Re: Bearing play

Postby Trhuster » Tue May 17, 2016 1:26 pm

Hard for me to know what is normal for a dual head N2. I suggest you create a support ticket and see what rasie have to say about it.

hardbc
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Re: Bearing play

Postby hardbc » Tue May 17, 2016 1:48 pm

Hi Trhuster,

Can you please let me know where have you bought the rods from? Also, have you changed the bearings as well? If so, where have you bought them from?

GoffyOne
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Re: Bearing play

Postby GoffyOne » Tue May 17, 2016 2:57 pm

I beleve they ware replacements from Raise that is why I am wondering if mine could also be replaced.

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Trhuster
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Re: Bearing play

Postby Trhuster » Tue May 17, 2016 3:51 pm

I actually bought new bearings and rods from VXB.com but one off the rods was crap. -0.05 so i can't recommend them. The one i use now is from Raise.

hardbc
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Re: Bearing play

Postby hardbc » Tue May 17, 2016 5:30 pm

Thanks! Can you please tell me know what size are they (both rods and bearings?). Or at least they should be :)

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Trhuster
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Re: Bearing play

Postby Trhuster » Tue May 17, 2016 5:41 pm

hardbc wrote:Thanks! Can you please tell me know what size are they (both rods and bearings?). Or at least they should be :)


Sure, bearings is LM8LUU and rods are 8mm/dia, 310mm long. For N1 that is, N2 has longer rods.

hardbc
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Re: Bearing play

Postby hardbc » Tue May 17, 2016 5:58 pm

Usually a good quality hardened shaft has at 8mm has a dia tolerance -0.009 to 0.000 mm. If more, there is a problem. But they do not seem easy to replace, they look machined at the end so it's not possible to use any shaft.

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Trhuster
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Re: Bearing play

Postby Trhuster » Tue May 17, 2016 6:02 pm

hardbc wrote:Usually a good quality hardened shaft has at 8mm has a dia tolerance -0.009 to 0.000 mm. If more, there is a problem. But they do not seem easy to replace, they look machined at the end so it's not possible to use any shaft.


It is easy to grind a flat spot with a dremel.

hardbc
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Re: Bearing play

Postby hardbc » Tue May 17, 2016 6:22 pm

I am not sure how precise this should be. But anyway be aware that the shaft is not good quality if you are able to do it easily with a dremel. Good quality shafts have a machinable version where about 5 cm at each end are annealed (softened).

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Trhuster
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Re: Bearing play

Postby Trhuster » Tue May 17, 2016 6:32 pm

hardbc wrote:I am not sure how precise this should be. But anyway be aware that the shaft is not good quality if you are able to do it easily with a dremel. Good quality shafts have a machinable version where about 5 cm at each end are annealed (softened).


No need for precise, it is just a grubscrew that stops the rod from rotating.

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Re: Bearing play

Postby hardbc » Tue May 17, 2016 7:04 pm

Great, thanks. Anyone knows how long are the shafts for N2?

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John@Raise3D
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Re: Bearing play

Postby John@Raise3D » Wed May 18, 2016 3:40 am

image.png
Here it is.

FreedomRules
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Re: Bearing play

Postby FreedomRules » Thu Feb 01, 2018 6:19 pm

Can someone at Raise3D specify what type of steel was used for the rods. I'm exhibiting excessive play in the carriage assembly as well. I do have the cast vs cnc carriage assembly. Do you guys offer the cad file for the newer CNC carriage? Only reason I ask is I purchased 2 of the auto lift Hotends from Dglass3D and will need to either modify them, the existing carriage or build a new carriage to use them.

I was also going to order some new rods but was first curious what material was used. Alot of the rods online are made of GCR15 from China and have a very low Tensile Strength, Yield around 500 Mpa. Originally I was going to go bigger as it seems these rods are a bit undersized for the size and mass of the printhead. But if the rods that are used only have around 500 Mpa for the yield then a person could get some rods made from Maraging Steel maybe like 18Ni 350 which can be from 1000 Mpa to 2400 Mpa. With that much increase in Yield it would likely completely abolish any deflection. Only question would then be with rapid movements would we start to see stress fractures on the frame if the rods were no longer flexing.

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Vicky@Raise3D
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Re: Bearing play

Postby Vicky@Raise3D » Fri Feb 02, 2018 4:14 am

FreedomRules wrote:Can someone at Raise3D specify what type of steel was used for the rods. I'm exhibiting excessive play in the carriage assembly as well. I do have the cast vs cnc carriage assembly. Do you guys offer the cad file for the newer CNC carriage? Only reason I ask is I purchased 2 of the auto lift Hotends from Dglass3D and will need to either modify them, the existing carriage or build a new carriage to use them.

I was also going to order some new rods but was first curious what material was used. Alot of the rods online are made of GCR15 from China and have a very low Tensile Strength, Yield around 500 Mpa. Originally I was going to go bigger as it seems these rods are a bit undersized for the size and mass of the printhead. But if the rods that are used only have around 500 Mpa for the yield then a person could get some rods made from Maraging Steel maybe like 18Ni 350 which can be from 1000 Mpa to 2400 Mpa. With that much increase in Yield it would likely completely abolish any deflection. Only question would then be with rapid movements would we start to see stress fractures on the frame if the rods were no longer flexing.


Please make contact with our support team via our Support System. http://help.raise3d.com/helpdesk

zemlin
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Re: Bearing play

Postby zemlin » Fri Feb 02, 2018 5:51 pm

FreedomRules wrote:With that much increase in Yield it would likely completely abolish any deflection. Only question would then be with rapid movements would we start to see stress fractures on the frame if the rods were no longer flexing.

Yield strength does not impact deflection - but it does change the amount of stress before you start to see plastic deformation. Both rods will deflect the same, but the stronger steel will spring back from higher stresses.

The elastic modulus is the property you need to look at - and that's pretty much constant across all grades of steel.

You need to increase the area moment of inertia in order to decrease deflection, and that requires a larger diameter shaft.

FreedomRules
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Re: Bearing play

Postby FreedomRules » Fri Feb 02, 2018 6:22 pm

I was wanting to use Maraging Steel which has a different components than mild steel. So to clarify are you saying that still won't make a difference and the rod will deflect the same? To go extreme since the size is the same it would deflect the exact same between Aluminum and Titanium if we applied a 8lbs of force to the center of each rod? Or are you also getting at while yield strength in it self isn't what determines deflection. One should pay attention to the elastic modulus of the material and while yield strength may go up with a material that would exhibit less deflection its not a direct correlation? Only reason I was going off this is we have a cnc cutter at work that had extreme deflection during operations and we ordered the same size rod just in alot stronger material and using a dial gauge we went from 1/8" deflection during the same operation to 1/64" of deflection with no change in diameter of the rod just a stronger material. Thanks for the info as I want the optimal outcome. Since I'm ordering some of the AutoLift heads from dglass3d I'll have to either machine a new head block or modify the existing so while i'm at it I could increase the diameter of the rods. Just figure if I did that I'd likely have to go to a more powerful steppers due to the increase in mass. So was trying to steer clear of that for now.

zemlin
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Re: Bearing play

Postby zemlin » Fri Feb 02, 2018 9:45 pm

https://www.engineeringtoolbox.com/youn ... d_417.html

Aluminum has an elastic modulus of 69 GPa
Titanium iranges from 105 to 120
Steel is 180-200

so titanium and aluminum will both deflect more than steel under the same load. The materials on this table with a modulus higher than steel are pretty exotic and will be hard to find or hard to afford in the length and precision required.

FreedomRules
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Re: Bearing play

Postby FreedomRules » Sat Feb 03, 2018 6:33 pm

Thanks for the link. I'm looking into Tungsten rods as they have a Modulus of 400.


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