Basically the title.
Trying to make a CNC machine for fun as my first project.
I am 3d printing the guide that has to slide on 8mm shaft. I have 2 options:
1) Make a 3d printed part with 8mm hole and hope that it will slide easily on aluminium shaft.
2) Make a 3d printed part with 15mm hole, and put metallic bushing bearings in it, to make sure 8mm slides easily through.
Which option makes more sense?
Thanks! (my first post on the forums, sorry if something wrong)
I can print your parts in Iglidur 180-PF and it would slide real nice.
https://www.3dhubs.com/miami/hubs/mindfull
-Jesse
1 Like
I think it will, but I think it will wear too fast
This would work well until the chrome started wearing as aluminum is a very soft metal and bearings are very hard it would start scoring very at minimum I would use tool steel
ducky
6
You can do #2 obviously. Create a 3D part with clearance for a LM8UU bearing.
However, if it was me, I’d first try to print off one of the igus bearing designs from thingiverse and see if it’s smooth enough for the application.
aluminium is a horrible choice for a cnc machines linear guide shafts, unless you are planing to never mill hard materials like, wood, plastic and metals.
printing the linear bearing is also a bad idea, tolerance need to be tight and you want it to slide smoothly without the “stick and slip” effect else your servo or stepper motor has to waste extra torque just on movement alone.
the second option makes more sense, and get a good quality shaft which is suited for the job.
yeah I figured I fucked up with choosing aluminium… it was just to easy to obtain. In my case, CNC will not be milling stuff, it’s more of a pen plotter really. I’ll attach a pan to it, it will draw on a paper, that’s all. I wonder when aluminium will wear off though, how long will it take.
Yeah my bad… going with aluminium was stupid. I’ll get steel ones, they are just harder to get, I did not want to use amazon for that, as it was very expensive for some reason. How long will it take till aluminium wars off btw?
ide3d
10
You can use the special bushing Filament from IGUS
2 Likes
In that case.
go for a plastic or printed linear bearing option.
something like these igus designs:
http://www.igus.eu/wpck/2407/DryLin\_R\_Lineargleitlager
stay awy from linear ball-bearings as they would roll a groove in your shafts and loose tolerance really quickly and damage the crome
good luck 
I came across these 3d printed bearings with PTFE liner on thingiverse the other day, I’ve not tried them but they might suit your needs.
Kind regards
Tom
dhruv96
13
Second option would be a better call!!
That’s pretty neat! and should be the cheapest option. I wonder where he get’s PTFE with 2mm OD, all I found on ebay was 3mm minimum.
pmcgarr
15
Here’s what is important in my opinion…
It is good design, for a sleeve-type bearing setup, for the bearing to be softer than the slide/rail/shaft. This way, the bearing wears out before the shaft. This would be the case for either of your options, but I presume option number two would lend itself to a quick swap of a sleeve should the bearing wear out. So, I think option #2 is good.
Also, as for material, aluminum isn’t necessarily bad if it is appropriately sized for the intended use. You do not want to run ball bearings against aluminum, no, but for a sleeve type bearing application, plated aluminum is fine. Chrome is good, anodize would also be good. The plating protects against oxidization and provides a hard surface to resist abrasive wear.
Hopefully this helps you with your project.
Paul
flyer
16
Hi Avetis
The second option I think is good,the metallic bushing bearings a perfect fit.
