My new 6040 improvement plan.

[Kev2960]

Hi there, that’s interesting about the bearing adjuster screws. Can you tell me or send a photo. I might check mine, to be honest I didn’t even know there were any
Kev

[PaisleyPCdoctor]

Hi there, that’s interesting about the bearing adjuster screws. Can you tell me or send a photo. I might check mine, to be honest I didn’t even know there were any
Kev

[Zeeflyboy]

Aren't those just grub screws holding the bearing cartridge in place? I don't see how those would do any adjusting on the bearings other than distorting the casing or possibly forcing things out of alignment slightly.

My first (well actually second, but first was tiny) CNC machine was a similar design... was good enough to get started with and do light work, but unfortunately you will never be able to address the flex you get on those unsupported rails without just getting rid of them.

Whether that's an issue depends on what the goals are... cutting foam or other very light duty stuff will never show a problem, harder woods or light aluminium work can be done but you have to really work within the limits of the machine and accept that the tolerances and finish may not be what you hope.

[magicniner]

Aren't those just grub screws holding the bearing cartridge in place? I don't see how those would do any adjusting on the bearings other than distorting the casing or possibly forcing things out of alignment slightly.

Tighten them enough and whatever is under them will eventually apply more pressure on one side of the rod, it isn't an engineering solution but if it works then the only remaining problems are wear and those floppy pesky unsupported rods ;-)

[PaisleyPCdoctor]

The main gain was in Y-axis bearings.

They are adjusters. When they are tight, there is no noticeable flex/movement on the gantry. I tighten til they stop, then quarter turn to nip up. Gantry feels rock hard.

When I loosen the grub screws, the gantry flexes as if it's on rubber mounts. Difference is remarkable.

I'm just left with the flexing of the 20mm unsupported x-axis shafts. There's a youtube video where the guy replaces them with supported rails, but improvement was MINIMAL at best. Waste of time.

I have a better, cheaper and easier solution. Just sketching out the plan and I'll post it.

[magicniner]

The main gain was in Y-axis bearings.

They are adjusters. When they are tight, there is no noticeable flex/movement on the gantry. I tighten til they stop, then quarter turn to nip up. Gantry feels rock hard.

Have you tried marking the rod with a marker pen to see if the contact is simply the screw against the rod? ;-)

[Zeeflyboy]

The main gain was in Y-axis bearings.

They are adjusters. When they are tight, there is no noticeable flex/movement on the gantry. I tighten til they stop, then quarter turn to nip up. Gantry feels rock hard.

When I loosen the grub screws, the gantry flexes as if it's on rubber mounts. Difference is remarkable.

But that simply isn't how these bearings work, there is no pre-load adjustment... they are just a few rows of bearings inside a tube. You are achieving a reduction in slop most likely by forcing them out of alignment and thus introducing an increased load on one side. It achieves the goal but the problem is that the load isn't evenly distributed and wear will likely be accelerated.

Whatever works for you, but they are retainer screws not adjustment screws.

I'm just left with the flexing of the 20mm unsupported x-axis shafts. There's a youtube video where the guy replaces them with supported rails, but improvement was MINIMAL at best. Waste of time.

I have a better, cheaper and easier solution. Just sketching out the plan and I'll post it.

Supported rail doth not equal profile linear rail. My current machine is effectively a 6040 with proper 20mm profile rails and the difference is very obvious compared to the old machine... I don't need a guy on youtube, I've extensively experienced both. Of course even with proper rails you are still left with the general somewhat lightweight design but it's still a significant improvement over the previous model I had with unsupported rails like yours.

I'm not belittling you, you are obviously keen to get stuck in and learn - just be aware that despite what you may think at the moment, those unsupported rails (and to a lesser extent the supported rail on the bottom) are a limiting factor in this machine which you will need to learn to work around and will limit the level of tolerance and finish you can ultimately achieve in harder materials.

[magicniner]

But that simply isn't how these bearings work.

Don't waste your time!
There are things we understand, there are things we don't understand and there are things which we don't understand why we don't understand them, we are dealing with the third circumstance here :D

[magicniner]

An engineer would understand that there is no way to adjust a linear bearing which has at least 4 bearing channels with a single grub screw.

I know you are hoping that you have found the Holy Grail that everyone else has missed but look at the way the system you are messing with actually works and you will understand that you are simply adding side load and wear in an attempt to resolve a problem with tolerance and clearance in the set of components you have unfortunately bought.

- Nick