How to improve the performance of cheap linear guides

Linear guides from RobotDigg

The RobotDigg linear guide rails, despite also coming from China, are in my experience of better quality than the cheapest Chinese guides. Both the machining and the materials used are of higher quality. They cost a bit more than the cheap Chinese ones, but nothing extravagant.
Out of all options this one seemed like the best value to me, so I used their 440C SUS MGN9 and MGN12 linear guide rails for all axes in my new 3D printer build.
As you can see above, each option comes with its own up- and downsides. In the end it comes down to choosing between spending more money vs. spending more time.
The expensive linear guides cost a lot more, but work perfectly right out of the box. Some of the cheaper guide rails come with problems and defects, which require an input of time and effort to deal with. In order to deal with the limitations of the Chinese linear guides several things can be done. I have listed some of the common methods to do this below.
Further down the page I have included a guide on how to disassemble and reassemble the carriage blocks.
Please note that in this article I will be using MGN-type linear guide rails as an example. However, the methods listed below also apply to similar types of linear rails, such as the HGR-, MGW- and HGH-series.
A metal MGN12H carriage block component with PTFE inserts.
The channels in the RobotDigg linear rail carriages have a smooth PTFE(?) insert. I haven’t seen them in the other Chinese linear guides, so this might be part of why the RobotDigg linear rails perform a bit better.
Here is a summary of the fixing methods
Removing the stock grease from the rail and carriage.
Lubricating the carriage with a proper lubricant.
Running in the carriage.
Replacing the stainless steel bearing balls.
Reaming the carriage channels.
Read on to learn how to disassemble the carriage blocks for cleaning.

Full article please refer to
https://clevercreations.eu/clean-repair-linear-guide-rails/