need ideas - linear bearings for cnc
2005-07-20 by David McNab
Hi, It doesn't need to be said that the makeshift linear bearing and transport I've been using with my CNC setup (http://www.freenet.org.nz/cnc) is less than ideal. The mill is working ok for drilling, with all holes landing within acceptable proximity to targets. However, for artwork drawing, the inadequacies start to stick out like the proverbial canine body parts. I've taken on board people's earlier suggestions to use aluminium on high-density plastic, but am concerned this will only improve the situation slightly. As the current CNC setup goes, the software is pretty well finished, and is performing well with managing drilling and artwork drawing runs, using data in exported Eagle files. But with the hardware, there's way too much play, x y and rotational. The threaded rod works by pulling/pushing on a thread which I tapped into the sides of the platforms, which are 3mm thick aluminium. I could reduce much of the X-Y play by welding nuts onto the platform sides, unless someone has a better (non-specialised) idea. But to really address the problem, I'll be needing to totally change to a proper linear bearing system, which needs to get as close as possible to my target of < 100 microns play. I've seen a few commercial linear bearing products, but these would cost more than the other parts in the drill put together. Can anyone please suggest a simple, accurate linear bearing solution which can be resourced and put together without specialised parts, and with minimal wallet injury? All suggestions appreciated. -- Cheers David