DIY Linear Rails - Building from scrap on a budget of next to nothing

[Neale]

I have built and am currently using an MDF machine built, more or less, to the JGRO design. Plenty of info if you do a Google search. Pro - materials to build are cheap. I went up a size on steel guide tubes, but it still uses skate bearings and threaded rod so didn't cost an arm and a leg. I did spring for bigger motors than recommended and reasonable drive electronics so that I could reuse these later. Fairly simple to build with ordinary tools, although I also used my lathe, milling machine, and 3D printer to produce parts (home-made motor couplings, anti-backlash delrin nuts, etc). Cons - it warps like nobody's business, and it's really, really difficult to keep the bearings in adjustment. Use of M10 threaded rod as a leadscrew may be cheap but the critical speed is low, so my maximum rapid speed is only 900mm/min.

I've done some useful work with it; I was using it today to make drilling jigs for some MDF furniture I'm building (the cutting area is too small to directly CNC cut the cabinet panels) and it's fine for that kind of thing. I've learnt an enormous amount from it (including a long list of what not to do!) at not a very great cost and had a CNC router available for use while planning the Mk2, which is now being built. I wouldn't stop someone building a wooden machine, and I'm sure that you could build something stronger than mine, but just keep in mind that it is going to have limitations and go into it with your eyes open.

[longy]

Neale, thanks for your honest opinion and advice. I had a look at the JGRP designs and did learn something from them. I'm not going to use much mdf only for the bed as I guess you mdf can swell as much as 4% even if sealed, left unsealed in damp conditions then 20% is not uncommon before it ruptures.

JAZZCNC, I don't intend spending much as I ain't got much to spent on the build.

Ger21, thanks for your input I would be interested to see some pics of your machine if you have any to post.

Silyavski, thanks for your input and advice. I have not seen the V casing on ebay can you post a link please. Also please post the pics of your Z axis please, yes I was thinking of using belt drives for the X and Y axis with liner round supported rails or profiled + blocks on the Z axis. NOTED your comments of V bearings LOL
Having costed up some stainless steel angle today as an alternative to round tube which I've several 4ft lengths I might as well buy supported rails as it would be cheaper.

Beone, thanks for your input. I know what you mean about shielded bearing and dust, as I was looking at a vertical panel saw with problems today and part of the problem was the bearings sticking apart from the resin build up on the rails, no wonder is was jumping out of the track. Can you post some pics of your machine please.

EddyCurrent, thanks for your input, yes I'll do some test and post them to the thread once I've got a machine built.

Mike :)