Time for mk2 upgrade!

[routercnc]

Whilst this new machine performs very well, there were 2 features which were on the list to upgrade when time and finance allowed. First was to replace the x axis bearings running on the aluminium profile, and the second was to replace the wooden side members of the gantry.

So I'm planning my next moves. The X axis will be changed to 16mm supported rail and I have ordered the parts. The gantry sides will be RHS, probably 6" x 2" sort of size, with spacers inside where bolts pass through to avoid crushing the section and maintain the bolt torque. For the top and bottom gantry rails these spacers will be a slice of extrusion, just big enough to slide inside the RHS. For the bearing mount they will be some large turned tubes.

Whilst waiting from the rail to arrive I've been sketching some ideas, and settled on the ones attached. I've yet to see a really neat way of adding a rail connection to a full picture frame style gantry with single leadscrew drive. Anyone seen anything better?

So considering the forces acting I think this method will work ok. The only significant load on this cantilever is the weight of the main gantry and the z plunge of the spindle into the work. This is resisted by a 30mm thick ali block bolted to the RHS with 3off M12 bolts. The clamp load will therefore be very high, and since the block is full width across the RHS it will be able to transfer this load nicely into the stiff side walls of the RHS.

I could add corner brackets to add extra support, but I'm going to try it like this first and see what happens.

In the X direction there is no load because the bearing can slide, and in the Y direction the weak link will be at the top of the gantry side where it joins the horizontal part, so this stubby cantilever shouldn't make any difference.

That's the plan anyway, here are some preliminary sketches showing the current machine but with new RHS ali sides and 16mm supported X rail.