Outrageous CNC Machine - 5axis - 2mins of amazingness

[routercnc]

PPPS Why are RSJs not used where long box section flexes/twists and 15-20mm plate is too expensive?

Hi Williamturner1,

RSJs are actually no better in bending than a similar sized box section, are are also very much worse in torsion. Plate, even thick plate, can also be poor because you need material away from the neutral axis for stiffness i.e. wide hollow sections.
See the 'gantry stiffness' spreadsheet in post#2:
http://www.mycncuk.com/forums/showth...ign-principles-.-.-.

If you have a box section which is bending or twisting too much you either to add additional supports, or need to increase the section size. Sorry, RSJs are not a panacea.

As for your new machine, sounds like you a have a nice list of bits - but naughty you for hiding them :whistling: ! Start up a new post with some sketches, scanned drawings, whatever you have, and we'll make some comments. It's worth adding what you want the machine to do.

[williamturner1]

RSJs are actually no better in bending than a similar sized box section, are are also very much worse in torsion.

Wicked Thread you linked to and epic spreadsheet!!

I'm considering 90 x 150mm RSJ over 120 x 80mm 4mm Box; partly as I have 4 meters of RSJ and no box but mainly as my brain tells me 90x150 RSJ wouldn't flex like Box Section would ... but the spreadsheet says otherwise

RSJ Data for the spreadsheet, 2nd entry in the table = 90x150mm : http://www.steel-beam.co.uk/universal-steel-beams.php

Hi Williamturner1,
As for your new machine ...Start up a new post with some sketches, scanned drawings, whatever you have, and we'll make some comments. It's worth adding what you want the machine to do.

I've got 9 sketches on the back paper out the office recycling bin ... I just need a bit more time to filter the embarrassing mistakes before I post a few up and ask you to say which will be the most bendy and the least!

Thank you for the quick feedback. I can't wait for more and to start building!!