Hovering over "Buy"... care to sanity check my thinking?!

[magicniner]

I made a start on the design anyway, made some assumptions....

Fasten the 4 fixed bearings to the lower and the rails on the underside of the component above, your support is then always optimally positioned for the point being machined.

- Nick

[brumster]

Interesting; can you elaborate (or link to somewhere that explains) the advantages in laymans terms? I don't think I've ever seen it done that way... any construction challenges (alignment?)...? I guess it's only the same but inverted....

As an aside, I reworked the motor mount to be underslung for a pulley arrangement... using a generic eBay-sourced motor mount bracket

[magicniner]

You want a design which keeps the alignment/support as close as possible to the cutting area, not one where the alignment/support moves away from the work area at either end of travel.
You can make the rails twice as long as the required travel and use multiple linear bearings to ensure support close to the cutting area.
Regards,
Nick

[brumster]

Right, I've made a decision! The design of a DIY machine can be parked because I'm going with this :-

http://www.mycncuk.com/threads/9412-Sieg-X3-and-Stand

...and I'll convert it over time. A home build came out at £1600 or so but my confidence that I'd build anything straight and true is low, probably more luck than anything. This X3 will let me do my aluminium parts without worry. Not sure how it'll be with accuracy on the PCBs but, pfft, we'll see. Nothing ventured, nothing gained - worst case I'll get an MF70 just for PCBs and convert that, using the X3 to make all the bracketry :)

If I had the space I've be doing a Bridgeport conversion but I don't have the space. If I was just doing large-area MDF and wood then likewise I'd be going with a home-made gantry system, but this approach just feels 'right' to me...

When I get round to starting it I'll post on here, might be a month or two yet, but I'll be honest at least :)

Thankyou all for your input; it has helped me make an informed decision and I've learnt a lot in the process, so that's been very useful and has helped me understand what I would be taking on.