A slighly iffy Rockcliffe machine...

[Kwackers]

I felt it was only fair to post some pics of my machine. Having had the bits quietly rusting in the kitchen for some months I had a sudden motivation rush and hacked it together over a weekend and it never occurred to me that it would be worth photographing the process so apologies for the lack of 'in-progress' pics.

I bought the linear components from Marchant Dice - standard 16mm bearings and blocks. 12mm ACME screw and nut. The stepper motors/drives and psu are from Motion Control Products.

My intention was to 'knock' this machine together quickly and cheerfully to play with then move the linear components over to another better machine when I had a better idea of what I wanted.
With that in mind I cut out the wooden parts and bolted the linear components onto them inside a couple of hours - I'd no intention of painting them or doing anything fancy.
I decided to simply cut the holes for the slides a tight fit and make them in pairs so that there was no need to use Rocklciffes 'end plate' (which makes final adjustment easier) if I'd thought on I could've made the parts slightly wider to give me an extra 36mm movement.
I then spent a day or so machining the ends of the screws, making the stepper/bearing mounts and the ACME nut holders (shown below). I didn't want to support the screw using the steppers bearing (again my intention was to move all this to a 'better' machine) so my stepper mount holds a pair of bearings back to back to take the load.
Finally I roughly bolted it all together, hacked the wiring, sellotaped a pen to it for testing (first pic) and tried writing 'Hello World'.

Although my idea was to re-use the parts in practise this didn't turn out to be as useful as I'd imagined. Now I know what I want my next machine will have a moving gantry, be much bigger and probably use ball screws and HiWin bearings. However I priced up the relevant parts and got to £1500 just for the linear components - so I'm now temporarily on plan B.

Plan B is to remake the machine using some aluminium plate for the xz axis. Use the extra 36mm on the XY axis. Move the bearings inboard a bit on the Y axis and allow the table to overhang the front and rear of the machine. At the moment the table range is around 13 by 12 inches. I think I can improve this to 14.5 by 19.5 without changing the linear components.
Hopefully I'll make a 'nicer' job of this machine and document it's construction...

Things I learned:-

No matter how big the cutting area it won't be big enough.
Watching a CNC machine is better than watching the tele.
A decent stepper and screw have no problems destroying an MDF machine if it jams.
Fit limit switches (see above).
Fit limit switches (seriously).
Just do it, the first machine is a learning experience - you'll want to build another.