Thank you both Jonathan & Jazz,

Subject: Twin Motors vs Single Motor & belts

Thank you both for helping me clarify this issue. In the light of your comments and a PM from AudioAndy who also recommended twin screws and belts. Since twin motors seem to be a riskier strategy than a single motor and belts. I'll play it safe, especially in the light of the following advantages of using the belts.

1) Flexibility of gearing,
2) Damping of drive
3) Removal of the weak spot of the couplings.
4) Fit and forget!
5) Simpler to sync leadscrews,
5) No risk of motors trying to tear machine apart - a big worry of mine!

One motor would allow me to mount the belt system at the back of the machine in what is effectively a "dead" space, I could then use the reduction of sticky out bits to gain a 100mm on X Axis travel - Win! Redesigning was inevitable so no worries there, measure twice cut once, as many a wise craftsman will advise!

One less motor & driver for the entire machine = effectively a cheaper 4th Axis when I get that far! Mmmm, fuzzy logic, but you catch my drift!

Q: This leads me to another question of course, is the 1x3.1Nm motor enough, or is it worth going to something more grunty?

Subject: Trapezoidal vs Ball screw.

While my Engineering head says Ballscrews have to be the best, my goal for this design was that involved a build where as much as possible the components would be compatable with the 20mm spacing of the slots on the extrusion, the aim being to design a machine to be built with a pillar drill and odd spaced holes always seem to fall on the edges of the sections and would be difficult to drill with said drill. I am fighting with what is best for me accuracy wise and what was intended as a design for other people with equally limited workshops... Okay writing this has allowed the grey cells to work in the background.

Since the support bearings for the ballscrews are more pricey than the solution I have drawn and at odds with the 20mm spacing intention, I'm thinking of a compromise. I am using 12mm ID Axial load bearings and a simple clamp system to fix them to the uprights.

Q: If I go with 12mm Ballscrews is there anything stopping me using this method of attachment? I gain significantly in accuracy and reduction in friction, while keeping cost as close to the Trapezoidal idea as I can AND still keep my 20mm spacing.
I will of course need to drop the ID at the motor end to allow the threading of the clamping nut, I need to do some more research now for the machining of the ends, I'm guessing it will be M10 and then hoping 10mm ID bearings are available!

Subject: Plating Gantry - No brainer

Onto Jazz's points...

Subject: Advice

My strategy for advice is now more concrete!

When it comes to advice. Evaluate it. Valididate it in the light of your own understanding. If the results prove to be incorrect, the responsibility is your own and not that of the advisor!

Subject: Heiz Machines

I have been re-evaluating these in the light of my readings here and yes for what you get they are expensive! Guess I was blinded a bit (lot?) as I thought I was getting one for 400 notes!

Subject: Pros & Cons

Advantages

1) Agreed, much more of a preference than an advantage, but as I really want to be able to engrave motorcycle casings it is going to have to be something I live with! I can minimise the compromise by measuring up the biggest clutch cover I can find and fixing permant braces in the bed upto that point, I can the add removable bracing to allow the access.
2) See question about motor above.
3) Twin leadscrews and belt drive it is!
4) Agreed, one less driver and wiring is a plus!
5) Ageed, two motors is too risky for me in the light of the above and errors in the work, screwing up a casing is a real worry and reduced risk is always worth it.

Disadvantages

1) I'm committed to belts and pulleys, the cost is now the cost
2) I can see that to be true, problem removed!
3-5) Problem and fear removed by belts!

As I mention above a redesign was inevitable and I can now see so many pluses for belt drives on all Axies (What is the plural of Axis? It's bugging the hell out of me!)

Yes belts aren't very pretty, but then it is a just a machine after all. It is more important the work comes out aesthetically pleasing and not the tool that made it!

Off to play about with design in the light of these changes, might even work a way of reducing the Gantry height an beef up the Z Axis, but since I was running low on ideas for this I will happyly take advice on these areas to!

Cheers both,

Geoff.