Some design questions

[cropwell]

Thanks for the comments Jazz, but I don't agree with the bit about the motors, they are certainly strong enough to rip the threads out of delrin and jam the whole axis. I am considering belt drives with a 2:1 reduction, so this would double the torque and halve the speed, but the leadscrews will have a bigger pitch anyway.

Flying in the face of advice, I have got the rails and screws I need sorted out from Chai. I have ordered longer than I will need (based on space considerations in my studio) , machined only on the driven end, as I will turn the floating ends of the ballscrews to the final dimensions. I am going with supported rails and probably a similar design to the MD machine (i.e. a gantry), but beefed up a lot. I can't get my head around Sketchup, so my design may be modelled in foamboard (cos I've got 15 A3 sheets of it) after the initial fag-packet drawings. Who knows, it may be rigid enough to run with it ....

I have been looking around the web for design ideas to evaluate and in my travels I found the V-slot system at www.robocutters.co.uk . Intriguing (!), but I would have misgivings about accuracy and rigidity. However, it seems a good idea for 3D printers, that need speed, don't have to handle cutting forces, or move a heavy spindle around, but for CNC milling, I can't have any faith that it would be strong enough or that the timing belt and pulley positioning system wouldn't stretch.

At some time in the future I may build a 3D printer using the Astrosyns and the Digiplan drivers I have, but I am trying to get projects completed, not take on any more new ones.

Anyway chaps, Grandson #2 is about to be born, so I will be away for a few days.

TTFN

Rob

As a bit of a PS, I will be using the old machine to build the new, and then it goes on eBay, but without the current PC and the controller my be repackaged, but still a plug and play system.

[JAZZCNC]

Thanks for the comments Jazz, but I don't agree with the bit about the motors, they are certainly strong enough to rip the threads out of delrin and jam the whole axis. I am considering belt drives with a 2:1 reduction, so this would double the torque and halve the speed, but the leadscrews will have a bigger pitch anyway.

I was meaning the Astrosyn motors not the existing ones.! . . . . Your idea regards 2:1 reduction is a good one if you don't need the speed and have a decent amount of volts on the motors.
Don't worry about timing belts stretching because other than initial settling in they don't if correctly tensioned and good quality belts.

[cropwell]

The machine will be sold as a package without PC as I want to build a new controller with 4 drivers and I can't get a matching driver for the existing 3 Tonman PD2064M's. I will repackage the BoB and drivers as there are 'features' on the kit that would be best taken off. So I am going to have to find out more about motors and drivers.