belt drive to ballscrew drive changeover advice required

[JAZZCNC]

To be honest, if it was me I'd just replace the belts and tweak what you have already because it will be a lot of work to fit ball-screws and no disrespect meant here but looking at the machine I don't think it's up to handling ball-screws. Ball-screws are not as forgiving regards alignment as belts and the power and torque they provide would tear that gantry to pieces if one of the motors stalled because the gantry was flexing and causing binding on the ball nut.

However, if you do go ahead then I'd go with Rm2020 and use 2:1 ratio. The reason for this is because it will give you the same speed as a 2010 but half the screw rotation speed so you are less likely to get whipping which is a major cause of stalling motors. With a weak machine, you cannot afford for one motor to stall while the other keeps spinning because no matter how fast you think you can reach that E-stop I guarantee you won't be fast enough to stop it before the gantry gets twisted up like a noodle.

You won't find machined ball-screws in UK at sensible prices. China is the place.

If you do go ahead with ball-screws then I'd also recommend while your buying from china you invest in some Round supported linear rail. This will give you more of a fighting chance and they won't cost a fortune.