Quote Originally Posted by deannos View Post
You mentioned earlier about the ballscrew being in a good position, i'm not to sure in what you mean. If you mean to bring it out closer to the Z plate, could i not use spacers on the bearings
The best position for the Y-axis ballscrew is between the Y-axis rails so that there can be no movement of the linear bearings without the ballnut moving. More precisely the ballscrew should lie on the plane occupied by both the Y-axis rails, parallel to the rails. With the RSJ design it's close enough, with the previous design using two 80x40 box sections and 10mm plate it would be perfect.

(meant to post this in the previous post)

Quote Originally Posted by deannos View Post
The only thing that worries me slightly is the weight of the gantry, i know weight is a good thing, but would this be to much to get decent speeds. Now i'm not looking to break any speed records, just to get a reasonable feed etc. The motors i have at the moment are nema23-3NM and MSD542 drivers with 50v power supply.
As long as you use RM1610 ballscrews to move the gantry it will still be fast due to the higher pitch and more importantly get better acceleration than RM1605. You'll want a 1:1 ratio with 10mm pitch, but I used pulleys anyway to reduce resonance. You can always swap the pulleys round to get a 1:2 ratio for better resolution. If you get the end machining for the ballscrew where the pulley mounts made 8mm, same as the motors, instead of 10mm then swapping the pulleys is simple. For instance use two 15T on Y and 30T on X you can swap them all round to get 15:30 if required.
Also I got the end machining for the pulley made 25mm long instead of 15mm as it makes it much easier to align and mount the pulleys.

RM1605 may still be fast enough, but when you're getting them from linearmotionbearings2008 on eBay I don't think there's much if any difference in price between the two so no point. Especially since you can use pulleys to get effectively the same pitch (if required, for the vast majority of things it wont be) as RM1605 with better v&a as the screw is only spinning half as fast.