New Build 1000x600x200mm (newbie)

[JAZZCNC]

Well with the Y axis rear plate(across gantry) you have room to have it wider than the front plate because it will over hang the bearings which the front plate can't or will crash into bearings. This will make Y axis much stiffer and be easier to access the bearing bolts. Yes put the bearings on the rear plate, rails on front moving plate.

For the Z axis you want hi-win HGH20CA Z0 which are the slim type and for the other Axis you want HGW20CA Z0 which are the wider bearing and will give a bit more support. Don't use 15mm the bearing blocks are too small and fiddly making building a Z axis more difficult due to clearences etc.

With the design I feel you are a little low on the height as it won't leave much room for cutters but then again I don't know what your cutting so may not matter.
Neils suggestion about X bearings looking poor is valid and has it is will need some bracing to help stiffen which is easy enough. But there's another change that I would make which will lessen the cantilever but more importantly allow for easier adjustment of the ballnut and allow some protection for the screws.?

Make the Gantry sides drop to the inside of the ballscrew not the outside.? This will shorten the gantry width and reduce bearing plate width and cantilever making it stiffer.
It allows access from the outside to the ballnut for adjustment and greasing etc.
Another important and often overlooked thing is screw protection, Your way makes it harder to protect the screw with a cover because of the gantry side being on the out side. If it's on the inside if the screw you can make a cover using C channel with a brush strip on top that covers any gap and wipes the gantry. This makes a very easy way to cover and protect which you'll want to do if cutting aluminium or wood even with screws on outside. (see pic)

[njhussey]

Make the Gantry sides drop to the inside of the ballscrew not the outside.? This will shorten the gantry width and reduce bearing plate width and cantilever making it stiffer.
It allows access from the outside to the ballnut for adjustment and greasing etc.

Make sure that you also think about how you are going to mount things like the ballscrew housings on, for example, the gantry sides.....(cough....don't ask me how I know!!) I'm using MGD16 ballnut housings which you can mount from the outside of the gantry endplates instead of some lower profile aluminium ones that I got from Aliexpress which I would have had to mount to the gantry side and then put the side on the gantry..............

[Noplace]

gents thanks a lot, I'm going to change a bit to make it more rigid, I have an idea on my mind I'll work on, I just hope its good enough

[Noplace]

I made a quick change to the gantry sides , reduced the width since its just going to be a waste with unnecessary cost and also hindering rigidity. gantry sides are now inside, will have to figure how to design the ballscrew holders with this design, but at least its not compromising (hopefully)

[Clive S]

Try and keep the gantry sides all one piece like Jazzcnc first pic. Clive

[JAZZCNC]

What Profile are you using that those rails sit onto because the rails look nearly as wide as the profile which if 20mm or 30mm the profile it is far too weak.

That or things are very much out of scale which makes designing very difficult.!

Your change is weak and complicated so I wouldn't take that route.

[Noplace]

What Profile are you using that those rails sit onto because the rails look nearly as wide as the profile which if 20mm or 30mm the profile it is far too weak.

That or things are very much out of scale which makes designing very difficult.!

Your change is weak and complicated so I wouldn't take that route.

It's 40x80mm