Aluminium Profile Type Router - Initial questions

[JAZZCNC]

So one thing I did notice on heavy mill were weak side's so my design there is similar to Andys log = http://www.mycncuk.com/attachment.ph...3&d=1573338796 . That is rails on top on the extrusion, then a carriage and aluminum block which the gantry rail site on top of,and fixed using side plates .

Yes, this is the L design I was suggesting, most of the L designs you'll see are based off my original design or someone else's who took from mine, it can be used both with or without Gantry sides and makes for a very stiff gantry with easy rail mounting etc. When mounting directly to the bearings just bear in mind access to the bearings bolts when deciding the bearing plate length. I've seen several designs that missed this little detail, which is why it's a good idea to draw it in cad to catch these things.

Do closed loop steppers work with standard nema motors ? I'll take a look.

No closed loop steppers have an encoder on the back which goes to the matching drives. Also often closed loop steppers are 3 phase steppers with smaller step angle of 0.9 or 1.2 deg whereas typical stepper is 2 phase. with 1,8deg step. The difference being closed-loop are smoother.

I'll be trying to draw this in a shareable format soon. But design steps wise, can I design/build the X/Y axis and gantry to a good standard, then consider the Z axis as the next "module" or is that a bad idea!

Yes you can but I wouldn't recommended it because your better designing the whole thing in CAD to see if anything clashes.

If I know the motors to be used, I can pretty much leave electronics until the build progresses, and certainly won't buy anything related to that yet.

All you really need to know is the motor frame size ie: NEMA 23 or 34. Now I've seen you mention Nema 34 is what you need.! This would be bad for a machine this size and mistake often made by new builders are thinking bigger is better, it's not.!
NEMA 34 motors require a much higher voltage to get the RPM needed for a router. A 4Nm NEMA 23 will perform much better than a 4Nm Nema 34 at the same voltage.

Will my existing 120 x 40 profile with 40x40 cross pieces suffice for X/Y axis with extra bracing?
And with the L design for gantry - just thinking how I can incorporate the 90x90 profile, perhaps a 60x60 attached to it at the back?

Yes, the 120x40 and 40x40 could be used for the frame with bracing.
Regards the Gantry then Bolting 60x60 onto the back won't do anything other than add weight. To get the stiffness and height you need one piece flat with the other bolted on top. So either buy a wider piece for the bottom and put the 90x90 on top or start again with 2 x 45 x 90.
I'm assuming that your using BR range profile because of the 90mm. This is good because when using 16mm screws then the BK End bearings mounting holes will line up with the 45mm slot spacing. If you used the IR with 40mm slot spacing then you would have to make plates or drill the profiles to bolt the bearings on.

It's these little things that catch you out and cause more work. Hence why drawing in CAD can save many wasted days and money.