Small rigid router - Design advise needed

[mitchejc]

Hi, this is my first stab at the design after having a good look at some of the great builds here. Any advice or comments would be greatly appreciated! Requirements for the machine as following
Exclusively for machining aluminium
Cutting area: 600mm x 450mm x 150mm.
Speed is not a great issue
I got hiwin HGR15 rails and blocks and Chinese 1605 ballskrews and ballnuts so I'll use those.
Since aluminium is not cheap here I'm going for a welded steel design and then alu on Z because there's a bit of machining required there.


Some basic dimensions for reference.
Distance between gantry side rails: 800mm
Distance between top and bottom rails on gantry: 300mm
Z plate with 250mm
Box section used is 160x80x3mm and 120x80x3mm
10mm 10mm sheet for flat parts to be laser cut
Y carrage and Z assembly is 25mm alu with a 10mm plate at the back


A few questions:
Will the long belts (+-650mm on Z and 550mm on Y) cause any issues? HTD 5mm pitch x 15mm width with 20tooth pulleys
The gantry is very rigid and HEAVY but I'm worried about ressonance. Can one fill it with something that's not going to add a lot more weight that will help with resonance.
Does the 3 rails on the gantry make sense? I've got 1 on top and two at the bottom.


Please comment if you spot anything that's not going to work or things I can improve without adding major cost