New CNC build, help needed dimensioning axis

[isvflorin]

Hi guys,
I'm currently scrounging parts for putting together a CNC router. It will mostly carve plastic parts and aluminium moulds. Some wood work also.

I got a 18000RPM spindle weighing 3.5kg for the Z axis.

I managed to get 6 Hiwins HGH15 (with very short rails - planing to get new longer rails), and 4 INA rails with 2 KWVE20 trucks each - 1440mm long.

Z axis will have aprox 20-25 cm travel.

Question is : can I use ONLY one rail (INA KWVE20) per each side of the X axis ?? The plan is to have the X axis mounted high above the table so the gantry won't have high lateral sides - thus lowering the rotation momentum on the X rail trucks. Does it make sense ? Or do I really need 2 rails on each side of the X axis ?

Next question: I'm planning to have all the 6 (2 rails - 3+3) 15mm Hiwin cars on the gantry axis with a 1350mm travel (1600mm OAL) - will the 15mm Hiwin rails be enough for the loads I will have while machining aluminium moulds ?

The machine will be for DIY use and light production. Sorry - I don't have skills for calculating the loads for the rails, that's why I'm asking those questions, please be understand...

The majority of the production machines I've seen with similar size have 20mm rails on the gantry axis, or even more, but I can't afford other rails...I hope the 15mm Hiwins will be enough (they are 4 row rails).

Hope somebody helps