Gantry design and FEA analysis

[eci22]

Hi all,
So a thread of mine asking about advice on different X axis rail configurations (http://www.mycncuk.com/threads/13497...arings-designs) kind of deviated into a discussion about the suitability of the material chosen which is 50x50x3mm mild box steel, I didn't mind as all advice is welcome, but I wanted to see some data to backup what I was being told, which is the main point of this thread so I did some FEA analysis:

Goal for the machine
mill 6082T6 Aluminium at 1 to 3mm DOC with an accuracy of between 0.1 to 0.3mm

Dimensions:


600x350mm not a huge gantry by any means

Fixed Ganry Designs- 50x50x3mm mild box steel

A: No bracing used more as a baseline for comparison against other designs


B: Vertical bracing


C: Diagonal bracing


All FEA analysis' uses 980 Newtons force = 100kg

FEA Analysis Type 1, no Z axis plate


Design A: Max displacement of 0.01 mm under a force of 100Kg


Design B: Max displacement of 0.009 mm under a force of 100Kg


Design C: Max displacement of 0.009 mm under a force of 100Kg

FEA Analysis Type 2, with Z axis plate (200x300x20mm Cast Tool Plate Aluminium)


Design A: Max displacement of 0.09 mm under a force of 100Kg


Design B: Max displacement of 0.07 mm under a force of 100Kg


Design C: Max displacement of 0.08 mm under a force of 100Kg

Questions

1.Which is a more realistic FEA setup, Type 1 or Type 2 or something different (and why) ?

2. Is 100kg force a good ballpark figure to use given the cutting parameters of my machine ? This number was a pure guestimate on my part, what is the correct way to calculate?

3.The displacement figures seem to suggest the material (50x50x3) is suited to the task- 0.09 to 0.07mm displacement under 100kg seems perfectly acceptable to me unless I've missed something ?

4. What else have I missed ?

All help appreciated

EDIT:
Voicecoil pointed out incorrect decimal places in second set of results, thank you!