Gantry design and FEA analysis

[routercnc]

Glad you found the CNC videos useful. It was a good way to pass on the ideas I had seen, and add some of my own thoughts.

In the analysis:
Yes, vertical direction forces are mostly due to gravity but they will be much higher than 100 N as this only represents a Y and Z assembly of about 10 kg. More like 25-50 kg depending on the design, possibly more. This is to see how much the gantry will sag if you are surfacing a plate as in the extreme you would cut a dished shape. There is also a pull down force when using spiral fluted cutters, and there will be forces when drilling or plunging.

The lateral direction analysis is correct for the load direction but because of the grounded sides in your simple analysis it won't mean much on the results you have there.

The fore/aft analysis is in the wrong direction - it would be in the 'Z' direction using the coordinate system you have in the top right corner and would cause the part of the Z axis plate which is hanging down to all bend forward or rearward, and cause the gantry to twist about the 'X' axis as per your coordinates in the picture. This is usually the worst case of all the load conditions.

There are lots of square and rectangular gantries out there but the L shapes gantries were 'invented' by JazzCNC: