Finite Element Analysis of CNC router gantry configurations
Proposed machine cutting area: 1220mm x 1220mm cutting area (1/2 plywood sheet)
Materials to be cut: Foam, Hardwood, Plywood, Aluminum to 6mm thick.
Proposed machine parameters:
Moving gantry with high wall frame
Gantry beam length about 1500mm
Twin X axis ballscrews, single Y and Z
Need decent but not perfect finish on edges of aluminum plate.
Would like to hold plus minus 0.1mm on dimensions
Materials available for the router build:
80/20 extrusion 3030 (76mm x 76mm)
80/20 extrusion 1530 (38mm x 76mm)
6mm aluminum plate
Little gantry design guidance was available for extrusion and plate configurations. An iterative beam stiffing and analysis process was started to determine relative stiffness between different gantry configurations.
Initial gantry analysis: Gantry 0
This was the base line configuration against which all other designs would be compared. Beams are 80/20 model 3030 extrusions. The FEA model is so simplified that results can only be used as comparisons between iterations. the absolute values of the resulting deflections do not have any real world relevance. A 500 N line load was applied along the edge of the Z axis block in a direction perpendicular to the beam. The deflection metric result from the baseline was 0.125mm deflection.
Twin Beam with Plate: Gantry 1
The first modification added a plate between the two separated beams. The same loads were applied and the 0.125mm deflection was reduced to 0.089mm.
Twin plates: Gantry 2
This configuration added a second plate to box in the two separated beams. The deflection was further educed to 0.052mm.
“L” section Gantry 3
Full size “L” section Gantry 4
Inverted “L” Gantry 5