Fig. 1. Structure of mainboard

Fig. 2. Gravity deformation of mainboard in different placement status

Fig. 3. Stylus direction of gantry CMM and bridge CMM

Fig. 4. Diagram of supporting structure(Pro/E)

Fig. 5. Constrain points location distribution of assembly and clamping analysis

Fig. 6. Gravity deformation of mainboard without reloading

Fig. 7. Local deformation of datum A (Scale factor 100000)

Fig. 8. Flatness error under different forces

Fig. 9. Position of unloading force

Fig. 10. CMM testing of mainboard

Fig. 11. Results of mainboard flatness testing in different situations