A robot module vibrates after acceleration. Should the frame simply be made heavier?
Follow the force to the floor
Trace the route of the process force through mounting, beams and joints down to the feet. Long cantilevers and flexible bolted joints can dominate the deformation. Adding more mass doesn't automatically fix an unfavourable load path. Where needed, increase the effective section height, shorten free lengths and place joints close to the load.
A useful first model
For a simple cantilevered beam with a point load at the free end, δ = F · L³ / (3 · E · I). The third power of L shows why a shorter cantilever helps so much. Halving the free length gives, in this ideal model, one-eighth of the deflection, for the same material, section and force.
Design the fabrication steps too
A welded frame can distort during welding. Decide in advance which faces will be machined after welding, where fixturing is possible and how the structure stays accessible. Bring critical mounting surfaces and functional references together on the drawing.
Assumptions and applicability limits
The beam model holds for small elastic deformation under the stated ideal support. Joints, local deformation and dynamic resonance are not included. For vibration problems, excitation, natural frequencies and damping must be investigated together.