Study of mechanical damage to tomato seedling stems to ensure the quality of grafting

Abstract Tomato seedling stems can suffer mechanical damage during automatic grafting, reducing the quality of grafting. This study examined two sources of damage: compression damage to scion stems and bending damage to rootstock stems. Two damage tests were conducted. The test factors were determined based on the finite element simulation method. The four test indicators were established through a stress analysis method. Based on the damage test, for seedlings aged 33–35 days, when the diameter compression ratio was less than 40% or when the deviation distance of the rootstock emergence point in the longitudinal and transverse directions on the substrate bowl surface was less than 10 mm, the equivalent bending and buckling forces significantly exceeded the weight (0.0228 N) imposed by the graft clip and scion. Consequently, the deformation distance between the mass centre of the grafted seedling and the centre of the substrate bowl decreased to 0 mm, and the grafting success rate was 100%, with upright grafted seedlings and high–quality graft formation. This study provides a foundation for optimising clamping and alignment mechanisms in grafting machines.