Meaning
Spatial distribution of clamping force among the main structural columns of an injection moulding machine. Achieving a proper tie bar strain balance is necessary to ensure that the mould plates close evenly and maintain a uniform seal during the high-pressure injection phase.
Measurement Method
Electronic strain gauges are mounted onto the four steel columns to measure their elongation under clamping force. As the machine closes, the tension on each bar is recorded and compared against the others. Adjusting the nuts on the tie bars allows operators to correct any load disparities and establish a tie bar strain balance.
Moulding Defect
An uneven distribution of force allows one side of the mould to part slightly during injection. This deflection leads to the formation of flash, where molten polymer escapes the cavity along the parting line. Parts may also suffer from dimensional variation and warpage due to the uneven pressure distribution.
Tooling Protection
Correcting the strain balance prevents uneven wear on the metal guide pins and bushing of the mould. Continuous operation with unbalanced forces can bend the platens and crack the expensive mold inserts. Ensuring that each bar carries an equal share of the clamp load extends the working life of both the machine and the tooling.
