How to Balance Hot Runner Cavities Without Trial and Error

Introduction

Hot runner cavity imbalance is present in most multi-cavity moulds to some degree. Even in well-designed tools, small thermal and flow differences cause some cavities to fill more easily than others. This leads to variation in part weight, dimensions, and cosmetic appearance, and can reduce overall process stability.

The traditional method for correcting imbalance is to manually adjust individual tip temperatures and observe the result. While this can improve balance, it relies on experience, judgement, and repeated adjustment. The correct settings are rarely obvious, and the process can take significant time to complete.

Cav-Bal® cavity balance software provides a structured and reliable alternative. By analysing measured cavity weight data, Cav-Bal® determines the appropriate tip temperature settings and manages the progression towards a balanced condition automatically.

The user performs short-shot studies and enters the cavity weights. Cav-Bal® performs the analysis and provides the required temperature settings at each stage.

Establishing the Baseline Condition

The first step is to run the mould with all hot runner tips set to the same nominal temperature.

Once the process is stable, controlled short shots are produced and the part from each cavity is weighed.

These weights are entered into the Flat Profile tab in Cav-Bal®.

This establishes the baseline condition and allows the software to evaluate the relative filling behaviour of each cavity.

Based on this measurement data, Cav-Bal® calculates and displays the first set of adjusted tip temperature settings. These settings are also automatically prepared within the software for the next study.

Applying the First Correction

The tip temperature settings provided by Cav-Bal® are applied to the hot runner controller.

A further short-shot study is then performed using these settings, and the cavity weights are entered into the Profile 1 tab.

This provides Cav-Bal® with additional measurement data reflecting how the mould responds to controlled temperature adjustment.

At this stage, a clear improvement in cavity balance is typically observed.

Cav-Bal® analyses this updated data and determines the next set of tip temperature settings. These are displayed and automatically populated into the Profile 2 tab.

The user simply applies the provided settings and continues the process.

Establishing the Balanced Profile

The Profile 2 tip temperature settings provided by Cav-Bal® are applied to the mould.

In most cases, these settings produce excellent cavity balance and can be used as the final production profile.

If verification or further refinement is required, additional short-shot measurements can be entered into the software. Cav-Bal® will analyse the updated cavity behaviour and provide further adjustment if necessary.

The software automatically manages each stage, ensuring that the progression is based entirely on measured mould response.

Automatic Progression Between Studies

At each stage, Cav-Bal® uses the measured cavity weights to determine the appropriate tip temperature settings and automatically prepares the next profile within the software.

The output from one study becomes the input for the next.

The user does not need to calculate, interpret, or manually transfer any values.

Each step builds on real measured cavity behaviour, allowing Cav-Bal® to determine the correct balance condition efficiently and reliably.

Practical Outcome

Using this structured approach, cavity balance can be achieved quickly and consistently.

In most moulds, excellent balance is achieved after the initial correction stages, with further refinement available if required.

Once established, the balanced profile can be retained and reapplied or updated at any time using the same measurement process.

Conclusion

Hot runner cavity balance is essential for achieving consistent part quality and stable process performance.

Manual adjustment methods rely on trial-and-error and experience, and may not reliably achieve optimal balance.

Cav-Bal® provides a controlled and repeatable method for determining the appropriate tip temperature settings based on measured cavity behaviour.

By analysing short-shot measurement data and managing each stage automatically, Cav-Bal® allows cavity balance to be achieved efficiently, reliably, and without trial and error.