Trial Moulding Processes for Tyre Moulds and Solutions to Common Problems

Mould testing is a critical stage in tyre mould manufacturing. By conducting trial production on actual vulcanising machines, the structural soundness, dimensional accuracy and operational performance of the mould are verified, ensuring that the moulds delivered to customers can consistently produce compliant tyres. Drawing on Nacuan Mould’s practical experience in mould testing, this article shares key points of the testing process and solutions to common issues.
I. Key Points of the Trial Moulding Process
Prior to trial moulding, a comprehensive inspection of the mould must be carried out, covering aspects such as visual quality, fitting clearances, the flexibility of moving parts, and the functionality of the heating and cooling systems. During trial moulding, process parameters such as vulcanisation temperature, pressure and time must be set according to the tyre specifications; trial production is generally conducted using standard compound formulations provided by the customer.
Throughout the trial moulding process, the vulcanisation process must be closely monitored, with records kept of the conditions during the closing, vulcanisation and opening stages. Upon completion of vulcanisation, the produced tyres must undergo comprehensive inspection, covering appearance, dimensional accuracy and physical properties. Concurrently, the mould condition must be checked to ensure there are no issues such as sticking, deformation or damage.
Nachuan Moulds implements a ‘one trial, one inspection’ system; every mould must undergo trial production verification, and substandard products are strictly prohibited from leaving the factory. For large and complex moulds, multiple trial runs are conducted to optimise performance until the optimal condition is achieved.
II. Common Issues and Solutions
1. Bubble Issues: The appearance of bubbles on the tyre surface or inside is primarily caused by poor mould venting or the presence of moisture or volatile substances in the rubber compound. Solution: Optimise the mould venting system by increasing the number and diameter of vent holes; check the storage conditions of the rubber compound to ensure it is dry; adjust the vulcanisation pressure curve and increase the number of venting cycles.
2. Short-Filling Issues: Incomplete filling of the tyre tread pattern or localised material shortages are primarily caused by insufficient rubber compound flow, uneven mould temperature, or inadequate clamping pressure. Solutions: Optimise the rubber compound formulation and preheating process; inspect the mould heating system to ensure uniform temperature; adjust clamping pressure and speed; optimise the mould gate position.
3. Flash Issues: Excess rubber flash on the tyre is primarily caused by excessive mould clearance or insufficient clamping pressure. Solutions: Re-machine the mould parting line to reduce clearance; adjust the clamping mechanism to ensure uniform force distribution; optimise vulcanisation pressure parameters.
4. Mould adhesion issues: Tyres sticking to the mould and being difficult to demould, primarily caused by a rough mould surface or improper use of release agent. Solutions: Improve the surface finish of the mould through chrome plating or spray coating; select a suitable release agent and control the application quantity; optimise the demoulding mechanism design and increase ejection force.
5. Dimensional Deviations: Tyre dimensions do not meet requirements, primarily due to insufficient mould dimensional accuracy or inaccurate calculation of vulcanisation shrinkage. Solution: Improve mould machining and assembly precision; accurately measure compound shrinkage and revise mould dimensions; control the stability of vulcanisation temperature and time.
III. Recommendations for Continuous Optimisation
Mould trials are not merely a means of inspection, but also an opportunity for improvement. It is recommended that mould manufacturers establish a trial moulding database to record the trial parameters and problem cases for each mould set, and use data analysis to continuously optimise design and processes. At the same time, strengthen technical exchanges with tyre manufacturers to gain a deeper understanding of the vulcanisation process and rubber compound characteristics, thereby preventing problems at source.
Through comprehensive trial moulding processes and strict quality control, Nachuan Mould ensures that every mould set is ready for immediate use and operates reliably upon delivery, thereby earning the long-term trust of its customers.