Burr formation refers to the unwanted formation of material residues on edges or the parting surfaces of tools during machining or primary forming production processes. In primary forming processes such as casting, injection moulding or compression moulding, the burr is caused by material escaping from the parting surfaces or joints of a tool. The burrs are usually removed after the production process in order to obtain the finished component.
How does flash form during primary moulding?
Burr formation occurs when:
- the mould does not close completely
- the internal mould pressure is too high or the material is too free-flowing
- there is wear or damage to the mould parting line
- the ventilation is insufficiently designed
Why is burr formation problematic?
- Impaired surface quality: Burrs change the visible and tactile surface, can be perceived as a quality defect and have the effect of a processing error in technical components.
- Difficult installation due to edges: Protruding material residues can get caught during installation or components can jam.
- Functional risks with seals: Even small burrs can disrupt the sealing line, create gaps or impair fits and thus lead to leaks.
- Additional post-processing work: The removal of burrs requires manual or mechanical reworking, which increases the unit costs.
Measures for prevention and reduction
In the production of rubber parts in particular, burr formation can often not be completely avoided, but it can usually be minimised.
- Selection of the right manufacturing process
- Precise tool design
- Optimisation of venting and separating edges
- Tool maintenance to prevent increased burr formation over time
- Adjustment of pressure, temperature and cycle time
In particular, the choice of the right manufacturing process is a key decision at an early stage: burrs are significantly reduced when injecting into a closed mould (injection moulding, transfer moulding) compared to traditional compression moulding.