Technical challenge: The precision required of cold-stamping moulds, or “…by a hair’s breadth!”

In everyday parlance, people often say this when they’ve ‘only just made it’. But this measure – 0.05 mm in this case – has a completely different meaning here at Brunner, which the following should illustrate.

When making high-precision chocolate moulds for the cold-stamping process, repeat accuracy is so narrowly defined that the maximum permitted deviation in a mould set is just 0.05 mm. To be clear: we’re talking about five hundredths of a millimetre here, which is equivalent to the width of a human hair.

In order to be able to reliably produce millions of identical items using these chocolate moulds, the moulds must also fulfill further criteria:

  • Cavities deviate partially from the determined reference points by less than 0.05 mm.
  • In total, the mould’s entire length must not deviate from the nominal length by more than 0.3 mm (so based on the total length, that’s a deviation of 0.0035%!). In comparison: just a 5 °C change in the ambient temperature can cause this change in length.
  • The mould’s flatness must be within a range of 0.2 mm.
  • And the weight of the moulds must not deviate from the average weight by more than 2 g (or 0.07%, based on the mould’s total weight!).

 

These demands for precision require an extraordinary amount of effort during the design, planning and mould production stages. First of all, the customer, plant engineer and mould supplier provide the details.

After a tool has been manufactured, a sample series of moulds is produced, which is then measured precisely.

Then, every single point measured is compared to the measurements in the specifications. Before the final mould is produced, every discrepancy is corrected individually, and the tool is adjusted accordingly so that all values remain within the specified tolerance levels.

 

Special machines in air-conditioned rooms, high-precision tools and injection moulding machines are all required, as are trained expert personnel who are focused and accurate in their work.

 

In order to guarantee the requisite repeat accuracy for these moulds, the environmental conditions during production must be strictly adhered to:

  • long before production begins, the injection moulding machines are preheated to production temperature.
  • The insulated production hall guarantees a constant room temperature.
  • Fluctuations in humidity are thereby prevented.
  • Drying of the granulate is closely monitored and controlled.

 

This careful planning and production is the basis for years of error-free production of chocolate items with wall thicknesses of sometimes less than 1 mm that delight chocolate lovers everywhere.

 

 Brunner – always in perfect shape!

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