Redesigned stack mould allows easy conversion to IML

  • The drawbacks of previous stack moulds
  • Stack mould allows up to 8+8 labels to be inserted
  • Easy conversion: most stack moulds can be converted to IML

The restriction of the use of stack moulds for IML decoration is a thing of the past: the company Waldorf Technik has developed a new process for inserting IML labels quickly and safely in the middle plates of stack moulds.

The drawbacks of previous stack moulds

Instead of decorating cups and lids in downstream processes such as offset or silkscreen, post-printing and sleeving, IML involves the insertion of printed foils into the injection molding tool to create an integrated process in just one operating step.

For single face moulds, this process has offered a wide range of options for inside and outside gated packaging geometries for many years. For stack moulds, on the other hand, insertion of IML labels was restricted to the outer platen of the tool. As a result, containers had to be injected from the inside. But inside gating always brings the danger of plastic threads in the material due to wear on the tools. In addition, it often leads to a reduction in productivity due to the lower cooling capability of tool cores. In order to avoid these problems, some mould makers use complicated sprue bar systems in an attempt to distribute the hot plastic to the outer plates. However, this technique is expensive and subject to wear.

Stack mould allows up to 8+8 labels to be inserted

The new development by Waldorf Technik simplifies the stack IML processes and eliminates these restrictions. Building on proven IML technologies, the company developed a further standard automation for IML stack moulds which allows up to 8+8 labels to be inserted into the inner plates of stack moulds as efficiently, precisely and safely as for single face tools.

“The danger of threads forming when using efficient stack moulds is lessened by injecting containers from the outside. Manufacturers who have hitherto been producing on single face tools for reasons of quality, can in future achieve almost double the output in the same space and with the same injection moulding machine. By comparison with IML containers already made with stack moulds, the outside gating to be used in future can be expected to result in shorter cooling times for many products and therefore to higher output”, explains Holger Kast, Sales Manager at Waldorf Technik.

Easy conversion: most stack moulds can be converted to IML

Injection moulders who are already using normal stack moulds to produce outside gated containers and who wish to convert from offset printing or labelling to IML decoration, can benefit from a further side effect: with the new automated option to insert the labels in the middle plates, the existing tools can normally be used for the IML process after a simple adjustment at resonable costs, whereas up until now it was usually necessary to buy a new stack mould. This makes the conversion to IML even more attractive for injection moulders.

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