Integrating IML into the stream

The popularity of in-mould labelling as a pre-decorating technique for various types of containers has encouraged vast improvements over the years. In-mould decoration of non-packaging plastic products has been well-accepted as a method of product enhancement that it has replaced self-adhesive or pressure sensitive method and heat transfer decoration in many industries.  What makes in-mould labels for blow moulding applications different from traditional glue-on labels is the heat seal coating that is applied to the back side of the in-mould label stock during the converting process. 

IML has many advantages. Since an in-mould label is embedded in the product, it is durable and difficult to remove. Another advantage is that all four sides and the bottom can be decorated with a single label during the moulding process which is not possible in pressure sensitive process. IML speeds up production and allows for improved appearance, stain resistance and sidewall strength of the products. Also, all post-mould labelling operations and additional costs are avoided because the in-mould product is taken off from the mould fully-labelled. Thus, in-mould labelling has been able to produce better decorated products at lower costs. 

IML used for the first time on cylindrical parts

Netstal-Maschinen AG created for the first time an IML system for silicone cartridges to satisfy a customer's order. The cylindrical geometry of the product presented a major challenge as regards the layout of the system components and the process parameters.  The degree of novelty in the planned IML application called for an exact definition of the production process, which is why the process sequences and parameters were developed in cooperation with the packaging specialists in Netstal.

Since the market didn't offer any IML solutions for cylindrical mouldings so far, it was particularly important to find the right partners for this production system. Eventually the mouldmaking company Otto Hofstetter AG and Beck Automation, manufacturers of removal devices, were selected to implement this project.

The demands imposed on the production system are very high. A big challenge, in particular, is the length compensation of the film which is stretched by up to 3-5 mm on injection of the high-viscosity HDPE, with direct effects on the surface quality of the cartridge. To come to grips with this decisive sequence of the process, dynamic and perfectly reproducible filling of the cavity is essential because the film's stretching is defined by the advancing speed of the melt. Apart from the exact layout of the injection mould, the process and reproduction accuracy of the moulding machine play an important role. Machine capability, the dynamic and accurate injection as well as the precise positioning of the mould in relation to the film insertion point have a direct influence on the quality of the cartridges and the availability of the system.

As usual, the film is wrapped onto a dummy in a pre-shaping station outside the machine. Unlike in conventional systems, however, the film is not statically charged, otherwise it might cling to the core, in which case it would be back-moulded. Instead, the film is mechanically passed from a sleeve to the cavity and centered there after the cartridges from the previous shot have been ejected by “falling freely“. With 8 cavities and a cycleAdidas