In-mould labelling (IML) is the name given to the process of applying labels to injection-moulded plastics parts as part of manufacturing process. IML can be used for countless products such as food trays and lids, plastics toys, patio furniture and countless other products. * What is electrostatic IML – a plastics label or decorative element is placed inside a mould.
As this label can be fixed precisely in position using a deliberately induced static charge, no vacuum holes are needed in the mould.
The mould closes and the hot plastic compound is injected, under pressure, fusing the label with the product.
IML therefore only involves one simple extra step, inserting the label into the mould.
* The advantages offered by electrostatic IML – using electrostatic charges have proved to be more economical then the traditional vacuum adhesion method as no modification is required of the tool.
Very little additional time or machinery is required for applying a label or decorative sleeve to the product, Furthermore; there is no need for additional printing, as the print quality and degree of coverage offered by IML is much greater than can be achieved by using a follow on printing process.
Limitations of the IML process – for electrostatic IML to function and operate correctly, it is essential that the surface resistatnce of the label is high enough.
A label which will bnot accept or hold a static charge will not be suitable for IML.
It is worth bearing in mind also that some labels are manufactured from more than one type of material or polymer and may carry different charges and polarities on either side.
In addition to this, thick or curved labels or sleeves can cause creasing and adhesion problems because of their size and shape.
Therefore, it is critically important to test the labels before embarking on IML.
* Options available – given the huge variations in degree of automation, size and shape of product, space availability, etc, static control recommends three different systems, which can be customised.
Manual – this method does not require a robot arm.
Indirect – this method requires no modification to the robot arm.
Direct – this method requires a robot gripper head to be modified.
* Manual – this process is used where no robot arm is present, or is unsuitable.
The operator activates the electrostatic charge process to manually charge the label which is then placed inside the mould by hand.
A specific handling device is used to allow the safe and easy handling of the charging electrode and to protect the operator.
* Indirect – with this method, the label is picked up and then passed in front of a stationary charging electrode so that a static charge is induced into the product.
The charged label is then placed inside the mould using a robot arm.
The robot arm carries out all the picking of the label, the charging process and the placing of the label into the mould automatically.
The potential disadvantage with the indirect method is that the charging process takes place outside of the mould.
Given that an element of static discharge occurs before the label actually reaches the mould, it can be more difficult to achieve acceptable results with labels that have a lower surface resistance, whilst some modification to the robot programming will be required.
* Direct – here, electrostatic charging takes place within the mould.
This is considered to be the optimum method of IML as the label is positioned, then electro-statically fixed in place.
The charging electrode is attached to and moves with the robot arm, which in turn picks and places the label.
The robot arm will need no major modification apart from the fixing of the charging electrode and High Voltage cable.
* Conclusion – in-mould labelling provides an economic alternative to both conventional fill-line labelling as well as screen-printing.
The results are finished products manufactured in a single operation with no label edges, no adhesives but, with an erosion protected design.
Static Control’s innovative and versatile electrostatic charging systems are an economical method of pinning labels to the mould, when using a robot pick and place system, this information can be stored in the machines memory for future use.