Complicated injection moulding tools tend to be treated poorly as regards corrosion protection and storage – often as a result of time constraints. Properly functioning means of production are essential for a reliable source of revenue.
A while ago, SKZ KFE held a seminar in Würzburg, which was an excellent opportunity to receive adequate advice and information on the topic. We learned that there are several straightforward means and measures to maintain tools, i.e., Total Productive Management (TPM). Andreas Creutz, managing director of the engineering consultancy with the eponymous name in Heppenheim, Germany, also promotes this approach. Mr Creutz suggests that this compelling TPM approach is an excellent way to increase added value by reducing unnecessary waste. He further highlights that it is a brilliant method overall to retain reliable suppliers as well as meet customer expectations but also to increase their satisfaction.
Mr Creutz bases his favourite TPM structure on several pillars, including discipline, cleanliness, standardisation, systematic organisation, continuous improvement process as well as self-governing and preventive maintenance. The self-governing maintenance he describes aims to maximise production times and only accept downtimes when they are essential for maintenance work.
Mr Creutz elaborates that the goals of the TPM principle pillar include clean machines, prompt recognition of defective tools or cooling mechanisms and resolution of straightforward issues, if possible, by the operator and not the specialist department, giving them more time for preventive maintenance. Lastly, employees must learn all these aspects independently.
Maintaining tools with “what is already available”
A good portion of time, Mr Creutz says, should be allocated to the maintenance of injection moulding tools, which can be protected with little effort, if it is done after each production cycle, for example, by conserving the cavity and surfaces before the tool is placed back into storage. It is also beneficial to clean any water-cooled circuits with compressed air to avoid corrosion. Proper lubrication is essential for smooth injection moulding. Thus, all mechanical parts like ejectors and guide rails must be lubricated sufficiently. Any existing multi-couplings must be checked for their impermeability. The last inspection is essential for registering problems in their early stages. For this, the last produced part should be inspected for burrs, ejector or injection marks, water streaks, or even charred surfaces caused by the diesel effect.
Other inspection measures include controlling all tension screws and lifting rings for damage as well as ensuring that they sit flush. The condition, functioning, and plugs of hot runners should also be checked, if applicable.
A thorough cleaning of tools is recommended on a regular basis. It should bring the machines into a like-new condition, if possible. It is advisable to strip down the entire tool. Specific inspection systems can assist with large types, such as those offered by EAS. Otherwise, an overhead crane and clean supporting table are sufficient. Attention must be paid that the tool is level horizontally and flat on the surface to avoid any canting of struts and thus damage to protruding edges or cavities.
The cleaning of all parts is then the fundamental approach, including testing of each component but also the tool areas that are critical for quality. The cooling circuit can be checked for its ability to hold liquids to determine whether it works as intended. How much volume it contains can be ascertained from the design drawing. Corrosion or debris can be the cause if the volumetric measurement shows that the value is below what it should be. Established deficiencies should be noted as part of a protocol to allow a permanent solving of the issue. Employee suggestions should also be noted and, if applicable, implemented; not only is this satisfactory for the provider of the idea but it also encourages the workforce to take further initiative independently.
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