General overhaul for hot runner: Lifecycle Service ensuring same product quality as on the first day

Injection-moulding tools from MHT AG have been designed for manufacturing top-quality components on a permanent basis. Since our customers are invariably striving for sustained competitiveness, we offer them overhauls at regular intervals and maintenance routines as part of our Lifecycle Service. MHT has developed tailor-made overhaul programs for the melt-carrying hot-runner system which is crucially important for maintaining top product quality. In this way, we not only increase your injection-moulding tool’s useful lifetime, we also spare you the nightmare of a “complete failure”. 

Why overhauling the hot runner is important

It is recommended – and indeed necessary – to overhaul your hot tool side at regular intervals for two reasons: Firstly, during operation soiling accumulates at the valve gate’s functional elements and between the tool plates. Deposits of PET dust throughout the entire interior compartment are typical for injection-moulding tools that handle PET. Secondly, components like valve pins, nozzle tips and insulations, plus sealing rings, are subject to continuous wear and tear.
 
By removing such deposits and replacing a few functional elements, our service technicians are able to restore the gate to as-new condition, enabling you to achieve quality levels similar to those obtained when the hot runner was new.

Tailor-made or predefined stages

No matter whether it is a hot runner from MHT or from a competitor: We will be pleased to have a look at it beforehand. After dismantling and inspecting the system, we will give you a list of the measures required for restoring original production output levels.

Depending on the number of cycles your tool has clocked up and its maintenance status, we offer a variety of predefined maintenance stages, ranging from a small overhaul right through to a general overhaul after six to eight years. Maintenance packages customised to meet your specific needs will factor in your utilisation patterns, the hot-runner system’s operating time, your quality aspirations and your budget. Our after-sales and service support team will be pleased to assist you in drawing up a tailor-made overhaul package for you. We use exclusively original MHT components, thus achieving optimum levels of productivity and performance.

When performing a maintenance routine, we also check whether any design makeovers or upgrades are available for the components you use. You benefit from tool components to the latest state of MHT art.

Step by step to “as-new” condition

In all overhaul stages, our service specialists will clean the tool plates and all associated components. We remove any organic soiling by means of a thermal gas-heated cleaning system. In this process, also known as hot cleaning, the melt manifolds and the nozzle and piston housings are heated for ten hours at 520 °C until all deposits have been dissolved from the flow runners by means of pyrolysis. Not only is this process suitable for removing remnants of polyethylene terephthalate, it removes almost all polymer residues as well. Subsequently, our specialists check the melt runners for any other remainders or foreign bodies.

Once the hot-runner manifolds have been removed, we clean the now-accessible tool plates by means of CO₂ cleaning technology. Dry ice constitutes an ideal cleaning medium since it is not abrasive, corrosive or electrically conductive. When it touches the tool plate, it sublimates completely, so no residual moisture whatever is left in the tool. Once we have removed the dirt deposits, the hot-cleaned manifolds can be easily re-installed. If it is necessary to replace the piston housings, or if you want us to do this, we will at need additionally regrind the hot-runner cover plate for a snug fit.

If so requested, we will of course rework the gate bushing’s radius. This makes sure the machine nozzle will continue to be accurately pressed against the gate bushing so that both components are properly sealed against each other.

All electrical items, like heaters and temperature sensors of hot-runners or gate bushings, will be meticulously inspected and replaced as necessary, in order to ensure uniform system heat-up. This means all heaters will have the same resistance and all actual values will be accurately measured. The system will be rewired and any damaged plug inserts or plug housings replaced. An electrics test guarantees precise heat-up and control of all heating zones at restart. 

After every overhaul routine, we install the hot side of your injection-moulding tool and then check its functional condition by heating up the manifold and nozzle heating zones and checking for any possible leaks. Once the overhaul is complete, the hot side is returned to you ready for operation. We thus considerably reduce your production downtimes.

Because every hour counts – our TecCenter in Wallau

Our care and maintenance routines offer a high degree of flexibility since we are, of course, aware that every hour counts. In January 2021, we therefore opened our new TecCenter in Wallau’s industrial estate. On more than 1,000 square metres of hall space, the applications-engineering and test center provides an option for carrying out state-of-the-art hot-runner overhauls that save you long production downtimes while simultaneously restoring top preform quality.
Furthermore, at our TecCenter we pursue a number of research projects in regard to applications engineering. Our goal is to continuously improve your injection-moulding process, using MHT tools and their components.

To make sure you benefit from maximised flexibility, we perform any necessary maintenance routines not only in our TecCenter Germany or at our facility in the USA but also at a number of Krones subsidiaries, or right on the spot at your premises. Just get in touch with us!

Performing a small inspection and maintenance yourself

It is not always necessary to send us the hot side of your tool or request one of our service technicians. We offer your employees a tailor-made maintenance training course, so that you will in future be able to perform overhauls yourself. In this training course, we bring your staff up to speed on the basics of hot-runner technology and explain how to safely proceed during basic maintenance routines. Correspondingly, your team will in future be able to take purposeful action for preventing production downtimes.

To many more years to come!

Has your hot side has already clocked up many millions of cycles and countless years in operation? Would you like to restore optimum process stability and top component quality? Then do not hesitate to get in touch with our experts. Our maintenance service is not restricted to hot sides made by MHT. We also raise tools from other vendors to new technical heights.

We will be pleased to provide you not only with active support but also with soundly based advice. Together with you, we perform an analysis identifying the causes for above-average wear and tear, in order to achieve lengthier continuous running times and better product quality.