Ultrasound-based detection of flow fronts in injection molds

Ultrasound-based detection of flow fronts in injection molds

In this paper, we describe a new method for dynamic detection of flow fronts in injection molds using ultrasonic sensors.
The Injection molding is a widely used process for manufacturing plastic parts. In this process, liquid plastic is injected into a mold (the injection mold) and transformed into a solid form by cooling and solidification.

The quality of the injection molding process depends largely on the filling process and on the ability to produce a uniform flow front of the plastic in the mold.

An uneven flow front can lead to weak spots in the material, undesirable weld lines and rejected parts, which in turn reduces the profit when selling the end product.

MoldFront with cable

Flow front detection challenges:

The detection of flow fronts in injection molds is a complex task.

An uneven flow front can be caused by these different influences:

  • Changes in material properties
  • Tool design
  • Changes in the injection molding process

So far, there are various approaches for flow front detection, such as optical sensors, pressure sensors or temperature sensors. However, these methods have certain disadvantages, such as sensitivity to abrasive materials or limited dynamics.

A promising alternative to this is non-contact measurement using ultrasonic sensor technology.

How ultrasound-based flow front detection works:

Ultrasound-based flow front detection is based on the permanent emission of ultrasonic pulses in the direction of the cavity during the injection molding process.

With an empty cavity, 100 % of the ultrasonic energy is reflected at the steel/air interface. If the plastic now hits the measuring point, part of the ultrasonic energy is coupled into the plastic and precisely this difference is subsequently detected by the MoldFront sensor system.

Moldfront Assembly Machine Tool

MoldFront electronics unit mounted on an injection molding machine

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Advantages of ultrasound-based flow front detection

Ultrasound-based flow front detection offers several advantages over other methods:

  • Die Methode erfasst dynamisch und in Echtzeit Veränderungen der Fließfront, was eine schnelle Reaktionszeit im Bereich von < 5 Millisekunden ermöglicht.
  • The method is robust against external influences such as abrasive media, high spray pressures or humidity.
  • The method is independent of material and tool design and can therefore be applied to a wide range of applications.
  • The method allows non-contact measurement at many different points in the mold, resulting in a high degree of design freedom.

Comparison MoldFront flow front detection and pressure sensor technology

The use of pressure sensor technology is a common method for pressure measurement as well as detection of flow fronts in industry.

The MoldFront ultrasonic sensor technology can be used analogously. While the pressure sensor system measures the increase in pressure in the cavity in order to detect the flow front, the MoldFront ultrasonic sensor system uses density changes in the cavity. This accurately detects whether the steel/air or steel/plastic interface exists at the measurement point. This works equally well for other metals, such as aluminum or copper.

Comparison MoldFront Pressure Sensor Tool
From the measurement data in the graph shown, it is clear that the Flow front detected cyclically, reliably and dynamically will.

The great advantage of ultrasonic flow front detection is thus the possibility of measuring the flow front independently of the pressure conditions in the cavity. This means that no response pressure is required and the restriction to a predefined maximum pressure is also eliminated.

In addition, due to the non-invasive or non-contact measurement, ultrasonic flow front detection can also be used with abrasive media or vacuum applications without any problems.

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Difference between structure-borne sound and directly measuring ultrasonic sensor technology

Difference between structure-borne sound and directly measuring ultrasonic sensor technology

In this article you will learn what exactly is the difference between structure-borne sound systems and directly measuring ultrasonic sensor technology.

Injection molds are essential for the production of plastic parts. This is a process in which plastic granules are injected into a mold, which is then formed under high pressure and temperature. To ensure that the process works properly, sensors are required to measure important quality parameters during the filling process.

In the injection molding industry, there are two main types of sound sensors: Structure-borne sound sensors and direct-measurement ultrasonic sensors. Although both are used for monitoring the injection molding process, they differ in their operation and application.

In this article, the difference between structure-borne sound sensors and direct-measurement ultrasonic sensors in injection molds will be explained in more detail.

Structure-borne sound sensors

Structure-borne sound sensors are used to measure vibrations in the injection mold. They are usually attached to the mold frame or other structural elements of the mold and detect vibrations that occur during the injection molding process. These vibrations are an indicator of the functioning of the mold and can thus be used, for example, for the

  • Condition-based maintenance of tools
  • Tool damage detection
  • or the tool qualification

be used.

This means that the structure-borne sound waves, which change as a function of the tool vibrations that occur, are interpreted and assigned to specific damage categories.

Structure-borne sound sensors can operate in several ways, including piezoelectric sensors, accelerometers, and laser Doppler vibrometers. Piezoelectric sensors convert vibrations into electrical signals, while accelerometers measure acceleration caused by tool vibrations. Laser Doppler vibrometers, on the other hand, measure the speed of tool vibrations by observing laser light, directing a laser beam at the surface and then analyzing the reflected radiation.

Direct measuring ultrasonic sensors (Moldsonics Sensorik)

Direct-measurement ultrasonic sensors are used to measure quality parameters directly on the injection molded part, i.e. directly on the resulting product.

They are usually placed at critical and quality-relevant positions in the injection mold and record a characteristic ultrasonic response curve of the injection and holding pressure process.

Curve-MoldUni-Comparison-Koerperschall-en

Characteristic ultrasonic response curve when using directly measuring ultrasonic sensor technology

Curve-MoldUni-Comparison-Koerperschall-en

Characteristic ultrasonic response curve when using directly measuring ultrasonic sensor technology

The mode of operation is based on the permanent emission of ultrasonic waves and the analysis of the reflected waves. These sensors use the piezoelectric effect to generate electrical signals when they are loaded by electrical voltage and, conversely, to generate sound waves when they receive electrical current.

The ultrasonic waves emitted by the sensors are reflected by the cavity wall and the plastic melt to be measured and return to the sensor. Based on the time it takes for the ultrasonic waves to return and the intensity of the reflected ultrasonic pulse, the sensor can determine a wide variety of quality-related parameters. These include:

  • The flow front detection, i.e. when the melt front reaches the sensor position
  • The velocity of the melt flowing by
  • The solidification rate of the cooling plastic material
  • The shrinkage of the plastic component from the cavity wall
  • The thermal equilibrium of the injection mold

The use of this direct measuring ultrasonic sensor technology in the injection molding industry is completely new. To date, the measurement of a characteristic ultrasonic response curve can only be achieved with Moldsonics' sensor technology and is therefore unique.

The use of this sensor technology is not limited to individual industries and is currently already being used in a wide variety of industries, including the medical industry, the automotive industry, the food industry and the toy industry, to name just a few.

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Application example Haidlmair and Moldsonics

Application example Haidlmair and Moldsonics

Haidlmair mold and Moldsonics sensors - a perfect match.

This application example illustrates how you can use the MoldUni sensor system in practice.

Moldsonics MoldUni on Haidlmair Mold at K2022

At this year's K2022 in Düsseldorf, Haidlmair and Moldsonics presented their latest innovation: the Sixpack mold, which uses ultrasonic sensor technology to continuously monitor the quality of its components.

One of the most important features of this mold is the use of the FDU (Flat Die Unit) as a hot runner system. This enables high-precision temperature control and faster cycle times, resulting in higher quality components.

An additional highlight is the integration of MoldUni sensor technology. The integration of ultrasonic sensors allows users to monitor and document the production process in real time without having contact with the melt, making sensor marks or leaks a thing of the past. This allows manufacturers to quickly identify problems and take corrective action to ensure each part meets the highest quality standards.

"Moldsonics' ultrasound-based sensor technology offers us completely new possibilities for analyzing processes in our filling operations and thus improving our tools."

Lukas WAGNER

Head of Advanced Simulations,HAIDLMAIR GmbH

In addition to advanced sensor technology, the mold is also a mix of conventional and 3D-printed components. This allows greater design flexibility in the construction and shorter cycle times as well as higher efficiency in the injection molding process.

Overall, the Sixpack mold is an innovative example of how sensor technology and advanced manufacturing techniques can be combined to create high-quality components with improved monitoring and shorter production times.

We are excited to see in which exciting projects these two innovations can still be combined and are looking forward to the applications still to come.

We have summarized everything in detail in one article:

Any questions?

That was the K2022!

That was the K2022!

K2022 in Düsseldorf, which is the leading trade show for the plastics and rubber industry, was a great success for the industry this year. Over 176,000 trade visitors from all continents traveled to the event, which was held at the Düsseldorf Exhibition Center. The trade visitors came from 157 different nations, and the show was a great opportunity for companies in the plastics and rubber industry to showcase their latest products and innovations.

Moldsonics as exhibitor for the first time at K

We at Moldsonics were one of the many exhibitors at K2022 and were pleased to showcase our latest ultrasonic sensor systems MoldFront and MoldUni, which are designed to increase accuracy and efficiency of the manufacturing process in the plastics and rubber industry. The sensor system is able to detect the smallest variations in the manufacturing process, which allows for better control and more consistent results. All parameters, which go far beyond pressure and temperature sensing, can be measured without coming into contact with the melt.

To demonstrate the many possibilities of our sensor system, we had set up a measurement case at our booth. Visitors to the show were able to see the system live in action, and many of them were impressed by its resolution accuracy and the new measurement possibilities. In addition to our own booth, our sensor system was also in operation at three partner booths so that even more visitors could see it in operation.

K2022 demonstrator
IMG 5190 scaled Moldsonics K2022
IMG 5192 scaled Moldsonics K2022

The K2022 trade show was an excellent opportunity for us to make valuable contacts in the plastics and rubber industry. We had many interesting discussions with potential customers, were able to network with other companies and find out about the latest developments in the industry. We are convinced that the contacts we made at the trade show will be of great benefit to our company in the future and we are very excited about the upcoming cooperations.

Overall, the K2022 trade show was a fantastic experience for our company. We were able to present our new sensor system to a large and diverse audience and made many valuable contacts in the plastics and rubber industry. We are already looking forward to the next show and hope to be part of this important and innovative industry event in the future.

K2022 - Official Press Release

K2022 - Official Press Release

K2022 - Trade fair results fulfill highest expectations

Innovation driver for the global plastics and rubber industry

Multitude of concrete solutions, machines and products for the transformation towards a circular economy

Another life for plastic. Because we care.

The joy of the plastics and rubber industry at finally being able to exchange ideas in person on a global level again after three years characterised K2022 Düsseldorf and ensured an excellent mood among the 3,037 exhibitors. The companies reported extraordinarily good leads and a marked willingness to invest among trade visitors, mentioning promising new customer relations and the conclusion of numerous, in part, spontaneous business deals.

"K in Düsseldorf has once again fulfilled highest expectations. It continues to be the most international, complete and innovative trade fair of the global plastics and rubber industry," says Erhard Wienkamp, Managing Director at Messe Düsseldorf, delighting at the good results and adding: "The trade fair has impressively demonstrated just how valuable face-to-face networking, chance meetings and physical brand and product experiences are. We are very satisfied to see that K2022 succeeded in sending out strong signals as an innovation driver of the industry and that our exhibitors did business with a high number of international customers with great decision-making powers."

176,000 trade visitors from all continents traveled to their most relevant sectoral event in Düsseldorf. At over 70% the proportion of international guests at K2022 remained at a constantly high level.

The verdict from Ulrich Reifenhäuser, Chairman of the Exhibitor Advisory Board at K2022, is also very positive: "After hardly any trade fairs could take place worldwide also on a national level over the past three years, K2022 was all the more eagerly anticipated as the world's No. 1 trade fair of the plastics and rubber industry and succeeded in providing fresh impetus in all sectors of our industry. The many, in part, unexpected concrete contract negotiations held at the trade fair speak for themselves!"

The current unpredictability and uncertainty of events does make for a tight situation in the sector overall, but this did not do any harm to exhibitor commitment and visitor interest, quite on the opposite: "Especially now in turbulent times and where the plastics industry is undergoing transformation towards the circular economy K2022 was the ideal place to jointly and actively chart the course for the future," sums up Ulrich Reifenhäuser.

It was especially the wealth of new technology developments that raw materials producers, machine manufacturers and plastics processors presented for implementing the circular economy, resource conservation and climate protection that thrilled the trade visitors. Commenting on this Ulrich Reifenhäuser says: "It can be clearly felt that all companies have embraced the need to take on social responsibility and think about plastics in a sustainable way from the beginning of the process chain. The variety of solutions, machinery and products for transformation towards a circular economy presented at K2022 was incredible."

The trade visitors at this year's K travelled from 157 nations to the Rhine. Next to Germany, those European countries strongly represented on the visitors' part included the Netherlands, Italy, Turkey, France, Belgium, Poland and Spain. With 42% of visitors coming from overseas, the reach of K is as high as usual among the international trade audience. While visitors from the East Asian region, in particular, were less well represented than at K three years ago due to the currently more difficult conditions in those countries on account of quarantine regulations, numerous visitors from the USA, Brazil and India were welcomed at K2022.

For around two thirds of all visitors polled machinery and plant construction ranked first in terms of interest. 57% and, hence 5% more than at K 2019, said they were interested in raw and auxiliary materials, with recyclates and bioplastics being particularly popular. For 28% semi-finished products and technical parts made of plastics and rubber were the main reason for coming (multiple responses possible). Over 70% of all visitors come from top and middle management.

Top marks were given by visitors to K2022 for the completeness of its ranges and its mapping of the entire supply chain. 98% of all professionals stated they had fully achieved the goals associated with their visit.

During the eight trade fair days it became clear that this year's K was right on target with its selection of hot topics, circular economy, climate protection and digitalization. In terms of investment intentions, machinery and equipment for processing and recycling stood out at 43%. The focus was particularly on sustainability, but also on circular economy and energy/resource efficiency in production. Around 40% of decision-makers said they were looking into the topic of decarbonization.

The K specials, which also focused on the three hot topics, were also very well received. The official special show, 'Plastics Shape the Future', focused on the economic, social and ecological challenges and potential solutions around the K guiding themes in high-calibre discussions and lectures, and this show was well attended throughout. The Circular Economy Forum, where the VDMA and 13 of its member companies impressively demonstrated the importance of technology in the implementation of the circular economy in the plastics industry, scored points with the international audience with live demonstrations and a great deal of well-founded knowledge as well as detailed information on the topic.

At this year's K in Düsseldorf, there was also a lot of discussion about the global production language, OPC UA. This standard allows the processing parameters of the machinery and equipment involved to be coordinated more precisely and in a more targeted manner. This, in turn, is considered an important prerequisite for optimised circular management. 40 companies from eight countries participated in an OPC UA demonstration project at the trade fair.

At the Science Campus both exhibitors and visitors at K2022 were provided with a condensed overview of scientific activities and findings in the plastics and rubber sector. Numerous universities, institutes and funding bodies offered opportunities for direct dialogue here.

The offer of the Plastics Training Initiative (KAI) was used by many pupils, trainees and students to gather information on the job profiles and career opportunities in the plastics industry.

The next K Düsseldorf will be held from 8 to 15 October 2025.

Moldsonics on the K2022

Moldsonics on the K2022

Founder photo Moldsonics GmbH with the three founders

70 years of K in Düsseldorf - a reason to celebrate! We are taking advantage of this anniversary and are represented at the trade fair for the first time with our own Moldsonics booth.

K is considered the world's No. 1 trade show for the plastics and rubber industry. The developments and innovations shown there set the course for a responsible future in which plastics are an important part of the solution. Thus, the three leading themes of K 2022 are also Circular Economy, Climate Protection and Digitalization.

We from Moldsonics will present our new products at the anniversary fair. Among other things, we will present our just released product MoldFront and our next planned solutions.

Click here for an overview of our currently offered products:

Visit us at the booth 12D36-05 in hall 12 and talk to us about the latest developments in ultrasonic sensor technology!

We are looking forward to your visit!

Fair K2022 in Düsseldorf

Date: 19 - 26 October 2022

Place: D-40474 Düsseldorf, Am Staad (Stockumer Höfe)

Location: Hall 12 / D36-05

 

General information on how to get there can be found here: Arrival K2022

 

k2022 plan Moldsonics