"Improving our products' quality and the production processes is the strongest driver towards digitalization," said Ingo Specht, managing director of Interroll SA in Sant'Antonino in the Swiss canton of Ticino. For injection molding production, this means smart assistance. Supported by machine manufacturing partner ENGEL, Interroll is further expanding its digital injection molding production worldwide.
Interroll with ENGEL on the way to a self-optimizing machine
Quality — just rely on it
Whether postal services and e-commerce, food and fashion, automotive and industry: As one of the world's leading suppliers of material handling solutions, Interroll ensures an efficient material flow in a wide range of industries. Its products include conveyor rollers, drives for conveyor systems as well as complete conveyors, sorters and flow storage systems. Almost all products contain plastic components.
Interroll Poly-V housing — this designation stands for a two-part component that transfers rotary motion in a key account's transport systems. The two components are produced on ENGEL victory injection molding machines at the company's headquarters in Ticino. The outer of the two round parts is particularly challenging, as it wraps around a ball bearing. On top of this there is the material, which is difficult to process: carbon fiber-reinforced polyamide.
"For a long time, we only injection molded the housing parts ourselves and had the bearings assembled by the customer," reported Production Manager Matteo Tonolla. "But the reject rate was too high."
This prompted the decision to shift the complete process to in-house and invest in a new integrated manufacturing cell. Another benefit for the customer results from the saving of production steps and the reduction of storage capacity for semi-finished components.
The manufacturing cell consists of a tie-bar-less ENGEL victory 120 injection molding machine and an ENGEL viper 12 linear robot. The viper robot takes the bearings off the infeed conveyor and deposits them in the cavities of the 2-cavity mold, where they are overmolded. The same robot removes the plastic-metal hybrid components and deposits them on a conveyor belt.
"The integrated process now ensures that we have stable rotational characteristics," as Piercarlo Balducci, from Technical Sales at Interroll emphasized. "Our focus is firmly on the quality of our products. In addition, we have streamlined the production process by overmolding."
High-quality, complex parts with a high degree of automation in injection molding and the downstream assembly processes are increasingly being produced in-house. The list of machinery in Sant'Antonino is growing.
"When we invest in new machines and equipment, we always have innovative technologies in mind," Specht said.
Smart assistance keeps the process constant
Equipped with smart assistance systems, the new victory 120 injection molding machine for Interroll points the way to the future. In the case of the Interroll Poly-V housings, it is primarily two smart assistants that ensure consistently high injection molding quality: iQ weight control and iQ flow control. For each individual cycle, iQ weight control analyses the pressure profile in the plasticizing screw during injection and compares the measured values with a reference cycle. The injection profile, the switchover point and the holding pressure are automatically adjusted to the current conditions. Readjustment takes place in fractions of a second and does not extend the cycle time. In this way rejects are proactively prevented.
iQ flow control in turn reduces rejects caused by temperature control. In each temperature control circuit, the software actively manages the temperature difference between the feed and return lines.
"Twenty percent of all reject moldings in injection molding production are caused by temperature control errors. This is precisely why smart products such as iQ flow control and iQ weight control belong to ENGEL's development priorities," emphasized Matteo Terragni, man-aging director of the ENGEL subsidiary in Italy, which also serves customers in the Italian-speaking area of Switzerland.
By investing in the new production cell and digital solutions, Interroll has not only shifted the Poly-V housing production process to completely in-house, but also streamlined the process.
"We have substantially reduced the overhead required for quality control," said Tonolla. "The process is now so stable that we can completely eliminate the need for external quality control."
Previously, the quality of each of the 800,000 components per year was manually inspected.
"Making greater use of smart solutions is our goal," said Specht. "We want to eliminate disruptive factors. When we open the door to the production floor, we don't want it to interfere with the process anymore."
"We are moving in the direction of guaranteed process stability through data monitoring on the one hand and a self-optimizing machine on the other," Balducci emphasized. "We don't want to have to check the quality, but rather be able to rely on the production cell to deliver consistently high quality."
Good parts soon after a batch change
iQ weight control compensates for fluctuating production conditions just as reliably as for fluctuations in the raw material. For some products, a certain percentage of recycled material from sprue waste is added, and for some materials there are two or more suppliers. iQ weight control ensures that good parts are produced again soon after a batch change. With the cur-rent volatile supply chains in the polymer sector, this aspect is becoming even more important.
“One ton comes from China, another from America, and 300 kilograms from Switzerland – and yet we have to deliver consistent product quality,” clarified Specht. “This is where, the injection molding machine with smart assistance does a very good job."
A total of 10 injection molding machines are already equipped with iQ weight control. The software was retrofitted on some of them. All new machines are ordered including iQ weight control and iQ flow control. In addition to process consistency, Interroll also has a second focus: energy efficiency.
"The temperature control ratios are now absolutely stable. On the machines equipped with iQ flow control, we can reduce the volume of water required for temperature control to 20% of previous consumption," said Tonolla.
Tie-bar-less technology boosts efficiency
Inspired by efficiency — Interroll's motto is hard to overlook on a visit to the company's head-quarters in Sant‘Antonino. You can see it in several places in large letters on the walls and doors.
Digitalization is an important key to efficient production processes, but not the only one, as Matteo Tonolla explained.
"We prefer to use tie-bar-less injection molding machines because they help us set up far faster," he said.
Product variance is high. On top of this, Interroll's customers have reduced their storage capacity, which means batch sizes are dropping.
"2019 was our record year. We had 4,200 mold set-ups on this site in that year," Tonolla reported.
In the meantime, this figure has leveled off at 2,500, but the challenge of faster mold set-up is still huge. On average, it takes the mold setters 23 minutes to set up a new victory machine with a barrier-free clamping unit. Compared with this, mold set-up on a tie-bar machine takes an average of 72 minutes at Interroll.
Another benefit of the tie-bar-less clamping unit: large molds can be mounted on relatively small injection molding machines. Given the increasing production volume that many Interroll products are currently experiencing, this simplifies the scale-up. For the Poly-V housing, too, a 4-cavity mold will soon be replacing the 2-cavity mold. Thanks to tie-bar-less technology, this component can still be produced on the 120 ton machine.
People are still the most important quality factor
"We are pursuing a clear strategy of growth and are looking around for new lines of business," said Specht.
New production plants are being established in the USA and China.
"We regularly evaluate which components we want to shift to in-house production. The decisive factors are the part complexity and the quantities,” he said.
Sant'Antonino remains the competence center for injection molding technology. Research and development for polymer materials are located there, and it is there that the production strategy decisions for plastic components are made and practiced.
"In ENGEL, we have a machine manufacturing partner who also supports us in the USA and China," said Specht.
Even though the product range varies from location to location, Interroll relies on standardized production technology worldwide, and that means tie-bar-less injection molding machines with smart assistance that are increasingly networked with each other. To this end, Interroll relies on solutions from ENGEL daughter company TIG.
"You get information that was previously inaccessible and are automatically notified if there are problems," said Specht, summing up one benefit of digitalization; he goes on to emphasize: "Having said this, it is still the human being who is responsible for quality. In the future, too, quality, and with it success, will depend on the skills of the people in production. They are the ones who set the limits for the systems. Whereas employees used to measure the product, it is now their job to configure the machines correctly."