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apra-plast sees itself as a solution provider for housings, cladding and parts of all kinds. The systems with which the company manufactures its products are just as individual as the products themselves. Special know-how is therefore also required here. This is why the company has relied on MiniTec as a partner and special machine manufacturer for many years - including for a semi-automatic groove milling system.
Manufacturing plastic housings, with round or square edges, with large or small radii - that is apra-plast's core competence. The company, based in Daun-Pützborn in the Eifel region, is part of the apra-group, which employs a total of around 470 people at several locations, 85 of whom work at apra-plast. According to Managing Director Jürgen Könen, individuality is the trump card for the products: “We don't have any standard items, but manufacture the enclosures individually according to the customer's requirements.
Wherever plastic enclosures or cladding are needed in small to medium quantities, we are the right partner - also because we usually manage without tooling costs.” The enclosures are used in a wide range of applications, from cladding for dental laboratory milling machines to display housings, airline ticket readers, Tens or EEG devices and measuring devices of all kinds. In many cases, they are also required for control or operating units for systems or devices.
The apra-plast enclosures are used in a wide variety of areas.
Different production techniques
Depending on the requirements, thermoforming or vacuum casting can also be used in addition to milling/bending technology. 3D printing also plays an important role. One advantage of milling/bending technology is that it does not require any tooling costs. Here, the housings are manufactured from a plastic sheet using various processing steps. Accordingly, it offers a high degree of flexibility, especially for smaller quantities, variant production or when different printing is required - from which apra-plast's customers benefit.
However, the company is not limited to this, says Könen: “With thermoforming technology, 3D printing and vacuum casting, we have other production technologies that we also use in combination for our customers' solutions. Through our parent company, apranorm, we can also offer metal components such as mounting plates, base plates, rear panels, stiffening profiles and the like.”
Many years of cooperation with MiniTec
MiniTec has already built numerous systems that are used in apra-plast's production. “We have been working together for over ten years,” says Könen. He adds: “This has involved a wide variety of projects, such as a grooving/milling system, an automatic bending unit and currently a heating unit for our round bending technology, which we are developing together.”
There are always new approaches for new systems, as there are no off-the-shelf machines for the special requirements, he says. “We have a very individual production method and therefore the machines and tools are almost all in-house developments or special parts.”
Slot-milling unit for housing machining
An interesting example of such an automation solution from MiniTec is the aforementioned groove milling unit. The task of this machine is to mill a precise groove in plastic sheets that corresponds exactly to the specifications for the respective component in terms of width, depth and length. The groove can later be used, for example, to specify the bending line for a housing part - i.e. the line along which the component is bent in the next work step. apra-plast had already been using a system for this task for a long time. There were increasing problems with the procurement of spare parts.
Above all, however, the machine was very outdated in terms of performance and capabilities. All adjustment options, for example, were still carried out manually. “We knew that completely different speeds can now be achieved, so we were hoping for more automation and therefore a higher throughput from a new system,” explains the Managing Director.
Concept study as a template
apra-plast initially commissioned two students from Kaiserslautern University of Applied Sciences to produce a rough draft of such a machine, as a kind of project work. A corresponding system was later to be realized on this basis. The search for a suitable partner quickly led to MiniTec. A requirements profile was derived from the concept, which MiniTec then used to design, construct and build the new machine, including the control system.
When inserting the components, a stop ensures their precise alignment.
The housing for the control system naturally came from the apra group - specifically from apra-Gerätebau, as it was a metal control cabinet. The control element for entering the key data and travel paths was supplied by apra-plast itself. After acceptance at the MiniTec factory, the machine was delivered. According to Könen, the system was stable right from the start: “Apart from a few fine adjustments, everything was fine straight away, and it is still running successfully today, after around five years.”
Two different grooving cutters can be mounted in the system at the same time.
NC approach saves on tool changes
The groove milling machine from MiniTec is an NC system. “We have different shape geometries as groove cutters that are required over the entire component length. On the system, we can use a wide variety of groove cutters on two drive units in order to reflect these profile contours in the material. For example, we have a bending groove cutter that produces a 90 degree groove, which has to be very sharp and free of burrs and chips,” explains Könen. The system also has locking or fastening systems where grooving cutters can be used in combination with different tools.
In principle, the whole thing could also be realized with a CNC machine, but this would then have to have two to three tools in use. “This gives us the advantage of being able to complete the task with a special slot milling cutter in just one operation and with much higher feed rates,” he adds. The MiniTec system works semi-automatically. An employee sets up the machine by fitting the appropriate grooving cutter. There are two drive units, which means he can mount up to two different grooving cutters on the machine. He then sets the depth and the stops using the control unit. He then places the components in the stack and starts the machine. The parts are then fed into the machine, processed and come out on the reverse side. At the end, the employee removes the finished parts and places them on a stacking trolley.
Numerous improvements
As part of the introduction of the new system, set-up times were optimized and there were also improvements in the area of chip extraction. Könen explains further improvements: “Today we can use a larger part cross-section and thicker material can also be processed. The old system could process material up to 3 mm, now we can go up to 8 mm. The old system was also completely manual. Today, everything can be entered electronically, which ensures greater precision and also significantly minimizes set-up times.”
Faster throughput
Order processing is significantly faster with the MiniTec system than before. The throughput is heavily dependent on the part size, says the Managing Director: “The machine has a certain feed rate, which ultimately determines the cycle time. But there are components with a length of 100 mm and those that measure 600 mm. And this results in different cycle times.”
Advantage of MiniTec
In addition to MiniTec's engineering expertise, the apra-plast boss also praises the advantages of the modular profile system: “Because our systems are really individual pieces, the profile design makes us very flexible and we can make changes or further optimizations relatively quickly.” Accordingly, he is positive about further system projects with MiniTec: “We basically only have individual machines that were built especially for us. And there will always be applications in the future where we need special solutions. We will certainly rely on MiniTec again as a reliable partner.”
For apra-plast Managing Director Jürgen Könen, the groove-milling system offers many advantages.
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