High-end machining places high quality demands on tools and tool clamping Milling at the limit

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Präwest in Bremen (Germany) and Prae-Aero in Schwanewede (Germany) are sister companies dedicated to sophisticated machining—particularly in the five-axis sector for aerospace and industry. What sets them apart is their commitment to achieving the highest quality in components; they develop and grind their own carbide and HSS (high-speed steel) milling cutters. These are clamped in shrink fit holders from Haimer, of which the two companies together use around 12,000 units. This integrated approach of creating and using specialized tools tailored to their specific needs allows them to maintain control over the quality and precision of their machining processes, crucial for the demanding sectors they serve.

Structural components for the aerospace industry, impellers, blisks, turbine blades and casings, as well as parts for the industrial sector such as compressor wheels, rotor disks, integral wheels, prototype blisks, etc.—the range supplied by Präwest is broad and consistently demanding in terms of geometry and materials. The contract manufacturer mills, turns, and grinds materials such as aluminum, titanium, and nickel-based alloys, along with stainless and heat-resistant steels. This diverse capability allows Präwest to meet the high standards required by the aerospace and industrial sectors, where precision and material integrity are critical for the performance and safety of the components. Their expertise in handling a variety of high-performance materials is a testament to their technical proficiency and commitment to quality, positioning them as a crucial partner for manufacturing complex, high-specification parts.

High-tech machinists have relied on 5-axis simultaneous milling since 1986

Since 1986, the high-tech machinists from Bremen began utilizing 5-axis simultaneous milling, a technology that now counts among their production focuses and is used for components up to a diameter of 2500 mm and a weight of up to 15 tons. For this purpose, their production halls are equipped with 77 five-axis milling machines and 20 also five-axis mill-turn machines, in addition to several 4- and 3-axis CNC machines. Many of these machines are automated with loading/unloading systems or robots. This substantial investment in advanced manufacturing technology and automation underscores their capacity to handle large-scale and complex production tasks with high precision and efficiency. The automation not only enhances productivity but also improves the consistency and quality of the parts produced, meeting the stringent demands of industries such as aerospace where precision is paramount. This technological edge facilitates the production of sophisticated components on a large scale, reinforcing their position as industry leaders in precision machining.

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Milling tools from our own production

To efficiently produce complex components with the highest quality, Präwest leverages its in-house tool development and manufacturing capabilities. Christian Hoppe is in charge of this sector. He is responsible for the development, grinding, and testing of the company's own carbide (HM) and high-speed steel (HSS) tools. Additionally, he oversees the procurement of third-party manufactured tools and tool holders, as well as the pre-setting of tools. This strategic focus on in-house tool management ensures that Präwest maintains tight control over the quality and performance of the tools used in their manufacturing processes. By developing and optimizing their own tools, they can tailor tool designs specifically to the unique needs of their production tasks and materials, resulting in better machining outcomes. Moreover, the ability to test and refine tools within their own facilities accelerates innovation and adaptation to new challenges, enhancing both the efficiency and flexibility of their operations. Christian Hoppe’s role is crucial as it bridges the gap between tool development and actual production needs, ensuring that the manufacturing processes are supported by the best possible tooling solutions. This integration of tooling expertise within the company helps Präwest maintain its commitment to delivering premium quality and maintaining competitiveness in the high-precision manufacturing market.

"Our own tools are crucial for us," emphasizes the qualified mechanical engineer. "With them, we can respond to the very specific requirements of customer workpieces and ensure high process reliability. Moreover, it's in our hands to always have a sufficient stock of the necessary tools in-house." This is particularly important for orders from the aerospace industry, where every manufacturing process, including the tools used, must be precisely defined and approved. This approach not only enhances the flexibility and responsiveness of Präwest to meet specialized demands but also ensures compliance with the stringent regulatory standards typical in aerospace manufacturing. By maintaining direct control over tool production and inventory, Präwest minimizes potential delays that could arise from external supplier dependencies, ensuring that production can proceed smoothly and according to schedule. Furthermore, having an internal development and fabrication of tools allows Präwest to continuously innovate and improve their tooling solutions based on real production experiences and challenges. This continual improvement cycle not only boosts the quality of the components they produce but also contributes to overall operational efficiency and cost-effectiveness, solidifying their competitive edge in a demanding industry.

Christian Hoppe points out further advantages: "Due to our own production, our tools are significantly more cost-effective than those purchased externally. Additionally, we can design the tools specifically for the application. What is a special tool for others, is standard for us."

The result: Präwest does not have to compromise with standard off-the-shelf tools or even order expensive custom solutions with long delivery times. Overall, the company achieves shorter processing times, which is a significant economic factor given the high hourly rates of high-tech machines.

Small component with a big impact: the tool holder

For economical, process-reliable machining as well as perfect results in terms of precision and surface quality, not only the tools matter, but also the tool holder.

For Christian Hoppe, it's clear: "In over 90 percent of cases, shrink fit technology is our first choice. It allows us to achieve fast tool changes and a very high power transmission." He points out that the slim design of the holders and the ability to use extensions enable the use of short tools, which reduces unwanted vibrations.

"When I joined Präwest in 2007, we had shrink fit holders and shrink machines from various suppliers," recalls Christian Hoppe. "However, we saw significant potential for improvement in their quality." In search of alternatives, the machining experts eventually found a promising partner in Haimer GmbH, based in Igenhausen (Germany). "Haimer is the leading manufacturer of shrink fit technology and thus exactly the right supplier for us. Of course, we have repeatedly tested other suppliers over the years. But they have never come close to the quality and performance of Haimer products." This testimony highlights the importance of choosing the right partners in manufacturing, especially when high precision and reliability are essential. Haimer’s specialization in shrink fit technology likely offers products that efficiently meet the specific demands of Präwest’s high-precision machining tasks. This enduring partnership underscores the value of sustained quality and performance in the components crucial for sophisticated manufacturing operations. Choosing Haimer products appears to align with Präwest’s commitment to maintaining high standards in their production processes.

Shrinking of HSS tool shanks up to 50 mm diameter

Lars Rose (Technical Sales Representative, Haimer): "The key that opened the door in 2009 was our most powerful shrink fit machine at the time, the Power Clamp with a 20-kW coil, which was the only one on the market capable of securely shrinking HSS tool shanks up to 50 mm." Christian Hoppe agrees and adds, "This Haimer shrink fit machine brought us a significant improvement, especially in terms of shrinking HSS tools." This statement underscores the crucial role innovative technology plays in enhancing operational capabilities within the precision machining industry. The ability of the Power Clamp machine to handle larger HSS tool shanks not only provided Präwest with a technological advantage but also increased efficiency and reliability in their machining processes. This technology asset helped Präwest meet more diverse and challenging customer requirements, reflecting the importance of continuous technological advancements in maintaining industry competitiveness.

Hundreds of shrink processes per shift and device

Convinced of the quality, Christian Hoppe gradually equipped Präwest and its sister companies with shrink machines as well as shrink holders—including the low-vibration Power Shrink Chucks, the Heavy Duty Shrink Chucks for heavy-duty machining, and the Mini Shrink Chucks, all from the same manufacturer mentioned above.

These extremely slim shrink fit chucks are primarily needed in the industrial sector, where milling is required in the channels beneath the blade on closed wheels.

Christian Hoppe explains: "We sometimes need 600 mm (approx. 23,62 inches) or more in protrusion length, which we achieve with multiple extensions. Despite the required length, the overall tool needs to be slim and have good concentricity, which we accomplish with the Mini Shrink Chucks."

Around 7,000 shrink fit chucks from Haimer are currently in circulation at Präwest. "Despite the many shrinking operations, the clamping force remains high," confirms Christian Hoppe, which he believes is due to the high-quality material and tight tolerances.

"We have never found that a Haimer product falls short in quality," says the head of tooling. "This is particularly important in our series production, where we have an extremely high tool consumption and accordingly need to perform hundreds of shrinking operations per shift and device. The shrink machine must be easy to use and the quality of the shrink chucks consistently high." This statement highlights the critical importance of reliability and usability in high-volume manufacturing environments like those at Präwest. High consistency in tool quality is vital for maintaining productivity and efficiency, especially when the production process involves extensive use of tools and frequent tool changes. Reliable and user-friendly equipment minimizes downtime and maintenance issues, thereby supporting continuous production cycles and ensuring that high standards of output are maintained without interruption. This reliability, coupled with ease of use, directly contributes to optimizing operational workflows and reducing potential for error—key factors in maintaining competitive advantage in precision manufacturing industries.

Special holders with vibration-damping carbide core

Over the years, a strong partnership developed, which even resulted in joint product improvements: for example, special chucks with a carbide core that acts as a vibration damper. The extremely effective cooling system, Cool Flash, available for shrink fittings, also originated at Präwest. This further development of the Cool Jet System allows the coolant lubricant to exit through multiple slits, slide along the mill shank into the flute, and up to the cutting edge of the tool—this is particularly effective in high-speed machining. These advancements illustrate the importance of collaboration between manufacturers and their suppliers in driving innovation. By working together, Präwest and Haimer have been able to develop specialized solutions that not only meet the unique needs of Präwest's production processes but also contribute to the broader field of precision machining technology. This collaborative approach ensures that both companies stay at the forefront of technological advancements, enhancing their offerings and providing value-added solutions to their customers.

In addition to shrink fit holders, the machining specialists at Präwest also use collet chucks and special grinding wheel holders from the clamping technology specialist, which they fine-balance on a Tool Dynamic TD Comfort balancing machine. According to Christian Hoppe, this machine is easier to operate than other similar devices available at the plant.

Präwest also uses the modular Duo-Lock system from the clamping tool manufacturer. The patented interface between the carbide milling head and the HSS holder guarantees maximum stability and load capacity through a unique threaded design with a double cone.

Christian Hoppe: "This modular tool system is doubly efficient for us. We save on carbide with the interchangeable head, and since we calibrate the tools in the machine in the aerospace sector, we can swap the Duo-Lock heads directly in the machine. This means we additionally save on the shrinking process and thus time."

Prae-Aero: Focus on machining components for aircraft engines.

Präwest is a dynamic company that has continuously evolved over the years. To avoid becoming too large, various areas were spun off. For example, Prae-Aero GmbH & Co. KG was established in Schwanewede in 2014.

Prae-Aero, while economically independent from Präwest, is managed by the same shareholders and executive leadership. Additionally, its offerings—though not identical—are similar in some aspects to those of Präwest. Prae-Aero's operations manager, Tobias Barthels, explains: "We are a contract manufacturer that specializes entirely in the machining of components for aircraft engines. We produce engine blades, rings, casings, but also smaller attachments such as brackets or adapter flanges." This specialization highlights the niche expertise of Prae-Aero in the aerospace industry, focusing on high-precision components essential for the functionality and safety of aircraft engines. By concentrating on this specific segment, Prae-Aero can ensure deep technical proficiency and high-quality production standards, which are critical in the aerospace sector due to the high demands for reliability and compliance with stringent regulatory standards.

Tobias Barthels cites as a strength of his company that "we can develop the processes for manufacturing customer components from A to Z ourselves. This includes making our own milling tools, five-axis machining, and at the end of the production chain, the fluorescent penetrant inspection method."

Shrink fit technology ensures high productivity and flexibility

Prae-Aero benefits extensively from the experiences gained at Präwest. This also applies personally to Tobias Barthels, who worked there as a machining mechanic for many years: "I was able to learn five-axis milling to perfection at Präwest. I am also very familiar with Haimer products from that time."

The current industrial foreman for metal appreciates their quality and the wide range offered: "We use Haimer shrink-fit chucks on all machines in various types and sizes. Since we often work with sister tools, we have a high circulating inventory of around 5000 units, allowing us to equip the tools externally in advance and ensure a smooth workflow in production." This approach not only optimizes efficiency but also minimizes downtime during the manufacturing process. By pre-setting tools externally and maintaining a large inventory, Prae-Aero can quickly swap out tooling as needed without significant interruptions to their operations, enhancing their overall productivity and responsiveness to production demands. This system is a testament to the importance of effective tool management in high-volume, precision manufacturing environments.

The components manufactured at Prae-Aero are almost all complex, each in its own way. Some are thin-walled and difficult to clamp, while others have highly complex geometries with complicated freeform surfaces.

Roughness of Rz = 1.0 µm and even lower

"The quality requirements for the components are always extremely high, as is standard in the aerospace industry," says Tobias Barthels. The tolerances to be maintained range from a few hundredths of a millimeter to just a few microns. According to Operations Manager Barthels, the requirements for surface finishes are also becoming increasingly demanding: "Depending on the application in the engine, roughness values of Rz = 1.0 µm and even less can be required. However, with our state-of-the-art machine park and our own tools in combination with Haimer holders, we are well equipped to meet these challenges. The runout accuracy of the Haimer holders or special features like Cool-Jet and Cool-Flash ensure high productivity and flexibility, and contribute significantly to consistent quality." This statement highlights the critical role that precise tooling and advanced machinery play in meeting the exacting standards of the aerospace industry. The ability to maintain such tight tolerances and achieve fine surface finishes is essential for producing components that can perform reliably under the rigorous conditions of aircraft engine operation. By investing in high-quality tool holders and innovative features that improve tool life and performance, Prae-Aero enhances its manufacturing capabilities and maintains the high standards required by its clients in the aerospace sector.

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