Precision Cylindrical and Surface Grinding with Kehren RI Machines

Advantages of Kehren RI Machines

• Cylindrical and surface grinding in a single setup
• High dimensional accuracy and repeatable quality
• Suitable for large and heavy workpieces
• Integrated in-process measurement control
• Flexible deployment for small and large production runs

Technical information about the Kehren RI 12-4

Capacity: Ø1500 x 950 mm
Operations:

• Vertical grinding
• Internal cylindrical grinding
• External cylindrical grinding
• Coordinate grinding

Technical information about the Kehren RI 8-4

Capaciteit: Ø1200 x 700 mm
Operations:

• Vertical grinding
• Internal cylindrical grinding
• External cylindrical grinding
• Coordinate grinding
• Hard turning

From the Legal World to Entrepreneurship

Interestingly, his career didn’t begin in the metal industry, but in the legal world. After earning his law degree, Marc worked for several years as a lawyer at various organizations, but he felt something was missing, something tangible.

“In the legal world, I missed the direct impact of my work. You give advice, draft documents, and conduct analyses, but the results often remain abstract. I wanted to build things. Make decisions. Be an entrepreneur.”

The family business continued to draw him in, not out of a sense of obligation, but out of conviction.

“At De Rooy, I could do everything: from finance and process improvement to contributing ideas on strategy. You’re involved in everything and see immediately what your efforts yield. That tangibility, that sense of building something together, really appealed to me.”

Strategic decisions that made a difference

In addition to securing facilities, strategically important decisions were also made. One of these was the decision to start milling in 2011, in addition to grinding.

“We were outsourcing more and more milling work. At some point, you have to ask yourself: why don’t we do it ourselves? That turned out to be a game-changer.”

A clear course was also set in the area of quality. The purchase of a large measuring machine made unique measurement reports possible and led to a significant increase in professionalism.

“That gave us a huge boost in quality. It elevated us to a higher level in terms of reliability and reputation.”

Letting Go and Making Room for Personal Growth

After more than twenty years, Marc realized he wanted to take a different approach to his entrepreneurship.

“I felt the need for space, space to chart my own course, explore new ideas, and start over.”

The process of stepping back was gradual.

“You talk a lot. You reflect. You look ahead. It’s a collaborative process in which you have to be generous with each other. The most important thing was to maintain good relationships. A business is important, but so is family.”

What Marc Takes Away from His Time at De Rooy

The years he spent at the family business shaped Marc as an entrepreneur.

“You learn to take responsibility, not just for results, but for people, for continuity, and for decisions that have repercussions for years to come. You learn that growth isn’t just about getting bigger, but about getting better.”

A New Chapter

Marc is fully focused on his own entrepreneurial endeavors through Jorhan Consult B.V., a company active in management, mediation, and administration. On his LinkedIn profile, Marc de Rooy | LinkedIn, you can clearly see how diverse his work is: from consulting and strategy to administration and involvement in various projects.

“It doesn’t feel like leaving something behind, but rather like taking something with me into a new phase. Everything I learned at De Rooy, I now use every day in my work. Of course, it’s exciting, but entrepreneurship is also about having the courage to take action when the time is right.”

With respect for the past and energy for the future, Marc is consciously choosing his own path.

“Sometimes you have to step away from something that’s good to make room for something that suits you better. My motivation now is to help projects and businesses grow further, to build connections, and to achieve results, both for the people involved and for the organization. It’s always important to keep the business healthy and the family happy.”

High accuracy and reproducible quality

Okamoto CNC CHiQ machines are designed for industrial precision grinding operations where dimensional accuracy and low surface roughness are crucial. The rigid machine construction and high-quality guides minimise vibration, resulting in:

• very high dimensional accuracy
• low surface roughness
• stable and consistent grinding results

This makes our grinding operations ideal for applications where precision surface grinding is essential.

Efficient surface and profile grinding

Our machines are equipped with intuitive and user-friendly controls similar to those of our other Okamoto surface and profile grinding machines. This ensures a high degree of process reliability and uniformity within our industrial grinding centre. Multiple machines can be deployed flexibly, enabling us to scale up efficiently and guarantee reliable delivery times.

Large capacity for long and heavy workpieces

With grinding lengths of 2 meters, 2.5 meters and 3.5 meters, our Okamoto CHiQ machinery has an exceptionally large capacity. This means we are ideally equipped for:

• surface grinding of large workpieces
• surface grinding of long workpieces up to 3.5 meters
• small and large series
• precise grinding of complex components

.

Heavy Frames, High Accuracy

Many of the frames we process weigh tens of thousands of kilograms and require machining across all sides. A typical example is a construction measuring 5,000 × 2,700 × 2,000 mm and weighing 23,000 kg, a size and weight that only a small number of machining suppliers in Europe can accommodate.

Welded or cast, these structures often come with their own challenges:

• Heat distortion
• Internal stress
• Geometric deviations
• Large, uneven surfaces

Correcting these issues with precision demands not only powerful machinery but also extensive expertise in handling complex heavy structures. De Rooy offers:

🔹 Large-capacity CNC machining for multi-ton frames in oversized dimensions
🔹 Specialists in welded and thick-walled constructions
🔹 Advanced fixturing and in-process measuring for accuracy over large distances
🔹 Stable, repeatable processes suited for both single pieces and recurring production

Supporting Europe’s Traditional Industries

Our machining services support OEMs in:

• Heavy agricultural machinery
• Mining and earth-moving equipment
• Offshore and marine systems
• Shipbuilding infrastructure
• Metal production and processing equipment
• Chemical and process industry machinery

In these sectors, durability is essential, but precision is too. Even small dimensional deviations in a 20-ton frame can lead to assembly issues, increased wear, or reduced system efficiency.

Our ability to machine extremely heavy frames to tight tolerances ensures these components integrate seamlessly into your final equipment.

Why a European Machining Partner Matters

For traditional industries, choosing a European supplier like De Rooy provides major advantages:

🔹 Lower Logistics and Shipping Costs
Transporting a 23,000-kg frame across continents is costly and complex. European production significantly reduces shipping time and expense.

🔹 Faster and More Flexible Delivery
Shorter supply chains mean quicker adjustments, faster lead times, and smooth handling of design changes.

🔹 Direct Communication and On-Site Collaboration
Engineers can visit, inspect, and collaborate easily improving quality and reducing project risk.

🔹 Reduced Risk in Complex Projects
Local machining eliminates long transit risks, customs delays, and logistical uncertainty.

.

Working in the CAD/CAM department: no two days are the same

Within the CAD/CAM department, multiple disciplines work closely together. The CAD/CAM programmers convert technical drawings into CNC programs that control the machines. These are digital instructions that describe, step by step, how a part is machined: which tools are used and which operations are required.

In addition, colleagues from Proxia and the tooling department play an important role. Proxia is the central platform where De Rooy brings together various digital processes. This system was deliberately chosen because it provides greater clarity, efficiency, and a standardized way of working.

Among other things, the Proxia team manages part and tool inventory, ensuring that everyone has access to up-to-date and reliable information. The tooling department then ensures that tools are built according to specifications and are available in a timely manner for production.

From a digital perspective, De Rooy is already well advanced. Many processes are fully digital and are supported daily by Proxia, which provides greater insight, control, and efficiency within the production process.

According to Tim, it is precisely this collaboration between CAD/CAM, Proxia, and tooling that is essential for the successful execution of complex projects.

“We make sure everything is correct before it goes to production. That requires precision, insight, and close collaboration within the team.”

The parts you work on are large and complex.

“Think of projects for sectors such as semiconductors, mining, and the food industry. Parts up to 16,000 mm in size, with high precision down to the micron level.”

It’s precisely that combination that makes the work challenging.

“The best part is when a complex project is spot-on down to the last detail. When you create a (final) product you can truly be proud of.”

Working on complex CNC projects

At De Rooy, you don’t work on standard or simple projects, but on complex, custom CNC machining jobs.

“Every project starts with a kick-off meeting. Then, together, you determine the strategy: how will you make the part, what clamping method will you use, and what tools do you need?”

Sometimes that takes a few days; sometimes several weeks.

“That’s exactly what makes the work interesting. You get the time to really refine a CNC program and optimize the process.”

Collaborating within CAD/CAM and production

Within the CAD/CAM department, you’ll work alongside experienced programmers and colleagues in training. Sharing knowledge is key.

“We help each other, share our experience, and are constantly learning. That’s what makes the team strong.”

Collaboration with other departments, including production, work planning, and quality control, is also important.

“From CNC programming to final inspection: you really do it together.”

What sets De Rooy apart:

“Programming is done centrally. This allows us to maintain an overview and prevent errors in production.”

Developing your CNC knowledge and CAD/CAM programming skills and continuing to grow in these areas

Trainees are trained step by step in CAD/CAM programming. If you want to advance internally to become a CAD/CAM programmer, you must have worked as a miller at De Rooy for at least 2 years. Are you applying directly for the position? Then at least 2 years of experience with HyperMill is required.

“You’ll start with smaller CNC parts and work your way up to more complex projects. You’ll receive guidance, but you’ll also be given responsibility.”

According to Tim, the right attitude is important.

“If you’re curious, work with precision, and show initiative, you can grow quickly at De Rooy.”

Working at De Rooy in the CAD/CAM Department

Working at De Rooy means working on technology that makes a difference, in an environment where you continue to learn about CNC and CAD/CAM programming.

“Here, you’ll have the opportunity to develop yourself, collaborate with skilled colleagues, and make a real impact on the production of complex parts.”

For anyone who loves technology, CNC, and CAD/CAM programming, the choice is clear, according to Tim:

“If you get energized by complex challenges and creating technical solutions together, you’ll quickly feel at home here.”

Ready for some BIG precision work?

Our modern, expanding fleet of machinery is ready for any challenge, and we are looking for a CAD/CAM programmer who has an eye for detail and isn’t afraid to take on BIG projects.

Solid foundation

The new PAMA Vertiram is one of the largest portal milling machines in the Netherlands. Its foundation is exceptionally heavy-duty. “There are 36 nine-meter piles underneath and about 500 cubic meters of concrete,” Adam explains. “The manufacturer tests the foundation by placing a 50-metric-ton weight on it. Afterward, it’s allowed to move by a maximum of four micrometers. If it moves more than that, they reject it, but ours passed.” The machine was ordered in 2023 from PAMA in Rovereto, Italy. Installation has since been completed, and the first machining job is done: a nearly 44-metric-ton cylinder made of tool steel for high-tech machine building. The Vertiram is equipped with four spindle heads: one high-speed head and three low-speed heads. The tool magazine can hold 384 tools, more than double the capacity of the first PAMA (180). The chip conveyors have also been expanded to better handle the large volumes of aluminum chips. “The first machine has a chain changer, while this one has a robotic system,” says Frans de Rooy. “That works faster and more reliably. We keep the machines as versatile as possible so that we can machine both aluminum and steel.”

Large and precise

De Rooy specializes in large and precision workpieces. Its largest grinding machine can process parts up to 8 x 3 x 1.5 meters. The largest milling machine, the PAMA, can handle workpieces measuring 14 x 4.6 x 2.8 meters with a maximum weight of 50 metric tons. Some products arrive as semi-finished goods and are sent on to De Rooy for further machining. “The best part is when we can combine milling, grinding, and measuring,” says Adam. “A workpiece that needs to be milled, ground, and measured is a perfect fit for us. That’s when we make the most of our strengths.” They complement each other nicely. Milling is faster, but grinding allows you to achieve tolerances that aren’t possible with milling. The ratio of milling to grinding at De Rooy is about fifty-fifty. All the production halls are fully climate-controlled at 20 degrees Celsius. “That’s crucial,” Adam explains. “We have machine beds measuring four to five meters that must be flat to within five micrometers. That’s not possible without a stable temperature. Large workpieces also need to acclimate first before we start machining them.” ’The company serves clients in the semiconductor industry, mechanical engineering, the food industry, offshore, and mining, among others. About twenty percent of its customers are located abroad. ‘We deliver to Germany, Belgium, France, and even Switzerland,’ says Adam. ‘When it comes to large-scale grinding work, they know exactly where to find us.’

Automation in Practice

De Rooy operates on a two-shift system and produces over 100 hours per week. Many workpieces have long cycle times, ranging from a few hours to eighty hours. That calls for smart scheduling. Frans: “We schedule the longer cycles in the evening and at night, so the machines can continue working autonomously. The PAMAs have two pallets. Machining takes place on one, while the other is loaded outside. This allows us to reduce setup time.” Programming is done entirely offline using Hypermill. Six programmers handle all the milling programs. “All machines run on Heidenhain controls,” says Adam. “That makes the milling machines highly versatile.”

Digitization

Digitization is a key priority. The milling and cylindrical grinding departments are now paperless, and the grinding department will follow in 2026. The administrative processes have also been largely automated. “Orders and work orders are automatically generated and verified,” says Frans. “The employee’s role is increasingly shifting toward monitoring what the software does.” He is cautiously optimistic about AI programming. “It’s coming quickly for small jobs, but not yet for large ones. There are too many variables involved there. We do create macros to automate repetitive tasks.”

Sustainable Production

In addition to precision, De Rooy invests in energy efficiency and sustainability. There are 4,200 solar panels on the roof, which account for approximately 40 percent of the company’s own energy consumption. “Since we operate 100 hours a week, we use that electricity off the grid,” says Adam. The company is ISO 14001-certified and has replaced older machines with more energy-efficient models in recent years. The six Unisign machines are being equipped with an eco-mode designed to further reduce energy consumption. A striking example of a sustainable investment is the purchase of the briquetting system for aluminum shavings. “When we started milling a lot of aluminum, the bins would fill up in ten minutes,” Adam explains. “With the briquetting machine, we compress the shavings, reducing their volume by a factor of eight, and extract the coolant, which we reuse. Plus, the briquettes yield a higher return during recycling.”

Training Skilled Workers

Finding skilled workers remains a challenge. “There’s no proper training program for grinding,” says Adam. “We train people in-house. Often, they’re young men who’ve worked in other fields but still want to learn a technical trade. We turn handy people into grinders or millers.” De Rooy has three HR staff members, one of whom focuses entirely on recruitment. New employees sometimes start through a staffing agency but are later hired on a permanent basis. “We want everyone to be on a permanent contract,” says Adam. The workforce is relatively young. “We’ve grown rapidly in a short period of time, so the average age is low,” he says.

Ready for the Future

With the second PAMA Vertiram and a new Unisign machine currently under construction, De Rooy will have sufficient capacity for the coming years. “We invested in 2023 when the market was booming,” says Adam. “Things are a bit slower now, but when the market picks up again, we’ll be ready to move forward.” In the coming period, the company plans to modernize its machining fleet, complete its digital transformation, and possibly expand.

“The machines we’re installing now will still be milling here in 25 years,” says Frans. “We buy for the long term. Machines often get bigger as they need to handle more capacity. Machines won’t become less precise or simpler in the coming years. Everything is getting more complex. And as it gets more complex, it automatically becomes more precise,” he concludes.

Machine List

Want to learn more about our machines and capacity?

Text: Kasper Weigrand

Advantages of 5-axis CNC milling

• Machining of multiple sides in a single setup
• High accuracy and dimensional stability
• Fewer setups and shorter lead times
• Suitable for large and complex workpieces
• Efficient production of single parts and small batches
• High machining capacity for large components

Technical Information About the Uniport

Capacity: 16,000 x 4,000 x 1,300 mm

Machining operations:

• 5-axis CNC milling
• Milling of large frame components
• Machining of top, bottom, and side surfaces
• Complex machining operations
• Machining of large workpieces

Dimensions of the machined frame

Frame dimensions: 5,855 x 3,400 x 1,015 mm

Workpieces of this size require specialized knowledge and ample machine capacity. Thanks to our extensive CNC milling capacity, we can machine even large components with precision and efficiency.