Precision Grinding of Large Shafts at De Rooy

Project in the spotlight: Grinding large shafts.

A recent project involved the grinding of a heavy-duty shaft.

Component specifications:

• Diameter: 250 mm
• Length: 3.000 mm
• Weight: 1.050 kg
• Surface to be ground: the entire roller surface and the shaft

Despite the size and weight of the component, tight tolerances were required to ensure proper sealing, alignment, and reliable operation in the final machine.

The Danobat G91 CNC Grinding Machine

For this project, we used our Danobat G91-S CNC cylindrical grinding machine, specifically selected for large and heavy shafts.

Danobat G91 capabilities:

• Maximum grinding dimensions: Ø 1000 mm × 4000 mm
• Maximum workpiece weight: 5,000 kg
• External cylindrical grinding
• Conical grinding
• Profile grinding (where required)

This machine allows us to combine size, stiffness, and precision—essential for consistent results on long shafts with large diameters.

Grinding Capacity for Shafts at De Rooy

In addition to the Danobat G91, our grinding department includes several other CNC grinding machines, allowing us to handle a broad range of shaft dimensions:

• Ø 670 × 3000 mm – AMC-Schou R3000
• Ø 550 × 1500 mm – WMW-Heckert
• Ø 500 × 2000 mm – Fermat BUB E50/2000 CNC
• Smaller machines up to Ø 350 mm × 1000–1500 mm

Applications and Industries

The shafts and cylindrical components we grind are commonly used in:

• Machine tools and rotating assemblies
• Pumps and mechanical systems
• Hydraulic and mechanical plungers
• Offshore and mining equipment
• Heavy industrial machinery
• High-tech machine building
• Semiconductor, food, and process industries where tight tolerances are essential

The combination of large dimensions and high precision makes De Rooy a reliable partner for both traditional and advanced industrial sectors.

Fast Lead Times and Flexibility

Speed is often just as important as accuracy. De Rooy is known for its flexibility and short lead times, even for heavy and complex components. Whether it’s a planned production order or a time-critical rush job, our team is equipped to respond quickly and deliver consistent quality.

Looking for Precision Grinding of Large Shafts?

If you require accurate grinding of long or large-diameter shafts with fast delivery and dependable quality, De Rooy is ready to support your project.

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

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

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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.

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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.