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The Complete Guide to CNC Machining Large Components


Industries ranging from mining to aviation depend on heavy CNC machining. However, the bulkiness of the created parts requires some specific considerations. Here are some things worth staying mindful of if you’re thinking about machining large pieces and want to avoid pitfalls.

Realize the Logistical Challenges Associated With the Size

The dimensions of large components may necessitate creating bigger work zones for the people handling the parts. Relatedly, you may need to open sections of the CNC machine’s enclosure or remove them entirely to accommodate the piece’s size.

The part’s size and weight will likely mean it requires special equipment to move. Accounting for those specifics early in the process reduces the likelihood of encountering surprises later that disrupt the workflow. Planning your strategy also tends to save time overall. Plus, if you realize too late that there’s not enough clearance in your facility to accommodate the part, it might hit surfaces or other machines during the creation process, causing damage.

Size also comes into play when you figure out work holding needs. These details encompass all the equipment needed to keep the piece secure while milling the material.

Garrett Gordon, a senior engineer at Bluco Corp., said, “The size and weight of large parts and work-holding components do factor into the overall time it takes to build a fixture. So, it’s important to find places in the process where you can save time without sacrificing quality. Whether that’s accessing CAD models on the floor to build against or using a system that pins together faster, each minute you save on fixturing is another minute of run-time in the machine.”

Understand the Temperature Control Challenges

Temperature control is a concern when machining parts of any size. That’s because of the coefficient of thermal expansion (CTE). It’s the rate at which a material linearly expands for every temperature degree change. CTE can affect the base material and even your CNC machine’s components.

Working with larger parts generates more significant amounts of heat, and machine operators must account for that. It’s vital to ensure the CNC machine’s cooling mechanism does not reduce the temperature to a degree outside of tolerance limits. If that happens, items could expand too much when becoming warm again.

These potential issues mean you may need to compensate for temperature changes by altering how you use the machine or more tightly controlling the coolant controls. However, knowing these things before starting to work reduces the chances of costly mistakes occurring.

Allow Time to Update Machine Operators’ Training

Even people who’ve created smaller parts with CNC machines for years often get overwhelmed when making larger components. That’s especially true if doing the job requires using different equipment. For example, capacities reach 50,000 pounds at some machine shops.

Norman Besand is the shop superintendent for American Machine & Gear Inc. That facility produces parts up to 12 feet long and 5 feet tall and has several cranes to assist with lifting them. The company has more than two dozen employees and works with a nearby community college to train CNC operators. “A lot of people are really scared to work on some larger parts. It’s intimidating to them at first,” Besand explained.

Blake Conner, the general manager of CBM Precision Parts, cited the importance of experience and planning, saying, “We bring guys in who are used to doing small parts, and you have to have a quality control plan and really see it through. Your workforce needs to be talented and have many years working on larger parts.”

Explore Other Technologies to Supplement CNC Machining

Additional technologies can be particularly beneficial when machining large parts. For example, some CNC shops keep efficiency high by installing sensors on equipment for predictive maintenance. Those facilities are more likely to avoid expensive outages that disrupt productivity.

Using additive and CNC machining is another option gaining popularity. Caracol is an Italian additive manufacturing company specializing in applying 3D printing to high-performance industrial needs, such as those related to the aerospace sector. Currently, the company’s standard system prints parts up to 4 meters wide. However, the maximum width expands to 10 meters if using an optional rail or trolley system.

In one recent case, Caracol made single-piece panels for aeroplane belly fairings. The part required dimensional tolerances within 0.1 ​​millimetres and 1.6 μm surface roughness, which the company achieved with CNC machining. Taking this approach cut the production timeline from six weeks to five days, plus reduced the customer’s costs by more than one-third.

When working on large parts with tight tolerances, it’s advantageous to set aside more time for periodic quality checks throughout the process. Whenever a piece has a bigger surface area, it becomes increasingly crucial to verify that the necessary repeatability occurs.

Recognize When Machine Upgrades Make Sense

If you plan to engage in heavy CNC machining over the long term, now may be the right time to invest in specialized equipment to handle large-scale tasks. Metalcraft is a company with John Deere, Caterpillar and Lockheed Martin among its clients. However, it became difficult to meet expectations when the company’s existing equipment could not handle the required tolerances. The situation worsened after the company was told an eight-month machine outage would cost $140,000 to resolve.

Company leaders decided to buy a pair of five-axis machines made by Toyoda instead of trying to get the old equipment running again. Metalcraft’s machining manager John Grotelueschen, who oversees more than 20 large CNC machining centres, said things started going well when installing the machines. “The installation of these machines couldn’t have gone any smoother. I have been in the industry for over 30 years and overseen upwards of 20 installs. This was the easiest install I’ve ever been involved with.”

The company integrated the two machines into the production schedule right away. They used them for five clients, and many needed large pieces to be made.

It didn’t take long to see the investments start to pay off. “We cut a bunch of different, mostly tougher, steel alloys made to withstand falling objects. Running these parts through the Toyodas was actually the easiest and most profitable,” Grotelueschen said, giving an example.

Heavy CNC Machining Requires Careful Attention

The recommendations here emphasize how machining large parts can introduce some challenges. Understanding these issues before starting the work and planning how to overcome them leads to better productivity and improved outcomes.

Emily Newton is the Editor-in-Chief of Revolutionized Magazine. She has over three years experience writing articles for the tech and industrial sectors. Subscribe to the Revolutionized newsletter for more content from Emily at

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