Computer Numerical Control (CNC) machining is indispensable in modern manufacturing. It uses pre-programmed software to control the movement of advanced tools and machines. This creates high-quality and detailed parts with minimal human intervention. However, even the most advanced 3-axis CNC machine may find it challenging to cut hard metals. Hard metal machining can lead to tool breakage and workpiece damage.
This article will explain what 3-axis CNC machining is, challenges of cutting hard metals on a 3 axis CNC machine and strategies for overcoming hard metal machining challenges.
What is 3-Axis CNC Machining
3-axis CNC machining is the most straightforward multi-axis machining process. It involves the simultaneous movement of the cutting tool or workpiece along three linear axes: X, Y, and Z. The X and Y axes represent horizontal movements from left to right and front to back, respectively. Furthermore, the Z axis is vertical movement up and down. This coordinated movement allows you to produce parts with high accuracy and precision.
3-axis CNC machining is relatively cost-effective because of the lower expenses associated with setup and operation. It is easy to use and is adaptable to various manufacturing industries. However, this operation is restricted to simple geometries because it involves no rotational movement. 3-axis CNC machining has a longer cutting time, especially for more challenging materials.
Challenges of Hard Metal Cutting in 3-Axis CNC Machining
3-axis CNC machines are beginner-friendly and have a shorter learning curve. However, they may be found wanting when shaping hard metals such as titanium, Inconel, and hardened steel. One can encounter the following challenges with hard metal cutting using three-axis CNC machining.
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Material Properties
Hard metals are difficult to cut and shape for many reasons. They are tough and strong, requiring more effort and force. Some of these metals have low thermal conductivity and do not dissipate heat readily. They cause heat build-up, which can lead to thermal damage. Furthermore, these metals get harder during machining, decreasing productivity.
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Rapid Tool Wear
Another reason hard metals are difficult to cut with 3-axis CNC machining is increased tool wear and tear. The toughness and abrasive nature of hard metals make standard cutting tools wear out faster. The force of cutting is more significant, and the tools work more than they should. Rapid tool wear increases the need for resharpening and replacing.
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Heat Generation
Heat generation is typical when using CNC machining on hard metals. This is because of the increased time and contact the cutting tool makes with the workpiece. The primary result of overheating is damage to the workpiece from changes in microstructure. Additionally, heat generation gradually destroys the cutting tool and increases the incidence of work-related hazards.
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Maintaining Dimensional Accuracy
It is difficult to get dimensionally accurate products with 3-axis CNC machining. You would find it challenging to achieve tight tolerances with hard materials because of size variations as a result of thermal expansion. Dimensional inaccuracies also arise when tool deflection occurs because of the higher cutting forces. Additionally, the need for manual repositioning for multi-sided parts leads to machining errors.
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Vibration and Chatter Issues
With three-axis CNC machining, you would experience unnecessary vibrations and workpiece movement. The machine is not optimized to withstand the extreme forces that come with shaping hard and tough metals. Furthermore, that vibration increases stress on the cutting tool and causes chatter issues. All these lead to rough edges that may need additional finishing operations.
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Chip Formation and Clearance
Another challenge of hard metal cutting in 3-axis CNC machining is chip formation and clearance. Hard materials produce sharp and abrasive chips that must be adequately evacuated. These chips can adhere to the tool and workpiece, leading to breakage and poor finish. Additionally, the chips clog the cutting zone and increase machining force.
Strategies for Overcoming Hard Metal Machining Challenges
It is challenging to shape hard metals with a three-axis CNC machine. However, you can still carry out the operation by carefully addressing the issues. Below is an extensive discussion of strategies for overcoming hard metal machining challenges.
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Tool Selection and Optimization
The tool material you use is key in hard metal machining. Consider going for those made with carbide, ceramic, or cubic boron nitride. These materials are optimized for ultra-hard metals. They can handle the abrasive nature of titanium, even in high-speed applications. Furthermore, tool coatings like titanium aluminum nitride or diamond-like carbon can be used to reduce friction and extend tool life.
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Fixturing and Workholding Devices
Another way to minimize distortion in 3-axis CNC machining is using appropriate work-holding jigs and fixtures. Jigs secure and guide the tool during a cutting action. On the other hand, fixtures prevent the workpiece from moving out of place. You can also incorporate dampening devices to absorb vibrations.
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Modifying Machining Parameters
You should optimize important machining parameters with the aim of improving tool performance and reducing errors. Focus on cutting speed, feed rate, and depth of cut. Adjust the cutting speed and lower it to prevent overheating. You should also reduce the feed rate to avoid excessive cutting forces. Additionally, opt for shallow depths and use multiple passes for deeper cuts.
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Use of Coolants and Lubricants
Coolants and lubricants are key to hard metal machining. CNC coolants can be oil or water-based. The type you use depends on the workpiece material and desired surface finish. They reduce heat and maintain dimensional accuracy. Additionally, oil-based coolants such as straight oils and synthetic fluids minimize friction and provide superior lubrication.
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Chip Management Strategies
The process of CNC machining hard metals will inevitably produce chips. Hence, you should implement effective chip management strategies to maintain surface quality. This involves optimizing the toolpath to ensure continuous chip evacuation. Additionally, chip breakers can be used alongside cutting tools to produce more manageable chips.
Conclusion
3-axis CNC machining is a high-precision process that gradually removes excess material from a metal stock, creating the desired shape. It is automated and reduces the incidence of errors. However, using three-axis CNC machining service for hard metals like titanium and steel can be challenging. Hard metal machining can cause tool deflection and chatter because of the increased cutting force. To avoid this, you should use appropriate clamping mechanisms, optimize cutting parameters, and use the right type and quantity of coolants.
