Insufficient sharpness or robustness of the tool, inconsistent feed rate, lack of lubrication, and wrong tool geometry often lead to CNC cutting tool chipping. This not only damages the tool but also ruins the workpiece.
To prevent this, you must select the right cutting tool and program the CNC machine with accurate parameters. So, let’s explore the reasons and solutions to solve frequent tool chipping during CNC machining.
What is CNC Cutting Tool Chipping?
The phenomenon where small pieces of the cutting tool’s edges break off while CNC machining is referred to as CNC cutting tool chipping. This occurs due to excessive force application on the tools or for using the wrong tools and cutting parameters.
As a result of cutting tool chipping, the CNC machining output is greatly affected. It leads to rough finishes, inaccurate cuts, and shorter tool life.
Reasons For Frequent CNC Cutting Tool Chipping
1. Hardness and Toughness of the Machining Material
Harder materials, like hardened steel, stainless steel, or titanium, create greater resistance while cutting. This increases the stress on the cutting tool, leading to tool chipping. If the cutting tool is not robust and sharp enough for the hardness of the material, it can crack or damage the tool permanently.
2. Too High or Too Low Machining Speed
Maintaining optimal machining speed is essential to avoid tool chipping. If the speed is too high, it generates excessive heat, which softens the tool and increases the chances of chipping. On the other hand, if you lower the cutting speed too much, it boosts the stress on the tool, accelerating the tool damage.
3. Tool Material and Coating
The tool material and coating impact the strength of the cutting tool. For instance, if you use a carbide tool to cut hardened steel (HRC 50+) without the right coating, it will chip out the carbide edges. This is because, though carbide is hard, it is brittle and can’t withstand the force required to cut hardened steel. However, TiAlN-coated carbide tools can significantly reduce wear and improve tool performance while cutting hardened steel. This is why considering the tool material and its coating is important to avoid frequent tool chipping.
4. Incorrect Feed Rates For Cutting
Excessive feed rate increases the tool stress. When operated for a long time, this can lead to tool chipping. Besides, a high feed rate causes machine instability when opting for a larger depth of cut. It creates vibration, which forms an uneven cut and can also lead to tool chipping.
In contrast, if the feed rate is too slow, it causes rubbing on the metal surface, which generates heat and causes uneven wear on the tool. This makes the tool more prone to chipping over time.
5. Insufficient Coolant or Improper Lubrication
Coolants and lubricants reduce heat, minimize friction, and flush away chips during machining. Without coolant, excess heat is built, weakening the cutting tools, which leads to chipping. Moreover, inconsistent or misdirected coolant flow can result in thermal shock, causing cracks and chipping.
Considering the machining material is crucial to choose the correct lubrication. For instance, materials like aluminum or stainless steel require specific lubricants to prevent built-up edge formation and improve tool performance.
6. Using Worn-Out Tools
A worn-out tool is not sharp enough to cut materials effortlessly. So, extra stress is applied to the tool during the cutting procedure, which overloads it, causing chipping. Additionally, uneven chips formed in the worn tool get stuck and push back against the tool that chips the cutting edge.
7. Incorrect Tool Geometry
How a cutting tool will handle the applied force depends on the shape, angle, and design of the tool. If the tool geometry is incorrect, it increases the stress on the cutting edge and causes tool chipping. For instance, a too-small clearance angle causes rubbing instead of cutting. This builds up heat on the tool and weakens it, which leads to chipping. So, you must keep the rank angle, clearance angle, and cutting-edge radius of the tool on point.
8. Excessive Cutting Depth
More force is applied to the cutting tool to make a deeper cut. This puts extra load on the tool edge, accelerating its tendency to chip. Besides, when you remove or cut down more material in one pass, it produces excessive heat. Such a phenomenon weakens the tool and causes tool edge chipping.
Preventing Measures For CNC Cutting Tool Chipping
Consider The Material For Cutting Speed Analysis
The optimal cutting speed varies for different materials. Too high or too low speed can impact the performance of the tool, causing the tool to chip frequently.
Low cutting speed is needed for harder materials like hardened steel and stainless steel to minimize heat buildup. For instance, the cutting speed of titanium is 30–60 SFM7, and that of stainless steel is 40–80 SFM. In contrast, high speed increases the cutting efficiency in soft materials like aluminum.
Below, we are adding the optimal cutting speed for machining different materials:
However, the tool material has a greater impact on the cutting speed. For example, carbide tools enable 2–4x faster speeds than HSS tools. Besides, PCD tools excel in cutting non-ferrous metals.
Select The Right Tool
Tool Material
To avoid frequent tool chipping, its material must be robust enough to cut the workpiece. To work with harder materials, such as high-strength alloys, requires more durable tools, like carbide or ceramic inserts. They maintain their hardness at high temperatures, making them ideal for cutting through tough alloys. Meanwhile, you can machine softer materials using tools made of high-speed steel (HSS).
Tool Coating
Coated cutting tools aid in minimizing tool chips. For instance, tools with titanium nitride (TiN), titanium carbonitride (TiCN), or aluminum oxide (Al2O3) coating offer better wear resistance and reduce the risk of chip buildup and heat generation.
Tool Geometry
The tool geometry must be designed for the specific operation to minimize stress on the tool.
- A larger negative edge inclination and a smaller entering angle help reduce shock loads and avoid chipping.
- Tools with a positive rake angle reduce cutting forces and aid in producing better chip flow.
- Grinding a negative chamfer or using a rounded edge reduces tool stress and enhances tool durability.
Reduce Vibration
Too much vibration while machining creates inconsistent force on the tool, which can lead to chipping. So, for greater stability of the machine, place it on an even surface to ensure stability and reduce vibration. The tool holder must be robust so that it does not shake while cutting.
Tool Path Optimization
In traditional milling, like the zigzag route, the cutter moves against the feed direction. This creates high pressure on the tool, leading to chipping and faster wear.
So, to minimize chipping, use climb milling where the cutter moves with the feed direction, which causes less rubbing and minimizes friction. Thus, the tool wears less and causes less chipping.
Moreover, while entering the cutting tool into the workpiece, enter the tool gradually instead of plunging it directly. This reduces stress on the tool and aids in minimizing tool chipping. Besides, it is also crucial to maintain a consistent feed rate and avoid sudden deceleration or acceleration in speed.
Correct Tool Handling and Setup
The tool posture is important to reduce chipping. For instance, a 10% increase in tool protrusion can double deflection, raising the chipping risk. This is why we reduce the deflection by using the shortest possible tool overhang.
Additionally, set the right parameters in your CNC machine; the cutting speed, feed rate, and depth of cut must be accurate to lessen the stress on the tool.
Conclusion
Cutting tool chipping while CNC machining damages the tool and reduces the accuracy of the machined parts. Tool chipping mainly occurs due to using worn-out tools, incorrect tool geometry, and wrong machine parameters.
However, no worries with RICHCONN CNC machining services. We are an ISO 9001:2015 certified company and maintain strict tolerance (down to ±0.005mm) for our machining. Highly professional operators handle all our tools, so our products are not affected by tool chipping. Moreover, we offer you a 99.8% precision match rate! Contact us now to get the most reliable CNC machining services.
