Feed Rate vs Cutting Speed: Detailed Comparison in Machining
When you’re running a machining job, two numbers matter a lot: feed rate and cutting speed. If you get them wrong, you waste time, wear out your tools fast, or mess up the part. If you get them right, everything runs smoother, faster, and more cost-effectively.
Let’s discuss feed rate vs cutting speed and see how they work together.
What is Feed Rate?
Feed rate is the speed at which your cutting tool moves during a machining process. It tells you how far the tool moves in one full rotation or how fast the workpiece moves toward the cutting tool, depending on what you’re doing. You might also hear it called the cutting tool engagement speed, especially in milling.
You’ll measure feed rate in millimeters or inches per minute (mm/min or in/min or IPM) for most operations, or in millimeters or inches per revolution (mm/rev or in/rev) for turning or boring.
The feed rate depends on several factors, like the material of the tool, the material of the workpiece, and other cutting factors like your CNC machine settings and the type of surface finish you need.
Feed rate affects how your finished product looks. That’s why it’s important to optimize it during CNC machining. To calculate it, you’ll look at how many teeth or flutes are on your cutting tool and how much each tooth contributes to the movement.
While cutting speed and feed rate are both influenced by similar factors, the feed rate has a bigger impact on how the final part looks, so optimizing it is crucial.
How to Set the Optimum Feed Rate?
Here are different factors you need to consider to find the best feed rate:
Cut Width
Cut width, or radial depth of cut (RDOC), is the distance along the surface of the workpiece that your CNC tool covers in one pass. When the cut width is less than half the tool’s diameter, chip thinning can happen.
Chip thinning occurs when your tool doesn’t remove enough material per rotation, which can slow down your production. To avoid this, increase your feed rate to improve productivity and extend the tool’s life. You can also try using a higher cutting speed to fix chip thinning.
Productivity
Your main goal in machining is to remove material quickly without damaging your tool or the quality of the part. Sometimes, increasing the feed rate will help you work faster, but it might affect the surface quality. Try to balance speed and feed rate to keep your production cost-effective.
Feed Rate Limit
Your CNC machine has specific feed rate limits; there’s a minimum and maximum that it can handle. Going beyond these limits isn’t allowed. Make sure you stay within your machine’s feed rate limits and follow the tool manufacturer’s guidelines.
Cutting Tool Geometry
The shape of your ferramenta de corte also affects the surface finish. If your tool is designed to handle higher feed rates, take advantage of that. Tools with more cutting edges cut less material per pass, allowing them to handle higher feed rates. Use your tool’s design to achieve the best feed rate.
Machine Tool Capacity
Higher feed rates create more cutting force and vibrations. Your Máquina CNC has limits based on its strength, power, and stability. Choose the right feed rate based on your machine’s ability to handle these forces and vibrations.
Acabamento da superfície
To get a smooth surface finish, use a lower feed rate for finishing operations and a higher feed rate for rough cuts. For example, use a feed rate of 0.01 to 0.05 mm/rev for finishing and 0.1 to 0.3 mm/rev for roughing. Adjust your feed rate to meet the surface roughness requirements.
What is Cutting Speed?
Cutting speed is how fast the surface of the material moves past the CNC cutter. It’s measured as the distance the tool covers in a minute, usually in feet per minute (ft/min), surface feet per minute (SFM), or meters per minute (m/min).
If the speed is too high, it can create too much heat, causing the tool to wear out quickly or even break. If the speed is too low, the tool may not remove material efficiently, lowering productivity. Using proper cooling and lubrication helps manage the heat and keeps both the tool and material in good condition.
Higher speeds can give smoother finishes, but if the speed is too high, it can cause vibrations or chatter, ruining the surface. Slower speeds may make the surface rougher, especially with harder materials.
Choosing the right cutting speed helps improve efficiency, as it can cut down on the need for extra finishing work.
How to Set the Optimum Cutting Rate?
Here’s what you need to consider:
- Harder materials need slower speeds to avoid wearing out the tool too quickly, while softer materials like aluminum can be cut at higher speeds.
- Tools made from stronger materials can handle faster speeds without wearing out quickly. Softer tools wear out faster at high speeds, so they don’t last as long.
- If the tool is expensive or meant to last a long time, you’ll want to use a lower cutting speed to reduce wear. But if the tool is inexpensive and you only need it for short jobs, you can use higher speeds.
- Deeper cuts create more heat and put more stress on the tool, so you’ll need to slow the speed to avoid damage. If you use a high speed with deep cuts, it can wear the tool out quickly, increasing cutting forces and creating a poor finish. Shallow cuts allow you to use higher speeds and make the process more efficient.
What is the Relationship Between Feed Rate and Cutting Speed?
Feed rate and cutting speed affect each other. If you increase the cutting speed without changing the feed rate, your tool may wear out faster, and the surface may not be smooth.
If the feed rate is too high for the cutting speed, it can put too much stress on the tool and cause vibrations, which can reduce tool life and accuracy.
It’s important to find the right balance between feed rate and cutting speed. This helps remove material quickly while keeping the tool in good condition and ensuring a smooth surface.
Importance of Feed Rate and Cutting Speed in CNC Machining
Em Maquinação CNC, feed rate and cutting speed are important because they affect how efficient the process is and the quality of your final product. Balancing feed rate and cutting speed helps your tools last longer and keeps the quality high. It also reduces mistakes and waste, especially in precise industries like aerospace.
Using the right speeds and cooling prevents heat buildup, especially with hard materials. The right settings give you a smooth surface, meet design specs, and keep the material’s strength and shape intact.
Comparing Feed Rate vs Cutting Speed Across Different Machining Processes
Here’s a simple breakdown of how feed rate and cutting speed vary in different machining processes:
CNC Milling: Cutting speed depends on spindle speed and tool size. Feed rate is influenced by chip load. Faster feed rates remove more materials but may affect surface finish.
Virar: Cutting speed stays the same for round workpieces, but feed rate changes depending on the depth of cut and tool design.
Perfuração: Cutting speed is controlled by spindle RPM. Feed rate affects how well chips are formed and removed.
Moagem: Feed rate is slow to get smooth finishes, but cutting speed needs to be high to speed up the process.
Enfiamento: Cutting speed is kept low to get precise threads, while feed rate stays steady to maintain the correct thread pitch.
How to Calculate Cutting Speed and Feed?
To calculate cutting speed in machining, use this formula:
Cutting Speed (SFM) = π x D x N / 12
Where:
- D = Diameter of the cutting tool (in inches)
- N = Spindle speed (RPM)
Comparing Cutting Speed and Feed Rate on Fifteen Factors
| Factor | Velocidade de corte | Taxa de alimentação |
| Definition | Speed at which the tool moves along the surface (SFM or m/min). | Rate at which the tool moves into the workpiece (IPM or mm/rev). |
| Measurement Units | SFM, ft/min, or m/min | mm/min, in/min, IPM, mm/rev, or in/rev. |
| Material Removal Rate | High speeds increase material removal rate (MRR), especially in high-speed machining. | Higher feed rates speed up material removal. |
| Tool Wear | Higher speeds cause faster tool wear if not optimized. | High feed rates can also cause wear, but not as much as cutting speed. |
| Vibration and Stability | Higher speeds can cause vibration, reducing accuracy. | High feed rates can cause instability, especially with deep cuts or fragile tools. |
| Power Consumption | Faster speeds use more power due to friction and heat. | Feed rate also affects power, but not as much as cutting speed. |
| Chip Formation | Speed affects chip flow, helping smoother material removal when optimized. | Feed rate affects chip size; higher feed rates create thicker chips. |
| Acabamento da superfície | Speed has a small effect, but can influence consistency. | Feed rate affects surface finish more directly; lower feed rates give finer finishes. |
| Cutting Temperature | Higher speeds generate more heat, which can damage tools and workpieces. | Feed rate has a smaller effect on temperature compared to cutting speed. |
| Tool Wear (Repeated) | Faster speeds increase friction and cause more wear. | High feed rates cause wear, but less than cutting speed. |
| Surface Roughness | Speed indirectly affects roughness by impacting chip flow and wear. | Feed rate affects roughness more; higher feed rates lead to rougher surfaces. |
| Scallop Marks | Speed has little effect on scallop marks. | Feed rate plays a key role; higher rates create more visible marks. |
| Machine Stability | High speeds can cause instability, especially with precise parts | High feed rates can also destabilize the machine, especially with fragile tools or workpieces. |
| Directrix and Generatrix | Cutting speed helps create the directrix in the machining path. | Feed rate creates the generatrix, controlling tool movement along the workpiece. |
| Geração de calor | Speed is the main factor in generating heat at the cutting edge. | Feed rate also contributes, but less significantly than cutting speed. |
Common Mistakes in Setting Feed Rate and Cutting Speed?
Here are common mistakes to avoid when setting feed rate and cutting speed, and how they can affect machining:
Ignoring Tool Wear: Worn tools can cause inaccuracies. Regular tool checks are important to keep cutting performance consistent.
Incorrect Tool Engagement: Using the wrong feed rates when starting to cut can cause vibrations, damaging the surface.
Ignoring Machine Limits: Not all CNC machines can handle high feed rates or cutting speeds, which may cause instability.
Not Making Regular Adjustments: Manufacturing processes change, so speeds and feeds need to be adjusted to stay efficient.
Advanced Techniques in Managing Feed Rate and Cutting Speed
To get the best performance and tool life from your CNC machine, you can use advanced techniques to manage feed rate and cutting speed.
Predictive Maintenance
This technique helps you monitor the condition of your cutting tools and machine to predict when maintenance is needed. By keeping track of things like tool wear and cutting temperature, predictive maintenance lets you adjust speeds and feeds before tool failure or machine downtime happens. This helps your tools last longer and your machine run more efficiently.
Adaptive Control
Adaptive control allows your machine to make real-time adjustments to feed rates and cutting speeds based on the conditions. It adapts to changes in material hardness, chip load, or machine stability.
This technique makes sure the process stays efficient and consistent. This helps you avoid tool breakage, improve material removal, and get a better surface finish, even when conditions change.
Precision CNC Machining Services with DEK
To get the best CNC machining results, focus on the right feed rate, cutting speed, depth of cut, tool type, and surface finish. But, you don’t have to worry about any of this when you outsource to DEK. With our skilled machinists and CNC programmers, you’ll always get the best-machined parts every time you work with us. Contactar a DEK today for all your CNC machining needs.
Conclusão
CNC machining relies on small details, and factors like feed RPM, cutting speed, feed depth of cut, and cutting speed are very important. These settings impact tool life and the quality of the final product.
While formulas can help you find the right settings, CNC machining is also about using your skills. It takes observation, knowledge, and quick adjustments to get the best results.
