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Achieving optimal results when using a CNC router router goes beyond just the precision of your machine. It also depends on setting the correct CNC feeds and speeds. Machinists and operators must understand how to calibrate the appropriate feed rates for a CNC router to boost production efficiency and optimize the use of their machines.

In this guide, we’ll cover various parameters that impact the feed and speed rate of your machine, including:

• Feed rates
• Cutting speed
• Slew rates
• Plunge rates
• Spindle speed
• Chip load

Getting the proper feeds and speeds for your CNC router is crucial to efficiently running your machine. If you are having difficulty calculating the speeds and feeds for your CNC router, a simple way to work out the information you need is to use a free online calculator. However, it is essential to note that each CNC router machine will have specific settings, which is why it is best to check the user’s guide provided by the manufacturer.

Fine Tuning CNC Router Settings

Reviewing the information in this guide, you will learn how to set CNC feeds and speeds depending on several crucial factors. As you figure out the different settings, it’s better to begin at the lowest end of the recommended feed rate and increase it until:

• The finish deteriorates because of the vibration of the cutting tool
• Tight radii cause the machine to adjust to a slower speed
• The part moves

Once you have determined the maximum speed, decrease the spindle speed until the finish deteriorates. Then, increase it incrementally until you achieve an acceptable edge finish. We will go over the details in the discussion below.

 

Understanding Feed Rate

Feed rate refers to the distance a cutting tool covers for every spindle revolution. It measures the speed at which a cutter advances into the material you’re working on. This measurement is quantified in inches per minute (IPM).

The significance of feed rate extends to multiple vital areas:

• Safety: Setting the appropriate feed rates for a CNC router ensures the safety of the operator, workpiece, and the machine being used.

• Productivity: Optimal feed rates enable faster completion of tasks, boosting overall productivity.

• Surface Finish: A well-matched feed rate can result in a smoother finish, minimizing post-processing.

• Part Quality: Optimum feed rates improve precision and accuracy.

• Machine Wear: Correct feed rates reduce wear and tear, prolonging the usable life of your CNC router.

 

Differentiating Cutting Speed

Cutting speed, on the other hand, refers to the relative rotational speed between the cutting tool and your workpiece. It is the speed at which a workpiece passes through your router’s cutting edge. The cutting speed of your machine is represented in meters per minute (MPM) or surface feet per minute (SFM).

The cutting speed of your CNC router is computed using this formula:

Cutting Speed = π × Diameter of the Tool × Spindle Speed

Where:

• π (pi): A mathematical constant rounded up approximately to 3.1416.
• Tool Diameter: The physical size of the cutting tool you’re using.
• Spindle Speed: The rotational speed of the spindle, which is measured in revolutions per minute (RPM).

 

Feed Rate vs. Cutting Speed

As mentioned earlier, the feed rate of your router refers to the speed at which the cutting tool moves along its linear path relative to the workpiece, affecting factors such as chip load, machining time, and efficiency.

Cutting speed, on the other hand, is all about the rotational speed of the cutting tool, determining how fast the tool’s edge spins and removes material from your workpiece. The factors that affect your machine’s cutting speed include expected tool life, cutting tool material, and workpiece material. The cutting speed of your CNC router impacts the material removal rate, heat generation, tool wear, and surface finish quality.

It is important to note that the interplay between your machine’s feed rate and cutting speed determines the rate at which material is removed from your workpiece.

 

Material Hardness and Cutting Speed

Material hardness is one of the factors to consider when determining the cutting speed to use for your project. Reference manuals from your router’s manufacturer usually include recommended cutting rates depending on the material you’re working on.

Material hardness is measured in HRC or the Rockwell Hardness C Scale, a measure of the hardness of different materials. Here are a few examples of the recommended optimal cutting speeds per material:

 

Material	Cutting Speed Under 32 HRC	Cutting Speed Above 32 HRC
High Alloy Steel	100-300	80-180
Low Alloy Steel	100-400	100-200
Stainless Steel	100-350	100-150
Cast Iron	100-400	80-140
Plastics and Acrylics	200-800	200-500

Note that the recommended cutting speed for your CNC router brand and model may differ slightly from the data in the chart above. Consult your product manual for the exact recommended rates.

 

Other Factors to Consider

Other factors come into play when it comes to CNC feeds and speeds. They include the following:

• Slew Rate:  Also referred to as rapid speed, slew rate refers to the speed at which your machine moves over a workpiece between cuts. Setting higher slew rates improves overall efficiency, reducing the total cycle time.
• Plunge Rate: This factor refers to the speed at which a router bit is driven into a material. When working on a workpiece, setting the appropriate plunge rate is crucial to prevent damaging the cutter’s tip.
• Spindle Speed: The rate at which your router’s spindle spins. You can increase the feed rate by setting a higher spindle speed. However, never put a low feed rate for your machine with a higher spindle RPM, which risks overheating and can burn or melt the workpiece.
• Chip Load: Chip load refers to the thickness of the material being removed as the cutting tool moves along the workpiece. Larger chip loads put more stress on your cutting tool, leading to poor surface finish. The goal is to set the optimal chip load. Hence, you remove enough material with each pass of your cutting bit without causing problems with your machine.

Apart from these factors, others can indirectly affect the optimal CNC feeds and speeds. These factors include tool rigidity, cutting tool material, workpiece material, and tool deflection. For instance, the harder the material of the workpiece, the slower the feed rate of your machine.

Suppose you’re working on metals and other rigid materials; using a lower RPM and higher torque is best, which creates a higher shearing force. However, if you’re working on softer materials, like wood, for instance, you can set your machine to a higher RPM, which allows you to glide through the workpiece, improving your overall efficiency and speed.

 

FAQ

Here are some of the frequently asked questions by machinists and CNC operators:

1. Does the cut depth affect CNC feeds and speeds?

 

A: Yes, the depth of a cut affects the chip load. The deeper the cut you set, the optimal feed rate decreases.

 

2. Is it guaranteed that you will get perfect results when you set the calculated feed and cut speeds?

 

A: No, manufacturers cannot guarantee perfect results every time. However, the calculated and recommended settings from the manufacturer have all the possible variables considered. Best practice indicates that you should perform test cuts using the recommended speeds and feeds and make the necessary adjustments based on your initial results.

 

3. Can I use the same cutting speed and feed rate for different materials?

 

A: No, using the same feed rates and cut speeds is not advisable. Certain manufacturer guidelines may provide ranges for these settings. However, it is still best to perform test cuts to determine how the cutting tool interacts with your workpiece material.

 

4. What happens if I set the cutting speed or feed rate too high?

 

A: Higher speeds above the recommended ranges will produce unpredictable results and other issues. It can also increase tool wear and poor surface finish.

 

5. How do I determine the appropriate feed rate and cutting speed?

 

A: Manufacturers often provide recommended speed ranges depending on the material and tool you’re using with your machine. Use them as starting points and test the results depending on the material you’re working on.

 

Optimize Your Router Settings with CAMaster

CAMaster is the leading supplier of industry-leading CNC router machines. Our team can equip your business with the tools that boost the efficiency and accuracy of your workflows. 

Since you want to stay ahead of your competitors in your field and value quality and efficiency, you will appreciate the dedication of the staff at CAMaster and the range of products and services we provide. Contact us today to get the answers to all your CNC router questions.