CNC routers are special tools that have revolutionized the cutting and carving industry. Through precision cutting and automation, these tools have enabled workshops and manufacturers to mass produce various parts with numerous applications across different industries.
Operating CNC machines have helped companies become more efficient in their manufacturing operations by reducing the need for manual labor, which translates into more savings in terms of time and money.
But to reach this level of efficiency, CNC operators must first have a clear understanding of each milling operation’s requirements, such as the CNC feed rate and cutting speed of each machine.
Defining Important Terms
Manufacturers choose CNC machines because of their ability to automate production with extreme precision. Although they can improve the overall productivity of manufacturing operations, it is still highly dependent on production speed.
Meanwhile, the overall speed of production will depend on your machine’s performance, which can be quantified through its feed rate, cutting speed, and rotational speed, defined below:
The feed rate in CNC machining is one of the most important factors to consider. It is defined as the velocity at which the cutter is fed. Put simply, it is the distance the tool travels during a single spindle revolution and is represented as distance per revolution.
When determining the optimum feed rates for CNC router operations, it is also important to consider the following:
- Tools Used. The cutting tool used in machining must be compatible with the material being fed. The feed rate will then be adjusted based on its compatibility as a cutting tool.
- Surface Finishing Requirement. The feed rate is inversely proportional to surface roughness. Depending on the level of smoothness required, the feed rate will be slowed down to get a smoother surface.
- Cut Width. Cut widths less than half a diameter may cause manufacturing defects due to thinning of the chip. The CNC feed speed is often increased to reduce or avoid this issue.
The cutting speed in CNC machining is also referred to as the surface speed. By definition, it is the relative velocity of the cutting tool against the surface of the material being fed. In simpler terms, it describes how fast the cutting tool moves along the workpiece surface. It is expressed as distance travel per unit of time.
Optimizing the operational cutting speed is crucial in improving CNC machining efficiency.
This will depend on different factors, such as:
- Material Fed. While the CNC machine is capable of working with a plethora of feed materials (wood, glass, metals, polymers, etc.), the speed through which the machine cuts through the material will depend on its hardness and thickness. Softer materials will be easier to cut through, making the cutting speed faster than hard materials.
- Cutting Tool Material. Lathe tools for CNC machines can be soft or hard and are made for varying applications. Hard tools are typically used in applications that require high-speed cutting, while softer tools are used in low-speed cutting operations.
- Tool Life. The life of the tool describes the period of peak effectiveness for a tool in cutting and decides the accuracy and cutting speed as its works through the material.
Revolutions per Minute
As the name indicates, revolutions per minute (RPM) describes the rotational frequency, or how many rotations are completed around the set axis within one minute. It is represented as a number per minute.
The chip load is defined as the size or thickness of the chip that is removed by one cutting edge of the tool in one single revolution. It is a measurement of the thickness of the material removed by each cutting edge (flute) during a cut and is a valuable piece of information that can be used to calculate new setups. It can be calculated using the following formula:
Higher chip loads are always recommended in CNC machining due to the following reasons:
- It improves the material surface finish.
- It controls heat produced during milling.
- It increases cutting speed, which decreases machining time.
Why are CNC Feed Rate and Cut Speed Important?
The cutting speeds and feed rates for CNC router operations are crucial elements in each process. As such, varying the magnitude of each element can impact the entire operation in the following ways:
Note: feed rate and cutting speed are inversely proportional. Increasing one can produce the same effect as decreasing the other, i.e., a high feed rate has the same effect as a low cutting speed.
- Tool life decreases when the feed rate is too low. Slower feed rates produce smaller chip loads. This means more time is spent grinding material to smaller particles, which produce high amounts of heat. In contrast, a higher feed rate produces larger chip loads, keeping your tool cooler and prolonging its life.
- Tools can break when the feed rate is too high. Feeding too much material at a constant RPM increases the chip load. The force exerted by the feed during this process becomes too much for it to handle, breaking the tool.
- A feed rate that’s too high can cause chatter. Increasing the feed rate also increases the vibration between the tool and the material, leading to chatter formation or a rough surface resulting from periodic unevenness.
Optimize Your CNC Projects with CAMaster
As a leading provider of CNC solutions, CAMaster is committed to providing knowledgeable advice to optimize your CNC milling operations and improve productivity in your facility.
For more information on how to streamline your processes and make the most of your CNC machine, technical support, or other services, get in touch with our experts through our contact form or by speaking to us directly by calling 1-866-405-7688.