CNC (computer numerical control) machines are tools that are used for making precise cuts with high accuracy and repeatability.
The ability to control different parameters and use different cutting tools makes them ideal for machining a vast variety of materials.
But can a CNC machine cut metal? What type of CNC machine should you have to cut metal?
This article discusses the ability of CNC machines to cut metal and provides a detailed guide on things that affect the machining ability of a CNC machine.
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CNC Metal Cutting—Is it Possible?
CNC machines can cut metals like steel, aluminum, and copper. However, metals are hard materials, and not all CNCs can cut metal. The ability of a CNC machine to cut metal depends upon factors such as its rigidity, spindle power, the cutting tool used, and the machinability of the metal.
CNC machines work by using a high-speed rotating tool that comes in contact with the surface of the workpiece and removes the material at the desired depth.
When the tool comes in contact with the workpiece, it delivers a strong cutting force, producing the required cut.
However, machining metal requires a comparatively stronger cutting force than machining materials like wood, plastics, etc.
As a result, not all CNC machines can cut metal, and you require a rigid machine capable of delivering a strong cutting force to cut through the metal surface.
How to Cut Metal on CNC?
However, there are certain things that you need to ensure to attain a clean cut in metal workpieces.
Get a Rigid CNC Machine
The first step to cutting metal on a CNC machine is to get a good CNC machine capable of cutting metal.
However, when buying a CNC or making a DIY machine, it is important to ensure that it has a rigid chassis as it houses all the other components and helps to deliver strong cutting forces with no or minimal flexing.
Ensure Firm Clamping of the Workpiece
After ensuring the rigidity of the CNC machine, it is important to ensure firm clamping of the workpiece to avoid displacement under the action of the cutting force.
Some of the common techniques used for clamping the workpiece include using double-sided tape, T-clamps, Cam clamps, L-clamps, etc.
While double-sided tape is used for clamping lightweight workpieces, clamps are suitable for holding metal workpieces firmly in their place.
Apart from this, you can also use a vacuum bed to hold the workpiece in place.
Depending upon the size and weight of the metal workpiece, you will require a powerful vacuum pump to operate it.
Generally, most CNC machine brands do not provide a vacuum bed table with the machine, but you can purchase it as an optional accessory or use your CNC machine to make a DIY vacuum bed.
Select an Appropriate Cutting Tool
The type of cutting tool used for machining metal determines the surface finish of the cut and the cutting speed.
Machining metals require a durable cutting tool to deliver strong cutting forces without snapping.
Generally, a carbide end mill is recommended for machining metal as it provides the strength to deliver strong cutting force with minimal tool wear.
Similarly, the number of flutes on the end mill also affects the cutting process.
A cutting tool with fewer flutes (1 or 2-flute) provides easy clearance of chips, making it suitable for machining ductile metals like aluminum and copper, whereas more flutes produce smoother cuts with less chip clearance.
Use Adaptive Cut
CNC machining involves contact between the high-speed rotating tool and the workpiece.
The contact results in a high impact load that can damage the cutting tool or workpiece.
As a result, it is advised to use an adaptive toolpath or ramp tool path to gradually increase the depth of cut and reduce the impact load.
This enhances the tool life and produces a smoother cut with a good surface finish.
Use Cutting Fluid
Machining metal workpieces involves high friction that generates immense heat, damaging the workpiece and the cutting tool.
Therefore, it is advised to use a CNC cutting fluid to prevent overheating of the workpiece and the cutting tool by regulating the temperature at the cutting area.
This cutting fluid also provides lubricating action to further reduce the frictional heat and improve the quality of cuts made in metal workpieces.
Generally, a coolant system consists of a fluid storage tank, a pump, and a delivery hose to deliver the cutting fluid to the work area.
Things to Consider When Buying a CNC for Metal Cutting
If you are planning to buy a CNC machine for cutting metal, there are various things to consider.
Rigidity of the Chassis
A CNC machine with an all-metal chassis provides comparatively greater rigidity than machines with wood chassis.
Moreover, entry-level CNC machines have an aluminum chassis that provides good rigidity but can undergo flexing when cutting hard metals like steel.
Hence, it is advised to identify your requirement and look for a steel chassis in your CNC machine to provide better rigidity.
Apart from that, you can further improve the machining ability of your CNC by using heat-treated metal workpieces, such as annealed steel, to enhance their machinability,
Power of the Router
The router or spindle used in CNC machines is characterized by its RPM and power.
Generally, CNC machines used for machining wood and plastic have high RPM spindles that provide fast cutting speed.
On the other hand, machining metal requires high torque to remove the material from its surface.
Unlike wood, machining metals at high RPM can cause various issues, such as high frictional heat and build-up edges that drastically reduce tool life.
Therefore, when selecting a CNC machine for metal cutting, it is advised to look for power rather than high RPM.
Work Area of the Machine
The work area of the machine might not sound like an important feature, but it plays an important role in determining the type of applications you can use your CNC for.
Although a CNC machine with a small work area might be suitable for cutting small metal workpieces, it is advised to look for a larger work area that provides you the ability to expand in the future without replacing the machine.
A larger work area enables you to machine multiple workpieces in a single go, reducing cycle time and increasing productivity.
Therefore, a small-sized CNC, such as Bantam desktop mill, Tormach 1100M, Tormach PCNC 440, etc., is suitable for small-scale metal cutting businesses, whereas larger machines are recommended for high-volume industrial applications.
Cost of the Machine
The cost of a metal-cutting CNC machine can be significantly high when compared to CNC machines used for cutting wood and plastics.
This is because of the rigid build quality and higher power needed to cut through metal surfaces.
Apart from that, an increase of a few inches in the work area also increases the cost of the machine significantly.
Therefore, it is advised to understand your application and evaluate the cost of the machine with the cost of outsourcing the job to a professional metal-cutting service.
Generally, if your application rarely requires metal cutting, it is advised to outsource the job rather than invest in costly metal-cutting CNC machines.
Cutting metal on a CNC machine can be challenging, but using an appropriate CNC, selecting the right cutting tool, working with machinable metals, and setting the optimal parameters will help you overcome these challenges and produce clean cuts in metals.
The rigidity and power of your CNC are the key factors in determining its ability to cut metal.
Therefore, a CNC mill is preferable over a CNC router for machining metals.
Furthermore, when using a CNC to cut metal, it is important to use cutting fluid and learn about different toolpaths, such as ramp or helix cut to minimize tool wear.
Frequently Asked Questions (FAQ)
How much does a CNC machine cost?
The cost of a CNC machine depends upon various factors such as machining ability, build quality, brand, etc. While entry-level CNC machines can cost around $150-$3k, industrial heavy-duty machines can cost as high as $50k, and even more, depending upon their number of axes.
What type of metal can a CNC cut?
An entry-level metal-cutting CNC machine can be used for cutting soft metals such as aluminum, copper, brass, etc., whereas high-end machines can be used to cut hard metals like steel and titanium.
Can a wood-cutting CNC be used to cut metal?
No, a wood CNC machine cannot be used to cut metal because of its less rigid chassis and low spindle power. However, high-end wood CNC machines are capable of performing shallow cuts in soft metals like aluminum and copper.