Can You Machine Stainless Steel With CNC Router

Routers are common types of CNC machines that offer a high level of precision and repeatability. It ensures consistent quality in every cut and is suitable for parts that require tight tolerances. Additionally, CNC routers increase production efficiency and can handle intricate designs and shapes. 

One common question that arises is if it is possible to use a CNC router on metals. This machine that was conventionally employed for wood and soft plastics has undergone recent advancements which makes it possible to handle stainless steel parts. This article explores the feasibility, challenges, and best practices of using CNC routers for machining stainless steel. 

Can You Machine Stainless Steel With CNC Router 

Yes, it is possible to machine stainless steel using a CNC router. However, it may be challenging for novices to pull this through. CNC routers are designed to work with softer materials such as wood, plastics, and sometimes aluminum. You will find it slower and more labor-intensive when machining stainless steel with a CNC router when compared to other materials. 

The reasons for this are not far-fetched. Stainless is hard and can wear cutting tools easily. Furthermore, this metal has a low thermal conductivity. This implies when cutting through, it retains heat that arises as a result of friction. This can lead to overheating and damage to both the workpiece and cutting tool. As a machinist, it is important to understand these challenges and tackle them so you can successfully machine stainless steel with a CNC router.

How to CNC Router Stainless Steel Like a Pro

Using a CNC router on stainless steel workpieces requires careful planning and execution. Below is a guide on how to go about it

• Design Preparation

The first step is to prepare a digital blueprint of what you want the final part to look like. You do this using CAD software such as AutoCAD. The CAD design can be in 2D or 3D depending on the complexity of your project. Note that the machine cannot interpret the model created. Hence, you have to convert it to programming languages that the computer can understand using CAM software. The machine-readable format called G-code contains instructions that control the movement of the CNC router. 

• Machine Set up

Following the design phase, you set up and configure the machine. Choose the appropriate tools and CNC router bits based on the particular stainless steel alloy you are working with. Install the tool and calibrate it to zero by setting the machine’s origin point. Then, clamp the workpiece on the table using suitable fixtures. 

• Start the Machining Process

Thereafter, load the G-code into the router and double-check the program. Start the machining operation and monitor it as it runs to the end. The router bits move in predetermined directions and cut excess material away from the workpiece to create the final part. Closely monitor the machining process and watch out for possible tool chatter, incorrect cutting, and excessive vibrations. If needed, pause the machine and adjust the parameters.

• Finishing and Inspection 

The final step when CNC routing stainless steel is finishing and inspection. Once routing is complete, stop the machine and carefully remove the final part. Inspect for errors and check for dimensional inaccuracies. If the as-machined finish is not good enough, you can use finishing operations such as sanding, polishing, and coating to make it better. 

Stainless Steel Alloys Available for CNC Routing

The following are common stainless steel alloys you can use when CNC routing

• SS 303

SS 303 is an austenitic-grade stainless steel that contains up to 20% chromium. It is a free-machining stainless steel that is nonmagnetic and has good resistance to oxidation at a high temperature. This alloy is not readily coldworkable and does not get hardened when heat treated. Furthermore, SS 303 has excellent machinability properties because of the added sulfur content. While sulfur increases machinability, it makes the alloy less tough and more susceptible to corrosive attack. This property makes SS 303 not suitable for marine applications. 

• SS 416

SS 416 is martensitic stainless steel with a chromium content of 12-13%. Just like SS 303, this type is also free machining because of the addition of sulfur. However, it is magnetic and you can heat treat it to higher strength levels. SS 416 is the most machinable of all stainless steel alloys available. You can cut through at a high speed without the fear of tool breakage or wear. SS 416 has moderate corrosion and impact resistance properties. Additionally, you can find it in different forms including unhardened, hardened, and tempered. 

• SS 304

You can also refer to it as SS 18/8 because it contains 18% and 8% of chromium and nickel respectively. SS 304 is the most commonly used stainless steel grade. It is versatile and suitable for many applications. Though SS 304 has excellent corrosion resistance properties you must use it with caution in acidic environments. This alloy has a low thermal conductivity and may lead to heat concentration while cutting. Furthermore, SS 304 is naturally nonmagnetic. However, its magnetic properties may increase after cold working. 

• SS 316

SS 316 is made up of about 18% chromium and 14% nickel as the main alloying elements. It has one of the best corrosion-resistant properties of all stainless steel grades because of its additional molybdenum content. SS 316 is nonmagnetic and you can coldwork to further improve its mechanical properties. This alloy is ideal for demanding and high-temperature applications. However, it is tough and needs careful consideration when machining with a CNC router. 

• SS Grade 17-4 

SS 17-4 is a precipitation-hardening martensitic stainless steel that contains up to 30% chromium. It has a high strength with moderate corrosion resistance properties. You can machine this alloy easily in the annealed condition with a rating of 70%. However, consider cutting at a low speed with sharp router bits because SS 17-4 is susceptible to heat build-up and damage. SS 17-4 can be further heat treated to achieve hardness of varying levels.

Considerations for Machining Stainless Steel with a Router

To get the best results, keep the following in mind when cutting stainless steel parts using a CNC router 

• Router Capacity

The capacity of the router is an important consideration. Conventional routers were optimized to handle wood parts mainly. Ensure that the router has sufficient power and is designed for metal working. Using a router with low power may not provide the torque needed to handle stainless steel. This can lead to incomplete cuts and poor surface finish. 

• Tooling

The tool you use will determine your CNC routing experience. Go for router bits made of carbide or solid carbide. Carbide bits are harder and can withstand the heat stainless steel generates when cutting through. You should also consider the tool geometry and size. Use tools with a helix angle of 30 degrees or less. Furthermore, choose the size of the router bits based on workpiece thickness and depth of cut required. 

• Cutting Speed and Feed Rate

The cutting speed and feed rate when using a CNC router on stainless steel are also important. Use a low cutting speed to prevent overheating and thermal expansion. Furthermore, optimize the feed rate based on the specific stainless steel alloy. The feed rate should be low to avoid the incidence of tool deflection, wear, and breakage. 

• Lubrication and Cooling

Lubrication and cooling are important aspects of CNC routing with stainless steel. Use suitable oil-based lubricants to keep the friction between the workpiece and cutting tool at a minimum. Reducing lubrication prevents heat build-up and thermal damage. Furthermore, coolants also help to keep the working temperature within acceptable limits. You can either use flood or mist cooling systems based on your project requirements. 

• Workholding and Fixturing

When CNC routing stainless steel, you must maintain stability and prevent unnecessary vibrations. One way to go about this is to use workholding fixtures. There are different fixtures you can utilize with the most common being vises and clamps. You can also opt for custom fixtures based on your project specifications. Custom fixtures may be necessary for delicate and thin-walled parts to prevent distortion and deflection. 

Conclusion

It is possible to machine stainless steel using a CNC router. However, it can be challenging, especially for beginners and novices. Stainless steel is hard and heats up rapidly which can affect the cutting tool and the workpiece itself. Hence, it requires careful consideration of several factors including the capacity of the machine, tool selection, cutting speed, and feed rate. Additionally, you have to use appropriate cooling and lubrication systems and properly clamp the workpiece to prevent vibration during machining. To avoid mistakes, consider using a reputable CNC routing service provider to leverage their experience and expertise.