Complete Guide for Stainless Steel CNC Machining

 

Stainless Steel CNC Machining

In CNC stainless steel (SS) machining, you will use computer numerical control (CNC) machine to cut material. Here, the CNC machine cuts SS according to your design.

Today’s guide explores everything you should know about CNC machining stainless steel. Whether you want to learn about best grades for CNC machining, CNC machining costs or techniques – all information is right here.

Let’s dive right in:

Choosing Stainless Steel Grade for CNC Machining

Properties such as corrosion resistance, strength and durability makes stainless steel popular for CNC machining.

Currently, there are many stainless steel grades available for any machining process. Let’s look at the vital aspects when choosing stainless steel for machining:

What to Consider Before Choosing Stainless Steel for Machining

Generally, there are many factors you should consider before choosing stainless steel for any machining process. They include:

  • Cost: Stainless steel material price varies depending on the grade.
  • Grade Availability: Some stainless steel grades are made on order and not available on demand. Ensuring your desired stainless steel grade is available is important especially where you have time concerns.
  • Heat Treatment: Impacts on the hardness of your stainless steel and thus overall mechanical properties. However, austenitic steel grades are not subject to heat treatment.
  • Magnetism: Some applications may require magnetic properties which you will find absent in austenitic stainless steel grades.
  • Strength: the tensile strength vary depending on individual elements in the stainless steel material.

Types of Stainless-Steel Grades

Generally, there are five classifications of stainless steel. From these grades, you can find suitable stainless steel grade for you application.

1. Austenitic Steel Grades

The SS 304 and SS 316 are some of the most popular grades available in the market. These grades are popular for their:

  • Excellent corrosion resistance
  • Easy to machine
  • Suitable for most welding techniques

Austenistic stainless steel grades

Austenitic Stainless Steel Grades

2. Precipitation Hardened Steel Grades

Includes the common 17-4 PH and 15-5 PH grades and are capable of heat treatment. At the same time, they exhibit outstanding strength and corrosion resistance.

These steel grades are CNC machinable finding use in making highly reliable and durable parts.

Tensile strength precipitation hardened stainless steel grades

Tensile Strength Precipitation Hardened Stainless Steel Grades

3. Duplex Stainless-Steel Grades

These steel grades are a hybrid of austenitic and ferritic structures with improved strength and corrosion resistance. They feature reduced nickel and molybdenum finding. As a result, they find use in many heavy industries.

Duplex stainless steel grades

Duplex Stainless-Steel Grades

4. Ferritic Steel Grades

They have about 12% chromium content with magnetic capability and impressive resistance to stress corrosion. It is usually induced by chlorides.

They however have a lower resistance to heat and corrosion compared to austenitic steel grades.

Ferritic stainless steel grades

Ferritic Stainless-Steel Grades

5. Martensitic Steel Grades

Martensitic steel grades are capable of heat treatment. As a result, they hardening with chromium levels at 10%. While easily machinable, its corrosion resistance pales in comparison to austenitic grades.

Consequently, they find use in cutlery, auto parts and medical utensils.

Martensitic steel grades

Martensitic Steel Grades

Advantages of CNC Machining Stainless Steel

Choosing CNC to fabricate stainless steel offer many benefit to both manufacturers and part users. Of course, it is the reason the technology is popular today.

Let’s look at he benefits:

I. It is possible to machine stainless steel in large volumes when using a CNC machine due to the process being highly repeatable.

II. Stainless steel is highly flexible and versatile allowing CNC machining even for complex parts especially austenitic grades.

III. The strength exhibited by stainless steel grades, especially martensitic, can tolerate the machining stresses when using CNC machines.

IV. When using a CNC machine in processing stainless steel, you achieve greater accuracy even when choosing tight tolerances.

V. You can machine stainless steel grades to tolerances within 1.00 mm minimizing wastage of material and hastening the process.

How Much CNC Machining Stainless Steel Cost

Knowing how much CNC machined stainless steel parts cost is a key important part in your budget. However, for accurate cost of CNC machining stainless steel parts a reliable manufacturer.

Among the key factors determining CNC machining costs include:

  • Stainless steel grade
  • Design complexity
  • Part size being worked on
  • CNC machining equipment required
  • Process duration

When undertaking a project, these factors can be considered given the design parameters and cost thus estimated.

Types of Stainless Steel CNC Machining Services & Operations

CNC machining stainless steel involves many operations such as cutting, milling, drilling, etc.

Of course, they determine the types of stainless steel parts.

1. Stainless Steel CNC Cutting

CNC cutting of stainless steel involves extracting smaller pieces of stainless steel from a larger piece to suit the design needs. There are two main CNC stainless steel cutting machines available: the CNC laser cutter and the CNC router.

stainless steel CNCcutting

Stainless Steel CNC Cutting

· CNC Laser Cutter

Employs a laser beam with immense power and a concentrated stream to cut out material from a stainless-steel sheet. A CNC laser cutter is especially useful when cutting intricate designs due to its high accuracy.

The cutting process when using a CNC laser employs heat application and is non-contact. The CNC laser cutter encompasses a laser head with a lens to focus the beam with high intensity through a nozzle.

CNC laser cutting

CNC Laser Cutting

Thereafter, the beam melts the stainless steel according to the computer-fed instructions. A compressed gas simultaneously cools the lens while also removing the cut out metal vapor.

Some of the advantages of employing CNC laser cutting with stainless steel sheets include:

  • Capability to undertake complex designs to a high accuracy level.
  • Since CNC laser cutters work on a non-contact approach, the stainless steel material remains unchanged and uncontaminated.
  • The resulting cut is usually clean without the need for secondary processing.
  • When using CNC laser cutters, there’s reduced need to incorporate other cutting equipment.

There are different types of CNC laser cutters classified according to the laser medium and its active state. The most common types are:

· CNC CO2 Laser Cutter

Is the most common, utilizing carbon (IV) oxide and offering high power while demonstrating elevated efficiency. These cutters are capable of undertaking fine and intricate cuts on both thin and thick stainless steel sheets.

· CNC Crystal Laser Cutter

Employs specially developed doped crystals and generate higher output power allowing use on very thick stainless sheet workpieces.

· CNC Fiber Laser Cutter

Utilize diodes in beam creation with fiber-optic cable finding use as a conduit. Facilitates finer cut quality at high process speeds particularly when working with very thin stainless steel sheets.

CNC Router to Cut Stainless Steel

A CNC router executes a three-axis cutting approach on stainless steel workpieces. It is capable of moving forward and backwards (x-axis) up and down (z-axis) and sideways (y-axis). CNC routers are faster and more accurate than manual operations and can support high volume processes.

CNC Router

CNC Router

2. CNC Turning Stainless Steel

CNC turning is a metalworking process that involves material removal by rotating a workpiece as a tool works on it. The CNC turning processes can involve operations such as drilling, grooving, boring, facing, parting and knurling.

Usually, a CNC lathe works on cylindrical stainless steel bars rotating on a spindle and worked on by a tool.

You can position the tool along multiple axis and feed the stainless steel bar to achieve the desired shape. CNC turning is useful in fabrication of stainless steel parts for use in different industries such as the automotive industry.

3. CNC Milling Stainless Steel

CNC milling stainless steel is a subtractive manufacturing process that employs a tool fitted on a spindle capable of rotation. The tool works on a stainless steel workpiece that is immobile until the desired design is achieved.

CNC milling machine can handle up to 5 axis. Consequently, you can work on designs that are uniquely complex without the need of employing multiple machines.

In executing CNC milling stainless steel, you first develop a design using CAD (Computer Aided Design). Next, you will convert the design to CNC program.

After this, you will load the program to execute the desired operation.

4. CNC Drilling Stainless Steel

The purpose of CNC drilling stainless steel is to make holes usually for assembly purposes such as accommodating bolts and screws. The machine uses a high speed rotating drill bit.

Employing CNC drilling of stainless steel begins with designing using CAD before conversion to machine ready instructions using CAM. Loading these instructions into the CNC drilling machine guides the drill operation according to the design.

CNC Drilling stainless steel finds use across various industries such as automotive engine making and bridge construction.

Miscellaneous Operations in CNC Machining Stainless Steel

Miscellaneous operations relating to CNC machining stainless steel employ machine tools and may or may not produce swarf.

Some of the most common operations include:

CNC Burnishing Stainless Steel

CNC burnishing is a cold working process that involves no material removal to achieve a smooth and even surface. You can employ lathes and milling machines in CNC burnishing stainless steel to improve surface hardness and achieve dimensional accuracy.

Burnishing finds wide use in industry ranging from making motor end covers, valve guides and rods, and fan rotor shafts. You can classify CNC burnishing machine depending on the tooling geometry as follows:

Ball Burnishing Stainless Steel

Tooling employs either a single or multiple ball held by a spring or fluid pressure and the workpiece. A hydraulic pump is responsible for the fluid flow that positions the ball for action on the workpiece.

Controlling the fluid pressure allows you to direct the CNC burnishing process. Alternatively, you can employ a spring to hold the ball in position while conducting the burnishing process.

Roller Burnishing  Stainless Steel

Tooling in the roller burnishing machine utilizes either one roller or several supported by a shank capable of rotation. You can join the shank to a lathe, milling or drilling machine to execute the burnishing process upon contact with workpiece.

CNC Threading Stainless Steel

CNC threading involves furnishing threads on a stainless-steel bar to make screws for use in assembly and fastening processes. CNC threading is mostly executed as a subtractive process employing lathe machines.

Threading Methods

There are several threading methods you can employ on your stainless-steel pieces. The most common methods are as follows:

I. Thread Cutting: Useful for small productions, when handling imprecise blanks or when the process demands full thread depth. Can include the following techniques:

  • Single-point Threading: Employs linear moving tooling woth a single point to create threads on a cylindrical or conical stainless steel workpiece.
  • Thread Milling: Employs a milling cutter capable of rotation to form threads only where you can organize a helical path for the tool.

II. Thread grinding: Employs a grinding machine employing wheels fashioned in the desired thread shape.

Applications of CNC Machined Stainless Steel Parts

Stainless steel parts produced via CNC machining finds wide usage across industries. Some of the leading applications of these parts include:

  • CNC Aerospace parts: The landing gear, airframes and some jet engine components employ stainless steel components fashioned from CNC machining.
  • Automotive Industry: CNC machined steel parts find use in making different automotive parts such as engine components like connecting rods. These may include CNC electronic parts and components.
  • Chemical Industry: Equipment employed in the chemical industry utilize stainless steel for its durability stemming from corrosion resistance.
  • Construction: Structures such as bridges employ stainless steel due to its strength and resistance to the elements allowing longevity.
  • Energy Sector: Power generation plants employ parts and components of stainless steel that are CNC machined in reactor tanks and heat exchangers.
  • Kitchenware: Several utensils, cookware like pans and pots and sink, cookers and grills are a result of stainless steel CNC machining.
  • Medical Industry: Equipment in the medical industry such as surgical tools are developed by CNC machining due to its outstanding properties. In fact, there are many CNC medical parts
  • Transportation: Different transportation vehicles such as ships, trains and motor vehicles employ parts and components made of stainless steel.

Stainless Steel CNC Machining Tips

CNC machining stainless steel is essential in the production of parts and components employed in various sectors. However, when CNC machining stainless steel, it is important to bear in mind the following tips:

Internal Edge Radii

Always employ radii for your stainless steel workpieces’ internal edges to prevent tool wear and deformation owing to machining stress.

Design Features

Do not include features you cannot make with CNC machine. In such situations, you will get other fabrication alternatives.

For instance, avoid having tiny features that will pose great difficulty to machine due to absence of required tools.

Parameter Sufficiency

Employ sufficient parameters such as Surface Feet per Minute (SFM) to ensure efficiency in the CNC stainless steel machining.

Tool Material

Ensure appropriate tool material selection to prevent chipping and quick wear when CNC machining. Cemented carbide, high-speed steel and tungsten HSS offer good strength showing when machining stainless steel.

Secure CNC Machines

Ensure the CNC machines are rigid and well secured to prevent extreme movements caused by vibrations during operation.

Protective Gear

Have protective gear when operating CNC machining of stainless steel such as protective glasses, overalls and gloves. The CNC machines and stainless steel chippings are some of the potential sources of danger.

Tolerance Use

Limit the use of tolerances to prevent high machining costs and processing times employing them only where necessary.

Coolant

Utilize an appropriate coolant to prevent heat induced deformation on the stainless-steel workpiece and manage chip formation. A coolant can impact the surface finish and speed of operation alongside capacity to resist corrosion.

Depth-to-Width Ratios

When designing cavities, consider their depth-to-width ratios as making them overly deep can cause tool deficiencies such as fracturing and deflection.

CNC Stainless Steel Machined Parts Surface Treatment

While stainless steel offers great resistance to corrosion and heat, you can still employ surface treatment to achieve other characteristics. Additionally, the CNC machining process can alter the surface of the stainless steel requiring treatment to restore it.

You can classify the surface treatments employed on CNC stainless steel machined parts based on their role as follows:

Removal of Black Oxide Layer

The manufacturing processes that stainless steel undergoes such as rolling and welding can result in an oxide layer formation. You can restore the luster of stainless steel by removing this oxide layer via the following treatments:

I. Sandblasting: Employs a stream of pressurized adhesive media which scrubs off the oxide layer.

II. Pickling: Employs nitric and hydrochloric acids to remove the oxide layer on the stainless steel part upon immersion.

Producing a Mirror Finish

Many stainless-steel products employ a smooth surface finish with mirror like characteristic. You can achieve this look by employing different polishing methods on the stainless steel parts as follows:

I. Mechanical Polishing: Employs mechanical abrasion to achieve a bright and fairly level surface. It is however time consuming, challenging for intricate parts, poses pollution threat and results in less luster.

II. Chemical Polishing: Employs chemical solutions to achieve the desired shine efficiently and at low cost in addition to working on intricate parts. However, it is only suitable for small volumes and requires large and well ventilated space.

III. Electrochemical Polishing: Employs a reduction process via application of DC current that ionizes metal surface dissolving it resulting in a shiny surface. Can support treatment of complex parts and high volumes making it affordable in the long run.

Producing a Colored Finish

Some surface treatments colorize the surface of the stainless steel while improving its characteristics such as resistance to corrosion and wear. You can achieve a colored finish by employing:

I. Chemical Oxidation: Color application is through an oxidation process employing chemicals solutions containing acids, bases and mixed salts.

II. Electrochemical Oxidation: Undertakes ion deposition from chemical solvents with the stainless steel as the cathode.

III. High-temperature Oxidation: Achievement of the desired colored coating is by immersion of the stainless steel part in salts under specific conditions.

Conclusion

Stainless steel CNC machining is essential in the production of parts and components of particular qualities finding use in diverse applications. The insight provided in this guide is sure to help in your next stainless steel project to ensure it is successful.

More Resources:

What is CNC Machining – Source: ThomasNet

Stainless Steel – Source: Wikipedia

CNC Milling Components – Source: HMAKING

CNC Turning Parts – Source: HMAKING

CNC Drilling Parts – Source: HMAKING

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