CNC Machining Material Selection Guide

19 Aug.,2024

 

CNC Machining Material Selection Guide

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Have a project with a great design? You&#;re off to a strong start, with the specs and prototype already finished. Now you are ready to start crafting your product. If you&#;re interested in using a CNC machine to manufacture the new part, you won&#;t be disappointed with your results, especially if you choose the proper material.

CNC machining has become a staple for a wide array of disciplines that need specialized parts manufactured for their projects. CNC materials have expanded to meet the demands of consumers, engineers, contractors and other fields to create solutions for very specific applications. Having a variety of materials to choose from is a luxury, but it can also be overwhelming and confusing if you don&#;t analyze what your needs are and ask yourself some questions before making a decision.

If you want your project to run efficiently and produce products that fit perfectly, this guide can help you during your decision-making process.

This guide will walk you through the following steps so you can choose ideal CNC materials for your project:

Essential Questions for Selecting the Right CNC Material

Choosing the right materials for your part is the difference between mediocre outcomes and optimum results. These important questions are the best place to start. The more you can narrow down the CNC materials that would be the best fit for your part, the easier it will be to select a material that will suit your needs and be cost-efficient.. Here are some things you should consider.

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How Will the Part Be Used?

Since CNC machining has expanded over the years, so have CNC machine components. Similar types of materials can be used for a variety of products and result in varying capabilities. Insulation is a great example. The materials used to insulate a Breathalyzer may differ from the materials that provide insulation in a camera. They&#;re both used for the same purpose, but not in the same way or for the same type of outcome. On the other end of the spectrum, materials for soundproofing walls have different specifications and uses. Start your material search by considering your product&#;s results.

Will the Part Be Used Outdoors or Indoors?

Outdoor and indoor environments are very different &#; one completely depends on the weather, whereas the other is usually a much more controlled environment. For instance, in outdoor environments, you need to plan for moisture. Your material will need to be able to resist the effects of corrosion, such as rusting, in order to maintain its integrity over time. Rigid foam provides a great example of a material that resists moisture and rusting while also maintaining structural integrity.

Extreme temperatures, both high and low, will also eliminate certain materials as the best option. You may also need to meet code for FDA-regulated specifications. Where your products will be used or stored and how they react to moisture and extreme temperature change becomes a cornerstone in deciding which material to go through with.

What Is the Material&#;s Stress Load?

High-stress loads can cause certain materials to strain or even break. When you&#;re considering which material to use for your part, make sure you&#;ve accounted for stress load. If your part will be exposed to high stress, the material it&#;s made of will need the ability to resist loads and prevent deformation.

What Is the Material&#;s Dimensional Tolerance?

When you&#;re considering CNC-machined components, pay close attention to dimensional tolerance. In addition to impacting the success of your manufacturing process, dimensional tolerance also affects your bottom line, the parts and tools you choose and their assemblies and cutting methods. 

You need to know the tolerance required for your part. If you&#;re working from an old part design or sketch, it&#;s a good idea to make sure the tolerance is appropriate. Typos can easily occur in documentation. Even if the information is correct, if you can make an adjustment to loosen the tolerance and still allow the part to work to its full potential, you could save money by re-evaluating tolerance. Tighter tolerances are often more expensive to produce.

Some machining tools use a standard dimensional tolerance as a default, but if you don&#;t specify a tolerance, or discover that your numbers are off, you&#;ll end up ordering a part that may not fit or work at all. While you can fix this, it will take more time out of your project to have the part resized or reordered, and will end up costing you more than if you had determined the correct tolerance upfront. This simple initial step can help you save money in the long run.

If you aren&#;t sure what the exact tolerance is for the part you need, instead of risking a guess, let a CNC machining company like American Micro Industries help you figure it out.

What Is the Required Fastening?

If the CNC-machined components you need are going to be used as fasteners, consider that as you choose a material. Materials influence how securely fasteners will fit together. Different materials have different properties &#; for example, strength, corrosion resistance, brittleness and galvanic corrosion &#; so you should choose a material that reflects the properties you want your fasteners to have. The most common material for fasteners is steel, but you can also create quality fasteners from other materials.

If you&#;re searching for a new part to fasten, it needs to fit perfectly. If you fail to consider the type of fastening you&#;ll need when you&#;re deciding on a material, your mechanism may not function properly.

What Are the Operating Temperatures?

Consider the operating temperature the part will need to withstand when it&#;s in place as a part of your manufacturing process. You want to be sure the melting point of the material you choose is lower than that of the operating temperature. You also want to ensure the material can handle operating temperature change. While some of the more durable materials are built to withstand these changes, many will show signs of warping, expansion or breakdown over time. Extreme temperatures can also negatively impact the durability of some materials.

Operating temperature is equally as important to know when you&#;re CNC machining materials, so you can be sure the temperatures that result from the cutting and shaping of the part will not distort it. Making the connection between the operating temperature and the material you&#;re using is essential to a successful design and production run.

High Temperatures and Their Impact on Materials

High temperatures play a crucial role when selecting what materials to use, as many materials will deteriorate under extreme heat. A popular plastic that loses strength under high temperatures is polyvinyl chloride, or PVC. While it has a good fire resistance rating, its working temperature is about 176° F. Stability tends to be lost around 280° F, making it unfit for some projects.

Some materials are resilient and durable under these high-heat conditions. For example, polyisocyanurate has properties that do not allow it to melt or freeze. The thermoset plastic is processed as a viscous material first, allowing it to form multiple shapes. After curing, it becomes rigid and exceptionally stable. When you&#;re wondering what materials you can use in a CNC machine to create the part you need, make sure you consider how the material handles high temperatures.

What Are the Weight and Stress Capacity?

Depending on what you want to do with your CNC&#;machined components, you should consider the weight of your materials. Bigger isn&#;t always better, and less doesn&#;t always mean more &#; especially when it comes down to cost.

Heavy materials absorb a great deal of stress. For projects that require excessive weight&#;bearing capabilities and resistance to high-stress loads, you may consider heavy materials. If you work on weight-sensitive projects, however, you might want to avoid heavy materials.

Lightweight materials are popular for weight-sensitive projects. While they are not as hefty as heavy materials, they still are durable and able to absorb a substantial amount of stress. Unfortunately, they are not very cost-effective, as they usually won&#;t include every material feature desired for your project. Lightweight materials are ideal for a number of products, but if cost is an important factor, they might not be a good fit.

Choosing between heavy and lightweight materials is just one reason why it&#;s important to prioritize the most important characteristics for your CNC-machined part. That way, you can specify what elements are crucial for your part in order for it function properly, eliminate materials that don&#;t meet those standards and then compare costs.

Strength doesn&#;t necessarily mean how much weight an object can withstand. There are more components that may need to be examined, such as:

  • Tensile strength: An object&#;s resistance to breaking under tension.

  • Endurance strength: 

    An object&#;s o

    verall 

    stress absorption

     capacity.

  • Wear resistance: 

    An object&#;s

     abilit

    y to

     handle friction or 

    be

     self-lubricatin

    g.

     A good example of this is Ultra High Molecular Weight Polyethylene, or UHMW. It&#;s a similar product to Teflon®, but it is more abrasion-resistant.

  • Hardness: 

    An object&#;s ability to

     withstand pinpoint surface loads. 

    Hardness

     is usually indicated with a Brinell or Rockwell hardness number.

What Are the Overall Project Costs? 

The most expensive materials are usually high-strength, lightweight materials. The best method for choosing a cost-effective component is selecting one that meets your strength profile, temperatures restrictions and fitment requirements. The more crucial requirements or restrictions you have for your materials, the easier it will be to focus on those key elements.

Finding an industry that provides free quotes and no minimum for your materials will help cut costs right off the bat. Once you narrow your details, you can decide on a more cost-efficient material that meets most of your needs.

What Materials Can Be Used in a CNC Machine?

A better question might actually be what materials can&#;t be used. CNC machines cut through nearly any material you can think of. While you can use a wide range of materials in a CNC machine, the most commonly employed materials used are:

  • Metals: Such

     as aluminum, brass or steel

  • Plastics: 

    Such as

     Acetal (POM), Acrylics (PMMA), Polycarbonate (PC) and Polypropylene (PP)

  • Wood: Such as

     hardwood, plywood 

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    or

     softwood 

  • Foam: Such as carving foam and rigid foam, which

     tend to be more lightweight yet durable

What Type of Material Should You Try?

What Type of Material Should You Try?

Once you&#;ve considered all of the factors listed above, chances are you&#;ll be able to determine which material is the best fit for your part. It may take some level of tweaking and experimenting to find the exact choice. Here&#;s an overview of four popular materials used in CNC-machined components:

  • Rigid foam: By methods of conduction, 

    rigid foam

     serves as the foam with the highest insulation value. It can perform in temperatures as low as -100° F and as high as 200° F. 

    Rigid foam

    also holds a higher R-value

    , which makes it a premium choice for floors, walls and other structure-based products that need to withstand moisture.

  • Carving foam: 

    Carving foam

     can take on nearly any shape. It&#;s usually used as a model for molds because of its flexibility, but it&#;s also used in components such as gaskets and seals. Carving foam contains polyisocyanurate, which is dense and resistant to extreme temperatures.

  • Phenolics: If you need to meet military-grade specifications such as MIL-I-, 

    phenolics

     can meet this requirement. There are several to choose from, such as CE, LE, G10, G10/FR4, G9, G11 and G

    7.

     Each has its own set of strengths. For example, the fine weave of phenolic linen yields good mechanical properties, dimensional stability and a better finish for machined components than CE material. However, 

    phenolic linen is

     not suggested for electrical primary insulation. LE phenolics meet Mil-I-/13 FBE requirements, while CE 

    phenolics meet

     Mil-I-/14 FBG requirements.

  • Plastics: 

    Plastics

     come in many types,

     and a majority are used for bushings, bearings or electrical insulation. That said, a market exists for the more popular types of plastics. 

    Plastic&#;s range of uses is

     broad and benefits many industries, such as aerospace, automotive, medical and electronics.

General Tips on CNC Machining Certain Materials

The decision of which of the CNC machining materials to use for your part ultimately depends on what you&#;re looking to create, but here are some general tips to use as a brief CNC materials guide:

  • Consider non-metallic materials: Don&#;t assume metals are your best option. Non-metallic materials have become popular because they are lightweight yet durable &#; like foam you can mold into various shapes. Non-metals also retain small details during cutting. If your project seems like one that may benefit from the use of non-metals, plenty of options can benefit your final product.

  • Know the difference between foams: Remember that rigid foam and carving foam serve different purposes. While both are lightweight, yet durable, rigid foam is best for parts with a focus on structural integrity and stability, while carving foam is often used as insulation and 

    prototypes for molds

    .

  • Consider phenolics:

     Phenolics are great options, especially when you need to adhere to specific regulations or specifications for military-related projects.

  • Learn about different plastics: You can choose from a wide variety of diverse plastics. Acetal is often used for bushing and bearing replacements. Polyvinylidene fluoride polymer, or PVDF, is used in insulation for electrical wiring. You can employ UHMW in medical biomaterial, such as knee, hip and spine replacement devices. These are just a few examples of the endless possibilities offered by plastics.

Contact American Micro Industries to Discuss CNC Machinin

g M

aterials

Ask yourself what type of company you want to work with to machine your materials. Look for turn-key industries with strong attention to detail and ability to create hard-to-find parts. Do your research and select your company based on values, quality and efficiency as well. American Micro Industries offers the solutions you need in a timely and affordable fashion.

This guide should provide some insight and guidance to your decision-making process. Get in touch with us to discuss any additional concerns about materials or the CNC machining process to clear up any lingering questions you may have. When you are ready to begin, we are ready to assist you.

CNC machining frequently asked questions

We are asked many questions about CNC machining during the week, many from those commenting on our articles. That&#;s why we have decided to start a series on the most frequently asked question we receive.

This month we start with CNC machining frequently asked questions. If you have any question you would like answering then please comment on this post and we&#;ll update this section as soon possible.

Keep checking back to see the latest answers.

What is CNC?

Computer numerical control (CNC) is the automation of machine tools by means of computers executing pre-programmed sequences of machine control commands. This is in contrast to machines that are manually controlled by hand wheels or levers, or mechanically automated by cams alone.

In modern CNC systems, the design of a mechanical part and its manufacturing program is highly automated. The part&#;s mechanical dimensions are defined using computer-aided design (CAD) software and then translated into manufacturing directives by computer-aided manufacturing (CAM) software. The resulting directives are transformed (by &#;post processor&#; software) into the specific commands necessary for a particular machine to produce the component and then are loaded into the CNC machine.

What is CNC Machining?

CNC machining is a manufacturing process in which pre-programmed computer software dictates the movement of factory tools and machinery. The process can be used to control a range of complex machinery, from grinders and lathes to mills and routers. With CNC machining, three-dimensional cutting tasks can be accomplished in a single set of prompts.

When a CNC system is activated, the desired cuts are programmed into the software and dictated to corresponding tools and machinery, which carry out the dimensional tasks as specified, much like a robot.

What is the difference between NC and CNC?

NC stands for Numerical Control whereas CNC stands for Computer Numerical Control. In NC Machine the programs are fed into the punch cards. But in the CNC machine, the programs are fed directly into the computer with the help of a small keyboard similar to our traditional keyboard.

What is the difference between CNC and DNC?

DNC (Direct Numerical control/ distributed numerical control) denotes the networking of CNC machines. DNC system uses a large mainframe computer to control a number of NC machines. The program is done externally then sent to individual machines.

What do CNC machinists do?

CNC machinists work with computer numeric controlled ( CNC ) heavy machinery from setup to operation to produce parts and tools from metal, plastic or other materials. Computer numeric controlled equipment is precision machinery that cuts, grinds, or drills into the material.

How many types of CNC machines are there?

There are basically five different types of CNC machines:

  • Plasma Cutting Machine.
  • Laser Cutting Machine.
  • Milling Machine.
  • Router Machine
  • CNC Lathe Machine.

Which materials are used in CNC Machining?

Almost any material can be used in a CNC machine. It really depends on the application. Common materials include metals such as aluminum, brass, copper, steel, and titanium, as well as wood, foam, fiberglass, and plastics such as polypropylene, ABS, POM, PC, Nylon, etc.

What are the 5 axis on a CNC machine?

The term &#;5-axis&#; refers to the number of directions in which the cutting tool can move. On a 5-axis machining center, the cutting tool moves across the X, Y and Z linear axes as well as rotates on the A and B axes to approach the workpiece from any direction.

Why is CNC important?

One reason for using CNC machining for production is efficiency. Since computers are used to control machines, it means that all major operations of production can be automated to increase speed and quality of manufacturing. &#; Another reason CNC machining is beneficial for manufacturing is its accuracy.

What is the difference between CNC milling and CNC lathe?

A lathe turns the material you&#;re machining and the tools are held stationary in the turret. *Lathes are used mainly for round parts. Milling machines hold the material stationary and the tools do the movement. Milling machines are used for any shape part.

Who is the father of CNC machining?

John T. Parsons. Born January 7, , Detroit, Mich.; the father of numerical control. Parsons discovered how to calculate airfoil coordinates on an IBM 602A multiplier. He then fed these data points into a Swiss jig borer. To date, this was considered the first true numerical control machine as it manufactured goods &#; helicopter blade templates, in this case &#; by feeding punched cards into a system, and the system then read and produced the parts based on preprogrammed information.

What language do CNC machines use?

The industry has standardized on G-Code as its basic set of CNC machine codes. G-Code is the most popular programming language used for programming CNC machinery.

What is the difference between CNC and VMC?

CNC is a type of motion control system. It basically means that instead of using cams or templates to cut a part, it is controlled by a computer.

A VMC is a type of CNC machine, typically enclosed and most often used for cutting metal.

What is the difference between CNC and PLC?

There are major differences between PLC (Programmable Logic Controller)  and CNC(Computer Numerical Control) is in the execution of the program. PLC is sequential but CNC is conditional. CNC is a type of application used to control a multi-axis machine tool for example milling machine or lathe.

What is the M code in CNC machines?

M-code (for &#;miscellaneous function&#;) is an auxiliary command; descriptions vary. Many M-codes call for machine functions like &#;open workstation door,&#; which is why some say &#;M&#; stands for &#;machine&#;, though it was not intended to.

What is a Part Program?

The part program is a sequence of instructions, which describe the work, which has to be done on a part, in the form required by a computer under the control of computer numerical control (CNC) software. It is the task of preparing a program sheet from a drawing sheet. All data is fed into the CNC system using a standardized format. Programming is where all the machining data are compiled and where the data are translated into a language which can be understood by the control system of the machine tool.

The machining data is as follows :

  • Machining sequence classification of process, tool start-up point, cutting depth, tool path, etc.
  • Cutting conditions, spindle speed, feed rate, coolant, etc.
  • Selection of cutting tools.

We hope you enjoyed the first part in a series of CNC machining frequently asked questions, check back for more answers.

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