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CNC Cutting: Definition, Processes, and Uses

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Computer Numerical Control, or CNC, manufacturing is continuing to grow in the world of modern manufacturing. As technology improves, computers can do more to handle the repetitive workload in production environments and produce parts in a fraction of the time that was possible not too many years ago in the manufacturing industry. 

One of the main advantages here at SendCutSend is that we utilize CNC machines to optimize our workflow. With much of our processes automated, we’re able to cut time and cost for all the parts we make. In this article we’re going to cover CNC manufacturing, what it is, where it’s used and why you might want to use CNC manufacturing processes for your projects.

CNC Cutting Process

In general terms, CNC manufacturing processes use a computer to control a tool. Yes, that’s technically a robot, if that’s what you’re wondering. Rather than a human holding a laser or a router or plasma cutter, a computer controlled machine holds the tool and moves it according to instructions given to it through a language called g-code. Let’s walk through the steps in that process from concept to finished product.

CAD model design

The first step is to model your design in CAD (Computer Aided Drafting or Computer Aided Design). This turns your idea into a digital format that you can reference in the next steps. A part may be designed with CNC manufacturing in mind, but not always. Take a look at SendCutSend’s design guidelines to see how to set up your design file for laser cutting, waterjet cutting, or routing.

Transfer of CAD file into a CNC program

This step involves a programmer to create the g-code, or the instructions for the machine to cut the part. This requires knowledge of both the manufacturing process as well as the computer program used to write the machine code. The computer needs to be told things like how fast to move, where to start and stop, how to use a particular tool and even which tool to use when. Sometimes the same software is used to both design and create the g-code files, but it doesn’t have to be. This sounds more complicated than it actually is. G-code is a programming language, but most software makes it intuitive to create usable g-code. It’s much more important to understand the machining process to select the appropriate speed and feed settings for the machine.

Setting up the CNC machine

Once the g-code is written, the machine has to be set up before the computer can take over. This might require raw material to be loaded and secured or a specific tool to be installed (some machines have automatic tool changers). This step might also include telling the machine where the material is relative to a known location.

Running the machining operation

After everything has been set up, the final step is telling the computer to do its thing. The computer will read the g-code you’ve given it and if everything goes well, it will produce the part you’ve designed. Depending on the machine, there may be intermediate steps where you have to intervene such as turning a part over or changing out a tool. These steps can be programmed into the g-code telling the computer to wait while you do what you need to do, before continuing on with the rest of the code.

Other CNC Machining Features

There are a huge number of tools that can be controlled by a computer, but often the final steps to complete a CNC part involve a manual process. These can include deburring, sanding or washing. Here at SendCutSend we manually deburr parts before they get packaged up for shipping. Sometimes parts aren’t cut completely from the material stock so that they don’t come loose and hit the tool. In those cases there needs to be a manual step of cutting that last tab of material.

Precision CNC Machining vs. Manual Machining

When it comes to holding a tolerance on machined parts, both CNC and manual can get the job done with the right machine stiffness, feed rates and cutting tools. What are the differences, advantages and disadvantages of the two processes?

Manual processes still have their place and have some advantages over CNC processes. 

  • Manual operations can be done faster if you just need to make a quick cut or two. 
  • Manual processes don’t require any software, which itself can be a huge time saver not to mention a cost savings.
  • Sometimes you need to fit two parts together which require taking small cuts and checking fit. These types of situations lend themselves to manual operations over CNC.

Let’s take a look at some of the advantages of computer controller processes.

  • Repeating cuts are one area where CNC machines shine. Once the code is written, you can load and unload the machine, but the machine can run mostly unattended (at least not requiring 100% attention). This can allow one operator to run many machines at the same time, like a 3d printer farm or multiple machining centers.
  • Precision operations for tools like routers and plasma cutters can be done without a jig. Straight edges, circle cutting jigs and even templates aren’t needed with a CNC machine.
  • Complex geometry is no more difficult than simple geometry with a computer controlled machine. Cutting letters out of ¼” thick steel can be done manually, but it’s time consuming. With a CNC laser it can be done in minutes.
  • High speed machining of complex 3D geometries, like molds, are only possible with a CNC machine.
  • CNC machines are more often enclosed since operators don’t need to be as close to the workpiece. This can make them safer for the operator.

Types of CNC Machining Systems

CNC machines come in a variety of types. There are open-loop and closed-loop systems, which define the type of control and whether or not there’s feedback. For example, a computer controlling motors to move a CNC router without feedback would be an open-loop type of system. The computer tells the motor to move a distance and the motor tries, but if the tool hits more resistance than the motor can overcome, the motor might slip or miss a step. Now the motor is in a different spot than the computer expects and the rest of the cuts are in the wrong location.

Alternatively, if the motor was constantly sending feedback on its current position to the computer, if it slipped, the computer would immediately know and be able to either compensate for it or stop running the program to save the part from damage. This type of control is called closed-loop. Closed loop systems are slightly more complicated and usually cost a little more, which makes them a little less common than open loop systems.

CNC Machining Software Technology

As we discussed above, in order for the computer to know what to do it has to be programmed. That programming is done in specific software applications. The market is full of great software from free DIY options to high end production software and everything in between.

CAD

Computer Aided Drafting or Computer Aided Design is the term for software that’s used to design parts. Those parts don’t necessarily have to be manufactured on a CNC machine, but if your parts are going to be made by CNC machines you probably need some form of CAD software. If you have SendCutSend make your parts, you’ll need some sort of CAD software to create the files to send to us. For us you want something that can create .dxf, .dwg, .ai or .eps files. Examples of CAD programs include 

  • Fusion 360
  • Solidworks
  • AutoCAD
  • Adobe Illustrator
  • SendCutSends Parts Builder

CAM

Computer Aided Manufacturing or CAM is the term for software that’s used to create g-code. It’s not uncommon to see some CAD software include CAM features, but there are also stand alone CAM software packages. If SendCutSend is making your parts, we handle this part so you don’t need to. Examples of CAM software include

  • Fusion 360
  • HSMWorks
  • SolidworksCAM
  • LightBurn
  • Cura

CAE

Computer Aided Engineering or CAE is a more general term for software used for engineering. This is often meant to include tools for analyzing the design of parts. Engineers use computers to develop all aspects of designs including planning, function, strength, shock and vibration behavior, thermal behavior, fluid flow, etc. This is often done in the form of Finite Element Analysis or FEA. Examples of CAE software include

  • ANSYS
  • Solidworks Simulation
  • Fusion 360 Simulation
  • NASTRAN

10 Types of CNC Machine Operations

We’ve discussed what a CNC machine is and how the process works, but what tools can a CNC machine control? New CNC tools are constantly being developed as technology improves. Let’s look at some example tools.

CNC Laser Cutting

We had to include this one, lasers are our thing. Some of the most common forms are diode lasers, CO2 lasers, fiber lasers. SendCutSend uses both high power fiber laser cutters as well as CO2 laser cutters. Fiber lasers are great for cutting metals while CO2 lasers do a great job with materials like wood and acrylic.

CNC Water Jet Cutting

Water jet machines use a high pressure stream of water with bits of abrasive in it to cut materials. Water jet cutting is great for materials that can’t be cut with lasers, either because they give off toxic fumes or the heat could negatively impact them. You may not realize it, but SendCutSend also uses CNC water jet machines for cutting some of our materials, like carbon fiber, G10 and phenolic.

CNC Routing

Routers are traditionally hand held tools, but hand one to a robot and it works like a mill. SendCutSend uses a CNC router for cutting composites, acrylic and wood.

CNC Milling Machines and CNC Lathes

Similar to routers, mills and lathes started out as manually operated tools, but they both lend themselves to computer control since the main controls are simple knobs. A CNC mill or lathe can cut complex 3D shapes in minutes that manual operators couldn’t dream of.

CNC Plasma Cutting

Similar to a CNC laser cutter, but a little less precise, plasma torches can be mounted in CNC machines to create complex 2D shapes with ease.

3D Printers

Not all CNC machines are subtractive, additive machines can be CNC also. 3D printers use g-code to know how hot to keep the nozzle and bed, how much filament to extrude and where to extrude it.

Vinyl and Fabric Cutting Machines

They may look like home office printers, but they are also computer controlled. 

Bonus: Your home office printer is technically a computer controlled machine, but the CAM software is typically operating behind the scenes without you realizing it. Does that make your word processor software a CAD program?

Wire EDM

Wire EDM (Electrical Discharge Machining) machines use a fine wire to cut through materials leaving a kerf even smaller than a laser. That kind of precision is hard to get manually.

CNC Wire Bending Machines

Did you think all those metal clothes hangers were bent by hand?

CNC Tube Benders

A lot of tube benders are still manually operated, but high end benders can be computer controlled to get precise repeatable bends.

SendCutSend has a number of different types of CNC cutting machines in our facilities. We evaluate your design, material, thickness, etc. to determine the best machine to use for any given part.

Materials Suitable for CNC Cutting

The wide range of cutting tools that can be controlled by a computer means there’s an even wider range of materials that can be cut. Almost anything you can cut manually can be cut with a CNC machine. From hard materials like steel to soft materials like cork, it’s hard to imagine a material that can’t be cut by some type of CNC machine.

SendCutSend offers quite a few materials that can be CNC cut. If you’d like to see a list of all the materials we can cut for you and which machines we use, visit our materials page. Some materials we offer can be cut with multiple machines in which case we’ll choose the best machine for your particular design.

Applications of CNC Machining for Your Next Project

Because of the level of automation, CNC manufacturing is used everywhere from home hobbyists to professional CNC machinists making aerospace parts. Let’s look at some examples of common parts made with CNC machines from SendCutSend. 

  • DIY drone frames out of carbon fiber
  • Sheet metal enclosures from bent aluminum
  • Decorative signs out of stainless steel and acrylic
  • Tons of brackets to hold all sorts of things like tools, suspension mounting points, stiffening braces, etc.
  • Instrument panels and switch panels
  • Knife and tool handles
  • Holiday decorations
  • Prototypes versions of parts out of less expensive materials like MDF, plywood and acrylic

If you want even more examples, there are hundreds of customer photos and videos on our website.

Discover a New World in CNC Machining with SendCutSend

We hope this article gave you a short tour around the world of CNC cutting and CNC manufacturing in general. CNC cutting is likely to continue to grow due to the cost and time savings it can offer manufacturers. Maybe there’s a CNC machine in your future. If you’d like to take advantage of all the benefits of CNC cut parts without having to learn CAM software or buy a CNC machine, SendCutSend is a great partner for producing custom parts for your needs.

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