September 24, 2021

How to Run a CNC machine for Novices

Trying to learn how to run a CNC machine can be difficult; there is a lot to learn. We will explain the basics of CNC in layman’s terms. Decide on the strategy you wish to use and write a guided program. Use CAD/CAM software and upload the Gcode to the machine control program. Gather all the tools and attachments as you set up your CNC machine. Make sure all the needed tools and software are readily available. When satisfied, run the program. Running a test first is more convenient and gives you precise results. 

Steps

Workpiece preparation

Before you start working, you must prepare your workpiece. To do this :

1) Cut out the shape of the part from sheet metal or other material using an appropriate cutting tool. The cutout should have at least one flat surface that will fit into the chuck of the spindle head. If possible, make the cutouts symmetrical to be rotated 180 degrees for machining both sides in the same operation.

2) Clean the area around the cutout with a solvent-based degreaser. This removes any oils or grease leftover from previous operations, and it also helps prevent rusting during storage.

3) Sand down rough edges and corners with fine sandpaper until smooth.

4) Apply primer if necessary. Primer coats protect against corrosion and help ensure good adhesion between the coating and the substrate.

5) Coat the entire piece with paint or lacquer. Paint provides better resistance to wear than lacquer does.

Workpiece clamping

It is always wise to clamp your workpiece when operating a CNC machine. Clamping prevents movement, which could cause damage to the machine itself or result in inaccurate cuts. There are several ways to accomplish this task:

1) Place the workpiece directly onto the tabletop. Be careful not to place too much weight on the workpiece because this may bend the workpiece.

2) Attach clamps to the sidewalls of the tabletop. These clamps hold the workpiece securely while allowing some freedom of motion. They come in many sizes and shapes depending upon what type of workpieces need to be held.

3) Mount a vise on the tabletop. A vise holds the workpiece firmly without bending it. Vises usually consist of two jaws that grip the workpiece using screws or bolts, and some machines include built-in vises. 

Choose your machining strategy

Planning is the way to go before you start using the machine, and it helps you gather necessary equipment and gives you an idea of the duration of the process. Deciding on the machining strategy sometimes is not done aware, but practically users do. 

Perfect results do not easily come when one starts the machine without planning, and you are prone to more mistakes when you start the CNC machine without planning. Since there are different approaches, choose equipment and tools that suit your strategy. 

There is no universal equipment to run the CNC machine. Use comfortable equipment for a smooth run. There are so many ways that give you the same results. When designing your part, draw it first on a paper or CAD program. Drawing helps you visualize the part and gives you an overview of how it is processed. 

Program writing

Writing programs for a CNC machine requires knowledge about the language used. This includes knowing which commands are available and their functions. In addition, you must know how to use them correctly. Writing programs also involves learning the basic concepts of CNC technology. 

The most common languages used today are:

G-Code: Used for controlling the movement of the cutting head. PID: Used to control speed and position.

MOVEMENT CONTROL SYSTEMS: Used to move the cutter along its axis.

You may need to learn other languages as well. They vary from manufacturer to manufacturer. 

If you want to get started right away, consider buying a ready made program. However, if you plan to make changes later, then buy a blank program. The latter will allow you to add new features at any time. 

CAD CAM PROGRAMMER: This allows you to design parts using software such as AutoCAD, SolidWorks, etc. Once designed, you can convert them into G-code files.

To write a good program, you should have a clear understanding of the following topics:

  • Basic programming principles
  • Knowledge of the language used.
  • Understanding of the concept of coordinate systems.

Write A Gcode Program

Choose an easier way to machine your part. Avoid doing it in one operation since it is easier in two operations. That helps you achieve accuracy. You still have to figure out how to hold the part of each setup. Decide on each setup you have to write your geode programs. These should be different programs since it evolves around tool changing. 

Use multiple programs for each setup. You are allowed to combine all the programs into one to reduce confusion, and that way, they remain short and simple. When you are familiar with the CNC tool, you are using, separating the programs will be ideal. 

When you switch to a different tool, create another program for that tool. For a standard g code program, look for a simple text editor and the basics of G Code programming and CNC terminology. If you have been to the CNC program training center, you can do this on your own. 

Keep a separate folder on your laptop with programs to avoid rewriting each program when using the machinery. That way, you only pick a CNC program for what you are running and edit numbers. The result is a better understanding of the writing skills of g code programming. Using  CAD/CAM software is quick and simple. 

Using Cad/Cam Software

You need the software if you do not intend to write your Gcode. Using the software saves time and effort. CAD is software for computer-aided design. Use if to draw your part. When done, save it as a digital file to be read by the CAM software. 

Cam is an abbreviation for computer-aided manufacturing. It produces cutter paths from the profile you imported from your cad software. Use it for a post-processor in your cam software to produce a Gcode program from those paths. Using cad/cam software is more convenient, and it does both processes in the same program.

Use a CAD program as a substitute to draw the part and write the Gcode yourself using the coordinates from the cad drawing. The cad drawing data give you start and endpoints for lines and arcs and positions for holes. That is effective if you need to program 2D shapes and profiles. Before you decide which program to use, consider the tools at hand. 

Upload Your G Code Program

Upload the g code program to the machine control software once you have created it. The software sometimes comes with a g code visualizer that helps you see the cutter paths created by the Gcode. The code does what you want it to do. A stray line is a sign that you should pay attention to and check your program for errors. 

Load the g-code program into the machine

Expect multiple errors in the g-code program. These include a syntax error, operator, and many more. The syntax error occurs when the software fails to recognize a letter or coordinates fail to match from one line to the other. 

The errors show up when you do a virtual run on your part. If you use incorrect values for your coordinates, operator errors occur, and they are challenging to figure out. Be confident as you operate the machine. 

Setup Your CNC Machine

Before starting the machine, check to ensure oil and coolant levels are full. Check the machine maintenance manual if you are unsure about how to service it. Ensure the work area is clear of any loose tools or equipment. If the machine requires an air supply, ensure the compressor is on and pressure meets the machine requirements.

Before switching on the machine, check the oil and coolant levels to see if they are full. Go through the manual and make sure you have serviced the machine well. The work area has to be clear of tools and equipment. 

Sometimes the machine requires a ventilation system. The compressor has to be on, and the pressure has to meet the requirements of the CNC machine. The machine power button is on the upper-left corner of the control face. 

When you are satisfied with the above steps, you can now move to set up your machine. Your stock has to be tight and secure. When the stock is firm and fixed, the chances of achieving accuracy are high. Avoid vibration at all costs. Set your datums. 

Keep the project simple and approach it one step at a time. Set your goal in mind and work towards it. When you have followed the above steps, you should be able to:

  • Understand how the CNC machine operates.
  • Explain all the steps to set up.
  • Identify the location and purpose of the operating controls.
  • Start the CNC machine.
  • Load tools.
  • Set Tool Length Offsets.
  • Set Part Offsets.
  • Run the machine.
  • Take all the safety measures needed. 
  • Adjust offsets to account for tool wear and deflection.
  • Shut down a CNC machine correctly. 

Feed rate setup

Setting up the feed rates is important because this will determine whether the cutting path follows the desired shape. It also determines the speed of the cutters. You may find it hard to understand why there would be different settings for each axis. This happens because most machines come equipped with two axes, and one axis moves along X while the second axis moves along Y. There are three types of feeds available: linear, angular, and circular. Linear feed means moving the table linearly across the bed.

Workpiece cooling

Cooling your workpiece will help prevent warping and distortion, and it also prevents overheating and burning. You may not notice these problems until after you have finished cutting. Cooling reduces friction between the cutters and the machined material, allowing the cutters to perform their job without damaging the surface finish. 

It would be best if you kept the temperature below 100 degrees Celsius. At this point, the metal begins to soften.

Workpiece inspection

You must examine your parts before sending them off to production. Inspect every piece thoroughly, and look for cracks, chips, dents, scratches, and other defects. Make a note of anything unusual. An excellent way to look for flaws is by using a magnifying glass. Use a sharp knife to remove small pieces of scrap. Do not forget to clean the blade regularly, and cleaning helps maintain its edge. 

If you find something wrong with your part, fix it immediately.

Do you need a degree to be a CNC programmer?

No, but there are some things you need to know first. These include:

The basics of programming languages such as G code, CAM software, and NC programs.

Knowledge of CAD/CAM design software.

  • Understanding basic math concepts like trigonometry, vectors, and calculus.
  • Working knowledge of English grammar and spelling.
  • Basic computer skills including typing, word processing, spreadsheets, databases, email, etc.

See our post: What is a CNC Machine Operator? Job Specs + How Much They Make.

Is it hard to run a CNC machine?

Basic knowledge is what you need to get started. You should be able to understand basic math and how the machine works. It takes days to grasp the concept. You learn some programming skills along the way, and that takes a year. You cannot be a pro in a short space of time since you have to master the machine. You learn new concepts and methods every day, and that takes years. 

What is a CNC Router?

A CNC router is your tool of choice if you’re working with wood while a CNC milling machine is what you need for creating parts with metal.

What is Multi-tasking?

Enter the multi-tasking technology of CNC machines CNC machines have long been a commercial staple, but they’re quickly gaining a footing in the hobby market.

How do I import my drawing into a CAM program?

When you’re happy with your drawing, export the file and import it into a CAM program.

What is computer numerical control?

All CNC machines use computer software to control their tools hence the acronym: computer numerical control.

What is g-code?

The part is drawn in a CAD program (computer-aided design) before a CAM program (computer-aided manufacturing) converts the drawing into a code called g-code.

Where Can I Get Free CAD Software?

CAD programs are available to buy from most software shops, but you can also access free versions online.

What is the best way to measure a part?

Use gridlines when drawing so you can be specific about your measurements.

How do I transfer g-code to a machine?

CNC machines usually transfer the g-code directly to the machine, but external PCs run hobby machines.

How do I find the basics for g-coding?

Several websites give you the basics for g-coding by hand, and a simple Google search will help you find them.

What is Manual Programming?

Manual programming is when you are manually writing out the codes.

What is CAM?

CAM stands for Computer-Aided Manufacturing, and it’s when you use a computer program to work with a model of the part you’re making.

What is Conversational Programming?

The true “conversational” programming will send the instructions directly to the machine.

What is manual programming?

It’s extremely practical to understand.

What is quick code?

It’s usually just a means of quickly putting together programs (maybe that’s why they call it “quick code”?) for the machinist that’s comfortable with manual programming.

What’s the best way to program a computer?

That comparison of the three approaches might make it seem that manual programming is obsolete.

What are the difficulties of CNC programming?

Ok, so earlier, I said that CNC programming is dependent on how complicated you can get.

What is 3 Axis Machining?

This is where all three axes of the mill are moving at the same time.

How do you program a lathe?

The standard lathes have only two axes, and they’re pretty easy to program manually.

What is three-axis programming?

This means that there are milling or drilling tools that rotate in the turret.

What is the use of this machine?

It’s the foundation of CNC programming.

What are the benefits of being able to do your programming?

Even if you don’t use it regularly, it allows you to make edits at the machine instead of running back and forth between the machine and your computer trying to figure out how to fix something.

What are the basics of CNC?

For more in-depth info than is covered here, look at the following: The Basics of Computer Numerical Control by Mike Lynch, CNC Concepts, Inc.

What axes can you have on a CNC machine?

CNC machines can have several axes of movement, and these movements can be either linear or rotary.

What is a five-axis milling machine?

A five axis milling machine has three linear axes and two rotaries, allowing the cutter to operate in a full 180º hemisphere and sometimes more.

What are the limitations of CNC machines?

Depending on their age and sophistication, CNC machines can be limited to the capabilities of their control and drive systems.

What is the difference between a five-axis machine and one?

In the case of five-axis machines, all five must be perfectly synchronized – no easy task.

What is the difference between a new computer and an old one?

Older and less expensive machines are less capable in this, much in the same way that an older computer will work less well and more slowly (if at all) on demanding tasks than a newer one.

What is CNC?

CNC – Computer Numerical Control – Taking digitized data, a computer and CAM program is used to control, automate, and monitor the movements of a machine.

What are the benefits of desktop machines?

These are lighter weight, less rigid, less precise, slower, and less expensive than their industrial counterparts but can do well for machining objects out of softer materials such as plastics, foam, and wax.

What is CAM programming?

CAM – Computer Aided Machining or Manufacturing – Refers to the use of various software packages to create toolpaths and NC code to run a CNC-controlled machine based on 3D computer model (CAD) data.

What is a typical problem?

A typical problem is how to set up your files and do your CAM programming so that the machine executing your parts will work smoothly and efficiently with the data.

What are the most common things you need to convert?

Typical things that need converting are splines, i.e., general NURBS curves that are not arcs or lines, and 3D surfaces.

What are the benefits of going finer?

Going finer increases the smoothness of the approximation but also dramatically increases the number of segments.

What are the benefits of arc conversion?

You can imagine that a series of arcs might be able to approximate your spline within tolerance with fewer, longer pieces.

What is the best way to make a 3D model?

This is the main reason for preferring arc conversion over simple polyline conversion, especially when working with older machines.

David D. Hughes
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