CNC machining service is one of the most well-known and common automated manufacturing processes. CNC machines make manufacturing processes more efficient and easier for individuals and companies. These machines are used for turning, milling, cutting, punching, and drilling. This article will cover CNC milling as a primary machining process and provide an overview of the terminology, workflows, and common operations.
The Coordinate Systems
3D software allows you to create geometry within coordinate systems. Your 3D software will output a G code program to tell the machining manufacturer what you should do and where you should move. The CNC machines also read 3D information from G-code programs using coordinate systems. It is important to specify the origin point (0.0.0) and ensure it matches your 3D computer-aided design software.
The machine must know its “home” position after it finishes an operation. This will allow it to correctly position and dimension the next operation. Most geometries for CNC machines can be modeled as “parts,” and the CAD software usually has one coordinate system.
Newer CNC software allows for more complex assembly preparations and allows you to machine each part individually. You must select the right coordinate system for computer-aided fabrication (CAM). This can differ for different parts or assemblies.
CNC machines usually have a control point defined as the center face or spindle of the machine. The Z-axis can be fully extended, and the table moved to its limits close to a corner; this position will define the coordinate system point “Home.”
Work Coordinate System
The motion of every operation is calculated by CNC machines using interpolation from the start position to its end position, with intermediate points if necessary. This is done by the CNC machine having an origin at 0,0,0, which allows it to measure the position of each operation point.
This helps identify the stock material’s location and prevents the tool from machining outside the limits. If you plan to machine multiple parts using the same program, it is necessary to replace the stock material after it has been machined. Then, restock the material for the next part. You might cut materials differently if you don’t have a consistent 0,0,0 origin. This could lead to parts that are not within the specifications.
This applies even if different operators work on the same program and machine. If the 0,0,0 is not defined in the stock part, and the result is large interpolation values for the CNC codes, you will get bugs in your program or a decrease in precision. You may have attempted to model large geometry in CAD software, and it ended up causing errors and bugs. This is also true for CNC machines.
This issue can be solved by CNC machines using a similar technique as CAD: local coordinates called “Work Coordinate Systems” (or WCS), which can be defined and used for each CNC code. CNC programmers use these WCS to select reference points but don’t always match the 0,0 or 0 in the CAD model.
The WCS location will usually be on an edge or other physical feature that can be easily identified. It is important that the point can easily be duplicated so that the machine can return to the same position with tight tolerances, regardless of the machining motion.
The CNC machine doesn’t give you the coordinates when you start it. That’s why the “Home” position is so useful. Pushing the “home” button will restart the machine and move all three axes to their limits. This is usually located in the back left corner. This will give you a reference point to use for your next operations.
Closed-loop CNC machines can position each axis within a tolerance range of +/- 0.02 inches. A controller board transmits the motion signal to each axis of the CNC machine control. The servo motor then rotates the ball screw attached to the table and moves it accordingly. Continuously measuring the axis position is done and compared with the programmed position.
CAD/CAM Process
The CNC machining process includes CAD (computer-aided design) and CAM (computer-aided manufacturing). Many CAD software programs have CAM functionality or plugins that can be used to connect to machining programs. 3D modeling allows you to create geometry, simulate machining and make predictions about errors that could result in money. You can practice simulations of CNC milling to optimize many parameters, including material waste, machining time, and tool wear.
Here’s how to simulate your 3D designs for beginners:
CAD Model and CAM Environment
You can use CAD to create 3D parts and assemblies. However, staying organized and eliminating features and parts that don’t need to be machined is important. If your company has a preferred software type, you can stick to it. These two requirements should be met by the software you choose.
It is easy to understand and use the software. If your job allows, you can choose the software you already know.
The software should allow your CNC Machine to communicate with it
You can ask your vendor to provide a sample program or trial to verify that your CNC can read your CAD if you want to purchase new software to replace a CNC machine.
Choosing the CAM Software
Many premium CAM software is on the market today, including MasterCAM and Solid Edge CAM. Autodesk Fusion, Solidworks CAM, and SolidCAM are just a few examples. Many factors can affect the cost of each program.
Before deciding, you need to ask the following questions: Does the software offer all of your operations? Cheaper software may not include the necessary operations for your product. Autodesk Fusion does not currently offer EDM operations. However, CAMWorks Solid Edge offers a Wire EDM version.
Next, learn how easy it can be to use the software. Autodesk Fusion excels in this area due to its user-friendly interface.
The toolpath visualization and interference checking discussed above is a third factor. These features are becoming more common, but free programs still do not have them. Be aware that free CAM programs often have interfaces that differ from CAD user interfaces. This means that it can take more time to learn them.
There are also trial versions and hobbyist versions available for premium software. These versions can be more affordable. Most trial versions of premium software don’t run machining simulations or toolpath visualizations. They won’t generate CNC codes until the full version is purchased.
CNC Coordinate System
Once you’ve created a 3D model using your CAD/CAM software, it is time to set up your references. Select your Home and WCS positions. It is also necessary to determine the size and shape of your material stock. However, most modern programs can do this automatically.
CNC process
The menus in CAD/CAM programs can be used to perform different machining operations and even add-on manufacturing operations. This allows you to simulate one machining operation and other processes. This allows you to compare the machining time, material loss, tooling, and cost to select the best process.
