Using computer-aided design (CAD) software is the first step to creating a physical part made by a CNC machine. The CAD software creates highly detailed 3D models. However, they don’t instruct the CNC machine how to operate to make the part you want. Here are some essential steps to take when you’re getting your CAD model ready for a CNC machine.
1. Export the CAD File Into a CNC Machine-Compatible Format
The first step requires getting the CAD file into a format the CNC machine can recognize. G-code, also known as RS-274, is the most widely used programming language for CNC machines. Sometimes, you’ll need to convert the file into a G-code language. For example, DXF is a CAD file format developed by Autodesk. It works well for sharing drawings. But, the primary downside is that most CNC machines cannot read it.
Fortunately, free file conversion exists to help. The Standard for the Exchange of Product Data or STEP format is a widely used file format that works with CNC machines. It is a vendor-neutral file format, and many CAD programs offer this file type as an export option.
However, you may also see three versions of STEP in your program, or AP203, AP214 and AP242. AP242 is generally accepted as the best option of the three. It’s the latest version of the STEP standard and will show your item in high detail. Another thing to note is that AP203 does not show colors.
There’s also Initial Graphics Exchange Specification or IGES. It’s an older standard, last updated in 1980. It is another format not tied to a particular vendor. One consideration is that IGES files are typically larger than those in the STEP format. That could be a concern for people sending their files through email.
It’s highly likely that the company you choose for CNC machining will convert your file into STEP anyway. Selecting it as your file type from the start allows you to check them before the final uploading, ensuring there are no conversion errors.
2. Create the CNC Technical Drawing If Required
In many cases, people need to make CNC technical drawings while getting their CAD models ready. These documents show the dimensions and other specifics that are not always evident from the CAD model alone.
A CNC technical drawing is necessary if:
- The CAD model includes internal or external threads
- There are features with tolerances exceeding the standards
- The part’s surfaces have particular finishing requirements
Even if the component does not fit into the above categories, it’s still a good idea to include a technical drawing. That’s because the CNC machinist can use it as a reference, increasing the chances of great results.
There’s even at least one company that uses artificial intelligence (AI) to interpret technical drawings. That approach works in cases where there is not an accompanying CAD model, too.
However, consider your options carefully if you’re thinking about using a provider that relies on AI to study the technical drawing or any other part of the process. AI algorithms typically need vast amounts of data to work well. One AI model developed by Google got trained on 1.2 million data points.
Take a detail-oriented approach with your technical drawing. For example, if the part has hidden geometries, think about adding sectional cutaways that show the internal specifics. Make sure to identify the size and location of all threads. Also, bear in mind that the standard tolerance will likely be ±.125 millimeters, so you’ll need to specify any desired tolerances requiring more precision.
3. Get Final Input From Stakeholders or Team Members
One of the biggest advantages of CAD files is that they allow for smooth communication between parties. Besides looking at a file in its current state, authorized people can view the changelog and see what has been done since they last viewed it. That capability minimizes confusion and mistakes by keeping everyone on the same page.
3D CAD models are also typically easier for people to understand if they don’t have technical backgrounds. Although engineering and design teams are well-versed in deciphering traditional drawings, that’s not usually true for others, such as C-suite members or people on marketing or sales teams.
It’s a good idea to let all stakeholders see the latest version of the CNC model and get their approval before sending it to a CNC provider. That way, you’re setting expectations and giving everyone a chance to provide feedback.
4. Engage With CNC Machining Providers
At this stage in the process, people are ready to contact CNC providers and see what kind of pricing they can offer. Fortunately, many companies have online quote request forms, which streamline communications. Some of them even provide instant results, depending on the inputted information.
However, you’ll need to know a few more pieces of information to make things go smoothly during these communications. For example, how many parts do you need produced and in what timeframe? What’s your chosen material? These factors will help determine how much you pay.
Several things are also within your control to reduce the overall cost. For example, a high machinability of the chosen material keeps expenses down. The same is true if you have only one finish for the part rather than several different ones in certain areas.
Specifying tight tolerances is another thing that will drive up your overall project costs. That’s because they require more machining time and manual inspections. If your part has holes, choosing a standard drill bit diameter will keep the costs down, too. Otherwise, the CNC machinist will need to spend more time crafting a less common hole size.
If it’s feasible for your project, consider ordering the CNC-machined parts in bulk. That approach can significantly reduce prices. However, you also don’t want to be in a position where you’ve purchased too many unnecessary items.
Become Familiar With the Process
Getting a CAD model ready for CNC machining is not a complicated process. However, unexpected outcomes are more likely to occur if you don’t follow these steps carefully. Taking the right preparatory measures increases the likelihood of your project turning out as expected and staying at or under budget.
Article by Emily Newton
Emily Newton is the Editor-in-Chief of Revolutionized. She has over four years experience covering the industrial sector.
