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How to Check CNC Machine Accuracy Before Buying

Accuracy is one of the most important aspects of the functioning of a CNC machine. Especially when doing the cutting work for heavy machines then you need to focus on accuracy more than anything else. When you buy a new first hand CNC machine, then you are sure of the fact that the machine will have top notch accuracy but when you buy a second hand one, you must not show that blind trust. But, we will also say that you should properly check the accuracy of the machine no matter if it’s first hand or second hand. So, let’s read till the end to know details about how to check the accuracy of the CNC machine before you buy it.

Top ways to check the accuracy of a CNC machine before buying it

Here is a list of the things you need to do to check the accuracy of a CNC machine before you make the final purchasing decision

Research and gather information about the machine – Before you check the accuracy of the machine, you need to know some data about the machine like –
- Axis movement capabilities – There are basically two types of axis movement capability, 3-axis and 5-axis, and both have different levels of accuracy depending on the product you want to build.
- Spindle speed – Spindle speed also plays a major role in the accuracy and execution of the machine.
- Feed rate – This is the speed at which the cutting tool operates across the workpiece and is a very important factor to determine the accuracy of the CNC machine.

Initial inspection – Once you find out these data about the machine you’re planning to buy then you should do some initial inspection about different things like –
- Build quality – You should check the build quality of the machine, it is important for heavy manufacturing. Brand reputation matters a lot in this case.
- Wear and tear – this is more important when you are buying a used CNC machine. Wear and tear of the parts can lead to severely low accuracy of the machine.
- Electrical elements – Proper wiring and electrical system is very important for the sake of high accuracy of the machine.

Check the geometric accuracy of the machine – How the structures and components of the machine are aligned is a very important objective to measure while checking the accuracy of a CNC machine –
- Spindle alignment – You must check the spindle point alignment with the z-axis of the machine, because any kind of misalignment can lead to severe fall in accuracy of the performance of the machine.
- Straightness of the axes – Use dial indicators to measure the straightness of all three axes of the machine – X, Y, and Z. You must make sure that the three axes are perpendicular to each other.
- Flatness of the table – Any kind of high and low curves in the table of the machine can affect the accuracy of the machine so make sure to inspect the flatness.

Check the thermal stability of the machine – The thermal stability of the machine is very important regarding the accuracy of the machine, as the heat generated by the machine during operation can affect the accuracy. So, here are the things need to do to check the thermal stability of the machine –
- Do a trial run of the machine – You must do a trial run of the CNC to check the amount of heat it’s generating and how the machine is reacting to that.
- Perform an accuracy test – Perform the accuracy test using a dial indicator after the machine is heated up, to get a better understanding of the machine.
- Do temperature monitoring – You must check the machine is maintaining the same accuracy at different thermal temperatures, you can also take help of the built in temperature censors for that.

Check the positioning accuracy of the machine – Next, in the line you should check the positioning accuracy of the CNC machine, which determines how the machine moves according to the given commands –
- Linear motion positioning accuracy – This is about measuring the straight line movement of the machine, ensuring the machine moves following the commands without any deviation.
- Repeat positioning accuracy – This test is to ensure that the machine repeatedly returns to its original points after repeated movements.
- Origin return accuracy – Check the accuracy of the return of the machine to its original point with the help of tools like laser trackers.

Check the machine’s control system – Now, lastly, you also need to check the control system which is the software mechanism of the machine to ensure that it works accurately for your desired results. Here are the things you need to keep in check –
- Ease of use – The first and foremost important thing when it comes to the software of a CNC machine is the ease of use of the system. The easier it is to use, the more accurate the results will be.
- Features – If you want a modern gen machine, then you must ensure that it supports 3D modeling, closed-loop feedback, and toolpath generation features. Modern features also help in more accurate production.
- Updates and support – The best manufacturers will give you regular update opportunities for better technicality and accuracy of the machine.

Take a third party review

The accuracy of a machine is not easy to determine, and so it will be a great thing for you if you take a third party expert’s review about the accuracy of your machine. Especially when you are buying a second hand machine, you must get a detailed expert review. Suppose, when you buy a used CNC from MachineStation, you get to know the details of the machine from our experts who will help you with the best hearts.

Conclusion:

In conclusion, the accuracy of a machine is very important. In the case of CNC it is even more important. The reason being its involvement in heavy manufacturing. So, it is a better thing to check the accuracy of the machine following the mentioned steps to ensure your purchase becomes worth every penny.