For every factory, purchasing a CNC machine is a significant investment. To ensure the equipment becomes a core asset in production, guarantees the machining of qualified parts, and allows for cost recovery as soon as possible, it is crucial to verify the machine’s performance. Experience shows that over 80% of machines require on-site commissioning during installation to meet their technical specifications. Therefore, during the acceptance of a new machine, verification must be carried out to ensure that the machine meets its technical specifications and achieves the expected quality and efficiency from the very beginning.

In addition, more than 80% of machines already in use eventually operate under abnormal or over-capacity conditions, even exceeding their designed performance limits. It is generally recommended that a new machine be re-verified after six months of use, and then annually thereafter. Periodic inspections of machine error and timely compensation for leadscrew pitch error and backlash can significantly improve machine accuracy during production, enhance the quality of machined parts, reduce scrap, and greatly improve equipment utilization. In short, timely detection of machine problems can prevent accuracy degradation and avoid damaging machine operation.

With the further adoption of CNC technology, more CNC machines are using built-in probe systems for workpiece and tool measurement, as well as digitizing contours. The realization of these functions is closely tied to the machine’s own accuracy—without regular calibration, precise execution of these functions is not feasible.

Renishaw XC-80 Laser Interferometer

The Renishaw XC-80 laser interferometer linear displacement measurement software provides data analysis based on standards such as:

• BS4656 (UK CMM standard)

• BS3800 (UK machine tool standard)

• ISO 230-2 (International standard)

• VDI/DGQ 3441 (German machine tool standard)

• VDI 2617 (German CMM standard)

• NMTBA (US machine tool standard)

• GB10931-89 (Chinese national standard)

• ASME B89.1.12M and ASME B5.54 (US ASME standards)

• E60-099 (French standard)

• JIS B2330 (Japanese national standard)

2. Renishaw’s Advanced Technology

Renishaw (UK) is a global company specializing in the design and manufacture of high-precision inspection tools and systems. Its main products include probes for CMMs and CNC machines, laser interferometers, and ballbar systems. These tools support quality assurance throughout the production process: pre-process (e.g., laser and ballbar), in-process (e.g., tool and workpiece probes), and post-process (CMM inspection). Renishaw’s technologies are designed to ensure CNC accuracy, improve machine performance, and enhance manufacturing efficiency, thereby improving accuracy at the mother machine level and expanding market potential for finished products.

2.1 XC-80 Laser Interferometer

The Renishaw XC-80 laser interferometer is a high-precision device for CNC machine verification. Key features include:

• Accuracy: ±1.1 ppm (0–40°C)

• Measurement range: up to 40 m (optionally 80 m)

• Speed: up to 60 m/min

• Resolution: 0.001 μm

• Portability: high

The XC-80 supports automatic linear error compensation, making it easier for users to restore machine accuracy.

Applications:

1. Geometric Accuracy Testing

    

   Measures straightness, squareness, pitch, yaw, flatness, and parallelism.

2. Positioning Accuracy and Compensation

    

   Automatically measures positioning, repeatability, and small displacements. RS232 communication enables automatic linear error compensation, saving time compared to manual methods and avoiding human error. It maximizes the number of compensation points, ensuring optimal accuracy without requiring knowledge of machine parameters or compensation logic.

    

   Supported software includes Fanuc, Siemens 800 series, UNM, Mazak, Mitsubishi, Cincinnati Acramatic, Heidenhain, Bosch, and Allen-Bradley.

3. Rotary Axis Accuracy and Compensation

    

   When paired with the XR20 rotary axis calibrator, the XC-80 can automatically measure rotary axes at any angle and interval. Accuracy reaches ±1 arc second. This method is endorsed by new international standards and is significantly faster and more detailed than traditional autocollimator and polygon mirror methods.
   
   

4. Dual-Axis Positioning and Compensation

    

   Dual-laser systems measure the synchronized dual-servo axis movement (e.g., gantry machines), and perform independent compensation of both axes via RS232.

5. Dynamic Performance Testing

    

   With Renishaw’s dynamic analysis software, the system can evaluate machine vibration (FFT), leadscrew dynamics, servo response, and guideway behavior (e.g., low-speed stick-slip).

2.2 QC20 Ballbar System

The QC20 ballbar and XC-80 laser interferometer are complementary tools in CNC machine verification. While the XC-80 focuses on precision measurement, the QC20 identifies the causes of machine inaccuracies and diagnoses faults. Despite its importance, the QC20 is still not widely understood compared to the XC-80.

2.2.1 What is the Ballbar?

The QC20 ballbar is a tool for quickly checking 2-axis circular interpolation accuracy and diagnosing faults. It uses a high-precision displacement sensor embedded in a telescoping rod with internal coils and a moving core, operating similarly to LVDT sensors. As the rod changes length, inductance changes are translated into position signals (resolution 0.1 μm), transferred to a PC via interface. Its accuracy (±0.5 μm at 20°C) has been validated by laser interferometers.

When the machine runs a circular interpolation program, the QC20 sensor detects radius deviations. Renishaw’s software analyzes this to extract information on straightness, squareness, backlash, axis gain mismatch, and servo performance.

2.2.2 Main Functions:

1. Quick Calibration of Machine Grade

    

   Test the machine at different feedrates to determine optimal cutting speeds that meet accuracy requirements and prevent scrap.

2. Quick Fault Diagnosis

    

   Quickly identifies backlash, ballscrew error, servo mismatches, perpendicularity errors, and pitch errors. After a crash, the ballbar can determine if the machine remains within acceptable tolerance.

3. Maintenance Support

    

   Tracks machine condition over time, enabling preventive maintenance and avoiding major failures.

4. Machine Development Feedback

    

   Helps machine builders analyze the impact of lubrication systems, servo tuning, and bearing selection on performance, speeding up development.

5. Acceptance Testing

    

   Manufacturers use the QC20 to verify that machines meet design specs before shipment. Users can use the ballbar for acceptance testing, replacing or supplementing test cuts like NAS test parts.

2.2.3 Working Accuracy

The QC20 is a fast (10–15 minutes), convenient, and cost-effective tool to verify 2-axis performance. It can replace time-consuming NAS test part cuts and is recommended by standards such as ISO 230 and ANSI B5.54.