Coordinate measuring machines — CMMs for short — are designed to gather data and produce measurements from complex geometric objects — an innovative tool that can be utilized across industries, from healthcare to aerospace.
In this article, we’ll provide a comprehensive understanding of the different types of CMM machines, their fundamental principles, and how they operate in various industrial settings.
The Basics of CMMs
A CMM is a tool used for measuring the physical geometrical characteristics of an object. CMMs determine the X, Y, and Z coordinates of points on the object’s surface, and their coordinates help in creating a detailed 3D representation of the object — which can be further analyzed for quality control, reverse engineering, or conduct dimensional verification.
Types of CMMs
There are three main models of coordinate measuring machines that can be found on production and manufacturing floors:
Bridge CMMs: A Bridge CMM consists of probe movements along three axes. The sensor point of contact allows the measuring of the surface.
Gantry CMMs: Gantry CMMs are similar to their Bridge CMM counterparts. However, they’re larger in stature, which equals a greater overall measuring volume.
Portable CMMs: Portable CMMs are precisely that — portable. This means operators can maneuver the tool, whether contact or no-contact measurements, around the object — which is ideal for complex pieces that are integral to a production line or that are too heavy to transport to a Bridge CMM.
Components of a CMM
A typical CMM is designed with three main components:
Machine Structure: This structure forms the frame of the CMM and supports the other components. It is designed to ensure stability and rigidity during measurements.
Probe System: The probe system is responsible for physically touching the object and recording spatial coordinates. Probes come in various types, such as touch-trigger, scanning, and non-contact probes, each designed for specific applications.
Control System and Software: The control system processes the data gathered from the probe and converts it into measurement results. Advanced metrology software operates the CMM, analyzes data, and produces reports.
How CMMs Operate
CMMs operate based on the principles of metrology and precision measurement. Here’s an overview of the operating process:
Programming: The measurement routine needs to be programmed into the CMM. This involves specifying the points, features, and dimensions that need to be measured. The programming can be done manually or through computer-aided design (CAD) models.
Alignment: The object to be measured is securely placed on the CMM’s measuring platform. Proper alignment is essential to ensure measurements are accurate.
Measurement Execution: The CMM’s software guides the probe to the specified measurement points on the object’s surface. Depending on the type of probe being used, it will either touch the surface to record the coordinate or use non-contact methods for measurement.
Data Collection: The CMM records the coordinates of the specified points on the object’s surface, gathering an accurate dataset. These data points create a digital representation of the object’s geometry.
Data Analysis and Reporting: The collected data is analyzed using metrology software. The software processes the data to determine the dimensions, tolerances, and deviations of the measured object—generating reports which are crucial for quality control and decision-making processes.
Applications of CMMs
CMMs find applications in various industries, including aerospace, automotive, manufacturing, and healthcare. These machines are used for quality control, reverse engineering, verifying tolerances, and much more. In the aerospace industry, for example, CMMs ensure the accuracy of aircraft components, while in healthcare, they help precisely measure medical devices and implants.
Advantages of CMMs
- Precision: CMMs provide incredibly accurate measurements down to micrometres, ensuring high-quality products.
- Efficiency: They offer a quick and efficient way to measure complex geometries and components.
- Repeatability: CMMs provide consistent and repeatable results, which are critical for maintaining quality standards.
By understanding CMMs, their advantages, and their features, manufacturers and shop floor operators can utilize these tools to streamline their productions.
