Portable Coordinate Measuring Machines or PCMM are high-precision measuring tools that play a key role in minimizing, if not eliminating, product defects.
PCMMs are widely used in manufacturing because of their reliability in providing accurate measurements with low tolerance ratings. In other words, PCMMs are highly precise and have low margins of error when measuring sizes and surface dimensions.
If you are in the manufacturing business and involved in parts fabrication, consider investing in a portable coordinate measuring machine. What is a PCMM, and how can it improve your processes, products, and customer satisfaction? This article explains it all.
What Is a PCMM?
Measuring the physical dimensions of fabrications for construction, automotive manufacturing, electronics, etc., is crucial for maintaining quality standards for form and function. Traditionally, the QA of parts is done manually: technicians use handheld tools to inspect surface dimensions and ensure they accurately mirror the design. And while these technicians are experts in their field, the risk of error and tolerance levels remain high.
It became necessary to develop more reliable metrology methods with lower tolerances and less dependency on human judgment, effectively reducing the pressure and liability on technicians. The PCMM fulfilled all of these needs.
PCMMs are some of the best tools available today for measuring surface geometry. Two things you need to know about it:
- 3D Measurements: Many metrology devices can only take single-axis measurements (2D measurements on a single linear dimension), but the PCMM can measure on three orthogonal axes. In other words, it can determine points as coordinates and measure distances in a 3D space.
- CAD (Computer-Aided Design) Integration: PCMMs can be integrated into computers, which means their capabilities can be machine-enhanced. Inspecting and measuring objects with complex designs with PCMM is easier and faster as a result. Integrate a PCMM in a computer-aided manufacturing environment, and you can quickly examine prototypes before deploying a design or conduct QA tests to ensure production meets your quality standards.
How Does a PCMM Work?
Imagine taking an automotive part that goes into a car’s engine. It has a complex shape with protrusions, dents, and spaces meant to connect to other parts of the engine. Imagine tracking those features with your finger and knowing the height of the protrusions, the diameters of bolt slots, and other surface geographic features in a snap.
This is exactly what you can do with a PCMM. With the device hooked into a computer, the PCMM instantly collects data as the measuring arm moves across the object, identifying coordinates as it moves from one point to another on the object’s face – exactly how you’d trace a finger over the part’s physical features.
How Accurate Is a Portable PCMM?
The tolerances vary per type and manufacturer. Generally, however, a portable CMM has an accuracy rate of less than one micron (1μ, which is equivalent to 1/1000 mm).
Types of Portable CMMs
PCMMs are classified according to the method used to “trace” an object’s surface geography and transmit coordinates to the computer-aided measuring machine.
There are three types of portable CMMS:
- Articulated Arms: These are physical arms with probes attached to the end. An articulated arm can rotate by six to seven degrees. It also contains optical rotary encoders. As the arm moves over an object, the encoders measure the rotation angle from one point to another, then send the data to the software program. The computer can then map those points on the 3D axis and generate measurements and computations.
- Laser Tracker: Laser PCMMs use laser light instead of a physical probe to map measurement points. It doesn’t need a physical probe, and since laser light can span long distances, laser tracker PCMMs can be used to measure surfaces over long distances – sometimes up to 240 feet. As such, you’ll often find laser tracker PCMMs in factories that fabricate large parts or assemble large machinery.
- Optical CMMs: This type of PCMM is not to be confused with an articulated arm’s optical sensors, even though it seems to take inspiration from it. A portable optical CMM setup consists of a light source and multiple cameras. The light source flashes a pattern on the surface of an object, and the surrounding cameras capture footage from different angles. The software analyzes the light patterns, generating measurements and dimensions with high accuracy. These PCMMs are best used on free-form objects with organic surface structures.
Contact vs. Non-Contact
We can classify laser trackers and optical PCMMs as non-contact devices. Articulated arms, of course, are contact PCMMs. Each classification has different pros and cons, but deciding between the two should be based primarily on the nature of the objects to be measured.
For example, using non-contact PCMMs on fragile objects would be wiser to eliminate the risk of damage from constant contact with the articulated arm. Non-contact PCMMs are also ideal when measuring items that can get contaminated or are unsafe when touched with a probe.
When mapping large surfaces with hundreds of data points or measuring objects at a distance, using the laser and optical PCMMs would be more efficient.
When should you use contact PCMMs, then? If you only need to map a few points on an object small enough to position directly before the device, a PCMM with an articulated arm will be ideal.
What To Look For in a Portable CMM
If you are seriously considering investing in a portable CMM, here are the important things to consider:
- Accuracy: PCMMs generally have low precision tolerances, which means they are highly accurate and have small windows for errors. The rule of thumb is the lower the tolerance, the more precise the measurements, so consider the tested/audited tolerance ratio when choosing a specific model.
- Size Limit: Portable CMMs have maximum part size limits. This means they can only measure objects within a specific size range (and distance for non-contact CMMs). Pay attention to the size limit so you don’t mistakenly buy a model that can’t measure the parts you handle.
- Speed: Measuring speeds of different models usually vary by only a few seconds. However, if you buy a slower PCMM, those five, ten, twenty, or more seconds can add up and set you back by an hour or more at the end of the day. Consider this factor if time and productivity is crucial to your operations.
- Objects to Measure: As previously mentioned, the nature of the objects or surfaces you measure is crucial in choosing a PCMM. Consider non-contact PCMMs for large or delicate objects, and if you need to map hundreds of points on just one object.
- Software: Choose a model whose software can integrate smoothly with your factory’s computer systems. Otherwise, you could waste valuable time and money trying to make incompatible software work together and end up spending for a separate network and hardware infrastructure to support the PCMM and make the most of your purchase.
- Usability: Any computing equipment in manufacturing and assembly would require technicians to receive training and instruction on how to use them properly. Make things easier for everyone by choosing a PCMM that is easy to use and master. Ease of use comes with time savings and a smaller window of error – huge wins for employees and the company at large.
When you know what to look for in a portable CMM, it will be easier to assess which model or manufacturer can give you the best value for your money.
Invest in PCMMs From a Reputable Metrology Solutions Provider
After learning more about what a PCMM is, how it works, its benefits, and applications, the next step would be to find a model that you can integrate into your production.
ATT Metrology Solutions can help you find the best PCMM solution for manufacturing, assembly, product development, and quality assurance needs. We offer customized, full metrology services and solutions to help customers reduce costs while keeping product quality and productivity levels up. Browse the PCMMs we offer on our website.
Contact us today to schedule an appointment.
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