PCMM – Portable Coordinate Measuring Machines
Taking everything you need to measure — big or small — to another machine at another location adds unnecessary complexity to your workflow. If you're working with a fixed coordinate measuring machine (CMM), doing this without disrupting the machine environment adds to the challenge.
Fixed CMMs are not always the ideal solution for every application. If you are working on a prototype, reverse engineering, or inspecting a recently manufactured part for faults, a mobile, portable solution is a better choice.
A Portable Coordinate Measuring Machine (PCMM) is a reliable solution that's also easy to use and quick to set up. Instead of using cranes to transport a part to another location, you can use a hand-held portable CMM to perform dimensional analysis in its original location, even in tight areas.
Read on to learn more about PCMMs and how to choose the best portable CMM.
Capture 3D's Guide to Choosing the Best Portable CMM For Your Application
A portal CMM comes in various configurations. The best portable CMM among the choices depends on the application.
What You Need To Look For In a Portable CMM
Not every portable CMM is suitable for every application, and there are many factors to consider when choosing a portable CMM. For a hobbyist experimenting with 3D printing, accuracy requirements are lower. However, if you are a manufacturing professional inspecting the first part, the accuracy requirements will be strict. Similarly, the time on hand and the size of the article are equally important factors to consider.
Let's go through each factor one by one.
• Accuracy — A portable CMM provides insight into your manufacturing process and structural details of a part. As these pieces of information are critical for your design process and overall decision making, the best portable CMM for you should fulfill your accuracy requirements.
• Size — Available portable CMMs have different recommended part size limits. They can measure a part within that size range — no more, no less.
• Part Complexity — In a production line, there are various parts with a range of complexity. Some parts may have straight edges and simple holes, while others may have complex surfaces. You need a portable CMM that can cater to your requirements, no matter how complex the part is.
• Time — Measurement speed matters. Even 30 seconds of scanning time adds up if you measure several parts each hour.
• Nature of Part — Portable CMMs come in contact and non-contact variations. For fragile objects, non-contact portable CMMs are an excellent choice.
• Software — Many portable optical CMMs come with software to process and analyze the resulting data. The software should be easy to use and include helpful features. GOM Software, for example, has a user-friendly interface and intuitive software functions that make data analysis fast and simple.
• Ease of Use — In addition to easy-to-use software, a portable CMM should also be easy to use for your workers. If it requires training, your business will have to allocate time and money to train the workers, so consider that when determining which type of portable CMM to use.
Keeping these factors in mind, let's go through the common portable CMMs.
Types of Portable CMMs
Portable CMMs come in two basic variations: contact and non-contact. Contact portable CMMs use a touch probe that lets the software know where a surface exists. The non-contact CMMs or 3D scanners use lasers (portable laser CMM) or structured light (portable optical CMM) to detect the surface structure of the part.
Beyond this basic variation, the portable CMMs are further classified based on configuration:
1. Articulated Arms
2. Laser Tracker
3. Portable Optical CMMs
In an articulated arm configuration, a probe is attached to the end of an arm with six to seven degrees of rotation. As the probe moves, the optical rotary encoders in the arms measure the rotation angle and send it to the software. The software then computes the location of the probe in space.
Typically, articulated arms are fitted with a touch probe. Operators move the probe around the part and touch a point to measure. However, articulated arms with laser probes are also available now, which allows the collection of a large amount of data quickly.
Articulated arms are available in various spherical radius sizes. They are lightweight and easy to carry for a single operator.
• Support for both laser and tactile probes
• Easy to operate
• Limited range — up to 13 feet
• Sensitive to vibrations
• Needs rigid structure for support
A laser tracker, or portable laser CMM, consists of a laser emitter mounted on a tripod stand. Retroreflector targets are placed on the part to be measured. Laser strikes the target and returns to the origin. Laser interferometer detects the difference in wavelength to calculate the target's location.
Portable laser CMMs give accurate measurement over long distances — up to 220-240 feet, making these portable CMMs a common choice for large part manufacturing and assembly.
• High accuracy
• High speed
• Continuous data
• Requires a clear line of sight
• Slow data processing
• Difficult to scan dark/shiny structures
Portable optical CMMs consist of a light source and multiple cameras. The light source emits a pattern on the object's surface. The cameras capture the distorted pattern from different angles and send the data to a computer for analysis.
Portable optical CMMs provide accurate, precise measurements of parts with complex geometries. They are the best portable CMMs for scanning objects with freeform or organic structures.
• Highly accurate detailed data
• Easy to operate
• Doesn't require rigid support
• Cost can be higher than portable CMM types
• Limited to line of sight
Contact vs. Non-contact
While choosing the best portable CMM for your application, you need to decide between contact and non-contact solutions. Both options come with their own set of pros and cons.
For scanning a large part, a contact-based portable CMM would require hundreds of data points, which is impractical to collect manually. A non-contact solution works better as an optical CMM or portable laser CMM to collect full-field data from the part quickly.
A contact-based portable CMM can damage a fragile part. If the touch probe of the portable CMM can't be in contact with the work material, a non-contact solution like laser CMM or optical CMM is an ideal solution.
How Much Does a Portable CMM Cost?
Portable CMMs range in price from around $10k-$150k. But that doesn't mean that you should get the cheapest one if you are low on finances and the most expensive one if you have the budget.
The best portable CMM for you depends on your application — accuracy requirements, nature of working material, and measurement purpose. If you are using the portable CMM for something requiring high accuracy, investing in a metrology-grade system will help ensure you get the high-quality results you need. For comparing the produced part with CAD reference, a non-contact portable CMM that captures full-field data fast is the best choice for efficiency.
How Accurate is a Portable CMM?
A high-quality, metrology-grade portable CMM can give you similar accuracy to that of a traditional CMM. The type of portable CMM — laser CMM, portable optical CMM, and portable CMM arm — and the environment in which you measure also matter for accuracy. If the floor vibrations are significant, an articulated arm will give poor measurements compared to an optical CMM.
So consider the accuracy requirements of the application and environmental factors that will affect a CMM before deciding on the best portable CMM for your application.
Find the Best Portable CMM for Your Application Today!
If you want to measure parts on the fly without walking to the metrology department for every inspection or check, a portable CMM is the best solution. You can get accurate measurements for a fraction of the time and price you spend using a traditional CMM. Always choose the best portable CMM for your specific requirements, whether it's a laser scanner, optical scanner, or another type of portable CMM.