Coordinate measuring machines evaluate a physical object’s geometry, using a probing system to map subtle rises and dips across a component’s surface. The first coordinate measuring machine appeared in the early 1960s, developed in Scotland by the Ferranti Company the decade previously. The original coordinate measuring machine worked on two axes, using a tracking device to display the surface of an object via a basic digital readout in three dimensions along the X, Y, and Z axes.

Initially used for precision parts in military apparatus, a three-axes model was developed in the 1960s. Today’s coordinate measuring machines are used mostly to test components or assemblies to ascertain whether they meet design requirements. Coordinate measuring machines are an integral part of manufacturers’ quality control efforts, with the device an important tool for their quality assurance departments.

How Coordinate Measuring Machines are Used in Plastic Injection Molding

Using coordinate measuring machines offers many advantages over manually inspecting plastic parts and products made via injection molding. Though devices like height gauges, micrometers, and other metrology devices can be used for measuring the dimensions of components, coordinate measuring machines offer greater speed and accuracy, along with a lower chance of human error.

Used to test components to see if they will work as intended, these machines can either be computer-controlled or controlled manually. A probe attached to the moving axis of the coordinate measuring machine records measurements of the part, noting points along its surface to evaluate the component’s construction. These measurements are used for multiple parts made from the same molds, which technicians then analyze for anomalies.

Benefits of Dimensional Testing 

Methods used before the introduction of the coordinate measuring machine have drawbacks. Traditional quality control methods for components require experience and a certain skill level for inspectors. If an inspector using traditional methods is not experienced enough with the procedures, it can lead to increased substandard parts coming off the production line. Additionally, parts produced in the 21st century tend to be more sophisticated, with intricate designs, so coordinate measuring machines work better when there’s greater complexity.

Reasons dimensional inspection is used in component manufacturing include: 

• Decision-making: Product designers aren’t infallible, and occasionally, processes or products that might work on computer-aided design (CAD) software don’t work well in the real world. Taking measurements from prototypes using tools like coordinate measuring machines helps designers make better decisions during development before it’s too late to alter the design.
• Determining capabilities: Dimensional testing helps determine what levels of force, pressure, shear, and other environmental conditions a component can withstand. Validating this involves a capability study that helps product designers ensure the part’s capabilities before it’s subjected to extreme conditions.
• Regulatory compliance: All industries require manufacturers to meet specific regulatory requirements, so it makes sense to audit designs by doing dimensional testing to ensure compliance.
• Risk management: Assessing the dimensions of injection molded parts lowers a manufacturer’s liability, as identifying and resolving problems before they lead to a disastrous outcome costs considerably less. Using coordinate measuring machines helps manufacturers make parts with precise dimensions to lower the chance of failure.

Coordination measuring machines offer accuracy and speed that manual methods cannot replicate. Using these machines reduces errors within the measuring process, augmenting productivity. They save time, money, and boost a manufacturer’s ability to put out quality products, thus improving its reputation.

Types of Coordinate Measuring Machines

There are several different types of coordinate measuring machines, each with unique characteristics. These include but are not limited to bridge, gantry, horizontal arm, cantilever, and portable measuring arm devices.

Bridge Coordinate Measuring Machine

One of the most accurate types of coordinate measuring machine, it uses a probing system that tracks along the X, Y, and Z axes at right angles with each other. The probe detects points on the part’s surface as it moves along each axis, while a sensor assists by monitoring where the probe is at any time to optimize dimensional accuracy within microns. These points produced by the coordinate measuring machine’s analysis are called a “points cloud,” denoting the part’s surface area. Its use provides an automated dimensional analysis that helps ensure better accuracy, duplicability, and production speed.

Gantry Coordinate Measuring Machine

The gantry coordinate measuring machine resembles the bridge model, though it’s larger. These machines are also more complex and don’t require operators to lift the object onto a worktable. This ensures better accuracy of measurements, though due to their larger size, they take up more space. A gantry machine must also be in a fixed position, bound directly to its base.

Horizontal Arm Coordinate Measuring Machine

Though typically ordinary measuring machines have vertical configurations, these devices have probes for measuring horizontally. They’re used primarily for measuring longer, thinner components, as their probes can stretch out considerably. Metal sheets and longer, flat parts typically use this device to measure their dimensions.

Cantilever Coordinate Measuring Machine

This coordinate measuring machine design features a measuring head fitted to one side of its base, which is inflexible and secure. Its build allows techniques to access all three axes while running easily. Like the gantry model, larger components can be easily loaded onto the worktable for measuring.

Portable Arm Coordinate Measuring Machine

Unlike other coordinate measuring machines that utilize worktables, this portable arm device is mobile. It’s easily carried and can measure components within a product while still connected to their assemblies. Its compactness, lightweightness, and small size allow for this portability. Mainly consisting of an articulated arm, it can measure a part along 6 or 7 axes. This allows it to measure complex components with intricate geometries.

How Coordinate Measuring Machines Work

Coordinate measuring machines operate on two basic working principles. The first involves a mechanical probe on the machine’s mobile axis that directly interacts with the component to measure its geometry. The second measurements are taken by probes that don’t contact the part’s surface but measure points using cameras or lasers to analyze whether a component has the same exact shape as designed.

As an example, this is how bridge or gantry coordinate measuring machines work: 

• Component to be measured is put on the worktable, which is stable enough to enable accurate measurements even with external forces acting against it.
• Mounted above the plate, the coordinate measuring machine controls a mobile gantry with a mechanical probe, which directs the probe along X, Y, and Z axes.
• This operation replicates all aspects of the component’s geometry to measure it accurately.
• Once the probe touches a point to be measured, it sends a signal electrically to the computer, which maps the component’s geometry.
• The probe continues to calculate many points along the part’s surface to determine exact measurements.

Once measured, the part’s geometry has been established along the X, Y, and Z axes. This data is then analyzed and compared to its intended design shape. The actions are essentially the same whether the coordinate measuring machine utilizes a laser or camera system.

Benefits of Using a Coordinate Measuring Machine for Dimensional Testing

Coordinate measuring machines is a real-time saver for companies that utilize plastic injection molding to fabricate parts. As time is money for component design, the more complex a part’s dimensions are especially useful. These devices give precise measurements of a component’s geometry, enabling manufacturers to consistently produce precision parts in volume.

For this reason, any manufacturer that utilizes the services of an injection molding company should ensure they offer dimensional testing capabilities. Coordinate measuring machines to ensure components to be used within products match those designed via CAD software. These devices help verify a component’s dimensions, other dimensional inspections, and the quality of the part itself while allowing manufacturers a relatively simple means for reverse engineering products.

Other benefits coordinate measuring machines offered include: 

• Added data points for those parts with curves, profiles, and more intricately shaped surfaces.
• Better accuracy for parts with more complex geometries.
• Capabilities for staging multiple parts on the worktable.
• Capacity to program machines offline.
• Lesser need to orient parts physically.

Coordinate measuring machines include powerful software used for measurements, with modern models also offering intuitive graphic interfaces that guide operators through the programming and inspection process. Programming the machine offline allows technicians to develop more efficient ways to inspect components while allowing the machine to conduct measurements. It allows for comparisons between the geometry of CAD models and actual physical parts. By utilizing data from CAD models, parts manufacturers that utilize coordinate measuring machines in their process not only save time but also greatly reduce the chance of any expensive mistakes.

Contact Spaulding Composites to Learn More About Dimensional Testing 

Spaulding Composites partners with manufacturers to make plastic injection molded components for various applications. We work with our partners from the design and prototype phase through the finishing of parts and fulfillment of orders. Spaulding can help you optimize your design, providing feedback to make the process more efficient while also helping determine what materials best suit your needs.

Spaulding delivers on its promise to make high-quality components with superior finishes. Our capabilities allow us to produce parts at speed and in volume. Besides injection molding, we offer various secondary services, including CNC machining, hot stamping, marking, packaging, and product assembly. To learn more about dimensional testing and how coordinate measuring machines are used to make injection molded parts, contact the experts at Spaulding Composites today.