Even as manufacturers of all types adopt increasing levels of automation for use throughout their operations, one production process in particular still relies heavily on human intervention. That process is quality control. The most common automation device encountered to replace or support the human eye in this process is machine vision. But this might not be the most suitable device for all applications, especially those processes where adherence to specific dimensional measurements is required.

Two manufacturers – Meyer Tool in Cincinnati and Eponsa of Barcelona, Spain – are breaking new ground in their industries by adopting an automated method of ensuring quality compliance of their finished products.

Aerospace Engine Components

Meyer Tool is a manufacturer of hot-section jet engine components for aerospace OEMs, employing more than 1,000 people at 10 locations. The company designs, builds and maintains dozens of hard gauges every year for in-process measurement of its products. For in-process dimensional measurement, Meyer Tool principally relies on work-cell-based, point-to-point contact gauges, using pneumatic digital probes. Using these gauges in the machining cell gives fast feedback. However, they also tend to be very expensive.

“The design and build of the part nest can cost $6,000, plus probes at $500 each, verification studies and maintenance,” says Beau Easton, quality manager at Meyer Tool. In total, these tools can cost the company as much as $20,000 each.

As an example of how these costs can quickly add up for use precision components of the type Meyer Tool manufactures, consider this: If the company is producing a make-complete nozzle (i.e., the company buys the casting and completes the part in-house) for quality testing of parts, it could require six to ten fixtures, each with six to twenty probes. Then, if a feature or tolerance on the part changes, the gauge must then be altered and verified. These design changes can add another $3,000- $10,000 to re-configure and qualify an existing gauge.

To reduce the costs encountered with hard gauge designing and building, Meyer Tool recently began using a new software-driven comparative gauge from Renishaw known as the Equator.

Equator is automated inspection device that has the appearance of a delta robot. In its inspection process, Equator uses the comparison method of mastering and measuring, in which a master component with features of known dimensions is used to “zero” the system. All subsequent measurements are then compared to this part. Though this simple and well-known mastering and measuring process is at the heart of what Equator does, Dave Emmett, Renishaw’s Computerized Maintenance Management Manager, says that Equator’s primary differentiator is its “high repeatability (less than ±2 μm) and radically different metrology mechanism based on a parallel kinematic structure.”

The Equator gauging system is delivered assembled, so it is usable out of the box and can reportedly be up and running in less than 20 minutes. It weighs 25kg (about 55 lbs.), and operates on single-phase power with no compressed air supply needed. Depending on configuration, Equator units range between $25,000 and $30,000.
Thousands of data points are collected by the device during the 3D scanning mastering phase using an industry standard SP25 probe. Every data point can be used for comparative measurement, meaning that one Equator can perform the same function of thousands of dial test indicators (DTIs), linear variable differential transformers (LVDTs) or handheld instruments.

Emmett says that up to five hard gauges in a Meyer Tool work cell can be replaced by one Equator. In addition, the
Equator can be used for multiple parts, switching between the parts in seconds. It can also be reprogrammed for use on many other parts over its lifetime.

The device can be used in a serial production line between turning centers, machining centers, grinders and other machines, or within a manufacturing cell to gauge components for multiple machines. Equator can also be integrated into automated cells, using an I/O interface to connect it to a robot, or by outputting the gauging results to an SPC package. Some SPC packages also offer the ability to connect to certain modern machine tool controls to update offset values for automated process control.

Meyer Tool is currently using the Equator system in a lean machining cell where it is integrated with Meyer’s Orion SPC system. Orion communicates with the Equator’s Modus software, presenting the operator with results in the form of dimensional data and SPC charts which allow the operator to determine computer numeric control (CNC).

“The machinist sees variable data and can compare the current part with recent measurements, ...