Advances in five-axis CMM inspection

However, manufacturers have been challenged to achieve similar gains in CMM inspection or to effectively apply five-axis strategies. Traditionally, CMM part inspection can present a serious bottleneck to faster processing, as well as compliance with ISO and QS9000 requirements, and Six Sigma disciplines. Quality control departments are being pressured to provide faster inspection feedback to the manufacturing line. Parts must be produced to ever-tighter tolerances. Inspection routines are more detailed, requiring higher data density and more documentation. However, 3-axis CMM's are frequently constrained by machine dynamics from achieving faster cycle times. Rapid acceleration/deceleration creates inertial errors and vibration that diminish accuracy.

Historically, few five-axis coordinate measuring machines (CMM's) have been available. The technology has been mainly limited to "three + two" machines with indexing heads. Such heads historically provided incremental adjustment (2.5°, 5° and 7.5°, for example). The head must be unlocked, rotated to position, then re-locked. Next, the head and stylus tip must be calibrated for each new angle position before measuring can begin. These steps slow the measurement process and complicate programming and calibration. Most importantly, they prevent CMM's from delivering rapid, automated throughput that can keep pace with the processing gains of five-axis machining. In practice, the overwhelming majority of parts today are inspected on conventional three-axis CMM's with access and approach issues being handled either by changing to a specialty probe (with calibration after each change) or reorientation/ refixturing of the part.

2-axis infinite positioning heads
Innovative CMM head designs offer technology solutions to this QC dilemma. Created to bring automated five-axis measurement capability to most CMM's - both new and existing machines - the new heads have a low-mass, low-inertia, motorised design, with rotary drives in horizontal and vertical planes to provide a wrist-like action for infinite positioning. Rather than incremental positioning, they can position to any angle within their sweep range, and unlike incremental heads, the new heads allow a stylus to be qualified only once using a calibration sphere.

The head and stylus can then be used for all angular positions without further calibration, providing a level of automation not previously available. This capability can save hours per day on calibration, enabling unmatched CMM utilisation. Two head designs include one optimised for high-speed continuous scanning operations and the other for high throughput touch probing. Each uses the same universal CMM controller, which adds true, continuous 5-axis motion control to the machine. This allows rapid repositioning of the probe and access to features. It also allows the lightweight, 2-axis head to give the probe "touch" motion, minimising the need for the stop/start motion of the CMM's full structure. The goal is to minimise CMM motion and machine dynamic errors that can degrade measuring accuracy.

REVO? scanning head
This head is engineered for high speed precision measurement of contoured surfaces and complex geometries requiring high-volume data-point collection to validate part fit and form with high accuracy. It gathers form data from blisks, turbine blades, cylinder bores, valve seats and valve guides, and provides most of the measurement motion in scanning routines, minimising CMM motion and error forces. It enables continuous measurement of complex geometries that would require probe changes, repositioning, calibrations or part refixturing when using a three-axis
CMM and indexing head. Infinitely adapting position while measuring on the move2019 Air Vapormax Flair