Demonstrating at EMO 2017 NCMT Fixture Solutions will be highlighting the advantages of the photo-activated adhesive system, Blue Photon.It is intended for the manufacture of workholding systems for use on machine tools and is suitable for securing awkwardly shaped parts for tight-tolerance machining and inspection.
The process involves applying an adhesive that is cured by ultraviolet light via an LED spot curing system. The adhesive can subsequently be melted and the machined workpiece removed by immersion in hot water or by application of another heat source, which optimally should be at 80°C. Alternatively, the adhesive contact points can be sheared to free the workpiece by rotating the gripper pins in the fixture plate with a spanner.
Use of the technique is predicted to grow rapidly due to its ability to hold components securely with an average shear resistance of 136kg per gripper point, yet allow cutters excellent all-round access for machining on five sides. Unlike magnetic clamping systems, it can be used to secure not only ferrous metals but also non-ferrous metallic parts as well as ceramics and composites, including delicate materials.
Blue Photon is suitable, for example, for clamping a turbine blade to enable the fir-tree and wedge face on the root as well as the shroud end features at the tip to be ground in one-hit. Traditionally, due to clamp interference, multiple operations are required on conventional CNC grinders. The single manufacturing process is not only faster, but also eliminates work-in-progress and the risk of introducing inaccuracy due to repeated refixturing.
The novel turbine blade fixture incorporates four gripper inserts that, once adhesive has been applied and cured, hold the blade securely by one side of the aerofoil. The fixture is then mounted on the table of a Makino iGrinder using a zero-point clamping system to ensure a high degree of repeatability. NCMT is licensed to sell this Japanese manufacturer’s VIPER grinding solutions not only in the UK but across Europe.
Tests have shown that the clamping force produced by the fixture can easily withstand the requirements of machining. Material removal rate actually exceeded that achieved when the blade was mechanically clamped, as the pressure had to be limited to avoid component distortion and loss of accuracy.
Other advantages of the Blue Photon clamping process are an absence of workpiece distortion, good damping properties to suppress chatter, reduced cost of fixtures for holding complex parts, and elimination of locating lugs on castings.