JEC COMPOSITES MAGAZINE - Issue #50 - July/August 2009 - 19

EQUIPMENT EQUIPMENT EQUIPMENT EQUIPMENT Faced with the need for a production process change associated with drilling composite materials, Lockheed engineers reached out to a third-party testing organization, the National Center for Defense Manufacturing and Machining (NCDMM, Latrobe, Pa., USA). NCDMM was asked to study the entire machining process and to develop a proven bestpractice procedure. As a result, Lockheed chose a coated carbide tool. NCDMM tests revealed that the combination of precise cutting-edge geometries, which are only possible with a tungsten carbide tool, and a coating application that greatly extended its resistance to wear, was by far the best solution for the project and process. The tool finally selected was a coated composite drill supplied by Amamco Tool (Greer, SC, USA) that allows operators to increase feed rates by over 12 times and substantially reduce span time. The tool and the process change netted a 450% increase in the number of holes drilled per tool. During the tests that enabled Amamco Tool to perfect geometries that cannot be duplicated by PCD tools, a protective coating was applied to the carbide so as protect critical cutting geometries and to cover the entire tool surface. The coating – applied by a chemical vapour deposition process (CVD) – was a multilayered diamond material provided by Diamond Tool Coating (North Tonawanda, NY, USA). The tool produced over 1,200 holes compared with the 275 produced by the original drill on the same task. Test results showed a 75% reduction in span time and huge increases in feed rates, which contributed to the significantly faster production rate. All in all, Lockheed achieved a 97% reduction in tool costs. Along with the process change savings and tool cost reductions, extraordinary efficiencies will be achieved during the planned manufacturing of more than 2,783 F-35 aircraft. Test results reported significant productivity gains, as seen in Table 1. Table 1: Amamco diamond-coated carbide composite drill vs. PCD. penetrate composites without separating the layered material (delamination). Coatings: the CVD diamond technology As a result of the NCDMM tests for Lockheed, Amamco Tool now recommends the CVD process, which applies layers of 100% real diamond crystals to the surface of their solid carbide tools. The result is an ultra-hard coating between 8 and 12 microns thick that significantly increases the life span of tools in abrasive CFRP applications. Natural diamond take hundreds of years to develop. But diamond grown in a hot filament chemical vapour deposition process requires only 20 to 60 hours depending on the size of the tool and desired coating thickness. The process involves introducing methane gas into a vacuum chamber that is super-heated by an array of hot filaments. The process temperature of 815.5°C prevents anything but solid carbide tools from being coated. An extensive pre-treatment process requires 6% fine grade carbides to ensure good adhesion. Tool life – Holes per tool Feed rate Span time Overall tooling cost 450% increase 12 times faster 75% reduction 97% reduction Carbide: the improved custom solution Tungsten carbides were first developed in Germany in the 1920s. They produced such advanced steel milling grades that they revolutionized most industries by the 1930s at a time where carbides containing both titanium and tantalum were introduced. A variety of hard metals were then further developed in response to the demands of the emerging steel, mining and manufacturing industries. A composite material itself, carbide combined with the binder cobalt can be formulated for specific hardness and bending strength ratios. By including chromium, nickel and other metals to carbide formulas, developers can now custom-produce tool base materials according to very specific user requirements and preferences for hardness, toughness and wear. It is also possible to accommodate for precise cutting geometries. Innovators most recently increased cutting edge sharpness substantially by using smaller grain sizes – even micro-grains – and by controlling grain growth during the sintering process. Although it outlasts any other metal tool, carbide’s one limitation has been its life span as compared with PCD diamondtipped tools. However, as the above data reveals, coated carbide tools now reduce friction along the entire tool surface, lowering cutting edge temperatures and greatly extending tool life, making it equivalent to or exceeding that of PCD (as shown in the case history above). CVD diamond coating also helps the carbide tool to smoothly and quickly Parts assembly on the Lockheed F-35 production floor. No50 July-August 2009 / jec composites magazine 19

JEC COMPOSITES MAGAZINE - Issue #50 - July/August 2009

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #50 - July/August 2009