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Emerald Group Publishing Limited
Copyright © 2005, Emerald Group Publishing Limited
Cryogenic treatment reduces cutting tool costs
Cryogenic treatment reduces cutting tool costs
Keywords: Cryogenic equipment, Machine tools, Costs
In March this year, building on their work with the Engineering Forum, entrepreneurs, Barry Lomas and Andy Priscott, set-up Cryogenic Treatment Services, in Mansfield, to bring a technique discovered by a Scotsman – Sir James Dewar – at the end of the 1800s back to the British market.
From its roots in Scotland, the cryogenic treatment of metals and plastics was developed by NASA during the space race and commercialised, through the 1990s, in the USA with many applications. And the greatest cost savings to be found have been shown when the process is applied to cutting tools.
Heat treatment implies the use of elevated temperatures, but the cryogenic process uses the below-zero range as well. This offers significant benefits to cutting tool users.
Andy Priscott, Managing Director, explains how the process works, “Using sophisticated cryogenic chambers that are computer controlled we can model a cooling and reheating curve down to -195°C and up to 300°C. The key to the process is the tight control of the temperature curve. Each process requires a different curve, some remain at -195°C for a number of hours and are slowly brought back to room temperature. Some materials require reheating to temper the material after cryogenic hardening”.
Andy continued, “In the past scientists discovered that immersing some metals in liquid nitrogen could increase their wear resistance, particularly in aircraft engines, giving a longer in-service life. This gave benefits, but there were disadvantages such as overly brittle material. Thanks to NASA, developments in computer modelling and thermal insulation of the chamber, we are now able to use gaseous nitrogen. The tightly controlled computer process allows us to produce significant improvements to the whole structure of the materials being treated. In particular, we can demonstrate extended life of cutting tools that significantly reduce replacement and set-up costs for manufacturers”.
Cryogenic processing of tooling is not a replacement to traditional heat treatment and coating techniques, stresses Andy Priscott. “It should be seen as a complement, an extension of heat treatment. We are in discussion with some of the better known heat treatment companies in the UK to encourage them to use this as an extension to their service”, he added.
Andy continued to discuss how the cryogenic processing of tooling developed, “Boeing, Lockheed-Martin and many smaller companies have adopted the process, In the US, it is independent companies rather than tooling firms that pioneered cryogenic treatment and it is end users that are the customers rather than cutting tool manufacturers.
It is understandable that cutting tool manufacturers might not be very enthusiastic about dramatically increasing tool life, through cryogenics, due to the cost of processing high volumes of product and the longer time before further cutters are bought. There is however, an argument for offering the treated products as a premium brand. Indeed, Cryogenic Treatment Services is in discussions with manufacturers to develop and offer 'premium brands' of cutting tools”, added Andy.
Cryogenic Treatment Services have demonstrated significant savings for clients using HSS, CoHSS cutters. Tungsten carbide, coated or uncoated can all be treated with quantifiable benefits being realised. Companies cutting Inconel and titanium should consider the process, as evidence has shown that tool life can be dramatically improved resulting in good cost savings.
Discussing the evidence for reducing costs, Andy points out, “There is no precise guarantee that any individual treated tool will have increased performance. This is because there are too many variables in the application of a tool. But increases of up 400 per cent in cutting hours have been proved possible. Additionally, the amount of material taken off during tool regrind is smaller, extending the cutting tool life.”
Andy continued, “Cryogenic Treatment Services will not oversell the process. We believe that much damage has resulted, to its wider application, by over-promising across the Atlantic (a search for `tooling cryogenics' on Google delivers a multitude of references). We prefer that companies try the process and experience it for themselves. And it is a user's experience that is important”, he added.
To encourage companies to experiment, the process is priced to be attractive. Cost to process an average single carbide insert is £1.50, drills average £2.50, and the company will accept orders from £75+VAT. The company offers this guarantee: “If your production records clearly indicate that the processed tools showed no cost advantage over the unprocessed tools, we will gladly refund the cost of the cryogenic processing”.