Simple approach gets a grip on many problems

Tom Shelley reports on an idea which started with cold joining metals, advanced into improving tool holding and now looks to take off into skin care and household cleaning



The Siloxane based anti-lubricants first reported in Eureka's October 1991 edition as a means of establishing cold welded joints, have since advanced into improving the performance of other jointing processes, such as impact bonding of normally incompatible metals and adhesive bonding.

In addition, they have also been found to be very effective in improving tool and work holder grip in machine tools.

This led onto a search for a good means to apply trace amounts of chemicals to drill shanks which has since led onto a novel dispensing method proving to be of great interest to makers of household cleaning products and an even more novel method of dispensing other compounds including skin care products.

Geoffrey Linzell, the proprietor of Ball Burnishing Machine Tools and the inventor of TribTechnology - his patented method of joining parts by inserting a shaft or tube into a hole and cold galling them together - is diversifying his ideas into new markets.

The TribTech technology is continuing to march on and is now licensed to Delphi Automotive which uses it to improve friction grip in the manufacture of critical fatigue sensitive engine parts in certain commercial vehicles.

Tribtech is still interested in further licensing opportunities, provided, they answer "Yes" when asked, "Are you experiencing pain?". Mr Linzell said, "The value of Trib is in solving problems where press fit strength falls below that needed, often found when testing new designs where Trib fixes the problem without changing the design. Tribtech prefers to devote its effort to solving problems for clients who really need a solution, as opposed to those who are merely interested in the technology."

But this has not prevented Geoff Linzell from investigating new technological avenues. In particular, applying some of his chemicals to the shaft of a drill increases tool holder grip by up to 70 per cent. This technology has been given the name, "TripGrip". And if the tool does start to slip, a peculiarity of the technology is that frictional grip then increases rather than decreases as usually happens with joints that start to slide. The reason for this is still obscure but Geoff Linzell believes it is because the process involves hydrogen wear, a phenomenon discovered by Russian scientists, particularly George Shpenkov, who describes it in a book entitled, "Friction surface phenomena". In this process, single hydrogen atoms diffuse into the body of plain carbon steel and greatly reduce its yield stress, which recovers when the process stops and the hydrogen atoms are able to diffuse out again.

Applied as liquid to a drill stem, grip is enhanced only the one time it is used, but if the chemical is applied with mild abrasion, the effect is said to work for 10 or 20 tightenings and releases. It is this that has led onto the applicator technology with so many other potential uses.

Gripping with a bang

Following a meeting at a conference in Cambridge, researchers from the Ukraine, particularly Dr L Dobruskin, at the E.O.Paton Welding Institute in Kiev have found that because the chemical temporarily reduces yield stress, it also reduces the impact velocity that is required to bond steel. In the Ukraine, researchers have long experience with explosive bonding. This is not a technology that has found much favour in the West in the light of health and safety considerations, but engineers here have done much work on bonding with electromagnetically propelled impacts to bond steel and aluminium parts, a technique that is extensively used in the United States.

In impact bonding, the chemicals help reduce the amount of force required to produce the jet of surface oxides and other contaminants that have to be ejected in order that the materials will bond properly. Geoff Linzell says that in order to achieve a marked improvement, it is necessary to align the direction of machine marks (surface roughness) on the two surfaces, in which case the energy required is approximately halved.

Geoff sees particular potential application in applying the technology to electromagnetic impact tack welds. He says that conventional resistance spot welding deforms both faces, behaves erratically on aluminium due to electrode pitting and cannot join normally incompatible metals such as steel and aluminium, whereas impact spot welds do not suffer from such problems. Magnetic impact spot welding has hitherto been limited by the need to focus intense magnetic flux, sufficient to accelerate and impact a small area on a relatively large plate into another plate, so that only point contact welds are made. By chemically treating small areas with Trib, the wetted area deforms more readily and welds at a fraction of the energy needed. Geoff Linzell believes this can be developed for the pre-assembly of sheet metal structures prior to applying structural adhesives.

Other possible uses include improving the impact welding of highly stressed cylindrical and machined parts for hydraulics, suspension and fuel injection parts

Sticking together

Using siloxanes as a method of surface preparation greatly enhances peel strength in some adhesive bonds, for example, the peels strengths of joints made with two pack epoxy were increased by more than 100 per cent.

Applicators and applications

The basic idea behind the applicator, named, "TribStick", is to have a plastic tube filled with disks of non-woven, coarse fabric, impregnated with liquid to a point just below saturation. The stick can then be used to apply the liquid without risks of spillage, and without the user having to come into contact with it. When one disk becomes exhausted, and/or contaminated, it is peeled off and discarded. It is this concept that US advisors find to be of particular potential interest to makers of skin care and household products.

And because the pads also remove dirt as well as apply chemical, this has led onto another idea, called "TribSheet" which is a potential way of applying cleaning products, including skin preparations, many of which work on the principle of mildly abrading dead skin, and applying chemical.

Demonstration samples shown to Eureka were made of thermoplastic polyurethane but could also be made of polyethylene or polypropylene for industrial uses. The basic method of manufacture is to form plastic sheet over a wire mesh so as to provide dirt channel traps where the wires were, which also have crystalline and so mildly abrasive edges, with micro pores to release liquid held on the other side between the sheet and a membrane.

All developments are covered by patents or patent applications. Trib Tech treatments can be tailored to have widely differing properties to meet the requirements of different applications.

TribTech
TribTech

Eureka says:

A breakthrough originally reported in Eureka more than ten years ago is just now beginning to advance into the real world of manufacturing engineering and has now shown a way forward for ideas way beyond those originally conceived by the inventor. Great news that such dogged persistence has finally paid off and opened the door into the big time

Pointers

*Trib Joint technology has at last broken through into mainstream engineering

* New areas of application include better tool holding and improvements to impact bonding that could make this a breakthrough technology, especially in the bonding of normally incompatible metals such as steel and aluminium

* The applicators developed for to apply chemical for improved tool holding may have even greater application in delivering household cleaning chemicals in a clean and eco friendly way, and in the dispensing of skin care products

Author
Tom Shelley

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