Toolholding that is fit for purpose

It is easy to think of shrink-fit technology as a relatively new technique. However, open-flame heating has been used to shrink-fit parts together since before the Industrial Revolution. The first documented application was to heat and then shrink iron rims onto wagon wheels. This method was then applied to smaller items, such as heating rings or bearings onto shafts. Eventually, open-flame units were developed to heat shrink-fit chucks using carbide tooling. These systems, as well as the ubiquitous oxy-acetylene torch, remain in use in some workshops to this day.

For safety reasons hot-air shrink units were offered as an alternative to the open-flame designs. The main drawback of hot-air was the time required to heat a chuck sufficiently to change a cutting tool. It offered the opportunity to automate the process to some degree, but this advantage was not enough to overcome the limitations of the very long cycle time.

In 1992, Tooling Innovations Inc, California, obtained a US patent for shrink-fit tooling, and for an inductive shrinking unit. The machine that was introduced was very powerful, but also very large. That unit developed high power in a relatively undefined area, which resulted in overheating of the cutting tools.

“At the same time, Marquart in Germany was developing a system of inductive shrinking, and in 1994, the company obtained a European patent for Thermo-Grip tooling and an inductive machine. At first, the company concentrated on smaller cutting tools, but gradually expanded the product line to all toolholder sizes and forms for most common sizes,” explains Jason Short, YMT Technologies’ Tooling and Equipment Manager.

During 2001, the ThermoGrip group was formed by the companies Diebold, Bilz, Marquart and Komet. Their goal was, and remains, to offer standardised, high-quality products using cutting-edge technologies. The group holds many patents for innovations in shrink-fit technology and they all manufactured shrink-fit holders using design specifications first introduced by Diebold GmbH for the ThermoGrip toolholders. This design eventually became a DIN standard, and is now accepted globally.

Today, the ThermoGrip group supplies roughly 30 per cent of the shrink-fit market worldwide and is an undisputed leader in the field. Many technological innovations have come from the group and its leading experts. Solutions range from simple, bench-top units for smaller workshops right up to self-contained units that have been designed for the more demanding machining environment.

For shrink fitting carbide shank tools from 3 to 32 mm diameter and HSS shank tools 6 to 32 mm diameter, Diebold offers the manually operated HS1100. The horizontal configuration of the HS1100 unit makes adjusting and setting the tool length very easy. However, an optional length setting unit for pre-setting the length of cutter protrusion makes transferring the tool offset data to the machine tool very quick and easy. Changeable adaptors allow various tool holders to be accommodated, from HSK 32 to HSK 100 or SK/BT 30 to SK/BT 50, with a broken tool removal unit installed in all holder adaptors.

For cooling the patented chiller unit, the FKS 04 is recommended; providing the perfect solution for rapid cooling ThermoGrip chucks. It is available for manual operation or as a single button automatic sequence with tool changes achieved in as little as 40 seconds. More than 1,500 units are in use by customers across the globe.

Self-contained shrink-fit tooling solutions from Diebold include the ISG 3400TWK and the ISG 3400WK, both of which feature water cooling to make the shrink fitting and cooling of cutting tools a simple operation. Both units can shrink-fit carbide shank tools from 3 to 32 mm diameter and HSS shank tools 6 to 32 mm diameter, and have been designed so the operator does not have any contact with hot tools.

While the bench top ISG 3400TWK offers a maximum shrink extension of 400mm and a maximum cooling capacity of 160mm, the free-standing ISG 3400WK has the same shrink extension and a larger, 200mm cooling capacity.

Jason Short concludes: “Using Diebold shrink-fit toolholding technology vibration is reduced and machining is noticeably faster and smoother. So, manufacturing times can be reduced while maintaining the quality and accuracy demanded in today's competitive markets.”