Introducing Thermal Stabilisation: Setting New Standards

The best machine tool manufacturers in the world employ thermal compensation to optimise component accuracy. Gruppo Parpas?have gone one step further and have an international patent on a system known as thermal stabilisation.

Gruppo Parpas are well known for their sophisticated machine tools and a supplier of gantry mills, horizontal boring machines, bed-type mills and 5-axis machines, many using linear drive technology to achieve high speeds, fast metal removing and ensuring long term reliability.

Their need to be constantly investing in new technology?has led to exceptional results in continuous precision and?the International Patent?allowing temperature-controlled sensors and in-built cooling systems, ensuring all parts of their machines?are kept at a constant temperature irrespective of ambient surroundings. This is one of several unique design features from Gruppo Parpas and they are the only manufacturer to implement this technology.?

Available on selected models of Gruppo Parpas machinery, the system of Thermal Stabilisation has taken the accurate machining of long cycle, complex parts to a whole new level and has been endorsed by an impressive list of users.

Thermal Expansion

Thermal expansion is a physical phenomenon that consists of an increase in the size of a body following an increase in temperature. The extent of expansion varies according to the nature of the material that makes up the body and its state of aggregation, solid, liquid or gaseous.

Why Thermal Expansion?

The increase in temperature of a solid body generally causes an expansion of each of its linear dimensions (linear thermal expansion). The phenomenon is explained because each atom that makes up matter, even in a "quiet" situation, makes very small vibrations. These vibrations, as the temperature rises, increase in amplitude and frequency, causing an expansion of the solid in the three linear dimensions of the volume: length, width and height. The same phenomenon, in reverse, is obtained by decreasing the temperature.

Effects on Machine Tools

It is evident that the larger the size of the machine, the more evident the effects of the environmental thermal variation in the structures will be. There are three effects of thermal expansion; volumetric, surface and linear thermal expansion.?

Gruppo Parpas' Experiments

In 2002, Gruppo Parpas,?after numerous experiments with applications of various software for geometric compensations, given the ineffective results of these applications for what has been described above, a solution was tested with a second insulating structure all around the structures of the machine themselves, creating a chamber/cavity inside which a continuous flow of air at a constant temperature flows.

The aim was to make the machine structures and Heidenhain measuring scales completely isolated and protected, making them immune to thermal variations from any external source:

• Variation in ambient temperature due to the seasons or normal daily or day-night ambient temperature variations
• Forced temperature variations due to heating of the environment that are often more concentrated on parts of the machine
• Temperature variations coming directly from solar radiation
• Temperature variations from door openings

This experimentation has led to exceptional results in terms of continuous precision of the machine, so much so that in 2003 an International Patent: XS, Invar and Formula.?

From over 10 years experience in the thermal stabilisation of the machine structures, such as the XS, FORMULA, INVAR, DIAMOND, ensuring the reliability of the machine's accuracy as the ambient temperature changes, the the SPEEDLINER, in addition to the thermal stabilisation of the columns and of the gantry (patented system), a new system of liquid circulation inside the ram has been implemented to keep its temperature constant and in line with the temperature of the rest of the machine.?

For more details on Gruppo Parpas and their range products visit Leader CNC Technologies : www.leadercnc.co.uk/gruppoparpas