CNC Thread Grinder Has Own CMM to Speed Set-Up


Holroyd has established new benchmarks for cycle times and levels of productivity with the launch of its TG 150 thread grinding machine.
Designed and manufactured in the UK, the TG 150 has high levels of onboard intelligence, overcoming the "black art" in precision machine set-ups. In addition, the flexibility provided by onboard-automated facilities - such as automatic co-ordinate adjustment and wheel dressing and CMM, combined with high stock removal rates, ensures dramatically reduced cycle times and considerable improvements in the speed and repeatability of the overall thread grinding process. The new machine is the latest introduction to Holroyd's high accuracy TG range of thread grinding machines.

Designed for parts up to 150mm in diameter, the TG 150 is an extremely versatile machine; allying many integrated facilities with an aggressive semi-finishing capability that can reduce overall machine requirements in many production environments. This same combination of features also provides for different production rates and production accuracies, as low as DIN 3 or even DIN 2, to suit modern manufacturing strategies.

In addition, the speed with which the set-up - work - rework cycle can be accomplished on the TG 150 enables manufacturing companies to react more quickly to develop and produce prototype items in global markets where innovation is at a premium.

CNC thread grinder

One of the major factors in the benchmark performance of the TG 150 is a design that replaces the variable of operator skill - "the black art" in precision machine set-ups - with machine intelligence. Operator skill level is always a variable in complex machining processes, and accurate adjustment often takes years of knowledge and experience to perfect. Holroyd has overcome this problem by distilling operator knowledge and experience into the operating intelligence of the Windows based TG 150 control system. As a result, using data from on-board measurement, the machine is able to predict the minute alterations to the profile of the grinding wheel required to achieve any desired finish and make these alterations on the fly.

A typical example highlighting the proficiency of this system in operation is a workpiece that does not meet tolerance requirements after a first grinding pass. Following on-machine measurement, the TG 150 calculates the necessary adjustments to grinding wheel form or axis position and then passes the data to a 2-axis CNC wheel dressing system to achieve on machine dressing of the grinding wheel. All of these operations are achieved automatically and rarely does the machine need to make further corrections after the first pass. On the occasion that it does; the subsequent correction is effective , and the second thread passes, then the grinding cycle proceeds as normal.

Apart from high levels of reliability, the main benefits to the user of making measurements and adjustments in this way , during the normal production cycle, are that set-up times are drastically reduced, and the speed and repeatability of the overall process is improved considerably.

The second major factor contributing to reduced development and overall cycle times on the TG 150 is the machine's built in CMM function. The TG 150 is actually designed, manufactured and calibrated to the same specifications and tolerances as a stand-alone CMM. To underline this point, the TG 150 employs the same 3D scanning probes that are used on high end CMM's, together with closed loop servo motion equipment and high precision encoders and scales similar to those found on a stand alone CMM. The CMM function is used at the start of each scan cycle; a 3D scanning probe being employed to provide a validated reference point to begin the grinding operation. The probing operation itself takes place without any machining forces and is therefore dynamically and kinematically stable - the weight, precision and stability of the machine bed being comparable to a CMM when the machining elements are static. In addition, as the workpiece is held in the same fixture as used for machining, there is no loss of position for corrective rework. Consequently, the measuring process, overall, is much more accurate and reliable.

Another factor that underlines the benefits of the TG 150's built-in CMM is that workpieces do not have to be removed for measuring, then be reloaded, reground and removed again for validation of the correction. Because of this, errors that inevitably arise during removal and transport of a part to a remotely sited CMM are eliminated. Furthermore, by avoiding breaks in production to check accuracy, costs are reduced, machine throughput is maximised, and the thread-grinding machine works at its most efficient and productive level. The fact that parts do not have to be removed for measurement also enables users of the TG 150 to overcome the problems of reliability experienced with external measurement techniques due to temperature fluctuations. As the TG 150's 3D CMM probe is mounted internally it exists in the same environment as the machine, and so temperature fluctuations between machine tool, work items and measurement device do not occur. Moreover, if environmental conditions change, the machine adapts.

Commenting upon the launch of the new TG 150, Holroyd Sales Director, Paul Hannah, said: "With the launch of the TG 150 Holroyd is equipping global manufacturing companies with the technology to reduce costs and achieve massive gains in productivity. The TG 150 allows companies to pursue flexible manufacturing strategies, and with its aggressive semi-finishing capability can , in many cases, reduce a company's overall machine requirement. The many onboard facilities provided by the TG 150 also mean that prototypes for new product types or variations can be produced in a matter of hours , fostering innovation and improved competitiveness in global markets."

For further information, please contact:

Harbour Lane North
Lancashire, OL16 3LQ

Tel: +44 (0) 1706 526590
Fax: +44 (0) 1706 353350