On every CNC machine there are preliminary operations that must be carried out before you can start ‘making chips’ - one of these is certainly the measurement of the tools. There are various methods to achieve this and within the following document we highlight the advantages and disadvantages for each.
The original and classic method is to touch the workpiece, or the machine table, using the tool itself in conjunction with a feeler gauge or even a piece of paper to establish the Z value (length) of the tool.
A little bit of addition or subtraction of the position values displayed on the numerical control can be used to calculate the required measurement for each tool assembly.
This operation using the machine takes about two minutes and often, especially for large machines, it can be particularly inconvenient to carry out as the operator must physically enter the machine. It is certainly the least accurate and most expensive method in terms of machine downtime!
Another method for measuring tools on CNC machines is to adopt a mechanical ‘feeler’ or gauge. Normally applied via a magnetic base to the machine table the tool contacts the gauge and is then wound to a specific reference position or value on the gauge to make the measure. The time to set each tool with this method is faster, at about one minute, which is certainly an improvement both in terms of measurement accuracy and time taken when compared to the first method.
The final method often considered and recommended to provide presetting inside the machine tool is normally for an accessory to be requested when purchasing the machine tool. Today this solution has become very common and almost a standard for most machine tool manufacturers and suppliers. The machine tool has a mechanical gauge inside, directly connected to the numerical control, which allows you to measure the height and diameter of the tool around thirty seconds. It is certainly the best of the solutions listed so far but the machine is still being used to measure tools and not to produce parts or ‘chips’!
The most effective option is certainly the use of an external presetter. Both the bench mounted and standalone presetters available from Elbo Controlli NIKKEN allow the preparation of the tools for every process in a manufacturing facility. Without question presetting is the fastest and most reliable way both in terms of measurement precision and in regard of capturing also geometric entities and features present on the profile of the tool (not possible on the machine tool). With an external presetter it is also possible to both capture and inspect the wear of the cutting edge and to transfer the measured data directly to the numerical control in order to avoid possible transfer errors of the tool offset data.
