All it takes is a wrong tilt and a collision takes place, leading to costly delays. How can this be avoided? Contributed by Heidenhain
Nobody is perfect, meaning that mistakes sometimes happen— often completely without intention and unpredictably. With complex 5-axis machining, for example, an erroneous tilting motion can never be completely excluded. When measuring workpieces, the touch probe along with the spindle may sometimes be subjected to damage.
This is when such misfortunes are not only inconvenient but also very costly—machine downtime, stoppages, costs for repair and other factors quickly accumulate to add up to considerable sums of money. It is here that machine operators are keen to benefit from the support of intelligent technology for avoiding such errors, or at least limit their effects.
Using What’s Available
A touch probe for workpiece measurement such as the TS 460 features a mechanical collision protection mounted between the touch probe and taper shank that compensates for smaller collisions and prevents larger ones. The protection makes use of what is already in place and available: The electronics of the touch probe and the readiness signal from the touch probe informing the control that it is activated.
With light collisions between the touch probe housing and the workpiece or fixture, the mechanical collision protection deforms to enable the touch probe to yield. Once the deflection reaches one mm, an integrated switch is actuated, in turn deactivating the readiness signal. This is the information that triggers the control to immediately stop the machine.
Since the touch probe traverses a certain response path from activation of the switch until the machine stops, the collision protection permits a further five mm of deflection through which the touch probe is able to yield without any damage being caused.
Recalibrating & Continuing
If collision protection has defused the critical situation and the touch probe has survived the collision without damage, the machine operator needs to recalibrate the touch probe with the calibration cycle of the control. After modifying the CNC program to prevent any future collision repetitions, the machine operator can then unconditionally continue machining without any major time losses, and more importantly without the need for repairs.
The collision protection incidentally also acts as a thermal decoupler, preventing the dissipation of heat from the spindle to the touch probe. Such flows of heat may occur particularly during longer measuring cycles if the spindle still has a high temperature from previous machining. The result would then be erroneous measurements.
Fit For Workshops
Touch probes can no longer be done without when it comes to reducing the idle times of machine tools. Together with the control, workpiece touch probes capture the position and orientation of workpieces, and this information makes it easy to align the workpiece to be machined and to set datums on it. Tool touch probes help to identify wear or tool edge breakage in good time via the precise measurement of tool dimensions and with cyclic wear control. The more workshop-oriented the machine operator is, the more the manufacturing process benefits from quality and cost efficiency.
The latest touch probes for measuring workpieces and tools on tool machines provide several fundamental developments—including a wear-free optical sensor, a blowing device for cleaning the measuring position and integral energy generation.
Some touch probes can also use infrared and radio technology. Operators specify the most suitable transmission mode within the production environment according to specific circumstances. Infrared provides maximum precision levels and rapid signal transition, whereas radio technology has a wide range and can be used on large-scale, non-enclosed machines.