Selection of Different Machine Tool Probes

Before choosing a machine tool probe, users will be entangled in which one is better to choose. It is generally believed that choosing a trigger probe will allow you to see the process more intuitively. You can first determine what type of machine tool you need, so that in the subsequent processing process, it will be more convenient for all subsequent operations.

The measuring head is the signaling switch for the measuring machine to touch the measured part. It is the key component of the coordinate measuring machine. The accuracy of the measuring head determines the measurement repeatability of the measuring machine. In addition, different parts need to select probes with different functions for measurement.

The probe can be divided into contact type and non-contact type (laser and other types). At present, touch probes are mainly used, and touch probes can be divided into two categories: switch type (trigger type or dynamic transmission type) and scanning type (proportional type or static transmission type).

The essence of the switch probe is the zero signal switch. Taking TP6 (RENISHAW) as an example, it is equivalent to three pairs of contacts connected in series in the circuit. When the probe moves in any direction, any contact will be separated. , the circuit can be disconnected to send a count. The switch type has simple structure, long life (106~107), good measurement repeatability (0.35~0.28μm), low cost and fast measurement, so it is widely used.

The scanning probe is essentially equivalent to a differential inductance micrometer in the three directions of X, Y, and Z. The movements in the three directions of X, Y, and Z are supported by parallel leaf springs in the three directions, and they rotate without gaps. , the offset of the probe is measured by the linear inductor. Scanning probes are mainly used to measure complex curves and surfaces.

Non-contact probes are mainly divided into two types: laser scanning probes and video probes.

The laser scanning probe is mainly used for non-contact measurement of soft materials or some characteristic surfaces. The measuring head is at a certain distance (for example, 50mm) from the detection workpiece, and measures within the range of its focus point! 5mm, and the sampling rate is above 200 points/second. Higher accuracy is obtained through the average processing function of a large amount of collected data.

Video probes further enhance the application of measuring machines, enabling many tasks that could not be done with non-contact measurement in the past. Some holes such as printed circuit boards, triggers, pads or diameters less than 0.1mm can be measured with a video probe. The operator can magnify the surface of the detected workpiece by more than 50 times, and use standard or convertible lenses to realize the measurement of small workpieces.

Ⅰ. When to use a trigger probe?

1. Parts are focused on size (such as small threaded bottom holes), spacing or position, rather than emphasizing their shape errors (such as positioning pin holes);

2. When you are sure that the processing equipment used can process parts with good enough shape, and the focus is on size and position accuracy, contact trigger measurement is suitable, especially due to the measurement of discrete points;

3. The trigger probe is faster than the scanning probe, and the trigger probe is smaller in size. When the measurement space is narrow, the probe is easy to approach the part;

4. Generally speaking, the cost of using and maintaining the trigger probe is relatively low;

In the mechanical industry, there are a large number of geometric quantity measurements that only focus on the size and position of the parts, so most of the measuring machines on the market, especially the medium-precision measuring machines, still use touch trigger probes.

Ⅱ. When to use the scanning probe?

1. Applied to the measurement of parts and contours with shape requirements: the main advantage of scanning method measurement is that it can collect data at high speed. These data can not only be used to determine the size and position of parts, but more importantly, it can be used to accurately measure with many points. Describe the shape and contour accurately, which is especially suitable for parts with strict requirements on shape and contour. The shape of the part directly affects the performance of the part (such as vanes, elliptical pistons, etc.); it also applies when you are not sure that the processing equipment you are using can process parts with good enough shape, and shape error is the main problem;

2. High-precision measurement: the scanning probe is used to measure discrete points at a uniform speed or constant force, and the accuracy of the measurement point can be higher;

Since the scanning probe can directly determine the normal vector of the contact point, the scanning probe also has advantages in the measurement of discrete points for occasions that require strict positioning and directional measurement;

3. For the scanning of unknown surfaces, that is, in the case of digitalization, the scanning probe shows its unique advantages. Because the digital working method requires a large number of points, the point collection method of the trigger probe is too slow; Since it is an unknown surface, the control method of the movement of the measuring machine is also different, that is, it works in the "exploration mode": the measuring machine calculates the trajectory of the next movement according to the trajectory that has already moved.