Working principle of 3D probe

The basic structure of the three-dimensional probe The

three-dimensional probes (hereinafter referred to as probes) produced by our company are divided into two categories: EP series and TP series. The EP series probes adopt the conductive working principle, and the TP series probes adopt the trigger working principle. The basic structure of the various types of probes introduced in this manual. The
working principle

of the conductive probe: There is an unclosed power supply circuit inside the probe. The two ends of the circuit breakpoint are respectively connected to the mutually insulated probe needle and probe handle on the probe. Therefore, the probe needle and handle of the probe are actually the two ends of the normally open switch of the probe internal circuit; when the probe is connected to the spindle of the machine tool through the handle, since the machine tool and the workpiece (metal material) on its workbench are both conductors, as long as the contact of the probe needle on the probe contacts the surface of the workpiece, the circuit inside the probe will form a closed loop, and the circuit will immediately start working and generate sound and light signals on the probe body to indicate its working status.

Working principle of trigger probe


The working principle of trigger probe: There is a closed active circuit inside the probe, which is connected to a special trigger mechanism. As long as the trigger mechanism generates a trigger action, it will cause the circuit state to change and emit sound and light signals to indicate the working state of the probe; the only condition for the trigger mechanism to generate a trigger action is that the probe needle produces a slight swing or moves toward the inside of the probe. When the probe is connected to the machine tool spindle and moves with the spindle, as long as the contact on the probe needle contacts the surface of the workpiece (any solid material) in any direction, causing the probe needle to swing or move slightly, it will immediately cause the probe to generate sound and light signals to indicate its working state.

Working principle of using probe for measurement on CNC machine tools

When using probe for measurement on CNC machine tools, the probe is first installed on the spindle of the machine tool, and then the operator manually controls the movement of the machine tool to make the contact on the probe needle contact with the surface of the workpiece. Since the CNC system of the machine tool records and displays the position coordinate value of the spindle in real time, the coordinate value of the measured point of the workpiece can be converted using the coordinate value of the machine tool spindle in combination with the specific position relationship between the probe needle and the workpiece. After obtaining the relevant coordinate values ​​of each measured point of the workpiece, the relevant calculation is performed according to the geometric position relationship of each coordinate point②, and the final measurement result can be obtained.

Working status of probe

During the measurement process, when the contact of the probe needle contacts the workpiece, the probe emits an indication signal, which is composed of the light on the probe and the buzzer. This signal mainly indicates to the operator that the contact of the probe has contacted the workpiece. For probes with signal output function, when the contact contacts the workpiece, in addition to sending the above indication signal, the probe also outputs a voltage change state signal through a cable that has been photoelectrically isolated.

The role of the probe in the measurement process

According to the above working principle, the probe can fully play its role in measurement on machine tools that can perform and display precise micro-displacements, such as various CNC and digital display machine tools; the probe is part of this "measuring device" (i.e., probe + machine tool). During the measurement process, it is responsible for determining the coordinates of the measuring point through precise contact with the workpiece④, issuing indication signals, ensuring accurate measurement results and convenient, rapid, safe and reliable measurement operations.

Working mode of measurement

The probe has two working modes on CNC machine tools, namely: manual working mode and programming working mode. For probes without signal output function, only manual working mode can be used. For probes with signal output function, both working modes can be used.

When the manual working mode is used, the movement of the machine tool is manually controlled by the operator, and the recording of the coordinate values ​​of the measuring points and the calculation of the measurement results are also undertaken by the operator. The manual working mode is suitable for single pieces, small batches or situations where the measurement items are changing. The advantage of this method is that it is safe to use and the operator does not need special training; the disadvantage is that it is not suitable for situations where there are many measuring points, complex calculations and large-scale production.

When the programming working mode is adopted, the movement of the machine tool, the recording of the coordinate values ​​of the measured points and the calculation of the measurement results during the whole measurement process are determined by the macro program written in advance by the operator. The programming working mode is particularly suitable for large-scale or complex measurement situations. The advantage of this method is that it has high measurement efficiency for the above-mentioned working conditions; the disadvantage is that it requires the operator to undergo special training.

For machining centers with automatic tool change functions, the programming working mode should use a probe with infrared communication function, which is another advanced product of our company: CNC-OMS CNC machine tool online measurement system. There is a separate "User Manual" to introduce how to use this part, and this manual does not explain it in detail.

Terminology explanation

Related coordinate value ①

refers to the X, Y, and Z coordinate values ​​of the measured point on the workpiece in the machine tool coordinate system. Generally, it is the coordinate value in a certain direction. In more complex situations, the coordinate values ​​in two or three directions are required.

Related calculation ②

refers to the calculation of each related coordinate value in order to obtain the measurement result. Generally, it is addition and subtraction calculation. In more complex situations, multiplication, division or trigonometric function calculation is required.

Voltage change state signal ③

refers to the signal output by the probe as a switch signal, and the change of this signal state is synchronized with the indication signal of the probe.

Precision contact ④

refers to the ideal state in which the contact on the probe needle is in contact with the surface of the workpiece, that is, the two are in contact but the amplitude of the movement (swing or retraction) of the probe relative to the probe is very small (generally 0.001-0.002 mm), so that the resulting measurement error can be ignored. In order to ensure measurement accuracy, the coordinate value of each measuring point should be recorded when the contact and the workpiece are in precise contact. The method to obtain a precise contact state is to make 2-3 micro-adjustments of contact and disengagement, and the machine tool feed rate should be gradually reduced during this process. (end)