In precision machining workshops, if you want to achieve “unmanned assembly lines” or completely eliminate mass product scrap, an in machine online detection system (probe) is standard.

Many people often use the spindleConfuse the probe with the tool setter on the workbench. Today, Jiangce Technology is going to talk about Marposs’ most classic workpiece inspection probe – T25 (and T25E)This measuring head adopts a hard wire connection, with ultra-high repeatability and durability, and is widely used in automatic centering of workpiece coordinate systems, online measurement of aperture, and inter process allowance detection inside machine tools.

This article is based onFANUC 0i-MF/31i-B5 system+Marposs T25 probeFor example, I will explain the hardware wiring, system parameters, and calibration to the actual macro program in one go.

Why does the workshop need T25 online testing?

In traditional machining, operators need to manually touch the workpiece with edge finders and centering rods, which is time-consuming, labor-intensive, and prone to human error.

By installing the Marposs T25 probe on the spindle and using macro programs, it is possible to achieve:

Automatic centering positioningAfter the blank is machined, the measuring head automatically touches the surroundings and writes the workpiece coordinate system (G54-G59) into the system with one click.
Online measurement between processesAfter rough machining, the measuring head automatically goes in to measure the key dimensions. If there is still excess, the system automatically calculates and supplements the machining without disassembling the workpiece for measurement.
Finished product size controlAfter precision machining, the dimensions are directly measured on the machine tool, and only after passing the inspection can they be removed from the machine, completely eliminating batch scrap.

Its industry rival is Renishaw’s OMP60/OMP40 (although Renishaw mostly uses optical or wireless transmission, while Marposs T25 is a highly cost-effective hard wired transmission solution).

2. Electrical wiring: Normally closed signal is the safest

The T25 probe comes out with a 4-core shielded wire, which is connected to Fanuc’s I/O board through Marposs’ E32U interface module (such as jump signal input point X8.0):

red line+24V DC (positive pole of power supply, reverse connection will burn)
black line0V GND (negative pole of power supply)
Green lineSKIP jump signal (strongly recommended to be set in PMC)Normally closed NCWhen the measuring needle does not touch, the point is 1, and when it touches, it disconnects and becomes 0. Once the middle line breaks, the machine tool will immediately sound an alarm and stop to prevent the probe from being crushed.
white lineThe shielding layer must be connected to the common grounding bar of the machine tool.

3. Calibration of the probe itself: two indicators that must not be omitted

After installing the measuring head on the spindle, it cannot directly measure the workpiece and must be used with oneCalibration ring gauge with known precise inner diameterGo calibrate it. Calibration mainly corrects two data points:

3.1 Measuring needle coaxiality (runout)

Install the probe onto the spindle and use a dial gauge to measure the radial runout of the ruby ball at the front end of the probe. Rotate the spindle and control the runout by using the four fine adjustment screws at the root of the measuring headWithin 0.005mm(The closer it is to 0, the better).

3.2 Measuring the actual “equivalent diameter” of a ruby ball with a measuring needle

Although the nominal diameter of the ruby ball may be Φ 6.000mm, the equivalent diameter in the system’s eyes may become 5.985mm due to slight hysteresis (overshoot) caused by mechanical triggering.

Calibration methodAsk the measuring head to measure a calibration ring gauge with a known inner diameter (such as Φ 50.000mm), and after measurement, the system will provide a measurement valueActual ring gauge diameter - system measurement valueThe difference obtained is compensated into the probe diameter variable of the macro program.

4. Industrial grade Fanuc online detection macro program (single directional touch alignment)

Here is a section of our product that has been optimized by Jiangce TechnologyDual contact (fast/slow) detectionUnidirectional alignment macro program for workpieces. This program can accurately capture the true absolute coordinates of the workpiece surface in the machine coordinate system:

Dual contact (fast/slow) detectionUnidirectional alignment macro program for workpieces

O9016(MARPOSS T25 WORKPIECE PROBING)
(====================================)
(CALL EX: G65 P9016 X100.0 F400.0)
(X: EXPECTED TARGET COORDINATE TO PROBE)
(F: RE-APPROACH FAST SPEED)
(====================================)

#100 = #4001 (SAVE CURRENT G CODE GROUP 01)
#101 = #4003 (SAVE CURRENT G CODE GROUP 03)

IF [ #24 EQ #0 ] GOTO 901 (ALARM IF NO X PARAMETER)
IF [ #9 EQ #0 ] THEN #9 = 400.0 (DEFAULT FAST SPEED TO F400 IF MISSING F)

G90 G80 G40 G49
M19 (SPINDLE ORIENTATION FOR CONSISTENT PROBING)
G04 X1.0 (DWELL 1 SECOND FOR SPINDLE LOCK)

(STAGE 1: FIRST FAST APPROACH)
G31 X#24 F#9 (FAST PROBE TOWARDS TARGET WITH G31)
IF [ #5061 EQ 0 ] GOTO 902 (ALARM IF NO PROBE SIGNAL DETECTED)

(STAGE 2: RETRACT AND PRECISION SLOW DETECT)
G91 G00 X-2.0 (RETRACT 2MM INCREMENTALLY)
G90
G31 X#24 F30 (SLOW INCHING AT 30MM/MIN FOR PRECISION DETECT)
IF [ #5061 EQ 0 ] GOTO 902

(STAGE 3: RECORD POSITION)
#601 = #5061 (RECORD EXACT X MACHINE COORDINATE AT PROBE TRIGGER)

(STAGE 4: SAFE RETRACT)
G91 G00 X-5.0 (RETRACT AWAY FROM WORKPIECE SURFACE)
G90
G#100 G#101 (RESTORE INITIAL G CODES)

#1 = #601 (OUTPUT RESULT TO VARIABLE 1 FOR COORDINATE WRITING)
M99

(====================================)
(SYSTEM ALARM CODES DEFINITION)
N901 #3000=1(MISSING TARGET X PARAMETER)
N902 #3000=2(PROBE NO SIGNAL OR OVERTRAVEL)
M99

Program logic analysis:

The probe first approaches the target X-axis surface quickly (such as F400) and touches the workpieceG31The jump signal is triggered, and the spindle immediately stops.
Then return 2mm toF30’s extremely slow speedPerform a second precise measurement. Why split it into two parts? Because the servo lag and overshoot of the system are extremely small at slow speeds, it can capture the most realistic ruby ball trigger point.
Store the final captured X-axis mechanical coordinates#1You can use it to directly update the X value of G54.

5. Daily inspection: the “minefield” of online detection

Although online detection is advanced, if maintenance is not paid attention to, it will be a disaster area for aircraft collision:

Interference from cutting fluid atomizationDuring online inspection, it is necessary to use a pneumatic gun to blow off the cutting fluid and iron filings on the surface of the workpiece. If a large iron chip sticks to the surface of the ruby ball, the measured size will inexplicably add an extra thickness of the iron chip.
Consistency of spindle positioning (M19)Before each call to the probe program, it must be executedM19(Main axis orientation). Ensure that the angle of the ruby ball is completely consistent every time the probe touches the workpiece, in order to offset the installation eccentricity of the probe itself.
Battery and cable inspectionAlthough T25 is a hard wired connection, it is necessary to regularly check for cable dragging fatigue caused by workbench movement.

总结

The use of Marposs T25 for in machine online inspection is a necessary path for machining centers to move from “workshop production” to “precision industrial production”. Just take itMain axis orientationTheDual contact slow detectionandNeedle jumpingThese three core details are stuck, and the repeated measurement accuracy of the internal probe can easily stabilize within 0.005mm.

When encountering problems in online machine tool detection and modification, PLC signal docking, or writing more complex four sided split macro programs, please feel free to contact Ningbo Jiangce Technology at any time. Let’s discuss and exchange ideas together!

This article is original by Ningbo Jiangce Technology, focusing on the maintenance and technical services of industrial precision measuring equipment. Please indicate the source when reprinting.

FAQ Selected Q&A

Q: How to call the measurement loop of Marposs T25 probe on Fanuc system?
Answer:Call O9300 series macro programs through G65. T25 probe activation O9301, calibration O9351, single point measurement and other detection O9371. The parameter transmission method is similar to Renishaw Inspection Plus, but the variable numbers are different. Please refer to the Marposs T25 programming manual.

Q: What is the most critical point when installing the Marposs T25 probe?
Answer:Ensure correct pre travel direction – T25 is a contact type workpiece probe, and installation angle deviation will directly introduce measurement errors. The signal cable uses Marposs specialized cable, with a shielding layer grounded at one end. Before the first use, the O9351 calibration cycle must be performed to establish a benchmark.

Q: Do the F-values of Marposs T25 calibration and measurement have to be consistent?
Answer:Yes, the Marposs MIDA system also follows the principle of calibrated F-value=measured F-value. Calibration using F300 measurement also requires F300, otherwise the pre stroke compensation will not match and will directly introduce micrometer level deviation. This is a general rule for contact probes, not limited to Renishaw.

Collect for backup! Practice of online detection of Marposs T25 internal probe and application of Fanuc Hong program