In-process measurement in CNC Programming - Step-by-Step Execution

Concept Flow - In-process measurement

Start CNC Program

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Machine moves to measurement position

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Activate probe sensor

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Probe touches workpiece

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Measure dimension

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Store measurement data

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Compare measurement to tolerance

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Within

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Tolerance

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Continue machining

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End or loop

The CNC program moves the probe to measure the workpiece during machining, stores the measurement, checks if it is within tolerance, and decides to continue or adjust.

Execution Sample

CNC Programming

G00 X50 Y50 Z10 ; Move to measurement point
M85 ; Activate probe
G38.2 Z-5 F100 ; Probe down to workpiece
G10 L2 P1 Z0 ; Set measured position
M86 ; Deactivate probe
; Compare measurement and continue

This CNC code moves the probe to a point, activates it, probes down to the workpiece, records the measurement, then deactivates the probe.

Execution Table

Step	Action	Command	Measurement Value	Tolerance Check	Next Action
1	Move to measurement point	G00 X50 Y50 Z10	N/A	N/A	Proceed to probe activation
2	Activate probe	M85	N/A	N/A	Ready to probe
3	Probe down to workpiece	G38.2 Z-5 F100	Z = -3.2 mm	N/A	Record measurement
4	Set measured position	G10 L2 P1 Z0	Z = -3.2 mm	N/A	Deactivate probe
5	Deactivate probe	M86	N/A	N/A	Compare measurement
6	Compare measurement	Custom logic	-3.2 mm	Within ±0.05 mm	Continue machining
7	Continue machining	Next machining commands	N/A	N/A	End or loop

💡 Measurement within tolerance ±0.05 mm, machining continues

Variable Tracker

Variable	Start	After Step 3	After Step 4	After Step 6	Final
Probe Position Z	N/A	-3.2 mm	-3.2 mm	-3.2 mm	-3.2 mm
Measurement Stored	No	No	Yes	Yes	Yes
Tolerance Check	N/A	N/A	N/A	Within ±0.05 mm	Within ±0.05 mm
Machining Status	Idle	Probing	Probing	Checking	Continue

Key Moments - 3 Insights

Why does the probe move down with G38.2 command instead of a normal move?

The G38.2 command is a probing move that stops automatically when the probe touches the workpiece, capturing the exact measurement (see execution_table step 3).

What happens if the measurement is out of tolerance?

If out of tolerance, the program would trigger an alarm or adjust machining parameters instead of continuing (not shown in this trace but implied after step 6).

Why do we store the measurement with G10 L2 P1 Z0?

This command sets the measured position as a reference offset for future machining, ensuring accuracy (execution_table step 4).

Visual Quiz - 3 Questions

Look at the execution table, what is the probe position Z after step 3?

A -3.2 mm

B -5.0 mm

C 0 mm

D Not measured yet

💡 Hint

Check the 'Measurement Value' column at step 3 in the execution_table.

At which step does the program store the measured position?

A Step 2

B Step 4

C Step 5

D Step 6

💡 Hint

Look for the command G10 L2 P1 Z0 in the execution_table.

If the measurement was out of tolerance, what would likely change in the execution table?

A Next Action would be 'Continue machining'

B Measurement Value would be 'N/A'

C Next Action would be 'Adjust or alarm'

D Probe would deactivate earlier

💡 Hint

Refer to the 'Next Action' column in the last rows of the execution_table.

Concept Snapshot

In-process measurement in CNC:
- Move probe to position (G00)
- Activate probe (M85)
- Probe down to workpiece (G38.2)
- Store measurement (G10 L2 P1)
- Deactivate probe (M86)
- Compare measurement to tolerance
- Continue or adjust machining accordingly

Full Transcript

In-process measurement in CNC programming involves moving the probe to a specific point, activating it, probing down until it touches the workpiece, recording the measurement, and then checking if the measurement is within tolerance. The program uses commands like G00 to move, M85 to activate the probe, G38.2 to probe down, G10 L2 P1 to store the measurement, and M86 to deactivate the probe. After measuring, the program compares the value to the allowed tolerance and decides whether to continue machining or make adjustments. This process ensures precision during machining.