Jiangce Technology | Technology Sharing

**In 1973, in a small workshop in Gloucestershire, England, an engineer was struggling with a difficult problem: the Rolls Royce Olympus engine blades of the Concorde supersonic aircraft had complex shapes and extremely high precision requirements, which traditional measurement methods could not meet. He made a bold decision to abandon the existing plan and design a completely new measurement tool from scratch. This decision later completely changed the global precision measurement industry. **

The engineer’s name is David McMurtry, and the tool he invented is called the trigger probe. In the same year, he founded a company called Renishaw with his partner John Deer.

Today, 50 years later, this small measuring head has been installed on hundreds of thousands of CNC machine tools and coordinate measuring machines, becoming an indispensable “eye” for intelligent manufacturing.

—

###1、 What is a probe? Why is it so important?

###1.1 Definition of measuring head

**Probe is the core component responsible for “sensing” workpieces in precision measurement systems. Simply put, it is the “finger” of the measuring machine – sensing the position, shape, and size of the workpiece surface through contact or non-contact means, and then transmitting the signal to the measuring system for processing.

###1.2 Two major classifications of probes

What we will focus on today is the most widely used contact probe.

—

###2、 What black technologies are hidden in the probe?

###2.1 Five core technologies

A seemingly simple probe actually integrates multiple precision technologies:

### **1. Mechanical trigger type**

-Principle: Mechanical mechanism deflection triggers micro switch

-* * Features * *: Simple structure, low cost

-* * Application * *: Early stage probes, entry-level devices

### **2. Strain gauges**

-Principle: Force measurement causes a change in the resistance of the strain gauge, which is converted into an electrical signal through a bridge circuit

-* * Features * *: High precision (taking Renishaw OMP400 strain gauge probe as an example, the unidirectional repeatability accuracy can reach 0.25 µ m 2 σ at 50mm probe/240mm/min touch speed), controllable force measurement

-* * Representative product * *: Renishaw OMP400

-* * Application * *: High precision (taking Renishaw OMP400 strain gauge probe as an example, the unidirectional repeatability accuracy can reach 0.25 µ m 2 σ at 50mm probe/240mm/min touch speed) for workpiece detection

### **3. Piezoelectric type**

-Principle: Pressure generates a charge signal

-* * Features * *: Fast response speed, extremely high sensitivity

-* * Application * *: Ultra high precision (mainstream brand probes typically have one-way repeatability accuracy in the range of 0.25~1.0 µ m 2 σ for machine measurement) measurement

### **4. Optical trigger type**

-Principle: Grating occlusion generates photoelectric signals

-* * Features * *: No wear and tear, long lifespan

-* * Represents product * *: Blum TC76

-* * Application * *: Tool measurement, high-frequency usage scenarios

### **5. Scanning style**

-Principle: Continuous contact with the surface of the workpiece to collect a large number of data points

-* * Features * *: High data density, able to restore complete shapes

-* * Representative product * *: Renishaw SP25

-* * Application * *: Complex surface, blade, mold detection

—

###3、 What are the technical difficulties of measuring heads?

Many people may ask, “Doesn’t the probe look like a switch? What is the technical content

In fact, to make a good probe, you need to overcome five major technical difficulties:

###3.1 Force measurement control ⭐⭐⭐⭐⭐

**Difficulty * *: The contact force must ensure reliable triggering without damaging the surface of the workpiece.

-Excessive force measurement: may scratch the surface of precision workpieces

-Too little force measurement: may not trigger reliably, resulting in measurement failure

**Solution * *: Using a precision spring mechanism and a force sensor to control the contact force between 0.3-1.5N (equivalent to the gravity of an object weighing 30-150g).

###3.2 Accuracy Guarantee ⭐⭐⭐⭐⭐

**Difficulty * *: The repeated positioning accuracy needs to reach the micrometer level (≤ 0.002mm).

What is this concept? Equivalent to 1/30 of the diameter of a hair strand.

**Solution * *:

-High precision (mainstream brand probes typically have a one-way repeatability accuracy in the range of 0.25~1.0 µ m 2 σ for machine measurement) bearings and guide rails

-Temperature compensation algorithm

-Multi point calibration

###3.3 Temperature compensation ⭐⭐⭐⭐

**Difficulty: Temperature changes in the workshop can affect the thermal expansion and contraction of the measuring head and workpiece, leading to measurement errors.

**Solution * *: Built in temperature sensor, real-time compensation for errors caused by temperature changes.

###3.4 Signal Transmission ⭐⭐⭐⭐

**Difficulty * *: How to ensure signal stability when the machine tool rotates and moves (mainstream brand optical probes use modulated infrared signal transmission, effective distance 6-15m) (mainstream brand optical probes use modulated infrared signal transmission, effective distance 6-15m)?

**Solution * *:

-Infrared transmission: short distance, low cost

-RF transmission: Long distance, strong penetration

-* * Wired connection * *: The most stable, but limited in applicability

###3.5 Over travel protection ⭐⭐⭐

**Difficulty * *: How to protect the precision mechanism inside the probe in case of accidental collision?

**Solution * *: Mechanical overload protection mechanism+electronic collision detection, which automatically retracts the measuring needle when a collision occurs.

—

###4、 How many applications are there for measuring heads?

The application scenarios of the probe far exceed the imagination of most people. The following are the six core application scenarios:

###4.1 Machine Tool Workpiece Inspection

**Scenario description: On a CNC machining center, the measuring head automatically detects the position and size of the workpiece to ensure machining accuracy.

**Typical process * *:

-After clamping the workpiece, the measuring head automatically aligns its position

-During the processing, the probe detects key dimensions

-After processing, the measuring head is used for final verification

**Value: Reduce offline detection time by over 70% and avoid errors caused by repeated clamping.

###4.2 Tool measurement

**Scenario description * *: Measure the length and diameter of the tool, and detect if the tool is damaged.

**Typical application * *:

-Measure tool length compensation after automatic tool change in machining center

-Detect tool wear and provide early warning for tool replacement

-Discovering a broken knife to avoid processing accidents

###4.3 Three coordinate measurement

**Scenario description: In the quality inspection laboratory, a coordinate measuring machine uses a probe to perform precise testing on workpieces.

**Typical application * *:

-Size detection: length, width, height, aperture, etc

-Geometric tolerances: flatness, roundness, coaxiality, etc

-Reverse engineering: Scan the surface of the workpiece to generate a 3D model

###4.4 Robot guidance

**Scenario description: On an automated production line, the probe helps the robot accurately locate the workpiece.

**Typical application * *:

-Robot grasping and positioning

-Assembly guidance

-Deburring path planning

###4.5 Additive Manufacturing Testing

**Scenario description * *: During the 3D printing process, the measuring head detects the quality of the printed parts on the machine.

**Typical application * *:

-Complex aerospace components

-Medical implants

-Mold shaped cooling water channel

###4.6 Gear/Blade Inspection

**Scenario description: Using a scanning probe to detect complex surfaces.

**Typical application * *:

-Aircraft engine blades

-Automotive gears

-Turbine wheel

—

###5、 Global Probe Market Landscape

###5.1 Main Manufacturers

###5.2 Technology Sources Unveiled: Are Zeiss, Hexagon, and Renishaw using the same technology?

This is a concern for many people. The answer is: Zeiss is independently developed, while Hexagon is acquired and integrated. **

### 🔍 ** ZEISS – independently developed technology**

-* * Company History * *: Founded in 1846 (with a focus on optics), 127 years earlier than Renishaw

-* * Source of Technology * *: Independently developed based on a century of optical accumulation

-* * Core advantages * *: Optical system, scanning probe, high precision (taking Renishaw OMP400 strain gauge probe as an example, the unidirectional repeatability accuracy can reach 0.25 µ m 2 σ at 50mm probe/240mm/min touch speed)

-* * Relationship with Renishaw * *: No direct technical connection, independent patent

Zeiss’ VAST scanning probe and RDS rotating probe are both independently developed, with a different technical route from Renishaw’s trigger probe.

### 🔍 ** Hexagon – Acquisition of Integrated Technologies**

Hexagon established a measurement empire through a series of acquisitions:

**Key point * *:

– Brown & Sharpe was founded in 1850 and is a well-established measurement company in the United States

-Possible early use of Renishaw’s patent authorization (1980s-1990s)

-But it has now formed an independent technical system

### 🔍 ** Renishaw’s patent protection situation**

-In 1972, David McMurtry invented the trigger probe

-The core patent protection period is 20 years, which expired in the 1990s

-Subsequent improved patents (such as signal transmission and force measurement control) are still within the protection period

-Authorized patents to multiple manufacturers in the 1980s and 1990s

### 💡 ** Why is there a misunderstanding of ‘continuing to use’? **

-The triggering principle is the same: the mechanical deflection triggering signal is a physical principle and cannot be patented

-* * Similar appearance * *: Function determines form, both are cylindrical+measuring needle structures

-Patent expiration: Early core patents have expired, and everyone can use the basic technology

-* * Industry standards * *: There are industry standards for probe interfaces and communication protocols (such as I++DME)

###5.3 Market Trends

-* * Intelligentization * *: The probe integrates more sensors to achieve adaptive measurement

-Wireless: RF transmission becomes mainstream, freeing itself from cable constraints

-* * Integration * *: Deep integration of probes with machine tools and robots

-Localization: Chinese manufacturers are catching up, but the high-end market is still monopolized by foreign investment

—

###6、 From Concorde aircraft to smart factories

Returning to the beginning of the story.

In 1973, David McMurtry invented the trigger probe to solve the measurement problem of Concorde aircraft engines. This invention has enabled Renishaw to grow from a small workshop to a leader in the global precision measurement industry.

Today, 50 years later, the probe has evolved from a single product to a vast technological system. It is applied to:

– ✈️ ** Aerospace * *: Aircraft engines, satellite components

– 🚗 ** Automobile manufacturing: engine, gearbox, body mold

– 📱 ** Consumer Electronics * *: Mobile phone cases, precision structural components

– 🏥 ** Medical devices * *: artificial joints, dental implants

– ⚡ ** Energy equipment * *: gas turbine blades, nuclear power components

—

###7、 Conclusion: The Future of Precision Measurement

The story of the probe is a microcosm of the development of the precision measurement industry.

From manual measurement to automatic measurement, from contact to non-contact, from single machine measurement to online detection, from data acquisition to intelligent analysis – measurement technology is undergoing a profound transformation.

The core of this transformation is to make manufacturing more precise, efficient, and intelligent.

As Renishaw’s slogan goes: “Intelligence Inside, Maintenance Reduced**

Intelligence begins with measurement.

—

**Reference:**

-Official websites of Renishaw, Bolong, and Marposs

-Baidu Baike: Renishaw Company

-Zhihu Column: Introduction to the composition of the measuring head system of a coordinate measuring machine

-MMSONLINE: Portal for Probe Products, Brands, Technologies, and Applications

—

*This article is compiled and published by the technical team of Ningbo Jiangce Technology Co., Ltd*

*JCE Ops – AI driven precision measurement and maintenance expert*

*Technical Consultation: 157-5780-7400*

—

**Topic tags: * * # Intelligent Manufacturing # Precision Measurement # Probe # CNC Machine Tool # Three coordinate Measurement # Renishaw # Industry 4.0 # Technological Innovation # Manufacturing # Science Popularization # Machine Tool Probe Maintenance

###

FAQ Selected Q&A

**Q: Are trigger probes and coordinate measuring machine probes the same thing? **
**Answer: The principle is similar, but the application scenarios are different. Triggered probes can be used on coordinate measuring machines (CMM) or installed on the spindle of CNC machine tools for on machine measurement. The core triggering mechanism of both is the same – generating electrical signals by touching the surface of the workpiece with a measuring needle – but the measuring head on the machine tool needs to cope with harsh environments such as cutting fluid, chips, and vibration, and has higher requirements for protection level and signal transmission methods (such as optical/wireless).

**Q: What does the unidirectional repeatability accuracy of 0.25 µ m of the probe mean? Can it be achieved in actual processing? **
**Answer: * * 0.25 µ m (0.00025mm) refers to the deviation range of the measuring head repeatedly touching the same point under the same conditions. This represents the mechanical repeatability of the probe, but in actual machining, the final accuracy is affected by various factors such as machine tool positioning accuracy, thermal deformation, and probe bending. Taking into account the error factors in various aspects of on-site measurement, the reference standard for equipment acceptance is usually within 2 µ m, and high-precision operating conditions can be controlled within 1 µ m.

**Q: Can non-contact probes (lasers) completely replace contact probes? **
**Answer: * * cannot be completely replaced. Laser probes have faster speed and no measurement force, suitable for scanning soft materials, thin-walled parts, and curved surfaces, but are sensitive to surface color, reflectivity, and cleanliness. Contact probes have more stable and reliable accuracy, and are not affected by surface optical characteristics. They are still the preferred choice in machining scenarios with strict dimensional tolerances. In practical applications, the complementary use of the two has the best effect.