三坐标测量机探针系统

Optical Probing Systems
Laser Triangulation
The distance between the camera and the laser emitter is known. The angle of the laser emitter corner is also known. The angle of the camera corner can be determined by looking at the location of the laser dot in the camera’s field of view.
Considerations
Chap. 6 Non-Cartesian CMMs
Definition
Probe is a sensor which provides the connection between the surface of the measured object and the length measuring system of the coordinate measuring machine.
Tactile Probing Systems
Effective Probing Techniques
Shanking is another cause of measurement error.
Tactile probing systems
Effective Probing Techniques
Tactile Probing Systems
Classification of Tactile Probes
hard probe
touch trigger probe
measuring probe
Tactile Probing Systems
Touch Trigger Probe Design
Probe
Probe Systems
Tactile Probing Systems Optical Probing Systems CMM Probe Manufacturers & Renishaw Probe Systems Probing System Selection Trends
Tactile Probing Systems
Double-Touch Trigger Probes
Detect workpiece contact at a very low force. To avoid false triggering, a kinematic resistive mechanism is used to confirm triggering. Between the two triggering, the values of the length measurement systems of the CMM are latched; by triggering of the kinematic mechanism they are finally recorded.
Lobing Effect
Tactile Probing Systems
Compare FL and FH
Tactile Probing Systems
3D Directional Response TP6 TP200
Tactile Probing Systems
Tip Compensation
Tactile Probing Systems
Touch Trigger Probe Design
Modular Design
• Probe head • Probe body • Stylus
Tactile Probing Systems
Modern Touch Trigger Probes
Tactile Probing Systems
Basic Principle of Probing Tactile Probing System Design: A Brief Introduction Directional Response Tip Compensation Effective Probing Techniques
Reference: A. Wozniak, M. Dobosz, Metrological feasibilities of CMM touch trigger probes I & II, 34 (2003): 273-299.
Tactile Probing Systems
2D Directional Response
FUNDAMENTALS OF COORDINATE MEASURING TECHNOLOGY
Prof. Dr. Liandong Yu Prof. Dr. Weishi Li
HEFEI UNIVERSITY OF TECHNOLOGY
Contents
Chap. 1 Evolution of Dimensional Measurement Chap. 2 Fundamentals of CMMs Chap. 3 Probe Systems Chap. 4 CMM Software Chap. 5 Error Compensation & Application
A touch trigger probing system has to have at least: a touching element (e.g. tip ball) a transmitting device (e.g. stylus shaft) a force generating element (e.g. spring) a sensor (e.g. electric switch) an output
CMMs generally gather their data by touching the workpiece with a probe attached the machine's measuring axis. Since it's the tip's circumference that touches the part, the probe's center and radius are determined by measuring a very accurate sphere.
Tactile Probing Systems
Effective Probing Techniques
Probe measurements should be taken perpendicular to the workpiece surface whenever possible. Ideally, the user should take hits within ±30° of perpendicular to avoid skidding the probe tip.
Tactile Probing Systems
Basic Principle of Probing
rm=rr+rp+b
Tactile Probing Systems
Classification of Tactile Probes
hard probe
touch trigger probe
measuring probe
Tactile Probing Systems
Directional Response
The distance travelled by a probe between touching a surface and the trigger event is referred to as pretravel. The varying directional sensitivity can be caused by the suspension of the stylus, asymmetric moment of inertia of stylus, arrangement of sensors in different directions, direction dependent sensitivity of sensors, set-up of the axes, direction dependent probing force, tip ball form deviation and the direction dependent dynamic behaviour of the probing system including styli combinations.
Probe Systems
Tactile Probing Systems Optical Probing Systems CMM Probe Manufacturers & Renishaw Probe Systems Probing System Selection Trends
Strain Gauges
• Stylus force: 0.1 to 0.4N
Leabharlann Baidu
Piezo Sensors
• Stylus force: 0.01N • Too sensitive…
Repeatability < 1.00µm
Repeatability of TP200: 0.40 µm~0.50 µm
Home Work
1. What kind of gauges are needed to calibrate a stylus with a cylinder tip? Why? 2. What kind of gauges are needed to calibrate a stylus with a disc tip? Why?
Optical Probing Systems
Time of Flight Triangulation Structured light CCD Cameras
Optical Probing Systems
Time of Flight
The laser rangefinder finds the distance of a surface by timing the round-trip time of a pulse of light. A laser is used to emit a pulse of light and the amount of time before the reflected light is seen by a detector is timed.
Tactile Probing Systems
Probe Calibration
The position of the tip ball center related to the reference point of the probing system The radius of the tip ball
Probe Systems
Tactile Probing Systems Optical Probing Systems CMM Probe Manufacturers & Renishaw Probe Systems Probing System Selection Trends
Generally, the larger the tip diameter, the deeper the stylus can go before it touches the workpiece feature. This is called the effective working length of the probe. The longer the probe tip extension, the larger the pre-travel error and the more residual error is left after probe qualification.