- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
Programming software Post-inspection software Control software Application-specific software Reverse engineering software
Fundamentals of CMM Software
Fundamentals of CMM Software
Three major steps of coordinate metrology
Probe calibration Obtain coordinate data (X,Y,Z) Fit ‘reference geometry/substitute geometry’, such as lines, planes, circles, cylinders etc., to the data using LS fit; Compute dimensions, such as distances, diameter etc. from the reference geometry
CMMs allow the acquisition of accurate dimensional data on most part surfaces and readily give the relationship(s) between various features. They are easily reprogrammed for changes in products and product design. CMM software contributes mostly to the flexibility of CMMs.
Substitute Geometry Computation
Reference Criteria
Least Squares Circle
Minimum Radial Separation
Substitute Geometry Computation
Reference Criteria
Fundamentals of CMM Software
CMM Classification: Another Viewpoint
Machines operated manually at their axes or probes Machines with motorised axes and manually operated joysticks Machines with motorised axes and computercontrolled operation (CNC mode)
Here we focus only on LS 2D circles
Substitute Geometry Computation
LS 2D Circles
Specify a circle by its center (x0,y0) and the radius r (x-x0)2+(y-y0)2 =r2 We are given n points (x1,y1), (x2,y2), … (xn,yn), and we want to fit a circle so that sum of squares of distances of those points from the circle is a minimum. Distance of a point (xi,yi) to the circle is given by di = (ri-r), where ri = sqrt((xi-x0)2+(yi-y0)2) However, if we use di as a measure of the distance, we end up with non-linearities.
CMM Software
• Fundamentals of CMM Software • Some Concepts • Substitute Geometry Computation: A Brief Introduction • Sampling Issues • DMIS & DMIS Programming • CMM Software Developers
Some Concepts
Alignment
With today’s CMM software, the CMM measures the workpiece’s datums, establishes the Part Coordinate System, and mathematically relates it to the Machine Coordinate System. Mathematical Alignment vs. Mechanical Alignment
Maximum Inscribed Circle Minimum Circumscribed Circle
Substitute Geometry Computation
• Least squares best fit geometries
– – – – – – Line Plane Circle Cylinder Cone Sphere
Fundamentals of CMM Software
Function of A CMM Computer
Evaluation
• • • • Tolerance monitoring, recording, data transfer, statistics CAD data transfer Controlling Point-by-point, scanning, collision, set-up operation
CMM Software
• Fundamentals of CMM Software • Some Concepts • Substitute Geometry Computation: A Brief Introduction • Sampling Issues • DMIS & DMIS Programming • CMM Software Developers
Considerations
Chap. wk.baidu.com Non-Cartesian CMMs
CMM Software
• Fundamentals of CMM Software • Some Concepts • Substitute Geometry Computation: A Brief Introduction • Sampling Issues • DMIS & DMIS Programming • CMM Software Developers
Application-Specific Software
Statistics and Process Control 2D & 3D Curve Measurement Free-Form Surface Measurement Integration & Processing of CAD Data Spur Gear Measurement Bevel Gear Measurement Blade Measurement Bent Tube Measurement
Some Concepts
The Part Coordinate System
Before the introduction of computer software to coordinate measurement, parts were physically aligned parallel to the machine’s axes so that the Machine and Part Coordinate Systems were parallel to one another.
Some Concepts
Measured/Constructed Circles
CMM Software
• Fundamentals of CMM Software • Some Concepts • Substitute Geometry Computation: A Brief Introduction • Sampling Issues • DMIS & DMIS Programming • CMM Software Developers
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
Fundamentals of CMM Software
CMM Software Classification
Core software
• • • • • Probe calibration Part coordinate system construction Error compensation software Substitute geometry computation Tolerance analysis
Some Concepts
Translations
Moving the starting point (origin) of the measurement from its present position to another place on the workpiece is called translation.
Fundamentals of CMM Software
Function of A CMM Computer
Correction
• Guide rail and squareness errors, stylus tip diameters and center point, vertical stylus bending, probe errors, table bending, dynamic influences, temperatures of scales and workpieces
Some Concepts
Rotations
Projections
Some Concepts
When a CMM can measure these features directly, by touching the surfaces that make up the feature with a probe, the features are referred to as measured features. Other features, such as distance, symmetry, intersection, angle and projection, cannot be measured directly but must be constructed mathematically from measured features before their values can be determined. These are called constructed features.
Transformation of coordinate systems
• Machine, workpiece, rotary table, probe
Computation
• • • • Features, form and position tolerance Pairing, linking Free form curves/surfaces Conversion of dimensions
