Surface Texture, Machining, non-contact and 3D Flashcards
WHY MEASURE SURFACE TEXTURE ?
It has long been recognized in engineering that careful finishing of components can give rise to improved:
Fatigue resistance
Bearing properties
Interchangeability
Wear resistance
which all lead to components having a longer operational life, or the same life but operating in more arduous conditions.
The categories of surface texture are divided into three form types?
- ROUGHNESS - The irregularities in the surface texture arising from the inherent action of the cutting process (cutting tool on the component).
- WAVINESS - The irregularities caused mainly due to machine vibration and deflections under cutting force.
- ERRORS OF FORM - The departure from the geometrical shape
Three basic surface texture GD & T symbols
Turning Process surface finish dominated by two issues
The finish produced by the primary cutting edge of the tool.
The finish produced by the secondary cutting edge of the tool.
Geometrical Analysis, Rt and Ra equal to?
What is FRACTURE ROUGHNESS?
Fracture roughness is one of several other contributory factors which are not taken into account by the geometrical analysis of the tool tip.
What is BUILT-UP EDGE (BUE)?
Built-Up Edge (BUE) occurs when the cutting speed increases, causing the friction between the chip and the tool to increase. When this friction component becomes large enough, it will cause a shear fracture in the vicinity of the tool face, causing a built-Up Edge to form.
Why use a non-contact?
The demand for non-contact measurements can come from a variety of sources and reasons:
- The surfaces are too delicate.
- The surfaces are too compliant/ductile.
- The surfaces have wide ranging topography.
- The technology provides more resolution/accuracy/precision.
- The technology looks/sounds better.
NON-CONTACT measurement TECHNIQUES?
- White Light Interferometry (Coherent Scanning Interferometry)
- Focus Variation
- Confocal Microscopy
- Triangulation techniques
- Chromatic Length Aberration Gauges
What are the PRINCIPLES OF OPTICAL TECHNIQUES?
Non-contact analysis using optical techniques can be generally put into two classes of technique: Incoherent and Coherent (in terms of the light source).
* In all cases, basic optical principles will dominate the ability of any optical technique to work.
What are FRINGES AND SCANNING?
The localization of the interference fringes allows one to determine the height of the object surface by e.g. identification of the scan position corresponding to the passage of the highest contrast fringe at each pixel in the field of view.
Produces bunker plots
What are the Problems with non contact scanning?
- Numerical aperture
- Edge effects
- Slope dependency
- Bat-wing effects
- Spatial resolution
- Transducer interaction with surface
- Correlation with alternative transducers
- Uncertainty analysis
- Traceability
