Category: Measurements and Controls

Measurements and Controls Mechanical Testing

Vision Gauge Digital Optical Comparator | Optical Comparator Measurement | Digital Optical Comparator Machine

By magnaparthi on 29/06/202008/03/2021

Vision Gauge Digital Optical Comparator / Profile Projector

The Vision Gauge Digital Optical Comparator is “The Fastest, Easiest, Most Accurate Way to Compare a Part to a CAD File. Vision Gauge Digital Optical Comparators are very robust. They are perfect for both the shop floor and the Quality Control lab. Standard 12″ travel X-axis stage with 0.5 micron resolution encoder and protective bellows around the 6” travel Y-axis column. All 3 axes (X, Y and Z) have high-accuracy crossed roller movements for optimal linearity and positional repeatability and high load carrying capability. Hard chrome plated X-axis stage, made of hardened tooling steel and with dual industry-standard dovetail grooves for easy part fixturing.

Vision Gauge Digital Optical Comparators are complete, ready-to-run Windows-based solutions and are delivered network-ready. They are available in both horizontal and vertical configurations. They have industry standard dovetail mounting grooves for easy part fixturing.

Vision Gauge Digital Optical Comparators are available with transmitted (i.e. back) and / or reflected (i.e. front) illumination. All illumination is LED-based for very stable and repeatable illumination conditions over a very long life (no more bulbs to replace!). Furthermore, the illumination is programmable and computer-controlled. Everything is done through a single simple an d intuitive software interface.

Vision Gauge Digital Optical Comparators have power focus. They are available in industry standard 5X, 10X, 20X, 50X and 100X optical configurations. They are available in both single and multi-mag configurations.

Vision Gauge Digital Optical Comparators and extremely easy to use. They are a “drop in” replacement for traditional optical comparators. An optional high-resolution LASER module is also available for depth & height measurements. Motorized fixtures and extended travels are also available.

What is a Profile Projector or Vision Gauge Digital Optical Comparator?

A Digital optical comparator or Machine Vision or Profile Projector is a comparator that tests products for defects and inadequate compliance using optics. This method can be managed electronically by the automated optical comparator, saving time and eliminating the need to manually collect data.

How Vision Gauge Works?

The concept behind an optical comparator can be compared to that of an old-school overhead projector. Remember those common transparent plastic transparencies projected on a projector in the classroom? In reality, an overhead projector can be used to create a basic comparator device.

You might try this little experiment if you can still find an overhead projector around the school, college, or office premises. To begin, position any two-dimensional component on the projector’s stage and project the image onto a large piece of paper pinned to the wall. A pen may be used to draw the shadow that is projected on the page. This pen outline serves as a baseline from which all subsequent items put on the stage can be measured.

They aren’t the same if the pieces don’t fit the drawing. As a result, the pen outline serves as a comparator template. We can’t even use an overhead projector to inspect pieces in practice. Overhead projectors are often position in a static, motionless location. The scale of the reference picture on the wall changes if the projection distance changes slightly as a result of the projector being disturbed or shifted, and your pen drawing becomes inaccurate.

The main idea behind an optical comparator for quality control is to take the overhead projector principle and bundle it all within a box so that the optical distance between the component and the panel is set, known, and can be calibrated.

Using a screen overlay or cross hairs as a reference point for projected points or edges, measurements of the component can be taken directly off the screen based on the known magnification of the lenses. The operator centers a point of interest on the cross hairs, then shifts the picture and records another point. Taking several points allows features like circles, slots, radii, and edges to be analytically constructed—typically using a microprocessor-based digital display.

Types of Vision Gauge

1D Vision Gauge
2D Vision Gauge
3D Vision Gauge
Area scan vs Line scan

1D Vision Gauge:

Instead of looking at the entire picture at once, a 1D vision gauge analyses a digital signal one line at a time. This methodology is widely used to identify and classify defects in continuous-process materials such as paper, metals, plastics, and other non-woven sheet or roll products.

2D Vision Gauge

Many popular inspection cameras conduct area scans involving the capture of 2D snapshots in different resolutions. Another form of line scan for 2D computer vision creates a 2D image line by line.

3D Vision Gauge

3D machine vision systems usually consist of several cameras or one or more laser displacement sensors which offers component orientation knowledge to the robot and they are positioned at different locations and traingulation position in 3D Space.

Area scan vs Line scan

Line scan systems include many distinct advantages over area scan systems in many industrial applications. Inspecting round or cylindrical parts, for example, can necessarily require the use of multiple area scan cameras to cover the entire part surface. Rotating the section in front of a single line scan camera, on the other hand, unwraps the image and captures the entire surface.

For example, once the camera has to look through the roller on a conveyor to see the bottom of the component, line scanning systems fit more easily into confined situations. In general, line scan cameras have a much higher resolution than conventional cameras. Line scan systems are well-suited for products in continuous motion because they involve moving parts to build the image.

Benefits of Vision Gauge:

Produce a very high contrast image with very sharp edge profiles so that there is no problem viewing it in full daylight.
Are much more accurate
Allow the user to be much more productive and get more work done with a single machine
Have “Auto Pass / Fail”
Can compute and display the part’s deviation from nominal and compare it to bi-directional tolerances
Work directly with the CAD data so that no overlays / templates / Mylars are required
Can be used to collect images (either with or without the CAD data overlay and with or without annotations), measurements and data .
Can also carry out fully automated measurements (like a video CMM)
Have a smaller footprint and use less floor space
Can be moved much more easily and without requiring re-calibration (i.e. “rolling cart” configuration is standard)
Have a much greater optical depth of field, i.e. “everything is in focus all at once”
Have a longer optical working distance ( i.e. more clearance between the part and the lens)
Allow you to compare a part to its CAD data beyond the optical field-of-view ! (because the CAD data tracks the part and follows the stage motion )
Have LED illumination for very stable illumination over a 10 year life. No more bulbs to change

Engineering Metrology Measurements and Controls

Terms in Engineering Measurements

By magnaparthi on 28/05/2020

Calibration:

If a known input is given to the measurement system the output deviates from the given input, the corrections are made in the instrument and then the output is measured. This process is called “Calibration”.

Sensitivity:

Sensitivity is the ratio of change in the output signal to the change in the input signal.

Readability:

Refers to the ease with which the readings of a measuring instrument can be read.

True size:

Theoretical size of a dimension which is free from errors.

Actual size:

Size obtained through measurement with permissible error.

Hysteresis:

All the energy put into the stressed component when loaded is not recovered upon unloading. so the output of measurement partially depends on input called Hysteresis.

Range:

The physical variables that are measured between two values. One is the higher calibration value Hc and the other is Lower value Lc.

Span:

The algebraic difference between higher calibration values to lower calibration values.

Resolution:

The minimum value of the input signal is required to cause an appreciable change in the output known as resolution.

Dead Zone:

It is the largest change in the physical variable to which the measuring instrument does not respond.

Threshold:

The minimum value of input signal that is required to make a change or start from zero.

Backlash:

The maximum distance through which one part of the instrument is moved without disturbing the other part.

Response Time:

The time at which the instrument begins its response for a change in the measured quantity.

Repeatability:

The ability of the measuring instrument to repeat the same results during the act measurements for the same quantity is known as repeatability.

Bias:

It is a characteristic of a measure or measuring instruments to give indications of the value of a measured quantity for which the average value differs from true value.

Magnification:

It means the magnitude of output signal of measuring instrument many times increases to make it more readable.

Drift:

If an instrument does not reproduce the same reading at different times of measurement for the same input signal, it is said to be measurement drift.

Reproducibility:

It is the consistency of pattern of variation in measurement. When individual measurements are carried out the closeness of the agreement between the results of measurements of the same quantity.

Uncertainty:

The range about the measured value within the true value of the measured quantity is likely to lie at the stated level of confidence.

Traceability:

It is nothing establishing a calibration by step by step comparison with better standards.

Parallax:

An apparent change in the position of the index relative is to the scale marks.

Posted in: actual size, backlash, Calibration, drift, hysteresis, Parallax, range, readability, repeatability, reproducibility, resolution, Sensitivity, span, Terms in Measurements, threshold, true size