Optic closure presence inspection with analog photo scanner

Optic Closure Presence inspection,

with analog photosensors

Introduction

The optic closure inspection, with analog photosensor, is one of the simplest inspections existing. It adopts an analog photosensor, with a projector irradiating passing closures by the top and a receiver giving out to an operational amplifier a signal whose extension, the duration counted in encoder pulses, is proportional to the reflection. It only detects closure presence, not its inclination. Then, a malpositioned closure shall be considered a “good closure” and not rejected. Refer to the figure below showing an example of the configuration, with one of such sensors lying a few centimeters after, as seen by the incoming PET bottles, the trigger position to which the closure inspection is geometrically based. Analog photosensor, geometrically referred to a precedent Trigger. An inspection window, whose amplitude in millimeters is equal to the closure diameter, is centred around a point corresponding to the sensor’s vertical: the distance-to-trigger of the optic closure inspection, with analog photosensor. The sensor outfeed signal is a zero volt, logic “1” in the NPN-logic, worldwide traditional inspectors’ standard.

The optic closure inspection and the Trigger to whose position is referred

Measurements' repeatability

The figure above shows the most important condition for repeatability of the measurements, after changeovers. The illumination spot has always to cross exactly the diagonal of the closure of bottle formats with different diameter. It implies a precise (measured and registered) adjustment of:

sensor bridge;

or:

conveyor side guides.

If the line is multiformat, it is vital to guarantee the same conveyor side guides’ opening and geometry shall be repeated during change-overs. The diagonal line of the different formats has always to pass under the sensor illumination spot

The figure below illustrates part of the height adjustments for three inspection bridges vital to assure repeatability to changeover operations, values which have to be programmed for each one format.

One of the changeover menus in an FBI. Changeovers imply manual setup to the correct height

How it is possible to assure repeatability to a closure inspection born ignoring this relevant requirement

The optic closure inspection with analog sensor must have the possibility to slide precisely to the diagonal line of the bottle format being processed. If the inspector itself is not fabric-equipped with millimetric reference rulers, they have to be added by Vendor Staff during startup. They are commercially easily available also stainless steel rulers thinly marked each one-half of millimetre (0.5 mm) with marks whose width is just ~0.15 mm. They allow changeovers repeatable to 0.25 mm in the horizontal dimension. We stress that 0.5 mm is much more relevant that the Reader may imagine, to determine the inspection operative performances (false rejects and defects’ hit ratio). It has not to be forgot that are the false rejects what only limit the guarantees regarding the detection of non-closed bottles.

Measurement

Figure below illustrates the measurement and comparison process applied to each one container. In the example, an inspection window (“distance de mesure”, in the original French language) of 40 mm: it has to be approximately corresponding to closures’ diameter. 22 mm set as sensitivity for the inspection: lower limit of the measurement. 40 mm set as measurements’ allowed maximum (“limite super. de la valeur de mesure”). Measurements out of the allowed range: (22; 40) mm shall be considered defective and rejected. “40” is a maximum adapt to 40 mm diameter closures.

Optic closure inspection, with analog photosensor. In this example the measurement (28 millimeters) of the portion of closure by which a reflection has been obtained, is compared by the algorithm with two limits: 22 and 40. A closure shall be considered “present” because 28 lies in the assigned range

Links to other pages:

Crown-Cork, Threaded Cap or LidUltrasound Inner Pressure Inspection IntroductionIn these web pages we have frequently remarked the necessity to answer the fundamental question:…is it safe, can be sold that bottle?

Plastic Cap Visual Check with 1 Camera. The optic closure inspection is the most modern, comprehensive and satisfactory way to control closures’ status, its only disadvantages being cost and complexity, as seen by the user side. It is devoted to detection of cocked (inclined) closures, broken TE (tamper evident) bands, closures applied too high or absent at all. All these factors implying contamination of the product and extremal risks for Consumers.

The basic operation principle implies a single CCD or CMOS-camera, allowing a partial coverage, < 180º, of the closure external lateral surface. The optic system includes 3 mirrors to increase the focal length, minimising optic aberrations due to parallax error.

Broken Tamper Evident Rings, missing and inclined cap, cap too high or too low are the controls most commonly performed by mean visual cap camera systems Links to other Closure controls pages:…

Links to other Closure controls: Contact

Optic Closure Presence inspection, with analog photosensorsIntroductionThe optic closure inspection, with analog photosensor, is one of the simplest inspections existing. It adopts an analog photosensor, with a projector irradiating passing closures by the top and a receiver giving out to an operational amplifier a signal whose extension, the duration counted in encoder pulses, is proportional to the reflection. …

Laser check of Closure InclinationLinks to other pages about Closure Inspection: The added value to apply a LASER slantedcap inspection to a Vision cap check Two different configurations exist for the LASER check of slanted caps:…

Inductive Closure or Lid Presence Inspection 4096x3079@1x. Introduction

The simplest and cheapest way to check for the closing status of a container, where the closure is metallic, is the inductive-digital. The sensor is then an inductive one, its output an NPN polarity, on-off signal.

The one figured on side shows an example of this basic solution, where the cap sensor is referred to a Trigger photosensor obscured by the container along its passage, before it starts to be detected by the inductive sensor. Disadvantages

The system is very cheap but it presents a relevant disadvantage.

It can be detected only:

cap presence;
cap absence;
metal caps (e.g., aluminium, steel or tin).
This meaning that a container capped by, i.e. a cap inclined 45º, then a container surely open, shall be considered correctly closed and passed to the Market.

The signal outcoming by these sensors is normally a quite fluctuating one: impossible to act on the signal duration, when trying to detect mal-positioned closures. Advantages

However simple, this system has however several important advantages:

capable to reach also the highest production speed, typically > 140000 cph;
economy; a sensor like the one partially visible in the image (Pepperl+Fuchs®) or one of the many equivalent by different Vendors, is very cheap (<100 $);
is always available wherever in the World.

IntroductionThe simplest and cheapest way to check for the closing status of a container, where the closure is metallic, is the inductive-digital. The sensor is then an inductive one, its output an NPN polarity, on-off signal. …

Inner Pressure Inspectionby InductionOscillograms deriving by the induction analog measurements of two different lids. Each oscillogram composed by the sequence of hundredths of individual samplings operated by a single-channel analog sensor. …

Ultrasonic fobbing systemsWhy the ultrasonic fobbing systems ?Common disadvantages of the closure optic inspection systems: Optic, with 1, 2, or 3 CCD-camerasTamper evidence band Missing closure, inclined and high closure…

3-D cap colour space. To perceive the rationale for the inspection of the caps’ colour, we recommended to see the video below. It has been filmed in a PepsiCo plant and in a beverage Bottling Line where, at the time of the film our staff commissioned twelve different formats, personalized by twelve different colours for the cap.

In this conditions the production face the risk of:

Operators errors in the special sort bottle + cap: entire cartons of wrong caps reaching the Capper;
caps of the wrong colour mixed in the lot of the caps of the correct colour. A solution pass thru the control of the colour of each one cap applied by the Capper Machine. Colour control made illuminating with a source of known spectrum (a halogen lamp) the cap. Part of the light reflected by the cap enters the lens of a trichromatic detector. This is a device with three separate channels, referred to the familiar fundamental colours red, green and blue.

The signal in the outfeed of each one channel is separately amplified and later digitised and processed, comparing the digitised value with upper and lower limits set during the commissioning.

The signals incoming by three separate channels, each one corresponding to a fundamental colour, are processed to deduce the cap colour. The couple of yellow colour vertical lines are the inspection window, the range of distances measured in millimetres equivalent to Encoder pulses. In the vertical axe of the diagram they appear, digitized in a scale of 4096 bits, the signals’ amplitudes. In the example shown, a cap has been measured thru all three channels with approximately the same amplitude ~1380 bits. The image setup in the meantime specifying a “good colour 1” implies that all caps whose chromatic mix similar to this one shall be considered correctly coloured. Where “correctly” means their colour is coherent with the currect production

As an example, refer to the graphic on right side:

a couple of yellow colour vertical lines represents the inspection window, the range of distances in the Inspector's Shifting-Register, where the three chromatic channels are evaluated;
red colour the red chroma signal, whose grey level is normalized (0 - 4096);
blue colour the blue chroma signal amplitude, whose grey level is normalized (0 - 4096);
green colour the green chroma signal, whose grey level is normalized (0 - 4096);
white colour their superimposed amplitude, whose grey level is normalized (0 - 4096).

Caps whose tri-chromatic mix is out of each one of the three allowed ranges, shall be rejected. In the example, a cap has been measured thru all three channels with approximately the same amplitude ~1380 bits. The image setup in the meantime specifying a “good colour 1” implies that all caps whose chromatic mix similar to this one shall be considered correctly coloured. Where “correctly” means their colour is coherent with the currect production

In the video above it is visible ad addition to the standard configuration of this kind of devices, namely a stainless steel curved screen, opposite to the source of light and trichromatic sensor.

The Sun in some special times of the day, gets into that PepsiCo Bottling Hall, infeeding the thrichromatic sensor. Knowingly, Sun’s spectrum is continous and centred on yellow colour. The screen allow to overwhelm these phases, preventing Electronic Inspector’s systematic errors: huge false rejects stopping the entire 50000 bph PET Bottling Line.

Caps' Colour InspectionTo perceive the rationale for the inspection of the Caps’ Colour, we recommended to see the video below. It has been filmed in a PepsiCo plant and in a beverage Bottling Line where, at the time of the film our staff commissioned twelve different formats, personalized by twelve different colours for the cap. …

Dewatering systemsRefer to the figure on right side, where a green colour scanning line intercepted a water drop scanning, and measured its distance to the bottle’s plastic, greater than toward the closure top surface: a wrong distance. …

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