Inspection System Integration with Reject Mechanism.

How to automate sorting in food production

One of the key drivers of profit is optimizing the flow of products through the production line.

Mounting an automated in-line or over-line inspection system at one or more points helps determine non-compliant items based on a customizable range of testing criteria and, when coupled with the correct automated sorting process, can increase the productivity efficiency and improve the quality of your product.

These automated inspection systems, such as those manufactured by the EyePro System and Sightline Process Control brands, couple high-speed cameras with imaging software to identify and measure objects at full line speed.

This article highlights the sorting mechanisms frequently used for the production of processed food products, outlining in particular waste and recirculation.

The intention is to help production and operations personnel looking to implement a fully automated solution and to know what options are available on the market and the main factors that should be considered when installing such systems.

Selection criteria

When choosing the best sorting technology to integrate into an inspection system, there are several important considerations that should be considered when conducting an assessment.

These include assessing the physical properties of the product for inspection, production line speed (i.e. productivity), production line setup, material handling requirements for particular applications, and compliance reporting requirements .

In some cases, the value of a rejected nonconforming item may require reprocessing rather than disposing of that item.

As a result, item redirection systems can be used to redirect the flagged product for secondary inspection or further processing. An example of this would be a poultry unit, which may not be up to the portion size required for processing such as frozen chicken breast, but may still be viable for use in breaded chicken nuggets if processed correctly. .

Physical properties of the product

The physical properties of a product will determine the best sorting solutions suitable for the specific application. For example, when handling relatively small and light baked goods such as buns or biscuits, air jets can generally be installed on top or to the side to precisely isolate and reposition individual items.

For larger items, such as a whole loaf, a power-assisted scoop, pusher, or other product-specific reject system usually prove more effective. Size, weight, surface, texture and dry versus wet must always be considered.

Production line configuration

The configuration of the production line will also have a significant impact on the waste sorting method to be applied. The surface structure, width, speed and physical constraints of the conveyor and its surroundings are all key factors that need to be considered.

For production lines that require routine cleaning, the inspection system is usually supplied compliant with IP69K standards. It is imperative that the waste sorting system also meets these environmental standards to ensure that the combined system operates reliably and safely.

Waste acquisition method

How waste is acquired will be determined by the intended disposal of those products. In the case of simple disposal of non-compliant goods, the main consideration will be the volume of the catch container, which will consequently be a function of the size of the product and the expected waste percentages.

Another element to consider for disposal situations should be the accessibility and mobility of the catch containers. Depending on the inspection system installed, it may be possible to create alerts for the capacity of the waste container to advise personnel to empty or replace when appropriate.

Rework Considerations

When a product shows signs of being eligible for rework, a number of the reject methods below can help redirect the appropriate products for manual inspection or to a secondary processing line.

When a visual inspection system is integrated into the manufacturing process, sophisticated images and data associated with repurposed products offer manufacturers the ability to gain insight into process issues and track batches involving reworked ingredients.

Integration of the inspection system

Both inspection systems and preconfigured software will generally have the ability to control PLCs (Programmable Logic Controllers), which consequently are able to drive other elements of the manufacturing process, including automated reject systems.

Once the inspection system has determined which item is non-compliant, the software will send an instruction to the PLC to activate the reject system (s), which consequently removes the non-compliant item from the conveyor for disposal or, in some cases, it redirects the item to a sub-process.

Types of waste systems

The range of rejection systems available is far-reaching and some would exceed the scope of this article. However, the task is to offer a meaningful insight into the selection of waste technologies that are used frequently.

Figure 1. Integration of the inspection system with reject mechanism. Image credit: KPM analysis

For goods marked for further inspection or alternative processing rather than for simple rejection and disposal, it is customary to install and apply diversion mechanisms to transfer the identified products to a secondary conveyor or capture system. These solutions are known as “diverter” or “diverter” systems throughout the remainder of this section.

Cast or turn off

In the most basic scenario, when the inspection system reports a non-compliant product, it pauses the conveyor belt and triggers an alarm that requires production personnel to review the rejected product and manually remove it from the production line as deemed necessary.

Air jet rejector

The air jet manifolds placed in the immediate vicinity of the inspection system offer a dynamic and reliable methodology for rejecting products with a higher surface / weight or height / weight ratio.

Air jets from individual jet nozzles can accurately target individual items that fall outside the preconfigured specifications and measurement criteria, even in multi-lane production lines.

Two of the main advantages of pneumatic ejection systems are that they can provide fast response times and generally have no moving parts, thus minimizing maintenance.

Examples of processed foods appropriate for blast rejection include small to medium-sized baked goods such as English muffins, plain round buns, and even bagels:

  • Side mounted air jets: Side air jets can be perfect when it comes to unwrapping lighter products that are processed in one-lane conveyor lines for products with positive “height to weight” ratios.

Side View of Top Mounted Air Jet Rejector (single or multi-lane).

Figure 2. Side View of Top Mounted Air Jet Rejector (single or multi-lane). Image Credit: KPM Analytics

Top View of Top Mounted Air Jet Rejector (single or multi-lane).

Figure 3. Top View of Top Mounted Air Jet Rejector (single or multi-lane). Image Credit: KPM Analytics

Top View of Side Mounted Air Jet Rejector (single-lane).

Figure 4. Top View of Side Mounted Air Jet Rejector (single-lane). Image Credit: KPM Analytics

Nosebar Rejectors

There are several conveyor “nosebar” rejection systems with the ability to drop, lift or retract a section of the conveyor for the purpose of rejecting or diverting non-conforming products.

Frozen pizza crust on a drop down paddle rejector conveyor.

Figure 5. Frozen pizza crust on a drop down paddle rejector conveyor. Image Credit: KPM Analytics

  • Drop bar reject conveyors it can be extremely effective for low profile, heavier and less rigid products that are processed in single lane conveyor lines. Nose bar waste temporarily lowers a section of the conveyor to divert non-compliant product to a waste container or, if not, to an alternate conveyor path for reprocessing. Examples of products compatible with drip bar ejection systems include flat baked goods such as topped pizzas, pizza shells, and tortillas.
  • Lift the nose bar, Also referred to as “pop-up” reject, it causes a segment of the downstream conveyor to be temporarily raised, which in turn allows the rejected product on a single lane production line to end up in the reject bin. Like the drip bar reject system, the nose lift reject is suitable for applications with processed food, including topped pizzas, pizza shells, and tortillas.
  • Reject systems of the retractable conveyor belt it can be used for larger and heavier items that pass through one-lane production lines. In these systems, it is possible to create a gap when a section of the conveyor in the production line is retracted, allowing the rejected items to fall. Once the dubious product has been captured in the waste basket, the conveyor front bar assembly will return to its original position, thus allowing compliant items to continue down the line.

Side View of Lift Nose Rejector (single-lane).

Figure 6. Side View of Lift Nose Rejector (single-lane). Image Credit: KPM Analytics

Side View of Retracting Nosebar Rejector (single-lane).

Figure 7. Side View of Retracting Nosebar Rejector (single-lane). Image Credit: KPM Analytics

Pusher Rejectors

Pusher rejectors are linear actuators that can operate under the guidance of pneumatic, hydraulic or electrical means. They are well-suited to single-lane production lines and larger products.

Push rejectors will quickly move the item flagged into a reject bin or, in some instances, pass it on to an alternate production lane while the compliant goods continue unimpeded down the line. Examples of processed food products well-suited to push rejectors include bread loaves or packaged goods.

Top View of Push Rejector (single-lane).

Figure 8. Top View of Push Rejector (single-lane). Image Credit: KPM Analytics

Top View of Sweep Arm Rejector (single-lane).

Figure 9. Top View of Sweep Arm Rejector (single-lane). Image Credit: KPM Analytics

Sweep Arm Rejectors

A sweep arm rejector can be set up to sweep across the line conveyor, pushing non-conforming products into a reject bin or passing it on to a secondary conveyor for re-processing.

Sweep arm rejectors are ideal for the processing of medium-weight goods in a single-lane production line. Examples of processed food products well-suited to sweep arm rejectors include meat products such as poultry, either raw, cooked or breaded, as well as tinned and packaged goods that may not be compliant with packaging and labeling inspection criteria.

Push Finger Rejectors

Push finger rejectors function in a similar manner to sweep arm rejectors and are generally used for diverting applications. Push finger rejectors can reposition a product on a conveyor gradually and with minimal force, thereby directing it to a secondary inspection or processing line.

Top View of Push Finger Rejector (single-lane).

Figure 10. Top View of Push Finger Rejector (single-lane). Image Credit: KPM Analytics


To increase production throughput and quality, selecting the appropriate sorting solution to complement an automated inspection system is crucial. Taking into account the physical properties of the product for inspection, the configuration of the production line, and other material handling factors are key factors when making this decision.

Used in parallel with Over-Line and In-Line inspection systems, the software facilitates automatic rejection detection, which ensures that defective objects are removed before reaching the end customer.

Rejection limits can be configured and customized to allow decisions to be more predictable and repeatable. Detailed records of rejected products are stored in a database, which enables consistent, detailed reporting and data visualization via analytics.

EyePro System and Sightline Process Control – two members under the KPM Analytics family of product brands – are the leading providers of vision technologies in the food industry, supporting manufacturers by allowing them to implement quality control and production automation solutions.

These systems provide objective, meaningful and actionable measurements in a production environment at full-line speed.

Whether as a fully-integrated in-line system with process control or a benchtop unit, with vision technology systems, food manufacturers are able to see the benefits in cost savings, efficiency improvements, and product quality enhancements almost immediately.

This information has been sourced, reviewed and adapted from materials provided by KPM Analytics .

For more information on this source, please visit KPM Analytics .


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