Grain Color Sorter

Overview

The Grain Color Sorter removes off-color kernels, foreign seeds, stones and discolored fragments from a bulk grain stream by photographing every particle in flight and blowing the bad ones out with a puff of air. Grain falls from a feeder through a polished chute, crosses an inspection zone lit by tuned light, and is imaged by line-scan cameras. A vision engine classifies each pixel, and if a kernel fails the accept criteria a high-speed air valve fires at the moment that kernel passes the nozzle line, deflecting it into a reject chute. Because the product is in free fall and never touches a belt, throughput is high and cleaning is straightforward.

Feeding and chute presentation

Consistent sorting depends on presenting grain as a thin, evenly spread, single-layer curtain. The Feed System handles this. Bulk grain sits in the Feed Hopper, and a Feed Level Sensor keeps the head of grain constant so flow does not surge. Below the hopper, a Vibratory Feeder Tray tray for each lane spreads the grain across its width, with the Feeder Drive Coil electromagnet driving the pan against its Coil Spring suspension. The Feeder Amplitude Controller sets the vibration amplitude, trading throughput against layer thickness. Grain then drops onto the Chute Array, where each Slide Chute accelerates the stream to a known, repeatable velocity so the timing between the camera and the ejector is fixed. A replaceable Chute Wear Liner keeps friction low and constant as the chute wears.

Optical inspection

The heart of the machine is the Optical Inspection Box, a sealed chamber where each grain is seen against a controlled background. A Line-Scan Camera Module on the front and rear scans the curtain line by line, its trichromatic CMOS Image Sensor reading red, green and blue intensity, and on advanced units near-infrared as well, so material differences invisible to the eye can be caught. The LED Illumination Bar arrays, built from many High-CRI LED Emitter devices, provide stable, flicker-free light, while the Reference Background Plate plate gives the camera a calibrated baseline so good kernels read consistently. Dust would blind the optics within hours, so each Optical Viewing Window window is kept clean by a Window Wiper Mechanism and a continuous Lens Purge Air Knife curtain across the lens.

Detection and ejection

The image stream is processed by the Image Processing Engine, an FPGA-based engine that compares every pixel against accept and reject color maps loaded from the recipe. When a defective particle is identified, its position and the chute velocity tell the controller exactly when it will reach the nozzle line. The Ejector Valve Bank then acts. It is a dense row of High-Speed Ejector Valve units, each a fast Ejector Solenoid driving a Valve Poppet that opens for under a millisecond. Air is distributed through the Ejector Manifold and fired through a precision Nozzle Block, driven by the Ejector Driver Board. The narrow, well-aimed pulse knocks the single bad kernel sideways without disturbing the good grain beside it.

Air supply

The ejectors and the lens air knives need clean, dry, regulated air, supplied by the Pneumatic System. Plant air first passes a Compressed-Air Filter to strip oil and water, then a Air Dryer lowers the dew point so condensation never reaches the valves. A Air Pressure Regulator sets separate pressures for ejection and purge, and a Air Reservoir Tank buffers the sharp demand spikes when many valves fire at once. A Pressure Sensor watches supply pressure and alarms if it sags, since under-pressure air gives weak, inaccurate ejection.

Control and operation

The Control Cabinet ties the machine together. Alongside the image engine, a Machine Controller Board sequences feeders, valves and alarms, and the HMI Touchscreen lets the operator pick a product recipe, set sensitivity and watch reject rates and per-lane statistics. Power for the logic and valves comes from the Power Supply rails inside the IP54 Control Cabinet Enclosure. Sorted product leaves through the Collection Hoppers: accepted grain falls into the Accept Hopper while the deflected stream drops into the Reject Hopper, divided by the Stream Splitter Plate behind the nozzle line.

Materials, variants and use

Wetted surfaces are stainless steel and food-grade UHMW-PE to allow washdown and avoid contamination. Variants range from single-chute laboratory and seed-cleaning units to wide multi-chute machines sorting eight or more lanes for rice mills and pulse processors. Sensitivity can be tuned for subtle shade defects, such as chalky or immature rice, or set aggressively to remove stones, glass and plastic by NIR signature. The Frame & Enclosure keeps dust contained and supports a Dust Extraction Port for connection to a central collector. The technology suits rice, wheat, pulses, coffee, nuts, seeds and many small free-flowing foods, and is a standard final-cleaning step where appearance and food safety both matter.