High speed seed/particle counter

Working prototype seed/particle counting machine

Requirement for a solution

Suttons Seeds were having great problems accurately dispensing seeds into their retail packaging. Too many seeds, and this was a loss to Suttons while too few left them liable to customer complaint and legal claims. The current dispensing method for smooth type seeds used vibratory bowl feeders attached to a sachet packaging machine. While this worked, it was not accurate enough and was very slow creating a bottle neck in production.

We worked with Suttons to develop a new machine with a demanding specification, an accuracy of ± 1% on a count of 1000 seeds per second. Our research found that of all common seeds sold by Suttons, 80% were either spherical or elongated and smooth enough to be mechanically handled. The fluffy, hairy and very irregular seeds were normally dispensed volumetrically.

Design

Various concepts were explored but a design study reveiled a compact and high speed concept. The principle was to feed seeds onto a drum perforated in a particular way to enhance dispensing. The drum rotated over a ported hub with vacuum and air pressure applied to the various ports. Vacuum was applied to a pick-up portion, this attracted seeds. An air-knife (high pressure stream or curtain of air) immediately after, dislodged any seed clusters around a perforation so that there was only one seed per hole. At the lowest point of rotation, the drum passed over a high pressure air port that ejected seeds past a counting sensor. This sensor was developed as a laser and fan generator projected onto a custom photodiode array to give the count accuracy and speed. This concept was prototyped and developed as it worked well. This became the start of a new product development and was patented.

Potential other uses

This machine has many other applications in dispensing particles or spherical objects from ball bearings, solder balls for ball grid arrays (BGA) in the electronics industry to time release particles inside pills for the pharmaceutical industry.