2011 Stellenbosch University – SunnySide Apple Packer

The design entry submitted by students from Stellenbosch University’s Mechanical and Mechatronic Engineering department - Norval Geldenhuys, Hardus Scheepers, Cornel Liebenberg and Daniël Malan won the 2011 PneuDrive Challenge competition. Their design is essentially a "high-speed, accurate and selective apple packer".

They noted that because apple packing is currently done by hand (with an average of below 45 apples per min), many potential problems with labour, including inconsistent packing quality, are experienced by farms and distributors.
Their proposed packing machine (with a packing speed of 190 apples per minute), is aimed at production managers and financial decision makers of packing houses that could serve the fruit and vegetable industry, and is essentially based on a design that improves the marketability of produce. That by boxing “coloured” apples (any apples with red, green or yellow colouring) with their best-looking and best-coloured side facing upwards more efficiently – that there would be a better perception of the produce, thereby improving the marketability of the produce.

Link to video of the Sunny Side Apple Packer application: YouTube

Click here to download a summary of the design.

The Environment

Apple packing in South Africa

The Problem

Packing of apple boxes is primarily done by hand in South Africa. This delivers inconsistent results in perceived quality of packed produce.

The Proposed Solution

The designed packer proposes to pack apples into boxes with their best-looking side facing upwards. It will deliver consistent results and at a rate that is more than double (190 apples/min) the accepted packing rate.

The Market

South Africa annually exports a relatively constant 42% of their 700 000 tonne apples. The apples are packed in bags or boxes. Most of the boxes are packed by hand in an attempt to present the apples with their best-looking side facing upwards.

How It Improves on Current Systems

The machine will deliver a more consistent perceived quality and create a “standard look” for a specific supplier. This could serve as a very good way to build the supplier’s brand. The machine will also be able to operate for 24 hours a day without much supervision.

The Cost

All the raw material, manufacturing and bought-out parts costs R450 000. This amount excludes on-site assembly and installation costs as well as overhead costs and product mark-up.

Specifications

Unique Features

As far as is known, the packer is the first that has the ability to pack apples while improving their perceived quality by facing the best-looking side upwards.

From a business perspective, besides packing boxes of produce quicker and more consistently (improving from 45 to 190 apples per minute) an important and arguably far more valuable consequence of the design is a higher perceived quality of the goods.
By using a FESTO camera, the Intelligent Compact Vision System (SBOC-Q/SBOI-Q), a camera designed to facilitate quality inspection; the Sunny Side Packer can detect and deliver consistent quality for each tray of apples that are packed. The cameras are designed to be placed at a distance of 553 mm above the rotating apples, giving it a viewing angle big enough to see 300 mm of the singular chain. Two cameras will then cover the 600 mm length required for six apples.

As described in this figure taken from the design report, the Sunny Side Packer system has of a total of 10 axes:
• Six DNCI’s
• The EGC
• A conveyor axis
• A flat belt, and
• A singulator chain axis.

Movement along these axes can result in the packing of twelve apples into two trays at a rate of 15 trays per minute.

The system is controlled by a Programmable Logic Control (PLC) unit that uses a personal computer (PC) for user input and output and image processing. The PLC needs to be capable of communicating with six pneumatic controllers, one electrical linear actuator controller and three motor drivers.
Figure 5.3 – taken from the design report – shows the layout of the control system.
The design proposed that the FESTO CPX-CMAX controller (a very effective and compact mounting topology for the system’s drivers and control hardware) should be used for the actuations of the FESTO DNCI cylinders, which indicates that the PLC must use the same CPX topology. The CPX – CEC control block was selected as the perfect for the system requirements for the Sunny Side Packer as it can control up to 31 axes – the design reflecting that 10 axes are required.

Apples are moved linearly and rotated through the system on a singulator chain. In order to ensure the efficient use of energy and motion (therefore money), suitable driving mechanisms for both the chain and flat belt need to be selected. Acceleration and speed control is also fundamental to the application.
Two SEW MoviGears were chosen to drive both the chain and the belt. The advantages of these close-coupled geared motor and drive system above traditional drive systems are:
• Great efficiency at basically any speed and torque
• The gearbox is not over designed as in other motor designs (thus minimising losses)
• A servo motor is used
• It has good speed control
• Installation is easy because no external encoder, drive or gearbox is required
• Cable losses are very small because the drive unit and the motor are so closely coupled, requiring shorter wires.

The FESTO vacuum generator – VADMI-95-P – was selected to generate the vacuum for the four suction grippers on each picker. This generator is suitable for this design since it is easy to install with its integrated solenoid valve and has an integrated vacuum switch and ejector pulse. The vacuum switch is required by the PLC to check whether an apple has been picked up or not. The “ejector pulse” ensures that the apples are set down quickly and reliably, by applying a short pulse of positive pressure to the gripper just after the vacuum has been switched off. The VADMI product is preferred above the OVEM product because it does not require the extra functionality that the OVEM offers and is less expensive.
FESTO EGC and DNCI equipment was selected to provide horizonatal and vertical movement because of its ability to be able to deliver precise, controllable movements and ensure reliable placement for successful pick-up and placing operations at a reasonable cost.