Making potato plates

Potatopak (now re-branded as earthpac) makes potato plates at a factory in Blenheim, New Zealand. The steps in the production process – from weighing ingredients to quality control of the final product – are described here.

Manufacturing equipment

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The machine used to manufacture the potato plates.

Rights: The University of Waikato Te Whare Wānanga o Waikato

The production process

1. Weigh ingredients: Water, starchcellulose and wax are weighed and mixed.

2. Input ingredients: The mixture goes into the hopper and is stirred constantly to prevent clumps forming.

3. Measure mixture: An auger carries the mixture onto a platform where a precise weight is measured.

4. Place in mould: The measured quantity is dispensed into swivel containers, which tip it onto the mould.

5. Heat press: A pressurised metal plate, heated to 250ºC, presses the mixture into the mould forming the shape and cooking it for a preset time. A small amount of waste is forced out through the vents along with steam.

6. Remove from mould: Robotic arms remove the products from the moulds, hold them briefly and then deposit them onto a pile.

7. Quality check: A production worker breaks off the extrusions of waste, checks for quality and sands rough edges. Quality products are stacked and rejects go into a bag for a local pig farmer.

8. Curing: Containers are stacked into boxes and plates are spread out on a trolley to go into a curing tent overnight. Controlled humidity prevents warping of the product.

9. Packaging: After curing, products are counted, shrink wrapped in preset quantities and labelled.

10. Despatch: Orders are made up in cartons and despatched to their destination.

Quality control

The performance of the moulds can be affected by changes in weather conditions, temperature, humidity and the external cladding and insulation of the building. These factors can cause variations on a daily and even hourly basis, resulting in products that don’t meet the required quality standard. Constant monitoring is required by the machine operator, and small electronic adjustments may be needed to compensate.

Quality checks

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The plates are finished with a light manual sanding to smooth the edges.

Rights: The University of Waikato Te Whare Wānanga o Waikato

During production, quality is controlled at the following stages:

1. Input ingredients: Hoppers are checked to ensure mixture is moving freely.

2. Remove from mould: Time, temperature and quantity of mixture is adjusted electronically in response to observed irregularities:

   • Delamination (separation of layers)

   • Burning – too much mix or edge spillage

   • Partial shells – not enough mix

   • Irregular colour spots – concentrated patches of wax

   • Cracks

   • Sticking to the mould (wax is added periodically to moulds that aren’t Teflon coated)

   • Sanding to smooth edges.

3. Curing: Environment is controlled to prevent warping.

4. Packaging: Visual inspections during counting and packaging pick up rejects that may have been missed initially or occurred during curing.