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Engineering Process; Watermelon Wedger

Watermelon wedging requires particular skills

I need a machine that can cut watermelons into six equal pieces. A customer needed this job to be automated and therefore asked us this question. They now have one or two people employed who could make this cutting movement in a good way. That made the production process very dependent on them and therefore a big risk. Especially during watermelon season.

Hard on the outside and brittle on the inside

We didn’t have such a machine in our range yet. But we did understand that it was in high demand. Not only for this customer. A good reason to dive deeper into the wedging process. This client had some very specific wishes; develop a machine that can cut a watermelon, weighing about four kilos, into six equal pieces, at a speed of about twelve melons per minute. The melon must stay undamaged. No breaking or tearing.

After several tests, a five-bladed knife did the job very nicely. To avoid pressure points on the fruit, we researched cutting at high speed. The mass inertia of the fruit should provide the counterforce. These tests mainly produced the necessary hilarity and fearful moments but did not yet lead to an acceptable cutting result. The final design works by making a punching movement. The knife is pushed through the fruit.

Sometimes the solution lies in making it yourself

During the tests, it turned out that a knife for six wedges was not easy to produce. We experienced a lot of breakage during testing in the blades, due to the hard shell of the melon. The knives were also too hard, especially in the places where they were welded. The knives used in the test setups did not meet our requirements. Then there is only one solution; make them yourself.

ZTI has invested in new machines to produce the knives in-house. And with success. Since the knives were made in-house, no breakage has occurred, and we realize beautiful cutting surfaces. These knives are now also used in our machines for cutting parsnip and celeriac.

After several months of production, the customer has ordered a second Watermelon Wedger to further increase capacity and to meet the increased demand.

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