Digging straight holes


“It’s a very professional piece of machinery that is now fully operational and doing a great job.”

Associate Professor Mike Duke

It seems a fairly simple thing, to dig a straight hole, but it took Associate Professor Mike Duke and graduate mechanical engineer Ben McGuinness several months to perfect a machine that drills holes accurate enough to ensure pine cuttings grow straight.

The hole-drilling dibbler was built at Waikato University for treestock company ArborGen, which uses it to drill holes for planting pine cuttings in its nursery beds.

Cuttings that don't grow perfectly straight are not suitable for planting. ArborGen NZ's Operations Manager Mark Ryan says the company plants "many millions of trees each year and reject trees are a significant and unwanted expense".

By drilling consistently deep, straight holes, the dibbler has helped improve treestock productivity by about 30%.

The dibbler – which is towed behind a tractor – is computer controlled and adjustable for type of tree and soil hardness, and can drill holes of different depths and operate at varying speeds. "It's a very professional piece of machinery that is now fully operational and doing a great job," Associate Professor Duke says.

The $110,000 project was jointly funded by ArborGen and TechNZ, and shows how an industry request for R&D can be fulfilled by research integrated with the University's teaching programme.

With a solution for planting out seedlings successfully implemented, ArborGen next asked the University's third year mechanical engineering design students to come up with a way to mechanise the seed planting process. Seven prototypes were designed and built and evaluated by ArborGen and the best design is now being developed into a product, with funding from ArborGen.

While planting seeds and dibbling is a major issue for ArborGen, its main problem is harvesting and grading seedlings before they're planted out. To solve this problem, Ben McGuinness has started a PhD to research and develop a robotic machine that can lift and grade seedlings using a vision system. The research is being part funded by Callaghan Innovation and ArborGen.