Thurn, a Norwich, UK-based manufacturer of underwater survey technology, is launching a new range of dipping sonars carried by roto-copter drones, designed to navigate and survey inaccessible and dangerous waterways where hidden sunken tangle hazards maybe present. The dipping sonars drag sensors through the water on a predefined route, autonomously. DLM’s attachment, which was delivered in one piece, will be fixed to the underside of the drone.

Dr. T.M. Hiller, General Manager (and founder) at Thurn Group Ltd., said: “We are hoping to supply these worldwide with dipping sonars, to many different customers and industries. This is an enabling technology that will allow safer drone operations over water wherever dipping sonars are employed, significantly reducing the risk of losing the drone. We looked at other suppliers too, but DLM’s solution was up to specification and we are looking forward to using it.”

The release can be activated in three ways: via a pull of a certain force for a length of time, for example, 2kg for four seconds; via a 3.3V signal from the drone triggered manually on the drone’s handheld controller; or via a 3.3V signal from the drone triggered by the drone control software. The drone software can be programmed to look for errors in flight behaviour, such as the payload swinging too much. The operator that is watching the drone, meanwhile, can look out for problems the software does not see. In all instances, the drone can return safely and the waterproof sonar picked up later utilising a tracking signal.

DLM printed the prototype using Stereolithography (SLA), which, as James Pawsey, Mechanical Design Engineer at DLM, explained, is a more costly but more accurate method of 3D printing versus “more typical” fuse deposition modelling (FDM). Pawsey said: “FDM uses a thread of plastic that gets melted and built up in layers; SLA uses an ultraviolet laser to cure liquid resin layer by layer. It’s an interesting technological development that we’re keen to leverage.”

A 3D-printed solution aligned with Thurn’s initial expectations for the release concept, and Pawsey said it was an easy decision to utilise the machine that has been part of DLM’s printing fleet since August, from when it has been in almost constant use.