One week before a major exhibition and conference in the USA, SentriLock LLC in Cincinnati, Ohio, had what it believed was a winning concept for a web-based electronic lock to help estate agents maximise property viewings, but the company had no demonstration units of production quality. It was crucial not to miss the launch, so SentriLock asked a local bureau, Morris Technologies, to produce a functional design and prototype in time for the show.
The deadline would have been missed if the component parts had been made on CNC machining centres, so the product development firm elected to use its EOS Direct Metal Laser-Sintering (DMLS) machine. The source of this technology in the UK is the German manufacturer's subsidiary, EOS Ltd, Warwick.
Called REALTOR Lockbox, SentriLock's new product is attached to a front door, safeguarding the key to the home while giving estate agents and potential buyers controlled entry to the property. Unlike mechanical versions, the electronic lockbox provides secure access with a smart card and is also able to log viewings.
To demonstrate these features at the exhibition, it was necessary to have a prototype that would be representative of a product made of metal.
Lockbox system contracts in the US are typically of at least five years duration, so it was especially important for SentriLock to display a product that looked real and would convince potential customers that they should hold off re-signing with their existing supplier.
SentriLock specified that the prototypes had to look, feel and function like production units, which was a big challenge as they are eight-piece, die-cast assemblies and were needed in one week. Greg Morris, COO of Morris Technologies, agreed: “A product such as this must have credible physical security. There is no way that estate agents would have taken painted, plastic parts seriously. We had to produce a product that communicated strength and protection.”
The complete assembly, measuring 254 mm long, 127 mm wide and 63 mm deep, consists of a two-piece outer housing, access covers and supporting parts. Although a few of the pieces are relatively simple, others are fairly complex. Continued Greg Morris, “There are features such as deep channels and ribs with no fillets that made it a tough job, especially in the time frame we were given.”
Like other layer-manufacturing technologies, DMLS builds parts one layer at a time directly from the CAD model. Laser-sintering powdered metal alloys produces solid, dense parts with functionality and appearance similar to a component machined from a solid billet, casting or forging. An advantage that Morris Technologies enjoys is that the 20-micron metal powder it uses produces very thin layers, which in turn results in parts with a smooth surface. Greg Morris likens the surface of DMLS to a fine EDM finish that requires only minimal secondary work.
His firm nested the eight-piece lockbox assembly so that all components could be built in one run of the EOSINT M 270 machine. The automated and unattended process took only 53 hours, or 2.2 days. Including part programming, Greg Morris estimated that CNC machining would have taken 10 working days, one week longer than the time that they were given for the entire project.
He concluded, “It sounds great to talk about 24/7, lights-out machining, but it is not realistic for a prototype run that has not had the programming fully proven out, so evenings and weekends are lost. However with DMLS technology, there is no need for operator intervention, so the machine runs around the clock.”
Since the successful launch and commercial release of the lockbox, SentriLock has sold more than 100,000 units used by 30,000 estate agents around the USA.