After five years of painstaking research followed by three years of developing his fledgling business, Olly Dmitriev — award-winnng entrepreneur and the founder of Edinburgh-based Vert Rotors — launched his patented range of ultra-compact low-vibration, quiet and extremely powerful compressors at last year’s IMTS Show in Chicago.

The Vert.04.W nano is a conical rotary compressor producing clean compressed air at pressures up to 115psi from a miniature system that is just 100mm long x 40mm in diameter and rated at 150W. Moreover, it is widely acknowledged as the smallest screw compressor in the world.

The conical-compressor technology has been recognised as a potential ‘step change’ by the Ministry of Defence’s Centre for Defence Enterprise; and while developing such complicated technology was one challenge, producing it was another.

It was here that Bicester-based Open Mind Technologies (www.openmind-tech.com) was able to help, with its HyperMill CAM software.

The male and female conical rotors are key to the effective operation of this compressor.

Mr Dmitriev said: “While many components — such as tubes, pipes, filters and fittings — are readily available, we were using a 3-D printer to produce the innovative and complex conical rotors that complete the compressor assembly, but it was incapable of achieving tolerances of less than 100µm.

Moreover, there were integrity and mechanical issues with the 3-D printing material that gave the prototypes a short running time and a high rate of failure.”

Unable to find a sub-contractor willing to take on the complicated manufacturing, Mr Dmitriev realised he would have to machine his own parts, so it bought a Hurco VMX30 vertical machining centre with a Kitagawa rotary table, to give a 3+2-axis configuration.

As this was Vert Rotors’ first machine tool acquisition, Mr Dmitriev had to select a CAM system. He approached most of the leading CAM vendors, but when the complexity of the parts was revealed, all but two dropped out.

Investigation by Vert Rotors showed that Open Mind’s HyperMill included comprehensive collision avoidance and would therefore provide complete confidence in the machining process. Furthermore, Vert Rotors’ Solidworks CAD system would integrate with the HyperMill CAM software.

Collision detection

Commenting on the software’s collision detection system, Open Mind sales manager Matt Coulson said: “The conical rotary compressor incorporates an inner conical rotor screw that works inside the outer conical rotor. This complicated and critical component needs HyperMill to continuously calculate and check for collisions ‘in process’. The depth of the hole and the required tool length were also factors making this process more difficult.

The form of the internal feature is such that HyperMill is required to continuously and simultaneously prevent workpiece collisions with the cutting edge, the tool shank and also the tool-holder of the lollipop-geometry cutting tools. Using HyperMill’s tube-machining strategy, the calculations are processed at remarkable speed; indeed, this was a key reason why Vert Rotors opted for this software.”

The Vert.04.W nano rotary compressor was developed for the delivery of compressed liquid or air. Its core components are machined from composite polymers, stainless steel or brass — depending on whether the compressor is specified for air or fluid applications.

In conclusion, Mr Dmitriev says: “While using the 3-D printer for development compressors, we searched for over three years for a sub-contractor that would take on the conical-compressor project.

“When we decided to manufacture the parts ourselves, even CAM suppliers were unable to help ,with many admitting that their packages weren’t up to the job. We found the situation somewhat frustrating, but Open Mind made the seemingly ‘impossible’ possible.”