Ayrshire-based NPI Solutions Ltd, a leading precision sub-contractor recently took delivery of its first Doosan collaborative robot (cobot) supplied by Mills CNC Automation to improve its productivity, efficiency and machine tool usage.

The M1013 cobot, with its 1.3m reach radius and 10kg payload, was delivered to the company in September last year and was integrated with a Doosan DNM 350 5AX (five-axis machine) previously acquired from Mills CNC in 2016.

Since being installed the cobot has proved its worth by helping NPI optimise the DNM 350 5AX’s spindle uptime, minimising operator interventions and singificantly improving the machine’s output.

NPI is a company committed to continuous improvement and best-practice; it regularly monitors, collects and analyses machine tool performance data — calculating the effectiveness and efficiency (OEE) of the equipment it uses.

The objective being to accurately identify production ‘pinch points’, to remove and/or reduce the issues that cause machine downtime, and to make manufacturing processes as productive as possible.

Kevin Priestley, NPI’s managing director, said: “We invested in a Doosan five-axis machine back in 2016 to help make us more productive, efficient and competitive. The ability to machine precision parts in one set up, via 3+2 and 4+1 machining was the appeal — and the goal.”

However, analysis of the machine’s performance over a period of time revealed that it was failing to deliver the expected results.

He explained: “It wasn’t the machine’s fault. It was directly related to the type of production work we do which is characterised by low volumes and small batches, as well as by short part cycle times.”

Being a high mix - low volume (HMLV) component manufacturer meant that the DNM 350 5AX could be idle for long periods each day to allow for frequent job set ups and changeovers to occur.

Mr Priestley said: “Machines do not make money if they are not making chips. To improve our profitability we needed to increase the DNM 350 5AX’s spindle up-time.”

As a consequence the company began to explore automation as a route to improving the machine’s utilisation and output.

The automation decision
NPI is no stranger to automation or to unmanned operations having previously invested in high-performance bar feeders to increase the productivity and performance of its CNC turning operations. To increase the productivity of its DNM 350 5AX machine, the company explored a number of automation options before deciding on the cobot route.

Mr Priestley added: “There were a number of potential automation solutions available. We looked at automatic workpiece pallet change systems and industrial robots but their cost, floorspace requirements and complexity ruled them out.”

NPI required a more economically-viable and ‘simpler’ solution — one that could be quickly installed to transform the DNM 350 5AX into a flexible, automated manufacturing cell.

He continued: “We investigated cobot technology and found their versatility, in addition to their safety, their relatively lower investment cost and their ease of deployment, made them an attractive propositions.

“When we found out that Mills CNC, through its newly created automation division, could supply us not only with a Doosan cobot but also project-manage, install and provide comprehensive training and applications support — we decided to put our plans into action.

“We visited Mills CNC Automation’s facility in Leamington to meet the application engineering team and discuss our specific requirements with them in more detail. Ultimately we gave the ‘green light’ to the investment.”

To undertake what are essentially machine tending operations, NPI worked alongside Mills CNC Automation engineers to identify the right cobot for the job. The one selected (based on the dimensions and weight of parts machined on the DNM 350 5AX) was the M1013 model which has a 10kg maximum payload and a 1.3m reach.

The cobot also features six high-torque sensors that provide ‘best-in-class’ collision protection and was supplied to NPI with a controller, a teach pendant, a RG6 (OnRobot) gripper and a Schunk workholding package.

Situated adjacent to the DNM 350 5AX which, as part of the installation was fitted with an automatic door opening/closing facility, the cobot is programmed to pick up blanks positioned on a peg table and load them, in turn, into the machine where they are machined to completion.

Once machining operations have been completed the cobot takes the finished (machined) component from the machine and places it back on the peg board in its predetermined position. This cycle is then repeated, with no operator intervention, until all the parts have been completed.

Components machined on the DNM 350 5AX are typically made from aluminium. They vary in size from 15mm x 15mm x 15mm through to 150mm x 150mm x 20mm. Cycle times can be from 2min up to 60min depending on part size, complexity and features.

Mr Priestley said: “The ambition to create a flexible automated manufacturing cell has been realised through the cobot investment. During the day the cell is programmed to machine components (with relatively short cycle times) unattended allowing operators to work on other machines or perform other tasks. For parts with longer cycle times the cell is programmed to run unattended overnight.”

NPI’s new cobot cell has helped dramatically improve its productivity, efficiency and competitiveness. The DNM 350 5AX is now running at 85% efficiency as opposed to just 50% efficiency prior to the cobot investment.

Mr Priestley added: “Everything went smoothly - from the design of the system through to its installation, proving out and on-site and remote training. Mills CNC Automation’s Peter McCullough and Cris Hearty took the time to understand our requirements.

“They demonstrated the productivity gains we could expect to realise from the investment - which have proved to be correct. The support they have provided throughout the project has been first-class, and I cannot recommend them highly enough.”

NPI’s automated cobot cell has no been operational for six months. Mr Priestley concluded: “Despite the pandemic and subsequent lockdowns, we have been unbelievably busy over the last 12 months. To meet demand from customers for our high-quality and competitively priced precision machining services we will be investing in more automation in the near future.”