Machine performance analysis time reduced from months to minutes

Products used

Background

Vert Technologies, based in Edinburgh, specialises in the design and manufacture of the patented, high pressure, Conical Rotary Compressor (CRC) technology. This unique product, invented and developed in-house, is supplied to key sectors such as refrigeration, heat pump and gas compression markets. The main USPs of this compressor technology are that it offers a compact yet scalable compression solution, capable of delivering high pressures in a single stage without compromising on noise levels. It was during continual production of the compressors that the company realised manufacturing was wrong in their machining process.

Nicol Low, Chief Operating Officer at Vert Technologies, explains: “When you’re dealing with high-tech, high precision parts, your process needs to be perfect in order to achieve the necessary accuracy. One USP of our technology is that it is a quiet compressor, however, the parts we were producing weren’t achieving the low noise levels that we would expect when in use, and flow performance was suffering too. This obviously needed to be rectified fast.

“Given the fact that we use a 5-axis machining strategy, we knew something was wrong with the process. Having tried, unsuccessfully, to leverage sub contract machining, we looked to see how we could improve the accuracy and repeatability of our own procedures. We were confident that improving the part location, and ensuring the accuracy of the machine tool was key to minimising non-conformance, but were unsure of how to best put that into practice. We hoped MSP could help”.

Challenge

Vert Technologies’ main ambition was to find the cause of any errors in their production process to stop their rotor parts from being machined inaccurately, causing poor performance of the compressor. The company also wanted to reduce the number of manual procedures required, to improve accuracy and productivity throughout the production process.

In an attempt to achieve the accuracy needed for such high-precision parts, Vert Technologies’ original process was time-consuming and required a highly-skilled operator to manually datum the part in the fixture to ensure the alignment was accurate before machining.

Nicol explains, “There was a lot of time wasted trying to get parts to come off the 5-axis machine accurately. We would create a fixture, datum the fixture and machine the part. The rotor design is relatively complex and the metrology of it is quite limited, so once machined, we scan the surface and check the 3D profile against the CAD model. Following this, we did some manual checks to ensure the run-out was within tolerance. This method worked initially, but the machine eventually drifted and the accuracy of fixture location reduced. This, therefore, had an impact on the quality of the machining resulting in non-conforming parts”.

Vert Technologies were producing a high volume of out of tolerance parts and this was the reason for the drop in performance, and the increase in noise of the final product. To try and solve these problems, the company invested a large amount of time and money in investigations, with limited success, increasing pressure on the machine shop floor.

During one of these investigations, the Vert Technologies engineering team recognised there was a problem with the CNC machine but were unable to diagnose it with the metrology data they had available to them.

Nicol says, “We were seeing issues on different parts that were being produced on the same machine, which led usto believe the machine wasn’t working to the accuracy it should be. Producing simple conical and cylindrical test parts, without the complicated forms of the conical rotor part, showed there was an unaccounted for, taper along the Z axis of the machine tool. If the machine wasn’t able to produce simple forms accurately, it was never going to produce a more complex 3D-part perfectly”.

Other tests performed by the engineering team showed the run-out of the part was drifting and being machined off-centre.

“To solve this, we tried to use clocks, manually updating the fixture datum on the machine tool, and also ran the OEM kinematic check for the 5th axis location. It worked to some extent, but because we were still having to manually shift datums, it wasn’t perfect, and not a suitable process for the high-precision parts we were machining,” says Nicol.

Solution

First, MSP looked to diagnose the machine problems and investigate why Vert Technologies’ 5-axis CNC machine tool wasn’t capable of accurately machining even simple forms. To do this, the MSP engineering team installed NC-Checker onto the machine tool. This software ensures the machine tool’s geometric performance is accurate enough for the part to be machined correctly. It produces automatic ‘benchmark’ reports which pinpoint exactly where the machine is under-performing, allowing Vert Technologies to identify where any problems lie and rectify them before any machining begins.

Nicol explains, “The benchmarking of the machine functionality was great as it instantly showed us where our machine inaccuracy was, and showed how accurate it could be, if the machine was working to its full potential.”

Next MSP focused on solving the company’s fixturing and alignment issues to stop the rotors from being machined off-centre. MSP’s NC-PartLocator software was installed on the CNC machine using standardised nominal programs. Vert Technologies was now able to automate part setup and automatically calculate accurate alignments for each machining operation. This removed the need for time-consuming manual alignments and shifting of datums that Vert Technologies’ highly-skilled personnel had to perform to achieve the necessary accuracy required for their parts.

“With the introduction of MSP’s 5-axis automation software, not only have all the manual steps been removed, but we can now check everything before cutting the part. This has resolved many of the problems that previously resulted in non-conforming parts,” comments Nicol.

Result

By diagnosing the errors in Vert Technologies’ 5-axis CNC machining process and automating each stage to remove the introduction of manual error, the company has seen their non-conformance rate go from 25% to near zero.

Before MSP’s solutions were introduced, run-out of parts could be up to as much as 120μm, and over the required tolerance threshold to pass final inspection. This number is now down to as little as 25μm and well within tolerance.

Nicol says: “The higher noise levels and lower performance we had been experiencing with the compressors stopped once the MSP software had been implemented. Using NC-Checker to diagnose and rectify the issues on our machine tool has also meant the machine parameters are the best we’ve ever seen. To have the confidence that our CNC machine tool is accurate and the parts it machines will be within tolerance and repeatable every time is invaluable.”

Adding automation to the alignment process has also provided many other useful benefits for Chief Operating Officer, Nicol: “Having MSP, and the automation it provides in aligning the part, reduces the number of personnel and resources needed on the shop floor. Senior engineers no longer need to be involved day to day - production can be successfully completed by any of our operators."

It was extremely important to Vert Technologies that they retained production of their conical rotor part in-house and, by implementing solutions from MSP, this was achieved. “We strive to be experts in producing our rotors and by keeping our manufacturing capability in-house we are in control of the learning that went into making our parts accurate,” explains Nicol.

And the future of manufacturing certainly looks bright for the Vert Technologies team, who’s product is unique in the marketplace. “Our plan is to embed our technology into products such as heat pumps, HVAC, processed gas, gas capture and recompression equipment, where our USPs fit well with the end user requirements,” continues Nicol.

MSP has a long-standing reputation of saving its customers time and money. Margaret Toberty, MSP’s Director of Operations comments: “We are delighted with the results Vert Technologies has achieved by implementing our solutions in their process. Advanced, automated CNC techniques are imperative to the success and future of the industry, and companies like Vert Technologies are ahead of the curve compared to some of their much larger peers. They have such a fantastic product and it’s exciting for us to work with a small business like this who have such ambition.”