As a global specialist in fluid engineering technology such as pumping, agitation, mixing, separation and application technologies, Sulzer has a network of 180 manufacturing facilities and service centres across the globe. With more than 25 service and manufacturing facilities in the UK; a reliable and reputable supply chain is critical for this OEM and service provider, which is why Sulzer recently committed to a three-year contract with metalworking and MRO experts MSC Industrial Supply Co.
Driven by quality, innovation and continuous improvement, Sulzer witnessed indifferent levels of support from its previous integrator of consumable products and made the bold move to change its supplier during the pandemic. It was only a matter of weeks from signing the contract before MSC was identifying savings worth hundreds of thousands of pounds at Sulzer.
Notably, MSC identified the savings ‘virtually’, during the UK lockdown.
The initial phase of the contract is seeing MSC implement vending solutions into two of Sulzer’s largest UK manufacturing sites in Birmingham and Leeds, with bespoke solutions introduced gradually at Sulzer’s other UK sites.
MSC application engineer Stuart Wiezniak was tasked with identifying ‘cost-down’ improvements to meet and exceed MSC’s contractually agreed commitments. Using its manufacturing expertise, a choice of unbiased suppliers, hundreds of best practice reference points and the combined experience of 15-strong application engineering team, MSC identified productivity gains and cost-down savings that would shatter the contractually obliged target on just two machine tools at the Sulzer manufacturing site in Leeds.
During his initial and socially distanced site ‘walk-round’, Wiezniak was introduced to the machine shop and staff, where early conversations identified concerns over a new project that involved turning a 4 m long Inconel shaft for a new high-pressure pump product line used in heavy-engineering sectors such as offshore.
Currently turning hundreds of 3 to 4 m long Super Duplex shafts, the introduction of Inconel for a new product line raised concerns for Sulzer. However, with hundreds of shafts turned annually on lathes over 20 years old, Wiezniak had no concerns over the performance of the machines.
“The older machines have construction and rigidity that far outweighs most modern machine tools, so we had the perfect foundation for trialling MSC’s range of tools,” he says. “We selected a couple of premium carbide grades for Inconel machining, achieving marginal gains on the speeds, feeds and overall cycle times. To attain the ‘step change’ we really wanted, we had to look at ceramic tooling.”
With the extensive range of Japanese ceramic cutting tools from specialist NTK recently added to the MSC range, Sulzer adopted a paradigm shift in strategy. For Sulzer, the concern around switching to ceramic tooling was the potential for additional heat and distortion. Wiezniak thus identified the need to change the machine coolant, as well as the slide wipers on the lathe bed from nylon to steel to protect the machine bed from the increased swarf temperatures created by high-speed and feed turning.
“With the machine fully prepared for trials, we worked closely with NTK’s application engineer Glyn Shaw and Sulzer’s machine operator and programmer Jamie Fieldhouse; a genuine team effort.”
Despite the stable machine platform, the new coolant and the slide guarding, the trio of engineers realised that the steady rest on one lathe required relocation from an average distance of 1 m from the cutting tool, to 350 mm, to increase the rigidity and stability for ceramic tooling. Ceramic tooling is inherently more brittle and susceptible to vibration than its carbide counterparts.
An initial batch of five Inconel 625 shafts required machining from a raw 200 mm diameter by 4 m long billet, down to a range of stepped diameters from 100 to 180 mm. After the primary work of preparing the machine and devising the rough machining strategies, the trials began. When rough machining the shafts to just leave +2 mm for semi-finish turning, the best carbide turning results typically yielded a finish machining time of 14 hours and 1 minute. Cutting data included depths of cut from 1 to 3 mm, cutting speeds of 40 to 50 m/min and spindle speeds of 80 to 200 rpm. These times, like all other times recorded by MSC at Sulzer account for cutting time only and do not include the additional reductions in set-ups and tool changes.
Wiezniak says: “Upon the recommendation of Glyn, we selected NTK’s Bidemic series of inserts and, in particular, the JX1 grade with a round RNMG12 insert geometry. This was because the Bidemic range offers better wear and notching resistance compared to whisker ceramic grades that are used widely in the industry.
“The NTK trials started at a cutting speed of 250 m/min, but we found the optimal speed for this job at 370 m/min, a massive increase over the 40 to 50 m/min we could achieve with carbide,” he continues. “We also increased the spindle speed from 80 to 200 rpm to over 740 to 1000 rpm, depending upon the diameter being turned.
“Cutting with an average depth of 1.5 to 2 mm, we reduced the rough machining time on the five Inconel 625 shafts from 14 hours, to just 2 hours and 4 minutes per shaft. This yielded a material removal rate (MMR) of 222 cm³/min, up from the previous rate of 30 cm³/min. An unexpected benefit was the improved concentricity after releasing the steady rest. With carbide tools, the rollers were showing a run-out of up to ±1 mm, yet with the ceramic inserts, which only increased workpiece temperature by 9°C during machining, the runout was consistently between ±0.15 to 0.20 mm.”
Aside from a nominal annual tooling cost increase of less than £1000, the six-figure financial savings justify the tool cost increase.
“From discussions with Sulzer, they have already identified more than 170 forward orders for the next 12 months for this particular pump,” says Wiezniak. “Based on our CAM and cutting-tool data, we project that we will reduce annual machining costs by 85%, reduce machining times by 85% and reduce the cost per part by 8%. To qualify this, total cutting hours will fall from 2380 per annum to less than 350, and this doesn’t include set-up and tool change reductions. This will yield a significant six-figure financial saving for Sulzer on the production of forward order Inconel 625 shafts and the respective pumps.”
With the groundwork and trials already successfully implemented on the Inconel parts, the cutting data has also been adapted for Sulzer’s large-bed turning centre that presently has more than 100 Super Duplex shafts scheduled for production.
“Although Super Duplex has a somewhat different and softer composition than Inconel, it is still an extremely difficult material to machine,” says Wiezniak. “We have already started work on this and are fully confident that we’ll replicate the ‘seven times’ overall cycle time reduction from the Inconel parts, doubling our already fantastic results.”
Indeed, MSC has already identified further and potentially equally impressive savings on the same shafts on a third machine. With the rough-turned shafts finished to +0.3 to +0.5 mm, the final process of grinding takes place on an 8-tonne Churchill BX cylindrical grinding centre.
Explains Wiezniak: “While we are optimising the turning process to minimise stock for finish grinding, we have identified potentially huge savings when grinding the Inconel shafts. By introducing new grinding wheel technology with the help of Kim Dean from Tyrolit, we can double the depth of cut from the existing 0.05 mm, to 0.1 mm, effectively halving the 36-hour cycle time. But taking this even further, we’ve also identified cycle-time savings from slashing non-grinding times with the introduction of a secondary wheel dressing unit to reduce wheel traversing distances and dressing times.”
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