When Leighton Buzzard-based BD Precision Engineers was presented with a machining challenge by a long-standing customer, it became apparent that its reputation of meeting all deadlines would be under serious threat. Due to poor tool life and quality that its existing tooling was achieving the job risked going over deadline and budget. However, with the assistance of WNT (UK), which stepped in to offer alternative tools and technical support, BD Precision Engineers’ reputation remained intact.
Over its 40 plus years in existence BD Precision Engineers has grown from a two man business, providing manual milling capacity, to become a modern precision sub-contractor operating the latest in CNC machining, assembly and inspection. Over this time it has resisted the temptation to specialise in any one industry sector, making its customer base as diverse as possible, a decision that has seen it ride out many recessions over the years. In spite of this diversification BD Precision Engineers found that the majority of the materials it was asked to machine revolved around aluminium, stainless steel, and brass components. Therefore, when it was asked to produce a batch of components in Inconel 718 it had to rely on the advice of its then preferred tooling supplier for cutting data.
“This was the first job in Inconel that we had been asked to machine in 20 years,” says BD Precision Engineers’ Works Manager, Jed Juster. “For advice we contacted our then tooling supplier to ask for cutting data for the drilling and milling operations. That advice was to avoid carbide tools and run a pecking cycle with .5 mm steps with a powder metal drill, the result was a cycle time to drill four holes in each component through 8 mm of material of 11 minutes; and each drill could only achieve five holes before it either broke or had to be removed. The pecking was simply creating a work hardened surface.”
These drilling problems were compounded by issues relating to profile and face milling the part, both areas that were generating lots of burrs and poor surface finish and an overall cycle time of 43 minutes per part, which was simply unacceptable for BD Precision Engineers, as was the fact that the end mill they had been recommended was only lasting for one component. “We were really struggling to meet deadlines and make any money on the job, and we simply couldn’t leave the machine unattended through fear of drill breakages and scrap components. Therefore we had to find an alternative and that was when we called in Duncan Slough, WNT’s Technical Sales Engineer.”
The first thing that Duncan changed was the drill, moving from powder metal to solid carbide with WNT’s WTX Ti drill with through coolant, this was held in a WNT Centro P collet chuck with guaranteed runout of less than 3 micron. The cutting data suggested, much to the nervous amazement of Jed Juster, was 55 m/min and 0.08 mm/rev and no pecking. His nerves were calmed when Duncan said he would be stood on the duckboard next to him when the cycle start button was pushed! As a result of this one change the drilling cycle time for the four holes in each part was reduced to 40 seconds, the drill achieved 200 holes and looked as good as new when it had finished.
In a similar vein the profiling of the part was also changed to a 10 mm diameter solid carbide WNT HPC Ti cutter running at 500 mm/min feedrate, a ten-fold increase on what was being achieved before. In addition, the HPC Ti cutter machined 26 parts before needing to be changed, compared to just four parts with the original suppliers cutter. The final piece in the jigsaw was to use a 63 mm diameter indexable insert face mill using WNT’s 5240 grade of inserts to finish mill the part and eliminate all of the burr and surface finish problems.
“The changes that Duncan made brought incredible results and the fact that he was happy to stand next to me while we cut the first few parts was very reassuring and the information he gave us was spot on. The overall difference is incredible, with the cycle time dropping from 43 minutes to 17 minutes 35 seconds, or 60 per cent shorter. The quality of the finished parts is superb and the cost savings are substantial. If we had stuck with the original drilling cycle we would have needed 50 drills to complete the batch, whereas with the WNT WTX Ti drill we only needed one, a saving of almost £3000 in tooling costs alone,” says Jed Juster.
The result of the switch has not only saved time and money, but the confidence that BD Precision Engineers now has in terms of process security is immense. This is allowing the operator to undertake other tasks while the machine is running. It has also opened up the opportunity to do more work of this type in these more difficult to machine materials. BD Precision Engineer’s Managing Director, Andrew Fogden explains: “Like a lot of things in life confidence plays a big part in decision making, now that we have the confidence and support of WNT we are more than happy now when quotes come in for parts made from Inconel or similar materials. The improved performance from the WNT tooling also means that we can be sure that we will meet promised delivery dates and we are able to free up machine capacity to do other things due to the reductions in cycle times.”