To support that, the company installed a German-built Index C200 mill-turn (Geo Kingsbury, 02392 580371).
The business came from an existing DKW customer that was putting the work out to a another subcontractor that was machining the parts from stainless steel castings. Following that machining, the parts had to undergo an expensive polishing step, with this often revealing porosity on the surface, making components unusable.
Initially following the same process path when his company won the business at the end of 2014, DKW managing director Nick Iacobucci saw that the design could be changed to machining from round stainless steel bar instead. In addition, this meant it would be possible to omit insertion of a pin into the component, doing away with an assembly operation. As an added bonus, the higher surface finish achievable would eliminate the need for polishing. The search for suitable machinery then commenced.
Iacobucci approached three potential suppliers of turning centres that could support the manufacture of the family of parts having diameters up to 65 mm.
Gosport-based Geo Kingsbury won out because it demonstrated that a three-turret Index C200 could produce the parts to the required ± 0.05 mm tolerance and also achieve 0.8 Ra surface finish. In addition, the new process route was a one-hit one, not a five-operation process as before, promoting accuracy and reducing work in progress.
A feature of the Index lathes is the kinematic actuation its three turrets -– 2-axis motion in a single plane, rather than via standard compound slides. This results in fast movements, both in and out of cut, as well as high stiffness and rigidity, helping to hold tight tolerances and the fine surface finish.
After Geo Kingsbury successfully ran off 45 samples at its Gosport technical centre, a package that included an Index C200, Iemca Master 80HF bar magazine (1st MTA, 01725 514000) plus gripper arm for picking each finished part out of the counter-spindle and placing it onto a conveyor was subsequently installed at DKW’s Portsmouth factory in October 2015.
Manufacturing cost per part is only 8% more expensive when using solid bar rather than castings, but good part yield is more than double. Overall, both cost and lead-time per part are reduced considerably across the range of nine different flow meter components currently being produced. As the value of each part is several hundred pounds, savings are substantial.
Says Iacobucci: “Part of the reason we are able to machine the components so economically from bar is that we are using a triple-turret, twin-spindle lathe. Two turrets can operate at either spindle and three tools are in cut simultaneously during large sections of the cycles, which include a lot of balanced turning and milling. Repeatability is excellent, partly due to the Index system of W-groove quick-change tooling and also as a result of refrigeration and filtration of the coolant.”
Supporting the investment was applications engineering from supplier Geo Kingsbury, described as “superb”. For instance, it recommended the use of trochoidal milling to produce a slot in the component. The process involves running a Delcam Vortex milling cycle (0121 766 5544) in the machine’s Fanuc series 31i-model B control. An Iscar solid carbide, 6.5 mm diameter side-and-face milling cutter (0121 422 8585) produces the feature, its width being machined to a tolerance of ±0.1 mm. If a cutter were to mill the full width of the slot in a linear pass, vibration would compromise accuracy and shorten tool life dramatically.
In addition, Iacobucci adds: “We have also been impressed with the provision of their three training modules covering programming, machine operation and maintenance.”